pouchdb/dist/pouchdb.find.js

// pouchdb-find plugin 9.0.0
// Based on Mango: https://github.com/cloudant/mango
// 
// (c) 2012-2024 Dale Harvey and the PouchDB team
// PouchDB may be freely distributed under the Apache license, version 2.0.
// For all details and documentation:
// http://pouchdb.com
(function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(_dereq_,module,exports){
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

var objectCreate = Object.create || objectCreatePolyfill
var objectKeys = Object.keys || objectKeysPolyfill
var bind = Function.prototype.bind || functionBindPolyfill

function EventEmitter() {
  if (!this._events || !Object.prototype.hasOwnProperty.call(this, '_events')) {
    this._events = objectCreate(null);
    this._eventsCount = 0;
  }

  this._maxListeners = this._maxListeners || undefined;
}
module.exports = EventEmitter;

// Backwards-compat with node 0.10.x
EventEmitter.EventEmitter = EventEmitter;

EventEmitter.prototype._events = undefined;
EventEmitter.prototype._maxListeners = undefined;

// By default EventEmitters will print a warning if more than 10 listeners are
// added to it. This is a useful default which helps finding memory leaks.
var defaultMaxListeners = 10;

var hasDefineProperty;
try {
  var o = {};
  if (Object.defineProperty) Object.defineProperty(o, 'x', { value: 0 });
  hasDefineProperty = o.x === 0;
} catch (err) { hasDefineProperty = false }
if (hasDefineProperty) {
  Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
    enumerable: true,
    get: function() {
      return defaultMaxListeners;
    },
    set: function(arg) {
      // check whether the input is a positive number (whose value is zero or
      // greater and not a NaN).
      if (typeof arg !== 'number' || arg < 0 || arg !== arg)
        throw new TypeError('"defaultMaxListeners" must be a positive number');
      defaultMaxListeners = arg;
    }
  });
} else {
  EventEmitter.defaultMaxListeners = defaultMaxListeners;
}

// Obviously not all Emitters should be limited to 10. This function allows
// that to be increased. Set to zero for unlimited.
EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
  if (typeof n !== 'number' || n < 0 || isNaN(n))
    throw new TypeError('"n" argument must be a positive number');
  this._maxListeners = n;
  return this;
};

function $getMaxListeners(that) {
  if (that._maxListeners === undefined)
    return EventEmitter.defaultMaxListeners;
  return that._maxListeners;
}

EventEmitter.prototype.getMaxListeners = function getMaxListeners() {
  return $getMaxListeners(this);
};

// These standalone emit* functions are used to optimize calling of event
// handlers for fast cases because emit() itself often has a variable number of
// arguments and can be deoptimized because of that. These functions always have
// the same number of arguments and thus do not get deoptimized, so the code
// inside them can execute faster.
function emitNone(handler, isFn, self) {
  if (isFn)
    handler.call(self);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self);
  }
}
function emitOne(handler, isFn, self, arg1) {
  if (isFn)
    handler.call(self, arg1);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1);
  }
}
function emitTwo(handler, isFn, self, arg1, arg2) {
  if (isFn)
    handler.call(self, arg1, arg2);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1, arg2);
  }
}
function emitThree(handler, isFn, self, arg1, arg2, arg3) {
  if (isFn)
    handler.call(self, arg1, arg2, arg3);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].call(self, arg1, arg2, arg3);
  }
}

function emitMany(handler, isFn, self, args) {
  if (isFn)
    handler.apply(self, args);
  else {
    var len = handler.length;
    var listeners = arrayClone(handler, len);
    for (var i = 0; i < len; ++i)
      listeners[i].apply(self, args);
  }
}

EventEmitter.prototype.emit = function emit(type) {
  var er, handler, len, args, i, events;
  var doError = (type === 'error');

  events = this._events;
  if (events)
    doError = (doError && events.error == null);
  else if (!doError)
    return false;

  // If there is no 'error' event listener then throw.
  if (doError) {
    if (arguments.length > 1)
      er = arguments[1];
    if (er instanceof Error) {
      throw er; // Unhandled 'error' event
    } else {
      // At least give some kind of context to the user
      var err = new Error('Unhandled "error" event. (' + er + ')');
      err.context = er;
      throw err;
    }
    return false;
  }

  handler = events[type];

  if (!handler)
    return false;

  var isFn = typeof handler === 'function';
  len = arguments.length;
  switch (len) {
      // fast cases
    case 1:
      emitNone(handler, isFn, this);
      break;
    case 2:
      emitOne(handler, isFn, this, arguments[1]);
      break;
    case 3:
      emitTwo(handler, isFn, this, arguments[1], arguments[2]);
      break;
    case 4:
      emitThree(handler, isFn, this, arguments[1], arguments[2], arguments[3]);
      break;
      // slower
    default:
      args = new Array(len - 1);
      for (i = 1; i < len; i++)
        args[i - 1] = arguments[i];
      emitMany(handler, isFn, this, args);
  }

  return true;
};

function _addListener(target, type, listener, prepend) {
  var m;
  var events;
  var existing;

  if (typeof listener !== 'function')
    throw new TypeError('"listener" argument must be a function');

  events = target._events;
  if (!events) {
    events = target._events = objectCreate(null);
    target._eventsCount = 0;
  } else {
    // To avoid recursion in the case that type === "newListener"! Before
    // adding it to the listeners, first emit "newListener".
    if (events.newListener) {
      target.emit('newListener', type,
          listener.listener ? listener.listener : listener);

      // Re-assign `events` because a newListener handler could have caused the
      // this._events to be assigned to a new object
      events = target._events;
    }
    existing = events[type];
  }

  if (!existing) {
    // Optimize the case of one listener. Don't need the extra array object.
    existing = events[type] = listener;
    ++target._eventsCount;
  } else {
    if (typeof existing === 'function') {
      // Adding the second element, need to change to array.
      existing = events[type] =
          prepend ? [listener, existing] : [existing, listener];
    } else {
      // If we've already got an array, just append.
      if (prepend) {
        existing.unshift(listener);
      } else {
        existing.push(listener);
      }
    }

    // Check for listener leak
    if (!existing.warned) {
      m = $getMaxListeners(target);
      if (m && m > 0 && existing.length > m) {
        existing.warned = true;
        var w = new Error('Possible EventEmitter memory leak detected. ' +
            existing.length + ' "' + String(type) + '" listeners ' +
            'added. Use emitter.setMaxListeners() to ' +
            'increase limit.');
        w.name = 'MaxListenersExceededWarning';
        w.emitter = target;
        w.type = type;
        w.count = existing.length;
        if (typeof console === 'object' && console.warn) {
          console.warn('%s: %s', w.name, w.message);
        }
      }
    }
  }

  return target;
}

EventEmitter.prototype.addListener = function addListener(type, listener) {
  return _addListener(this, type, listener, false);
};

EventEmitter.prototype.on = EventEmitter.prototype.addListener;

EventEmitter.prototype.prependListener =
    function prependListener(type, listener) {
      return _addListener(this, type, listener, true);
    };

function onceWrapper() {
  if (!this.fired) {
    this.target.removeListener(this.type, this.wrapFn);
    this.fired = true;
    switch (arguments.length) {
      case 0:
        return this.listener.call(this.target);
      case 1:
        return this.listener.call(this.target, arguments[0]);
      case 2:
        return this.listener.call(this.target, arguments[0], arguments[1]);
      case 3:
        return this.listener.call(this.target, arguments[0], arguments[1],
            arguments[2]);
      default:
        var args = new Array(arguments.length);
        for (var i = 0; i < args.length; ++i)
          args[i] = arguments[i];
        this.listener.apply(this.target, args);
    }
  }
}

function _onceWrap(target, type, listener) {
  var state = { fired: false, wrapFn: undefined, target: target, type: type, listener: listener };
  var wrapped = bind.call(onceWrapper, state);
  wrapped.listener = listener;
  state.wrapFn = wrapped;
  return wrapped;
}

EventEmitter.prototype.once = function once(type, listener) {
  if (typeof listener !== 'function')
    throw new TypeError('"listener" argument must be a function');
  this.on(type, _onceWrap(this, type, listener));
  return this;
};

EventEmitter.prototype.prependOnceListener =
    function prependOnceListener(type, listener) {
      if (typeof listener !== 'function')
        throw new TypeError('"listener" argument must be a function');
      this.prependListener(type, _onceWrap(this, type, listener));
      return this;
    };

// Emits a 'removeListener' event if and only if the listener was removed.
EventEmitter.prototype.removeListener =
    function removeListener(type, listener) {
      var list, events, position, i, originalListener;

      if (typeof listener !== 'function')
        throw new TypeError('"listener" argument must be a function');

      events = this._events;
      if (!events)
        return this;

      list = events[type];
      if (!list)
        return this;

      if (list === listener || list.listener === listener) {
        if (--this._eventsCount === 0)
          this._events = objectCreate(null);
        else {
          delete events[type];
          if (events.removeListener)
            this.emit('removeListener', type, list.listener || listener);
        }
      } else if (typeof list !== 'function') {
        position = -1;

        for (i = list.length - 1; i >= 0; i--) {
          if (list[i] === listener || list[i].listener === listener) {
            originalListener = list[i].listener;
            position = i;
            break;
          }
        }

        if (position < 0)
          return this;

        if (position === 0)
          list.shift();
        else
          spliceOne(list, position);

        if (list.length === 1)
          events[type] = list[0];

        if (events.removeListener)
          this.emit('removeListener', type, originalListener || listener);
      }

      return this;
    };

EventEmitter.prototype.removeAllListeners =
    function removeAllListeners(type) {
      var listeners, events, i;

      events = this._events;
      if (!events)
        return this;

      // not listening for removeListener, no need to emit
      if (!events.removeListener) {
        if (arguments.length === 0) {
          this._events = objectCreate(null);
          this._eventsCount = 0;
        } else if (events[type]) {
          if (--this._eventsCount === 0)
            this._events = objectCreate(null);
          else
            delete events[type];
        }
        return this;
      }

      // emit removeListener for all listeners on all events
      if (arguments.length === 0) {
        var keys = objectKeys(events);
        var key;
        for (i = 0; i < keys.length; ++i) {
          key = keys[i];
          if (key === 'removeListener') continue;
          this.removeAllListeners(key);
        }
        this.removeAllListeners('removeListener');
        this._events = objectCreate(null);
        this._eventsCount = 0;
        return this;
      }

      listeners = events[type];

      if (typeof listeners === 'function') {
        this.removeListener(type, listeners);
      } else if (listeners) {
        // LIFO order
        for (i = listeners.length - 1; i >= 0; i--) {
          this.removeListener(type, listeners[i]);
        }
      }

      return this;
    };

function _listeners(target, type, unwrap) {
  var events = target._events;

  if (!events)
    return [];

  var evlistener = events[type];
  if (!evlistener)
    return [];

  if (typeof evlistener === 'function')
    return unwrap ? [evlistener.listener || evlistener] : [evlistener];

  return unwrap ? unwrapListeners(evlistener) : arrayClone(evlistener, evlistener.length);
}

EventEmitter.prototype.listeners = function listeners(type) {
  return _listeners(this, type, true);
};

EventEmitter.prototype.rawListeners = function rawListeners(type) {
  return _listeners(this, type, false);
};

EventEmitter.listenerCount = function(emitter, type) {
  if (typeof emitter.listenerCount === 'function') {
    return emitter.listenerCount(type);
  } else {
    return listenerCount.call(emitter, type);
  }
};

EventEmitter.prototype.listenerCount = listenerCount;
function listenerCount(type) {
  var events = this._events;

  if (events) {
    var evlistener = events[type];

    if (typeof evlistener === 'function') {
      return 1;
    } else if (evlistener) {
      return evlistener.length;
    }
  }

  return 0;
}

EventEmitter.prototype.eventNames = function eventNames() {
  return this._eventsCount > 0 ? Reflect.ownKeys(this._events) : [];
};

// About 1.5x faster than the two-arg version of Array#splice().
function spliceOne(list, index) {
  for (var i = index, k = i + 1, n = list.length; k < n; i += 1, k += 1)
    list[i] = list[k];
  list.pop();
}

function arrayClone(arr, n) {
  var copy = new Array(n);
  for (var i = 0; i < n; ++i)
    copy[i] = arr[i];
  return copy;
}

function unwrapListeners(arr) {
  var ret = new Array(arr.length);
  for (var i = 0; i < ret.length; ++i) {
    ret[i] = arr[i].listener || arr[i];
  }
  return ret;
}

function objectCreatePolyfill(proto) {
  var F = function() {};
  F.prototype = proto;
  return new F;
}
function objectKeysPolyfill(obj) {
  var keys = [];
  for (var k in obj) if (Object.prototype.hasOwnProperty.call(obj, k)) {
    keys.push(k);
  }
  return k;
}
function functionBindPolyfill(context) {
  var fn = this;
  return function () {
    return fn.apply(context, arguments);
  };
}

},{}],2:[function(_dereq_,module,exports){
(function (factory) {
    if (typeof exports === 'object') {
        // Node/CommonJS
        module.exports = factory();
    } else if (typeof define === 'function' && define.amd) {
        // AMD
        define(factory);
    } else {
        // Browser globals (with support for web workers)
        var glob;

        try {
            glob = window;
        } catch (e) {
            glob = self;
        }

        glob.SparkMD5 = factory();
    }
}(function (undefined) {

    'use strict';

    /*
     * Fastest md5 implementation around (JKM md5).
     * Credits: Joseph Myers
     *
     * @see http://www.myersdaily.org/joseph/javascript/md5-text.html
     * @see http://jsperf.com/md5-shootout/7
     */

    /* this function is much faster,
      so if possible we use it. Some IEs
      are the only ones I know of that
      need the idiotic second function,
      generated by an if clause.  */
    var add32 = function (a, b) {
        return (a + b) & 0xFFFFFFFF;
    },
        hex_chr = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];


    function cmn(q, a, b, x, s, t) {
        a = add32(add32(a, q), add32(x, t));
        return add32((a << s) | (a >>> (32 - s)), b);
    }

    function md5cycle(x, k) {
        var a = x[0],
            b = x[1],
            c = x[2],
            d = x[3];

        a += (b & c | ~b & d) + k[0] - 680876936 | 0;
        a  = (a << 7 | a >>> 25) + b | 0;
        d += (a & b | ~a & c) + k[1] - 389564586 | 0;
        d  = (d << 12 | d >>> 20) + a | 0;
        c += (d & a | ~d & b) + k[2] + 606105819 | 0;
        c  = (c << 17 | c >>> 15) + d | 0;
        b += (c & d | ~c & a) + k[3] - 1044525330 | 0;
        b  = (b << 22 | b >>> 10) + c | 0;
        a += (b & c | ~b & d) + k[4] - 176418897 | 0;
        a  = (a << 7 | a >>> 25) + b | 0;
        d += (a & b | ~a & c) + k[5] + 1200080426 | 0;
        d  = (d << 12 | d >>> 20) + a | 0;
        c += (d & a | ~d & b) + k[6] - 1473231341 | 0;
        c  = (c << 17 | c >>> 15) + d | 0;
        b += (c & d | ~c & a) + k[7] - 45705983 | 0;
        b  = (b << 22 | b >>> 10) + c | 0;
        a += (b & c | ~b & d) + k[8] + 1770035416 | 0;
        a  = (a << 7 | a >>> 25) + b | 0;
        d += (a & b | ~a & c) + k[9] - 1958414417 | 0;
        d  = (d << 12 | d >>> 20) + a | 0;
        c += (d & a | ~d & b) + k[10] - 42063 | 0;
        c  = (c << 17 | c >>> 15) + d | 0;
        b += (c & d | ~c & a) + k[11] - 1990404162 | 0;
        b  = (b << 22 | b >>> 10) + c | 0;
        a += (b & c | ~b & d) + k[12] + 1804603682 | 0;
        a  = (a << 7 | a >>> 25) + b | 0;
        d += (a & b | ~a & c) + k[13] - 40341101 | 0;
        d  = (d << 12 | d >>> 20) + a | 0;
        c += (d & a | ~d & b) + k[14] - 1502002290 | 0;
        c  = (c << 17 | c >>> 15) + d | 0;
        b += (c & d | ~c & a) + k[15] + 1236535329 | 0;
        b  = (b << 22 | b >>> 10) + c | 0;

        a += (b & d | c & ~d) + k[1] - 165796510 | 0;
        a  = (a << 5 | a >>> 27) + b | 0;
        d += (a & c | b & ~c) + k[6] - 1069501632 | 0;
        d  = (d << 9 | d >>> 23) + a | 0;
        c += (d & b | a & ~b) + k[11] + 643717713 | 0;
        c  = (c << 14 | c >>> 18) + d | 0;
        b += (c & a | d & ~a) + k[0] - 373897302 | 0;
        b  = (b << 20 | b >>> 12) + c | 0;
        a += (b & d | c & ~d) + k[5] - 701558691 | 0;
        a  = (a << 5 | a >>> 27) + b | 0;
        d += (a & c | b & ~c) + k[10] + 38016083 | 0;
        d  = (d << 9 | d >>> 23) + a | 0;
        c += (d & b | a & ~b) + k[15] - 660478335 | 0;
        c  = (c << 14 | c >>> 18) + d | 0;
        b += (c & a | d & ~a) + k[4] - 405537848 | 0;
        b  = (b << 20 | b >>> 12) + c | 0;
        a += (b & d | c & ~d) + k[9] + 568446438 | 0;
        a  = (a << 5 | a >>> 27) + b | 0;
        d += (a & c | b & ~c) + k[14] - 1019803690 | 0;
        d  = (d << 9 | d >>> 23) + a | 0;
        c += (d & b | a & ~b) + k[3] - 187363961 | 0;
        c  = (c << 14 | c >>> 18) + d | 0;
        b += (c & a | d & ~a) + k[8] + 1163531501 | 0;
        b  = (b << 20 | b >>> 12) + c | 0;
        a += (b & d | c & ~d) + k[13] - 1444681467 | 0;
        a  = (a << 5 | a >>> 27) + b | 0;
        d += (a & c | b & ~c) + k[2] - 51403784 | 0;
        d  = (d << 9 | d >>> 23) + a | 0;
        c += (d & b | a & ~b) + k[7] + 1735328473 | 0;
        c  = (c << 14 | c >>> 18) + d | 0;
        b += (c & a | d & ~a) + k[12] - 1926607734 | 0;
        b  = (b << 20 | b >>> 12) + c | 0;

        a += (b ^ c ^ d) + k[5] - 378558 | 0;
        a  = (a << 4 | a >>> 28) + b | 0;
        d += (a ^ b ^ c) + k[8] - 2022574463 | 0;
        d  = (d << 11 | d >>> 21) + a | 0;
        c += (d ^ a ^ b) + k[11] + 1839030562 | 0;
        c  = (c << 16 | c >>> 16) + d | 0;
        b += (c ^ d ^ a) + k[14] - 35309556 | 0;
        b  = (b << 23 | b >>> 9) + c | 0;
        a += (b ^ c ^ d) + k[1] - 1530992060 | 0;
        a  = (a << 4 | a >>> 28) + b | 0;
        d += (a ^ b ^ c) + k[4] + 1272893353 | 0;
        d  = (d << 11 | d >>> 21) + a | 0;
        c += (d ^ a ^ b) + k[7] - 155497632 | 0;
        c  = (c << 16 | c >>> 16) + d | 0;
        b += (c ^ d ^ a) + k[10] - 1094730640 | 0;
        b  = (b << 23 | b >>> 9) + c | 0;
        a += (b ^ c ^ d) + k[13] + 681279174 | 0;
        a  = (a << 4 | a >>> 28) + b | 0;
        d += (a ^ b ^ c) + k[0] - 358537222 | 0;
        d  = (d << 11 | d >>> 21) + a | 0;
        c += (d ^ a ^ b) + k[3] - 722521979 | 0;
        c  = (c << 16 | c >>> 16) + d | 0;
        b += (c ^ d ^ a) + k[6] + 76029189 | 0;
        b  = (b << 23 | b >>> 9) + c | 0;
        a += (b ^ c ^ d) + k[9] - 640364487 | 0;
        a  = (a << 4 | a >>> 28) + b | 0;
        d += (a ^ b ^ c) + k[12] - 421815835 | 0;
        d  = (d << 11 | d >>> 21) + a | 0;
        c += (d ^ a ^ b) + k[15] + 530742520 | 0;
        c  = (c << 16 | c >>> 16) + d | 0;
        b += (c ^ d ^ a) + k[2] - 995338651 | 0;
        b  = (b << 23 | b >>> 9) + c | 0;

        a += (c ^ (b | ~d)) + k[0] - 198630844 | 0;
        a  = (a << 6 | a >>> 26) + b | 0;
        d += (b ^ (a | ~c)) + k[7] + 1126891415 | 0;
        d  = (d << 10 | d >>> 22) + a | 0;
        c += (a ^ (d | ~b)) + k[14] - 1416354905 | 0;
        c  = (c << 15 | c >>> 17) + d | 0;
        b += (d ^ (c | ~a)) + k[5] - 57434055 | 0;
        b  = (b << 21 |b >>> 11) + c | 0;
        a += (c ^ (b | ~d)) + k[12] + 1700485571 | 0;
        a  = (a << 6 | a >>> 26) + b | 0;
        d += (b ^ (a | ~c)) + k[3] - 1894986606 | 0;
        d  = (d << 10 | d >>> 22) + a | 0;
        c += (a ^ (d | ~b)) + k[10] - 1051523 | 0;
        c  = (c << 15 | c >>> 17) + d | 0;
        b += (d ^ (c | ~a)) + k[1] - 2054922799 | 0;
        b  = (b << 21 |b >>> 11) + c | 0;
        a += (c ^ (b | ~d)) + k[8] + 1873313359 | 0;
        a  = (a << 6 | a >>> 26) + b | 0;
        d += (b ^ (a | ~c)) + k[15] - 30611744 | 0;
        d  = (d << 10 | d >>> 22) + a | 0;
        c += (a ^ (d | ~b)) + k[6] - 1560198380 | 0;
        c  = (c << 15 | c >>> 17) + d | 0;
        b += (d ^ (c | ~a)) + k[13] + 1309151649 | 0;
        b  = (b << 21 |b >>> 11) + c | 0;
        a += (c ^ (b | ~d)) + k[4] - 145523070 | 0;
        a  = (a << 6 | a >>> 26) + b | 0;
        d += (b ^ (a | ~c)) + k[11] - 1120210379 | 0;
        d  = (d << 10 | d >>> 22) + a | 0;
        c += (a ^ (d | ~b)) + k[2] + 718787259 | 0;
        c  = (c << 15 | c >>> 17) + d | 0;
        b += (d ^ (c | ~a)) + k[9] - 343485551 | 0;
        b  = (b << 21 | b >>> 11) + c | 0;

        x[0] = a + x[0] | 0;
        x[1] = b + x[1] | 0;
        x[2] = c + x[2] | 0;
        x[3] = d + x[3] | 0;
    }

    function md5blk(s) {
        var md5blks = [],
            i; /* Andy King said do it this way. */

        for (i = 0; i < 64; i += 4) {
            md5blks[i >> 2] = s.charCodeAt(i) + (s.charCodeAt(i + 1) << 8) + (s.charCodeAt(i + 2) << 16) + (s.charCodeAt(i + 3) << 24);
        }
        return md5blks;
    }

    function md5blk_array(a) {
        var md5blks = [],
            i; /* Andy King said do it this way. */

        for (i = 0; i < 64; i += 4) {
            md5blks[i >> 2] = a[i] + (a[i + 1] << 8) + (a[i + 2] << 16) + (a[i + 3] << 24);
        }
        return md5blks;
    }

    function md51(s) {
        var n = s.length,
            state = [1732584193, -271733879, -1732584194, 271733878],
            i,
            length,
            tail,
            tmp,
            lo,
            hi;

        for (i = 64; i <= n; i += 64) {
            md5cycle(state, md5blk(s.substring(i - 64, i)));
        }
        s = s.substring(i - 64);
        length = s.length;
        tail = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
        for (i = 0; i < length; i += 1) {
            tail[i >> 2] |= s.charCodeAt(i) << ((i % 4) << 3);
        }
        tail[i >> 2] |= 0x80 << ((i % 4) << 3);
        if (i > 55) {
            md5cycle(state, tail);
            for (i = 0; i < 16; i += 1) {
                tail[i] = 0;
            }
        }

        // Beware that the final length might not fit in 32 bits so we take care of that
        tmp = n * 8;
        tmp = tmp.toString(16).match(/(.*?)(.{0,8})$/);
        lo = parseInt(tmp[2], 16);
        hi = parseInt(tmp[1], 16) || 0;

        tail[14] = lo;
        tail[15] = hi;

        md5cycle(state, tail);
        return state;
    }

    function md51_array(a) {
        var n = a.length,
            state = [1732584193, -271733879, -1732584194, 271733878],
            i,
            length,
            tail,
            tmp,
            lo,
            hi;

        for (i = 64; i <= n; i += 64) {
            md5cycle(state, md5blk_array(a.subarray(i - 64, i)));
        }

        // Not sure if it is a bug, however IE10 will always produce a sub array of length 1
        // containing the last element of the parent array if the sub array specified starts
        // beyond the length of the parent array - weird.
        // https://connect.microsoft.com/IE/feedback/details/771452/typed-array-subarray-issue
        a = (i - 64) < n ? a.subarray(i - 64) : new Uint8Array(0);

        length = a.length;
        tail = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
        for (i = 0; i < length; i += 1) {
            tail[i >> 2] |= a[i] << ((i % 4) << 3);
        }

        tail[i >> 2] |= 0x80 << ((i % 4) << 3);
        if (i > 55) {
            md5cycle(state, tail);
            for (i = 0; i < 16; i += 1) {
                tail[i] = 0;
            }
        }

        // Beware that the final length might not fit in 32 bits so we take care of that
        tmp = n * 8;
        tmp = tmp.toString(16).match(/(.*?)(.{0,8})$/);
        lo = parseInt(tmp[2], 16);
        hi = parseInt(tmp[1], 16) || 0;

        tail[14] = lo;
        tail[15] = hi;

        md5cycle(state, tail);

        return state;
    }

    function rhex(n) {
        var s = '',
            j;
        for (j = 0; j < 4; j += 1) {
            s += hex_chr[(n >> (j * 8 + 4)) & 0x0F] + hex_chr[(n >> (j * 8)) & 0x0F];
        }
        return s;
    }

    function hex(x) {
        var i;
        for (i = 0; i < x.length; i += 1) {
            x[i] = rhex(x[i]);
        }
        return x.join('');
    }

    // In some cases the fast add32 function cannot be used..
    if (hex(md51('hello')) !== '5d41402abc4b2a76b9719d911017c592') {
        add32 = function (x, y) {
            var lsw = (x & 0xFFFF) + (y & 0xFFFF),
                msw = (x >> 16) + (y >> 16) + (lsw >> 16);
            return (msw << 16) | (lsw & 0xFFFF);
        };
    }

    // ---------------------------------------------------

    /**
     * ArrayBuffer slice polyfill.
     *
     * @see https://github.com/ttaubert/node-arraybuffer-slice
     */

    if (typeof ArrayBuffer !== 'undefined' && !ArrayBuffer.prototype.slice) {
        (function () {
            function clamp(val, length) {
                val = (val | 0) || 0;

                if (val < 0) {
                    return Math.max(val + length, 0);
                }

                return Math.min(val, length);
            }

            ArrayBuffer.prototype.slice = function (from, to) {
                var length = this.byteLength,
                    begin = clamp(from, length),
                    end = length,
                    num,
                    target,
                    targetArray,
                    sourceArray;

                if (to !== undefined) {
                    end = clamp(to, length);
                }

                if (begin > end) {
                    return new ArrayBuffer(0);
                }

                num = end - begin;
                target = new ArrayBuffer(num);
                targetArray = new Uint8Array(target);

                sourceArray = new Uint8Array(this, begin, num);
                targetArray.set(sourceArray);

                return target;
            };
        })();
    }

    // ---------------------------------------------------

    /**
     * Helpers.
     */

    function toUtf8(str) {
        if (/[\u0080-\uFFFF]/.test(str)) {
            str = unescape(encodeURIComponent(str));
        }

        return str;
    }

    function utf8Str2ArrayBuffer(str, returnUInt8Array) {
        var length = str.length,
           buff = new ArrayBuffer(length),
           arr = new Uint8Array(buff),
           i;

        for (i = 0; i < length; i += 1) {
            arr[i] = str.charCodeAt(i);
        }

        return returnUInt8Array ? arr : buff;
    }

    function arrayBuffer2Utf8Str(buff) {
        return String.fromCharCode.apply(null, new Uint8Array(buff));
    }

    function concatenateArrayBuffers(first, second, returnUInt8Array) {
        var result = new Uint8Array(first.byteLength + second.byteLength);

        result.set(new Uint8Array(first));
        result.set(new Uint8Array(second), first.byteLength);

        return returnUInt8Array ? result : result.buffer;
    }

    function hexToBinaryString(hex) {
        var bytes = [],
            length = hex.length,
            x;

        for (x = 0; x < length - 1; x += 2) {
            bytes.push(parseInt(hex.substr(x, 2), 16));
        }

        return String.fromCharCode.apply(String, bytes);
    }

    // ---------------------------------------------------

    /**
     * SparkMD5 OOP implementation.
     *
     * Use this class to perform an incremental md5, otherwise use the
     * static methods instead.
     */

    function SparkMD5() {
        // call reset to init the instance
        this.reset();
    }

    /**
     * Appends a string.
     * A conversion will be applied if an utf8 string is detected.
     *
     * @param {String} str The string to be appended
     *
     * @return {SparkMD5} The instance itself
     */
    SparkMD5.prototype.append = function (str) {
        // Converts the string to utf8 bytes if necessary
        // Then append as binary
        this.appendBinary(toUtf8(str));

        return this;
    };

    /**
     * Appends a binary string.
     *
     * @param {String} contents The binary string to be appended
     *
     * @return {SparkMD5} The instance itself
     */
    SparkMD5.prototype.appendBinary = function (contents) {
        this._buff += contents;
        this._length += contents.length;

        var length = this._buff.length,
            i;

        for (i = 64; i <= length; i += 64) {
            md5cycle(this._hash, md5blk(this._buff.substring(i - 64, i)));
        }

        this._buff = this._buff.substring(i - 64);

        return this;
    };

    /**
     * Finishes the incremental computation, reseting the internal state and
     * returning the result.
     *
     * @param {Boolean} raw True to get the raw string, false to get the hex string
     *
     * @return {String} The result
     */
    SparkMD5.prototype.end = function (raw) {
        var buff = this._buff,
            length = buff.length,
            i,
            tail = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
            ret;

        for (i = 0; i < length; i += 1) {
            tail[i >> 2] |= buff.charCodeAt(i) << ((i % 4) << 3);
        }

        this._finish(tail, length);
        ret = hex(this._hash);

        if (raw) {
            ret = hexToBinaryString(ret);
        }

        this.reset();

        return ret;
    };

    /**
     * Resets the internal state of the computation.
     *
     * @return {SparkMD5} The instance itself
     */
    SparkMD5.prototype.reset = function () {
        this._buff = '';
        this._length = 0;
        this._hash = [1732584193, -271733879, -1732584194, 271733878];

        return this;
    };

    /**
     * Gets the internal state of the computation.
     *
     * @return {Object} The state
     */
    SparkMD5.prototype.getState = function () {
        return {
            buff: this._buff,
            length: this._length,
            hash: this._hash.slice()
        };
    };

    /**
     * Gets the internal state of the computation.
     *
     * @param {Object} state The state
     *
     * @return {SparkMD5} The instance itself
     */
    SparkMD5.prototype.setState = function (state) {
        this._buff = state.buff;
        this._length = state.length;
        this._hash = state.hash;

        return this;
    };

    /**
     * Releases memory used by the incremental buffer and other additional
     * resources. If you plan to use the instance again, use reset instead.
     */
    SparkMD5.prototype.destroy = function () {
        delete this._hash;
        delete this._buff;
        delete this._length;
    };

    /**
     * Finish the final calculation based on the tail.
     *
     * @param {Array}  tail   The tail (will be modified)
     * @param {Number} length The length of the remaining buffer
     */
    SparkMD5.prototype._finish = function (tail, length) {
        var i = length,
            tmp,
            lo,
            hi;

        tail[i >> 2] |= 0x80 << ((i % 4) << 3);
        if (i > 55) {
            md5cycle(this._hash, tail);
            for (i = 0; i < 16; i += 1) {
                tail[i] = 0;
            }
        }

        // Do the final computation based on the tail and length
        // Beware that the final length may not fit in 32 bits so we take care of that
        tmp = this._length * 8;
        tmp = tmp.toString(16).match(/(.*?)(.{0,8})$/);
        lo = parseInt(tmp[2], 16);
        hi = parseInt(tmp[1], 16) || 0;

        tail[14] = lo;
        tail[15] = hi;
        md5cycle(this._hash, tail);
    };

    /**
     * Performs the md5 hash on a string.
     * A conversion will be applied if utf8 string is detected.
     *
     * @param {String}  str The string
     * @param {Boolean} [raw] True to get the raw string, false to get the hex string
     *
     * @return {String} The result
     */
    SparkMD5.hash = function (str, raw) {
        // Converts the string to utf8 bytes if necessary
        // Then compute it using the binary function
        return SparkMD5.hashBinary(toUtf8(str), raw);
    };

    /**
     * Performs the md5 hash on a binary string.
     *
     * @param {String}  content The binary string
     * @param {Boolean} [raw]     True to get the raw string, false to get the hex string
     *
     * @return {String} The result
     */
    SparkMD5.hashBinary = function (content, raw) {
        var hash = md51(content),
            ret = hex(hash);

        return raw ? hexToBinaryString(ret) : ret;
    };

    // ---------------------------------------------------

    /**
     * SparkMD5 OOP implementation for array buffers.
     *
     * Use this class to perform an incremental md5 ONLY for array buffers.
     */
    SparkMD5.ArrayBuffer = function () {
        // call reset to init the instance
        this.reset();
    };

    /**
     * Appends an array buffer.
     *
     * @param {ArrayBuffer} arr The array to be appended
     *
     * @return {SparkMD5.ArrayBuffer} The instance itself
     */
    SparkMD5.ArrayBuffer.prototype.append = function (arr) {
        var buff = concatenateArrayBuffers(this._buff.buffer, arr, true),
            length = buff.length,
            i;

        this._length += arr.byteLength;

        for (i = 64; i <= length; i += 64) {
            md5cycle(this._hash, md5blk_array(buff.subarray(i - 64, i)));
        }

        this._buff = (i - 64) < length ? new Uint8Array(buff.buffer.slice(i - 64)) : new Uint8Array(0);

        return this;
    };

    /**
     * Finishes the incremental computation, reseting the internal state and
     * returning the result.
     *
     * @param {Boolean} raw True to get the raw string, false to get the hex string
     *
     * @return {String} The result
     */
    SparkMD5.ArrayBuffer.prototype.end = function (raw) {
        var buff = this._buff,
            length = buff.length,
            tail = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
            i,
            ret;

        for (i = 0; i < length; i += 1) {
            tail[i >> 2] |= buff[i] << ((i % 4) << 3);
        }

        this._finish(tail, length);
        ret = hex(this._hash);

        if (raw) {
            ret = hexToBinaryString(ret);
        }

        this.reset();

        return ret;
    };

    /**
     * Resets the internal state of the computation.
     *
     * @return {SparkMD5.ArrayBuffer} The instance itself
     */
    SparkMD5.ArrayBuffer.prototype.reset = function () {
        this._buff = new Uint8Array(0);
        this._length = 0;
        this._hash = [1732584193, -271733879, -1732584194, 271733878];

        return this;
    };

    /**
     * Gets the internal state of the computation.
     *
     * @return {Object} The state
     */
    SparkMD5.ArrayBuffer.prototype.getState = function () {
        var state = SparkMD5.prototype.getState.call(this);

        // Convert buffer to a string
        state.buff = arrayBuffer2Utf8Str(state.buff);

        return state;
    };

    /**
     * Gets the internal state of the computation.
     *
     * @param {Object} state The state
     *
     * @return {SparkMD5.ArrayBuffer} The instance itself
     */
    SparkMD5.ArrayBuffer.prototype.setState = function (state) {
        // Convert string to buffer
        state.buff = utf8Str2ArrayBuffer(state.buff, true);

        return SparkMD5.prototype.setState.call(this, state);
    };

    SparkMD5.ArrayBuffer.prototype.destroy = SparkMD5.prototype.destroy;

    SparkMD5.ArrayBuffer.prototype._finish = SparkMD5.prototype._finish;

    /**
     * Performs the md5 hash on an array buffer.
     *
     * @param {ArrayBuffer} arr The array buffer
     * @param {Boolean}     [raw] True to get the raw string, false to get the hex one
     *
     * @return {String} The result
     */
    SparkMD5.ArrayBuffer.hash = function (arr, raw) {
        var hash = md51_array(new Uint8Array(arr)),
            ret = hex(hash);

        return raw ? hexToBinaryString(ret) : ret;
    };

    return SparkMD5;
}));

},{}],3:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
Object.defineProperty(exports, "v1", {
  enumerable: true,
  get: function () {
    return _v.default;
  }
});
Object.defineProperty(exports, "v3", {
  enumerable: true,
  get: function () {
    return _v2.default;
  }
});
Object.defineProperty(exports, "v4", {
  enumerable: true,
  get: function () {
    return _v3.default;
  }
});
Object.defineProperty(exports, "v5", {
  enumerable: true,
  get: function () {
    return _v4.default;
  }
});
Object.defineProperty(exports, "NIL", {
  enumerable: true,
  get: function () {
    return _nil.default;
  }
});
Object.defineProperty(exports, "version", {
  enumerable: true,
  get: function () {
    return _version.default;
  }
});
Object.defineProperty(exports, "validate", {
  enumerable: true,
  get: function () {
    return _validate.default;
  }
});
Object.defineProperty(exports, "stringify", {
  enumerable: true,
  get: function () {
    return _stringify.default;
  }
});
Object.defineProperty(exports, "parse", {
  enumerable: true,
  get: function () {
    return _parse.default;
  }
});

var _v = _interopRequireDefault(_dereq_("./v1.js"));

var _v2 = _interopRequireDefault(_dereq_("./v3.js"));

var _v3 = _interopRequireDefault(_dereq_("./v4.js"));

var _v4 = _interopRequireDefault(_dereq_("./v5.js"));

var _nil = _interopRequireDefault(_dereq_("./nil.js"));

var _version = _interopRequireDefault(_dereq_("./version.js"));

var _validate = _interopRequireDefault(_dereq_("./validate.js"));

var _stringify = _interopRequireDefault(_dereq_("./stringify.js"));

var _parse = _interopRequireDefault(_dereq_("./parse.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
},{"./nil.js":5,"./parse.js":6,"./stringify.js":10,"./v1.js":11,"./v3.js":12,"./v4.js":14,"./v5.js":15,"./validate.js":16,"./version.js":17}],4:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

/*
 * Browser-compatible JavaScript MD5
 *
 * Modification of JavaScript MD5
 * https://github.com/blueimp/JavaScript-MD5
 *
 * Copyright 2011, Sebastian Tschan
 * https://blueimp.net
 *
 * Licensed under the MIT license:
 * https://opensource.org/licenses/MIT
 *
 * Based on
 * A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
 * Digest Algorithm, as defined in RFC 1321.
 * Version 2.2 Copyright (C) Paul Johnston 1999 - 2009
 * Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
 * Distributed under the BSD License
 * See http://pajhome.org.uk/crypt/md5 for more info.
 */
function md5(bytes) {
  if (typeof bytes === 'string') {
    const msg = unescape(encodeURIComponent(bytes)); // UTF8 escape

    bytes = new Uint8Array(msg.length);

    for (let i = 0; i < msg.length; ++i) {
      bytes[i] = msg.charCodeAt(i);
    }
  }

  return md5ToHexEncodedArray(wordsToMd5(bytesToWords(bytes), bytes.length * 8));
}
/*
 * Convert an array of little-endian words to an array of bytes
 */


function md5ToHexEncodedArray(input) {
  const output = [];
  const length32 = input.length * 32;
  const hexTab = '0123456789abcdef';

  for (let i = 0; i < length32; i += 8) {
    const x = input[i >> 5] >>> i % 32 & 0xff;
    const hex = parseInt(hexTab.charAt(x >>> 4 & 0x0f) + hexTab.charAt(x & 0x0f), 16);
    output.push(hex);
  }

  return output;
}
/**
 * Calculate output length with padding and bit length
 */


function getOutputLength(inputLength8) {
  return (inputLength8 + 64 >>> 9 << 4) + 14 + 1;
}
/*
 * Calculate the MD5 of an array of little-endian words, and a bit length.
 */


function wordsToMd5(x, len) {
  /* append padding */
  x[len >> 5] |= 0x80 << len % 32;
  x[getOutputLength(len) - 1] = len;
  let a = 1732584193;
  let b = -271733879;
  let c = -1732584194;
  let d = 271733878;

  for (let i = 0; i < x.length; i += 16) {
    const olda = a;
    const oldb = b;
    const oldc = c;
    const oldd = d;
    a = md5ff(a, b, c, d, x[i], 7, -680876936);
    d = md5ff(d, a, b, c, x[i + 1], 12, -389564586);
    c = md5ff(c, d, a, b, x[i + 2], 17, 606105819);
    b = md5ff(b, c, d, a, x[i + 3], 22, -1044525330);
    a = md5ff(a, b, c, d, x[i + 4], 7, -176418897);
    d = md5ff(d, a, b, c, x[i + 5], 12, 1200080426);
    c = md5ff(c, d, a, b, x[i + 6], 17, -1473231341);
    b = md5ff(b, c, d, a, x[i + 7], 22, -45705983);
    a = md5ff(a, b, c, d, x[i + 8], 7, 1770035416);
    d = md5ff(d, a, b, c, x[i + 9], 12, -1958414417);
    c = md5ff(c, d, a, b, x[i + 10], 17, -42063);
    b = md5ff(b, c, d, a, x[i + 11], 22, -1990404162);
    a = md5ff(a, b, c, d, x[i + 12], 7, 1804603682);
    d = md5ff(d, a, b, c, x[i + 13], 12, -40341101);
    c = md5ff(c, d, a, b, x[i + 14], 17, -1502002290);
    b = md5ff(b, c, d, a, x[i + 15], 22, 1236535329);
    a = md5gg(a, b, c, d, x[i + 1], 5, -165796510);
    d = md5gg(d, a, b, c, x[i + 6], 9, -1069501632);
    c = md5gg(c, d, a, b, x[i + 11], 14, 643717713);
    b = md5gg(b, c, d, a, x[i], 20, -373897302);
    a = md5gg(a, b, c, d, x[i + 5], 5, -701558691);
    d = md5gg(d, a, b, c, x[i + 10], 9, 38016083);
    c = md5gg(c, d, a, b, x[i + 15], 14, -660478335);
    b = md5gg(b, c, d, a, x[i + 4], 20, -405537848);
    a = md5gg(a, b, c, d, x[i + 9], 5, 568446438);
    d = md5gg(d, a, b, c, x[i + 14], 9, -1019803690);
    c = md5gg(c, d, a, b, x[i + 3], 14, -187363961);
    b = md5gg(b, c, d, a, x[i + 8], 20, 1163531501);
    a = md5gg(a, b, c, d, x[i + 13], 5, -1444681467);
    d = md5gg(d, a, b, c, x[i + 2], 9, -51403784);
    c = md5gg(c, d, a, b, x[i + 7], 14, 1735328473);
    b = md5gg(b, c, d, a, x[i + 12], 20, -1926607734);
    a = md5hh(a, b, c, d, x[i + 5], 4, -378558);
    d = md5hh(d, a, b, c, x[i + 8], 11, -2022574463);
    c = md5hh(c, d, a, b, x[i + 11], 16, 1839030562);
    b = md5hh(b, c, d, a, x[i + 14], 23, -35309556);
    a = md5hh(a, b, c, d, x[i + 1], 4, -1530992060);
    d = md5hh(d, a, b, c, x[i + 4], 11, 1272893353);
    c = md5hh(c, d, a, b, x[i + 7], 16, -155497632);
    b = md5hh(b, c, d, a, x[i + 10], 23, -1094730640);
    a = md5hh(a, b, c, d, x[i + 13], 4, 681279174);
    d = md5hh(d, a, b, c, x[i], 11, -358537222);
    c = md5hh(c, d, a, b, x[i + 3], 16, -722521979);
    b = md5hh(b, c, d, a, x[i + 6], 23, 76029189);
    a = md5hh(a, b, c, d, x[i + 9], 4, -640364487);
    d = md5hh(d, a, b, c, x[i + 12], 11, -421815835);
    c = md5hh(c, d, a, b, x[i + 15], 16, 530742520);
    b = md5hh(b, c, d, a, x[i + 2], 23, -995338651);
    a = md5ii(a, b, c, d, x[i], 6, -198630844);
    d = md5ii(d, a, b, c, x[i + 7], 10, 1126891415);
    c = md5ii(c, d, a, b, x[i + 14], 15, -1416354905);
    b = md5ii(b, c, d, a, x[i + 5], 21, -57434055);
    a = md5ii(a, b, c, d, x[i + 12], 6, 1700485571);
    d = md5ii(d, a, b, c, x[i + 3], 10, -1894986606);
    c = md5ii(c, d, a, b, x[i + 10], 15, -1051523);
    b = md5ii(b, c, d, a, x[i + 1], 21, -2054922799);
    a = md5ii(a, b, c, d, x[i + 8], 6, 1873313359);
    d = md5ii(d, a, b, c, x[i + 15], 10, -30611744);
    c = md5ii(c, d, a, b, x[i + 6], 15, -1560198380);
    b = md5ii(b, c, d, a, x[i + 13], 21, 1309151649);
    a = md5ii(a, b, c, d, x[i + 4], 6, -145523070);
    d = md5ii(d, a, b, c, x[i + 11], 10, -1120210379);
    c = md5ii(c, d, a, b, x[i + 2], 15, 718787259);
    b = md5ii(b, c, d, a, x[i + 9], 21, -343485551);
    a = safeAdd(a, olda);
    b = safeAdd(b, oldb);
    c = safeAdd(c, oldc);
    d = safeAdd(d, oldd);
  }

  return [a, b, c, d];
}
/*
 * Convert an array bytes to an array of little-endian words
 * Characters >255 have their high-byte silently ignored.
 */


function bytesToWords(input) {
  if (input.length === 0) {
    return [];
  }

  const length8 = input.length * 8;
  const output = new Uint32Array(getOutputLength(length8));

  for (let i = 0; i < length8; i += 8) {
    output[i >> 5] |= (input[i / 8] & 0xff) << i % 32;
  }

  return output;
}
/*
 * Add integers, wrapping at 2^32. This uses 16-bit operations internally
 * to work around bugs in some JS interpreters.
 */


function safeAdd(x, y) {
  const lsw = (x & 0xffff) + (y & 0xffff);
  const msw = (x >> 16) + (y >> 16) + (lsw >> 16);
  return msw << 16 | lsw & 0xffff;
}
/*
 * Bitwise rotate a 32-bit number to the left.
 */


function bitRotateLeft(num, cnt) {
  return num << cnt | num >>> 32 - cnt;
}
/*
 * These functions implement the four basic operations the algorithm uses.
 */


function md5cmn(q, a, b, x, s, t) {
  return safeAdd(bitRotateLeft(safeAdd(safeAdd(a, q), safeAdd(x, t)), s), b);
}

function md5ff(a, b, c, d, x, s, t) {
  return md5cmn(b & c | ~b & d, a, b, x, s, t);
}

function md5gg(a, b, c, d, x, s, t) {
  return md5cmn(b & d | c & ~d, a, b, x, s, t);
}

function md5hh(a, b, c, d, x, s, t) {
  return md5cmn(b ^ c ^ d, a, b, x, s, t);
}

function md5ii(a, b, c, d, x, s, t) {
  return md5cmn(c ^ (b | ~d), a, b, x, s, t);
}

var _default = md5;
exports.default = _default;
},{}],5:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _default = '00000000-0000-0000-0000-000000000000';
exports.default = _default;
},{}],6:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _validate = _interopRequireDefault(_dereq_("./validate.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function parse(uuid) {
  if (!(0, _validate.default)(uuid)) {
    throw TypeError('Invalid UUID');
  }

  let v;
  const arr = new Uint8Array(16); // Parse ########-....-....-....-............

  arr[0] = (v = parseInt(uuid.slice(0, 8), 16)) >>> 24;
  arr[1] = v >>> 16 & 0xff;
  arr[2] = v >>> 8 & 0xff;
  arr[3] = v & 0xff; // Parse ........-####-....-....-............

  arr[4] = (v = parseInt(uuid.slice(9, 13), 16)) >>> 8;
  arr[5] = v & 0xff; // Parse ........-....-####-....-............

  arr[6] = (v = parseInt(uuid.slice(14, 18), 16)) >>> 8;
  arr[7] = v & 0xff; // Parse ........-....-....-####-............

  arr[8] = (v = parseInt(uuid.slice(19, 23), 16)) >>> 8;
  arr[9] = v & 0xff; // Parse ........-....-....-....-############
  // (Use "/" to avoid 32-bit truncation when bit-shifting high-order bytes)

  arr[10] = (v = parseInt(uuid.slice(24, 36), 16)) / 0x10000000000 & 0xff;
  arr[11] = v / 0x100000000 & 0xff;
  arr[12] = v >>> 24 & 0xff;
  arr[13] = v >>> 16 & 0xff;
  arr[14] = v >>> 8 & 0xff;
  arr[15] = v & 0xff;
  return arr;
}

var _default = parse;
exports.default = _default;
},{"./validate.js":16}],7:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _default = /^(?:[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}|00000000-0000-0000-0000-000000000000)$/i;
exports.default = _default;
},{}],8:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = rng;
// Unique ID creation requires a high quality random # generator. In the browser we therefore
// require the crypto API and do not support built-in fallback to lower quality random number
// generators (like Math.random()).
let getRandomValues;
const rnds8 = new Uint8Array(16);

function rng() {
  // lazy load so that environments that need to polyfill have a chance to do so
  if (!getRandomValues) {
    // getRandomValues needs to be invoked in a context where "this" is a Crypto implementation. Also,
    // find the complete implementation of crypto (msCrypto) on IE11.
    getRandomValues = typeof crypto !== 'undefined' && crypto.getRandomValues && crypto.getRandomValues.bind(crypto) || typeof msCrypto !== 'undefined' && typeof msCrypto.getRandomValues === 'function' && msCrypto.getRandomValues.bind(msCrypto);

    if (!getRandomValues) {
      throw new Error('crypto.getRandomValues() not supported. See https://github.com/uuidjs/uuid#getrandomvalues-not-supported');
    }
  }

  return getRandomValues(rnds8);
}
},{}],9:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

// Adapted from Chris Veness' SHA1 code at
// http://www.movable-type.co.uk/scripts/sha1.html
function f(s, x, y, z) {
  switch (s) {
    case 0:
      return x & y ^ ~x & z;

    case 1:
      return x ^ y ^ z;

    case 2:
      return x & y ^ x & z ^ y & z;

    case 3:
      return x ^ y ^ z;
  }
}

function ROTL(x, n) {
  return x << n | x >>> 32 - n;
}

function sha1(bytes) {
  const K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];
  const H = [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0];

  if (typeof bytes === 'string') {
    const msg = unescape(encodeURIComponent(bytes)); // UTF8 escape

    bytes = [];

    for (let i = 0; i < msg.length; ++i) {
      bytes.push(msg.charCodeAt(i));
    }
  } else if (!Array.isArray(bytes)) {
    // Convert Array-like to Array
    bytes = Array.prototype.slice.call(bytes);
  }

  bytes.push(0x80);
  const l = bytes.length / 4 + 2;
  const N = Math.ceil(l / 16);
  const M = new Array(N);

  for (let i = 0; i < N; ++i) {
    const arr = new Uint32Array(16);

    for (let j = 0; j < 16; ++j) {
      arr[j] = bytes[i * 64 + j * 4] << 24 | bytes[i * 64 + j * 4 + 1] << 16 | bytes[i * 64 + j * 4 + 2] << 8 | bytes[i * 64 + j * 4 + 3];
    }

    M[i] = arr;
  }

  M[N - 1][14] = (bytes.length - 1) * 8 / Math.pow(2, 32);
  M[N - 1][14] = Math.floor(M[N - 1][14]);
  M[N - 1][15] = (bytes.length - 1) * 8 & 0xffffffff;

  for (let i = 0; i < N; ++i) {
    const W = new Uint32Array(80);

    for (let t = 0; t < 16; ++t) {
      W[t] = M[i][t];
    }

    for (let t = 16; t < 80; ++t) {
      W[t] = ROTL(W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16], 1);
    }

    let a = H[0];
    let b = H[1];
    let c = H[2];
    let d = H[3];
    let e = H[4];

    for (let t = 0; t < 80; ++t) {
      const s = Math.floor(t / 20);
      const T = ROTL(a, 5) + f(s, b, c, d) + e + K[s] + W[t] >>> 0;
      e = d;
      d = c;
      c = ROTL(b, 30) >>> 0;
      b = a;
      a = T;
    }

    H[0] = H[0] + a >>> 0;
    H[1] = H[1] + b >>> 0;
    H[2] = H[2] + c >>> 0;
    H[3] = H[3] + d >>> 0;
    H[4] = H[4] + e >>> 0;
  }

  return [H[0] >> 24 & 0xff, H[0] >> 16 & 0xff, H[0] >> 8 & 0xff, H[0] & 0xff, H[1] >> 24 & 0xff, H[1] >> 16 & 0xff, H[1] >> 8 & 0xff, H[1] & 0xff, H[2] >> 24 & 0xff, H[2] >> 16 & 0xff, H[2] >> 8 & 0xff, H[2] & 0xff, H[3] >> 24 & 0xff, H[3] >> 16 & 0xff, H[3] >> 8 & 0xff, H[3] & 0xff, H[4] >> 24 & 0xff, H[4] >> 16 & 0xff, H[4] >> 8 & 0xff, H[4] & 0xff];
}

var _default = sha1;
exports.default = _default;
},{}],10:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _validate = _interopRequireDefault(_dereq_("./validate.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * Convert array of 16 byte values to UUID string format of the form:
 * XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
 */
const byteToHex = [];

for (let i = 0; i < 256; ++i) {
  byteToHex.push((i + 0x100).toString(16).substr(1));
}

function stringify(arr, offset = 0) {
  // Note: Be careful editing this code!  It's been tuned for performance
  // and works in ways you may not expect. See https://github.com/uuidjs/uuid/pull/434
  const uuid = (byteToHex[arr[offset + 0]] + byteToHex[arr[offset + 1]] + byteToHex[arr[offset + 2]] + byteToHex[arr[offset + 3]] + '-' + byteToHex[arr[offset + 4]] + byteToHex[arr[offset + 5]] + '-' + byteToHex[arr[offset + 6]] + byteToHex[arr[offset + 7]] + '-' + byteToHex[arr[offset + 8]] + byteToHex[arr[offset + 9]] + '-' + byteToHex[arr[offset + 10]] + byteToHex[arr[offset + 11]] + byteToHex[arr[offset + 12]] + byteToHex[arr[offset + 13]] + byteToHex[arr[offset + 14]] + byteToHex[arr[offset + 15]]).toLowerCase(); // Consistency check for valid UUID.  If this throws, it's likely due to one
  // of the following:
  // - One or more input array values don't map to a hex octet (leading to
  // "undefined" in the uuid)
  // - Invalid input values for the RFC `version` or `variant` fields

  if (!(0, _validate.default)(uuid)) {
    throw TypeError('Stringified UUID is invalid');
  }

  return uuid;
}

var _default = stringify;
exports.default = _default;
},{"./validate.js":16}],11:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _rng = _interopRequireDefault(_dereq_("./rng.js"));

var _stringify = _interopRequireDefault(_dereq_("./stringify.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

// **`v1()` - Generate time-based UUID**
//
// Inspired by https://github.com/LiosK/UUID.js
// and http://docs.python.org/library/uuid.html
let _nodeId;

let _clockseq; // Previous uuid creation time


let _lastMSecs = 0;
let _lastNSecs = 0; // See https://github.com/uuidjs/uuid for API details

function v1(options, buf, offset) {
  let i = buf && offset || 0;
  const b = buf || new Array(16);
  options = options || {};
  let node = options.node || _nodeId;
  let clockseq = options.clockseq !== undefined ? options.clockseq : _clockseq; // node and clockseq need to be initialized to random values if they're not
  // specified.  We do this lazily to minimize issues related to insufficient
  // system entropy.  See #189

  if (node == null || clockseq == null) {
    const seedBytes = options.random || (options.rng || _rng.default)();

    if (node == null) {
      // Per 4.5, create and 48-bit node id, (47 random bits + multicast bit = 1)
      node = _nodeId = [seedBytes[0] | 0x01, seedBytes[1], seedBytes[2], seedBytes[3], seedBytes[4], seedBytes[5]];
    }

    if (clockseq == null) {
      // Per 4.2.2, randomize (14 bit) clockseq
      clockseq = _clockseq = (seedBytes[6] << 8 | seedBytes[7]) & 0x3fff;
    }
  } // UUID timestamps are 100 nano-second units since the Gregorian epoch,
  // (1582-10-15 00:00).  JSNumbers aren't precise enough for this, so
  // time is handled internally as 'msecs' (integer milliseconds) and 'nsecs'
  // (100-nanoseconds offset from msecs) since unix epoch, 1970-01-01 00:00.


  let msecs = options.msecs !== undefined ? options.msecs : Date.now(); // Per 4.2.1.2, use count of uuid's generated during the current clock
  // cycle to simulate higher resolution clock

  let nsecs = options.nsecs !== undefined ? options.nsecs : _lastNSecs + 1; // Time since last uuid creation (in msecs)

  const dt = msecs - _lastMSecs + (nsecs - _lastNSecs) / 10000; // Per 4.2.1.2, Bump clockseq on clock regression

  if (dt < 0 && options.clockseq === undefined) {
    clockseq = clockseq + 1 & 0x3fff;
  } // Reset nsecs if clock regresses (new clockseq) or we've moved onto a new
  // time interval


  if ((dt < 0 || msecs > _lastMSecs) && options.nsecs === undefined) {
    nsecs = 0;
  } // Per 4.2.1.2 Throw error if too many uuids are requested


  if (nsecs >= 10000) {
    throw new Error("uuid.v1(): Can't create more than 10M uuids/sec");
  }

  _lastMSecs = msecs;
  _lastNSecs = nsecs;
  _clockseq = clockseq; // Per 4.1.4 - Convert from unix epoch to Gregorian epoch

  msecs += 12219292800000; // `time_low`

  const tl = ((msecs & 0xfffffff) * 10000 + nsecs) % 0x100000000;
  b[i++] = tl >>> 24 & 0xff;
  b[i++] = tl >>> 16 & 0xff;
  b[i++] = tl >>> 8 & 0xff;
  b[i++] = tl & 0xff; // `time_mid`

  const tmh = msecs / 0x100000000 * 10000 & 0xfffffff;
  b[i++] = tmh >>> 8 & 0xff;
  b[i++] = tmh & 0xff; // `time_high_and_version`

  b[i++] = tmh >>> 24 & 0xf | 0x10; // include version

  b[i++] = tmh >>> 16 & 0xff; // `clock_seq_hi_and_reserved` (Per 4.2.2 - include variant)

  b[i++] = clockseq >>> 8 | 0x80; // `clock_seq_low`

  b[i++] = clockseq & 0xff; // `node`

  for (let n = 0; n < 6; ++n) {
    b[i + n] = node[n];
  }

  return buf || (0, _stringify.default)(b);
}

var _default = v1;
exports.default = _default;
},{"./rng.js":8,"./stringify.js":10}],12:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _v = _interopRequireDefault(_dereq_("./v35.js"));

var _md = _interopRequireDefault(_dereq_("./md5.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

const v3 = (0, _v.default)('v3', 0x30, _md.default);
var _default = v3;
exports.default = _default;
},{"./md5.js":4,"./v35.js":13}],13:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = _default;
exports.URL = exports.DNS = void 0;

var _stringify = _interopRequireDefault(_dereq_("./stringify.js"));

var _parse = _interopRequireDefault(_dereq_("./parse.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function stringToBytes(str) {
  str = unescape(encodeURIComponent(str)); // UTF8 escape

  const bytes = [];

  for (let i = 0; i < str.length; ++i) {
    bytes.push(str.charCodeAt(i));
  }

  return bytes;
}

const DNS = '6ba7b810-9dad-11d1-80b4-00c04fd430c8';
exports.DNS = DNS;
const URL = '6ba7b811-9dad-11d1-80b4-00c04fd430c8';
exports.URL = URL;

function _default(name, version, hashfunc) {
  function generateUUID(value, namespace, buf, offset) {
    if (typeof value === 'string') {
      value = stringToBytes(value);
    }

    if (typeof namespace === 'string') {
      namespace = (0, _parse.default)(namespace);
    }

    if (namespace.length !== 16) {
      throw TypeError('Namespace must be array-like (16 iterable integer values, 0-255)');
    } // Compute hash of namespace and value, Per 4.3
    // Future: Use spread syntax when supported on all platforms, e.g. `bytes =
    // hashfunc([...namespace, ... value])`


    let bytes = new Uint8Array(16 + value.length);
    bytes.set(namespace);
    bytes.set(value, namespace.length);
    bytes = hashfunc(bytes);
    bytes[6] = bytes[6] & 0x0f | version;
    bytes[8] = bytes[8] & 0x3f | 0x80;

    if (buf) {
      offset = offset || 0;

      for (let i = 0; i < 16; ++i) {
        buf[offset + i] = bytes[i];
      }

      return buf;
    }

    return (0, _stringify.default)(bytes);
  } // Function#name is not settable on some platforms (#270)


  try {
    generateUUID.name = name; // eslint-disable-next-line no-empty
  } catch (err) {} // For CommonJS default export support


  generateUUID.DNS = DNS;
  generateUUID.URL = URL;
  return generateUUID;
}
},{"./parse.js":6,"./stringify.js":10}],14:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _rng = _interopRequireDefault(_dereq_("./rng.js"));

var _stringify = _interopRequireDefault(_dereq_("./stringify.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function v4(options, buf, offset) {
  options = options || {};

  const rnds = options.random || (options.rng || _rng.default)(); // Per 4.4, set bits for version and `clock_seq_hi_and_reserved`


  rnds[6] = rnds[6] & 0x0f | 0x40;
  rnds[8] = rnds[8] & 0x3f | 0x80; // Copy bytes to buffer, if provided

  if (buf) {
    offset = offset || 0;

    for (let i = 0; i < 16; ++i) {
      buf[offset + i] = rnds[i];
    }

    return buf;
  }

  return (0, _stringify.default)(rnds);
}

var _default = v4;
exports.default = _default;
},{"./rng.js":8,"./stringify.js":10}],15:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _v = _interopRequireDefault(_dereq_("./v35.js"));

var _sha = _interopRequireDefault(_dereq_("./sha1.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

const v5 = (0, _v.default)('v5', 0x50, _sha.default);
var _default = v5;
exports.default = _default;
},{"./sha1.js":9,"./v35.js":13}],16:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _regex = _interopRequireDefault(_dereq_("./regex.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function validate(uuid) {
  return typeof uuid === 'string' && _regex.default.test(uuid);
}

var _default = validate;
exports.default = _default;
},{"./regex.js":7}],17:[function(_dereq_,module,exports){
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _validate = _interopRequireDefault(_dereq_("./validate.js"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function version(uuid) {
  if (!(0, _validate.default)(uuid)) {
    throw TypeError('Invalid UUID');
  }

  return parseInt(uuid.substr(14, 1), 16);
}

var _default = version;
exports.default = _default;
},{"./validate.js":16}],18:[function(_dereq_,module,exports){
'use strict';

function _interopDefault (ex) { return (ex && (typeof ex === 'object') && 'default' in ex) ? ex['default'] : ex; }

_dereq_('events');
_dereq_('uuid');
var Md5 = _interopDefault(_dereq_('spark-md5'));

function isBinaryObject(object) {
  return (typeof ArrayBuffer !== 'undefined' && object instanceof ArrayBuffer) ||
    (typeof Blob !== 'undefined' && object instanceof Blob);
}

/**
 * @template {ArrayBuffer | Blob} T
 * @param {T} object
 * @returns {T}
 */
function cloneBinaryObject(object) {
  return object instanceof ArrayBuffer
    ? object.slice(0)
    : object.slice(0, object.size, object.type);
}

// most of this is borrowed from lodash.isPlainObject:
// https://github.com/fis-components/lodash.isplainobject/
// blob/29c358140a74f252aeb08c9eb28bef86f2217d4a/index.js

var funcToString = Function.prototype.toString;
var objectCtorString = funcToString.call(Object);

function isPlainObject(value) {
  var proto = Object.getPrototypeOf(value);
  /* istanbul ignore if */
  if (proto === null) { // not sure when this happens, but I guess it can
    return true;
  }
  var Ctor = proto.constructor;
  return (typeof Ctor == 'function' &&
    Ctor instanceof Ctor && funcToString.call(Ctor) == objectCtorString);
}

function clone(object) {
  var newObject;
  var i;
  var len;

  if (!object || typeof object !== 'object') {
    return object;
  }

  if (Array.isArray(object)) {
    newObject = [];
    for (i = 0, len = object.length; i < len; i++) {
      newObject[i] = clone(object[i]);
    }
    return newObject;
  }

  // special case: to avoid inconsistencies between IndexedDB
  // and other backends, we automatically stringify Dates
  if (object instanceof Date && isFinite(object)) {
    return object.toISOString();
  }

  if (isBinaryObject(object)) {
    return cloneBinaryObject(object);
  }

  if (!isPlainObject(object)) {
    return object; // don't clone objects like Workers
  }

  newObject = {};
  for (i in object) {
    /* istanbul ignore else */
    if (Object.prototype.hasOwnProperty.call(object, i)) {
      var value = clone(object[i]);
      if (typeof value !== 'undefined') {
        newObject[i] = value;
      }
    }
  }
  return newObject;
}

// like underscore/lodash _.pick()

var hasLocal;

try {
  localStorage.setItem('_pouch_check_localstorage', 1);
  hasLocal = !!localStorage.getItem('_pouch_check_localstorage');
} catch (e) {
  hasLocal = false;
}

const nextTick = typeof queueMicrotask === "function"
  ? queueMicrotask
  : function nextTick(fn) {
    Promise.resolve().then(fn);
  };

function guardedConsole(method) {
  /* istanbul ignore else */
  if (typeof console !== 'undefined' && typeof console[method] === 'function') {
    var args = Array.prototype.slice.call(arguments, 1);
    console[method].apply(console, args);
  }
}

class PouchError extends Error {
  constructor(status, error, reason) {
    super();
    this.status = status;
    this.name = error;
    this.message = reason;
    this.error = true;
  }

  toString() {
    return JSON.stringify({
      status: this.status,
      name: this.name,
      message: this.message,
      reason: this.reason
    });
  }
}

var UNAUTHORIZED = new PouchError(401, 'unauthorized', "Name or password is incorrect.");
var MISSING_BULK_DOCS = new PouchError(400, 'bad_request', "Missing JSON list of 'docs'");
var MISSING_DOC = new PouchError(404, 'not_found', 'missing');
var REV_CONFLICT = new PouchError(409, 'conflict', 'Document update conflict');
var INVALID_ID = new PouchError(400, 'bad_request', '_id field must contain a string');
var MISSING_ID = new PouchError(412, 'missing_id', '_id is required for puts');
var RESERVED_ID = new PouchError(400, 'bad_request', 'Only reserved document ids may start with underscore.');
var NOT_OPEN = new PouchError(412, 'precondition_failed', 'Database not open');
var UNKNOWN_ERROR = new PouchError(500, 'unknown_error', 'Database encountered an unknown error');
var BAD_ARG = new PouchError(500, 'badarg', 'Some query argument is invalid');
var INVALID_REQUEST = new PouchError(400, 'invalid_request', 'Request was invalid');
var QUERY_PARSE_ERROR = new PouchError(400, 'query_parse_error', 'Some query parameter is invalid');
var DOC_VALIDATION = new PouchError(500, 'doc_validation', 'Bad special document member');
var BAD_REQUEST = new PouchError(400, 'bad_request', 'Something wrong with the request');
var NOT_AN_OBJECT = new PouchError(400, 'bad_request', 'Document must be a JSON object');
var DB_MISSING = new PouchError(404, 'not_found', 'Database not found');
var IDB_ERROR = new PouchError(500, 'indexed_db_went_bad', 'unknown');
var WSQ_ERROR = new PouchError(500, 'web_sql_went_bad', 'unknown');
var LDB_ERROR = new PouchError(500, 'levelDB_went_went_bad', 'unknown');
var FORBIDDEN = new PouchError(403, 'forbidden', 'Forbidden by design doc validate_doc_update function');
var INVALID_REV = new PouchError(400, 'bad_request', 'Invalid rev format');
var FILE_EXISTS = new PouchError(412, 'file_exists', 'The database could not be created, the file already exists.');
var MISSING_STUB = new PouchError(412, 'missing_stub', 'A pre-existing attachment stub wasn\'t found');
var INVALID_URL = new PouchError(413, 'invalid_url', 'Provided URL is invalid');

function createError(error, reason) {
  function CustomPouchError(reason) {
    // inherit error properties from our parent error manually
    // so as to allow proper JSON parsing.
    var names = Object.getOwnPropertyNames(error);
    for (var i = 0, len = names.length; i < len; i++) {
      if (typeof error[names[i]] !== 'function') {
        this[names[i]] = error[names[i]];
      }
    }

    if (this.stack === undefined) {
      this.stack = (new Error()).stack;
    }

    if (reason !== undefined) {
      this.reason = reason;
    }
  }
  CustomPouchError.prototype = PouchError.prototype;
  return new CustomPouchError(reason);
}

function generateErrorFromResponse(err) {

  if (typeof err !== 'object') {
    var data = err;
    err = UNKNOWN_ERROR;
    err.data = data;
  }

  if ('error' in err && err.error === 'conflict') {
    err.name = 'conflict';
    err.status = 409;
  }

  if (!('name' in err)) {
    err.name = err.error || 'unknown';
  }

  if (!('status' in err)) {
    err.status = 500;
  }

  if (!('message' in err)) {
    err.message = err.message || err.reason;
  }

  if (!('stack' in err)) {
    err.stack = (new Error()).stack;
  }

  return err;
}

// shim for Function.prototype.name,

// Checks if a PouchDB object is "remote" or not. This is

function isRemote(db) {
  if (typeof db._remote === 'boolean') {
    return db._remote;
  }
  /* istanbul ignore next */
  if (typeof db.type === 'function') {
    guardedConsole('warn',
      'db.type() is deprecated and will be removed in ' +
      'a future version of PouchDB');
    return db.type() === 'http';
  }
  /* istanbul ignore next */
  return false;
}

// originally parseUri 1.2.2, now patched by us

// Based on https://github.com/alexdavid/scope-eval v0.0.3

// this is essentially the "update sugar" function from daleharvey/pouchdb#1388
// the diffFun tells us what delta to apply to the doc.  it either returns
// the doc, or false if it doesn't need to do an update after all
function upsert(db, docId, diffFun) {
  return db.get(docId)
    .catch(function (err) {
      /* istanbul ignore next */
      if (err.status !== 404) {
        throw err;
      }
      return {};
    })
    .then(function (doc) {
      // the user might change the _rev, so save it for posterity
      var docRev = doc._rev;
      var newDoc = diffFun(doc);

      if (!newDoc) {
        // if the diffFun returns falsy, we short-circuit as
        // an optimization
        return {updated: false, rev: docRev};
      }

      // users aren't allowed to modify these values,
      // so reset them here
      newDoc._id = docId;
      newDoc._rev = docRev;
      return tryAndPut(db, newDoc, diffFun);
    });
}

function tryAndPut(db, doc, diffFun) {
  return db.put(doc).then(function (res) {
    return {
      updated: true,
      rev: res.rev
    };
  }, function (err) {
    /* istanbul ignore next */
    if (err.status !== 409) {
      throw err;
    }
    return upsert(db, doc._id, diffFun);
  });
}

var thisAtob = function (str) {
  return atob(str);
};

// Abstracts constructing a Blob object, so it also works in older
// browsers that don't support the native Blob constructor (e.g.
// old QtWebKit versions, Android < 4.4).
function createBlob(parts, properties) {
  /* global BlobBuilder,MSBlobBuilder,MozBlobBuilder,WebKitBlobBuilder */
  parts = parts || [];
  properties = properties || {};
  try {
    return new Blob(parts, properties);
  } catch (e) {
    if (e.name !== "TypeError") {
      throw e;
    }
    var Builder = typeof BlobBuilder !== 'undefined' ? BlobBuilder :
                  typeof MSBlobBuilder !== 'undefined' ? MSBlobBuilder :
                  typeof MozBlobBuilder !== 'undefined' ? MozBlobBuilder :
                  WebKitBlobBuilder;
    var builder = new Builder();
    for (var i = 0; i < parts.length; i += 1) {
      builder.append(parts[i]);
    }
    return builder.getBlob(properties.type);
  }
}

// From http://stackoverflow.com/questions/14967647/ (continues on next line)
// encode-decode-image-with-base64-breaks-image (2013-04-21)
function binaryStringToArrayBuffer(bin) {
  var length = bin.length;
  var buf = new ArrayBuffer(length);
  var arr = new Uint8Array(buf);
  for (var i = 0; i < length; i++) {
    arr[i] = bin.charCodeAt(i);
  }
  return buf;
}

function binStringToBluffer(binString, type) {
  return createBlob([binaryStringToArrayBuffer(binString)], {type});
}

function b64ToBluffer(b64, type) {
  return binStringToBluffer(thisAtob(b64), type);
}

//Can't find original post, but this is close

// simplified API. universal browser support is assumed

// this is not used in the browser

var setImmediateShim = self.setImmediate || self.setTimeout;

function stringMd5(string) {
  return Md5.hash(string);
}

// this would just be "return doc[field]", but fields
// can be "deep" due to dot notation
function getFieldFromDoc(doc, parsedField) {
  var value = doc;
  for (var i = 0, len = parsedField.length; i < len; i++) {
    var key = parsedField[i];
    value = value[key];
    if (!value) {
      break;
    }
  }
  return value;
}

function setFieldInDoc(doc, parsedField, value) {
  for (var i = 0, len = parsedField.length; i < len-1; i++) {
    var elem = parsedField[i];
    doc = doc[elem] = doc[elem] || {};
  }
  doc[parsedField[len-1]] = value;
}

function compare(left, right) {
  return left < right ? -1 : left > right ? 1 : 0;
}

// Converts a string in dot notation to an array of its components, with backslash escaping
function parseField(fieldName) {
  // fields may be deep (e.g. "foo.bar.baz"), so parse
  var fields = [];
  var current = '';
  for (var i = 0, len = fieldName.length; i < len; i++) {
    var ch = fieldName[i];
    if (i > 0 && fieldName[i - 1] === '\\' && (ch === '$' || ch === '.')) {
      // escaped delimiter
      current = current.substring(0, current.length - 1) + ch;
    } else if (ch === '.') {
      // When `.` is not escaped (above), it is a field delimiter
      fields.push(current);
      current = '';
    } else { // normal character
      current += ch;
    }
  }
  fields.push(current);
  return fields;
}

var combinationFields = ['$or', '$nor', '$not'];
function isCombinationalField(field) {
  return combinationFields.indexOf(field) > -1;
}

function getKey(obj) {
  return Object.keys(obj)[0];
}

function getValue(obj) {
  return obj[getKey(obj)];
}


// flatten an array of selectors joined by an $and operator
function mergeAndedSelectors(selectors) {

  // sort to ensure that e.g. if the user specified
  // $and: [{$gt: 'a'}, {$gt: 'b'}], then it's collapsed into
  // just {$gt: 'b'}
  var res = {};
  var first = {$or: true, $nor: true};

  selectors.forEach(function (selector) {
    Object.keys(selector).forEach(function (field) {
      var matcher = selector[field];
      if (typeof matcher !== 'object') {
        matcher = {$eq: matcher};
      }

      if (isCombinationalField(field)) {
        // or, nor
        if (matcher instanceof Array) {
          if (first[field]) {
            first[field] = false;
            res[field] = matcher;
            return;
          }

          var entries = [];
          res[field].forEach(function (existing) {
            Object.keys(matcher).forEach(function (key) {
              var m = matcher[key];
              var longest = Math.max(Object.keys(existing).length, Object.keys(m).length);
              var merged = mergeAndedSelectors([existing, m]);
              if (Object.keys(merged).length <= longest) {
                // we have a situation like: (a :{$eq :1} || ...) && (a {$eq: 2} || ...)
                // merging would produce a $eq 2 when actually we shouldn't ever match against these merged conditions
                // merged should always contain more values to be valid
                return;
              }
              entries.push(merged);
            });
          });
          res[field] = entries;
        } else {
          // not
          res[field] = mergeAndedSelectors([matcher]);
        }
      } else {
        var fieldMatchers = res[field] = res[field] || {};
        Object.keys(matcher).forEach(function (operator) {
          var value = matcher[operator];

          if (operator === '$gt' || operator === '$gte') {
            return mergeGtGte(operator, value, fieldMatchers);
          } else if (operator === '$lt' || operator === '$lte') {
            return mergeLtLte(operator, value, fieldMatchers);
          } else if (operator === '$ne') {
            return mergeNe(value, fieldMatchers);
          } else if (operator === '$eq') {
            return mergeEq(value, fieldMatchers);
          } else if (operator === "$regex") {
            return mergeRegex(value, fieldMatchers);
          }
          fieldMatchers[operator] = value;
        });
      }
    });
  });

  return res;
}



// collapse logically equivalent gt/gte values
function mergeGtGte(operator, value, fieldMatchers) {
  if (typeof fieldMatchers.$eq !== 'undefined') {
    return; // do nothing
  }
  if (typeof fieldMatchers.$gte !== 'undefined') {
    if (operator === '$gte') {
      if (value > fieldMatchers.$gte) { // more specificity
        fieldMatchers.$gte = value;
      }
    } else { // operator === '$gt'
      if (value >= fieldMatchers.$gte) { // more specificity
        delete fieldMatchers.$gte;
        fieldMatchers.$gt = value;
      }
    }
  } else if (typeof fieldMatchers.$gt !== 'undefined') {
    if (operator === '$gte') {
      if (value > fieldMatchers.$gt) { // more specificity
        delete fieldMatchers.$gt;
        fieldMatchers.$gte = value;
      }
    } else { // operator === '$gt'
      if (value > fieldMatchers.$gt) { // more specificity
        fieldMatchers.$gt = value;
      }
    }
  } else {
    fieldMatchers[operator] = value;
  }
}

// collapse logically equivalent lt/lte values
function mergeLtLte(operator, value, fieldMatchers) {
  if (typeof fieldMatchers.$eq !== 'undefined') {
    return; // do nothing
  }
  if (typeof fieldMatchers.$lte !== 'undefined') {
    if (operator === '$lte') {
      if (value < fieldMatchers.$lte) { // more specificity
        fieldMatchers.$lte = value;
      }
    } else { // operator === '$gt'
      if (value <= fieldMatchers.$lte) { // more specificity
        delete fieldMatchers.$lte;
        fieldMatchers.$lt = value;
      }
    }
  } else if (typeof fieldMatchers.$lt !== 'undefined') {
    if (operator === '$lte') {
      if (value < fieldMatchers.$lt) { // more specificity
        delete fieldMatchers.$lt;
        fieldMatchers.$lte = value;
      }
    } else { // operator === '$gt'
      if (value < fieldMatchers.$lt) { // more specificity
        fieldMatchers.$lt = value;
      }
    }
  } else {
    fieldMatchers[operator] = value;
  }
}

// combine $ne values into one array
function mergeNe(value, fieldMatchers) {
  if ('$ne' in fieldMatchers) {
    // there are many things this could "not" be
    fieldMatchers.$ne.push(value);
  } else { // doesn't exist yet
    fieldMatchers.$ne = [value];
  }
}

// add $eq into the mix
function mergeEq(value, fieldMatchers) {
  // these all have less specificity than the $eq
  // TODO: check for user errors here
  delete fieldMatchers.$gt;
  delete fieldMatchers.$gte;
  delete fieldMatchers.$lt;
  delete fieldMatchers.$lte;
  delete fieldMatchers.$ne;
  fieldMatchers.$eq = value;
}

// combine $regex values into one array
function mergeRegex(value, fieldMatchers) {
  if ('$regex' in fieldMatchers) {
    // a value could match multiple regexes
    fieldMatchers.$regex.push(value);
  } else { // doesn't exist yet
    fieldMatchers.$regex = [value];
  }
}

//#7458: execute function mergeAndedSelectors on nested $and
function mergeAndedSelectorsNested(obj) {
    for (var prop in obj) {
        if (Array.isArray(obj)) {
            for (var i in obj) {
                if (obj[i]['$and']) {
                    obj[i] = mergeAndedSelectors(obj[i]['$and']);
                }
            }
        }
        var value = obj[prop];
        if (typeof value === 'object') {
            mergeAndedSelectorsNested(value); // <- recursive call
        }
    }
    return obj;
}

//#7458: determine id $and is present in selector (at any level)
function isAndInSelector(obj, isAnd) {
    for (var prop in obj) {
        if (prop === '$and') {
            isAnd = true;
        }
        var value = obj[prop];
        if (typeof value === 'object') {
            isAnd = isAndInSelector(value, isAnd); // <- recursive call
        }
    }
    return isAnd;
}

//
// normalize the selector
//
function massageSelector(input) {
  var result = clone(input);

  //#7458: if $and is present in selector (at any level) merge nested $and
  if (isAndInSelector(result, false)) {
    result = mergeAndedSelectorsNested(result);
    if ('$and' in result) {
      result = mergeAndedSelectors(result['$and']);
    }
  }

  ['$or', '$nor'].forEach(function (orOrNor) {
    if (orOrNor in result) {
      // message each individual selector
      // e.g. {foo: 'bar'} becomes {foo: {$eq: 'bar'}}
      result[orOrNor].forEach(function (subSelector) {
        var fields = Object.keys(subSelector);
        for (var i = 0; i < fields.length; i++) {
          var field = fields[i];
          var matcher = subSelector[field];
          if (typeof matcher !== 'object' || matcher === null) {
            subSelector[field] = {$eq: matcher};
          }
        }
      });
    }
  });

  if ('$not' in result) {
    //This feels a little like forcing, but it will work for now,
    //I would like to come back to this and make the merging of selectors a little more generic
    result['$not'] = mergeAndedSelectors([result['$not']]);
  }

  var fields = Object.keys(result);

  for (var i = 0; i < fields.length; i++) {
    var field = fields[i];
    var matcher = result[field];

    if (typeof matcher !== 'object' || matcher === null) {
      matcher = {$eq: matcher};
    }
    result[field] = matcher;
  }

  normalizeArrayOperators(result);

  return result;
}

//
// The $ne and $regex values must be placed in an array because these operators can be used multiple times on the same field.
// When $and is used, mergeAndedSelectors takes care of putting some of them into arrays, otherwise it's done here.
//
function normalizeArrayOperators(selector) {
  Object.keys(selector).forEach(function (field) {
    var matcher = selector[field];

    if (Array.isArray(matcher)) {
      matcher.forEach(function (matcherItem) {
        if (matcherItem && typeof matcherItem === 'object') {
          normalizeArrayOperators(matcherItem);
        }
      });
    } else if (field === '$ne') {
      selector.$ne = [matcher];
    } else if (field === '$regex') {
      selector.$regex = [matcher];
    } else if (matcher && typeof matcher === 'object') {
      normalizeArrayOperators(matcher);
    }
  });
}

function pad(str, padWith, upToLength) {
  var padding = '';
  var targetLength = upToLength - str.length;
  /* istanbul ignore next */
  while (padding.length < targetLength) {
    padding += padWith;
  }
  return padding;
}

function padLeft(str, padWith, upToLength) {
  var padding = pad(str, padWith, upToLength);
  return padding + str;
}

var MIN_MAGNITUDE = -324; // verified by -Number.MIN_VALUE
var MAGNITUDE_DIGITS = 3; // ditto
var SEP = ''; // set to '_' for easier debugging

function collate(a, b) {

  if (a === b) {
    return 0;
  }

  a = normalizeKey(a);
  b = normalizeKey(b);

  var ai = collationIndex(a);
  var bi = collationIndex(b);
  if ((ai - bi) !== 0) {
    return ai - bi;
  }
  switch (typeof a) {
    case 'number':
      return a - b;
    case 'boolean':
      return a < b ? -1 : 1;
    case 'string':
      return stringCollate(a, b);
  }
  return Array.isArray(a) ? arrayCollate(a, b) : objectCollate(a, b);
}

// couch considers null/NaN/Infinity/-Infinity === undefined,
// for the purposes of mapreduce indexes. also, dates get stringified.
function normalizeKey(key) {
  switch (typeof key) {
    case 'undefined':
      return null;
    case 'number':
      if (key === Infinity || key === -Infinity || isNaN(key)) {
        return null;
      }
      return key;
    case 'object':
      var origKey = key;
      if (Array.isArray(key)) {
        var len = key.length;
        key = new Array(len);
        for (var i = 0; i < len; i++) {
          key[i] = normalizeKey(origKey[i]);
        }
      /* istanbul ignore next */
      } else if (key instanceof Date) {
        return key.toJSON();
      } else if (key !== null) { // generic object
        key = {};
        for (var k in origKey) {
          if (Object.prototype.hasOwnProperty.call(origKey, k)) {
            var val = origKey[k];
            if (typeof val !== 'undefined') {
              key[k] = normalizeKey(val);
            }
          }
        }
      }
  }
  return key;
}

function indexify(key) {
  if (key !== null) {
    switch (typeof key) {
      case 'boolean':
        return key ? 1 : 0;
      case 'number':
        return numToIndexableString(key);
      case 'string':
        // We've to be sure that key does not contain \u0000
        // Do order-preserving replacements:
        // 0 -> 1, 1
        // 1 -> 1, 2
        // 2 -> 2, 2
        /* eslint-disable no-control-regex */
        return key
          .replace(/\u0002/g, '\u0002\u0002')
          .replace(/\u0001/g, '\u0001\u0002')
          .replace(/\u0000/g, '\u0001\u0001');
        /* eslint-enable no-control-regex */
      case 'object':
        var isArray = Array.isArray(key);
        var arr = isArray ? key : Object.keys(key);
        var i = -1;
        var len = arr.length;
        var result = '';
        if (isArray) {
          while (++i < len) {
            result += toIndexableString(arr[i]);
          }
        } else {
          while (++i < len) {
            var objKey = arr[i];
            result += toIndexableString(objKey) +
                toIndexableString(key[objKey]);
          }
        }
        return result;
    }
  }
  return '';
}

// convert the given key to a string that would be appropriate
// for lexical sorting, e.g. within a database, where the
// sorting is the same given by the collate() function.
function toIndexableString(key) {
  var zero = '\u0000';
  key = normalizeKey(key);
  return collationIndex(key) + SEP + indexify(key) + zero;
}

function parseNumber(str, i) {
  var originalIdx = i;
  var num;
  var zero = str[i] === '1';
  if (zero) {
    num = 0;
    i++;
  } else {
    var neg = str[i] === '0';
    i++;
    var numAsString = '';
    var magAsString = str.substring(i, i + MAGNITUDE_DIGITS);
    var magnitude = parseInt(magAsString, 10) + MIN_MAGNITUDE;
    /* istanbul ignore next */
    if (neg) {
      magnitude = -magnitude;
    }
    i += MAGNITUDE_DIGITS;
    while (true) {
      var ch = str[i];
      if (ch === '\u0000') {
        break;
      } else {
        numAsString += ch;
      }
      i++;
    }
    numAsString = numAsString.split('.');
    if (numAsString.length === 1) {
      num = parseInt(numAsString, 10);
    } else {
      /* istanbul ignore next */
      num = parseFloat(numAsString[0] + '.' + numAsString[1]);
    }
    /* istanbul ignore next */
    if (neg) {
      num = num - 10;
    }
    /* istanbul ignore next */
    if (magnitude !== 0) {
      // parseFloat is more reliable than pow due to rounding errors
      // e.g. Number.MAX_VALUE would return Infinity if we did
      // num * Math.pow(10, magnitude);
      num = parseFloat(num + 'e' + magnitude);
    }
  }
  return {num, length : i - originalIdx};
}

// move up the stack while parsing
// this function moved outside of parseIndexableString for performance
function pop(stack, metaStack) {
  var obj = stack.pop();

  if (metaStack.length) {
    var lastMetaElement = metaStack[metaStack.length - 1];
    if (obj === lastMetaElement.element) {
      // popping a meta-element, e.g. an object whose value is another object
      metaStack.pop();
      lastMetaElement = metaStack[metaStack.length - 1];
    }
    var element = lastMetaElement.element;
    var lastElementIndex = lastMetaElement.index;
    if (Array.isArray(element)) {
      element.push(obj);
    } else if (lastElementIndex === stack.length - 2) { // obj with key+value
      var key = stack.pop();
      element[key] = obj;
    } else {
      stack.push(obj); // obj with key only
    }
  }
}

function parseIndexableString(str) {
  var stack = [];
  var metaStack = []; // stack for arrays and objects
  var i = 0;

  /*eslint no-constant-condition: ["error", { "checkLoops": false }]*/
  while (true) {
    var collationIndex = str[i++];
    if (collationIndex === '\u0000') {
      if (stack.length === 1) {
        return stack.pop();
      } else {
        pop(stack, metaStack);
        continue;
      }
    }
    switch (collationIndex) {
      case '1':
        stack.push(null);
        break;
      case '2':
        stack.push(str[i] === '1');
        i++;
        break;
      case '3':
        var parsedNum = parseNumber(str, i);
        stack.push(parsedNum.num);
        i += parsedNum.length;
        break;
      case '4':
        var parsedStr = '';
        /*eslint no-constant-condition: ["error", { "checkLoops": false }]*/
        while (true) {
          var ch = str[i];
          if (ch === '\u0000') {
            break;
          }
          parsedStr += ch;
          i++;
        }
        // perform the reverse of the order-preserving replacement
        // algorithm (see above)
        /* eslint-disable no-control-regex */
        parsedStr = parsedStr.replace(/\u0001\u0001/g, '\u0000')
          .replace(/\u0001\u0002/g, '\u0001')
          .replace(/\u0002\u0002/g, '\u0002');
        /* eslint-enable no-control-regex */
        stack.push(parsedStr);
        break;
      case '5':
        var arrayElement = { element: [], index: stack.length };
        stack.push(arrayElement.element);
        metaStack.push(arrayElement);
        break;
      case '6':
        var objElement = { element: {}, index: stack.length };
        stack.push(objElement.element);
        metaStack.push(objElement);
        break;
      /* istanbul ignore next */
      default:
        throw new Error(
          'bad collationIndex or unexpectedly reached end of input: ' +
            collationIndex);
    }
  }
}

function arrayCollate(a, b) {
  var len = Math.min(a.length, b.length);
  for (var i = 0; i < len; i++) {
    var sort = collate(a[i], b[i]);
    if (sort !== 0) {
      return sort;
    }
  }
  return (a.length === b.length) ? 0 :
    (a.length > b.length) ? 1 : -1;
}
function stringCollate(a, b) {
  // See: https://github.com/daleharvey/pouchdb/issues/40
  // This is incompatible with the CouchDB implementation, but its the
  // best we can do for now
  return (a === b) ? 0 : ((a > b) ? 1 : -1);
}
function objectCollate(a, b) {
  var ak = Object.keys(a), bk = Object.keys(b);
  var len = Math.min(ak.length, bk.length);
  for (var i = 0; i < len; i++) {
    // First sort the keys
    var sort = collate(ak[i], bk[i]);
    if (sort !== 0) {
      return sort;
    }
    // if the keys are equal sort the values
    sort = collate(a[ak[i]], b[bk[i]]);
    if (sort !== 0) {
      return sort;
    }

  }
  return (ak.length === bk.length) ? 0 :
    (ak.length > bk.length) ? 1 : -1;
}
// The collation is defined by erlangs ordered terms
// the atoms null, true, false come first, then numbers, strings,
// arrays, then objects
// null/undefined/NaN/Infinity/-Infinity are all considered null
function collationIndex(x) {
  var id = ['boolean', 'number', 'string', 'object'];
  var idx = id.indexOf(typeof x);
  //false if -1 otherwise true, but fast!!!!1
  if (~idx) {
    if (x === null) {
      return 1;
    }
    if (Array.isArray(x)) {
      return 5;
    }
    return idx < 3 ? (idx + 2) : (idx + 3);
  }
  /* istanbul ignore next */
  if (Array.isArray(x)) {
    return 5;
  }
}

// conversion:
// x yyy zz...zz
// x = 0 for negative, 1 for 0, 2 for positive
// y = exponent (for negative numbers negated) moved so that it's >= 0
// z = mantisse
function numToIndexableString(num) {

  if (num === 0) {
    return '1';
  }

  // convert number to exponential format for easier and
  // more succinct string sorting
  var expFormat = num.toExponential().split(/e\+?/);
  var magnitude = parseInt(expFormat[1], 10);

  var neg = num < 0;

  var result = neg ? '0' : '2';

  // first sort by magnitude
  // it's easier if all magnitudes are positive
  var magForComparison = ((neg ? -magnitude : magnitude) - MIN_MAGNITUDE);
  var magString = padLeft((magForComparison).toString(), '0', MAGNITUDE_DIGITS);

  result += SEP + magString;

  // then sort by the factor
  var factor = Math.abs(parseFloat(expFormat[0])); // [1..10)
  /* istanbul ignore next */
  if (neg) { // for negative reverse ordering
    factor = 10 - factor;
  }

  var factorStr = factor.toFixed(20);

  // strip zeros from the end
  factorStr = factorStr.replace(/\.?0+$/, '');

  result += SEP + factorStr;

  return result;
}

// create a comparator based on the sort object
function createFieldSorter(sort) {

  function getFieldValuesAsArray(doc) {
    return sort.map(function (sorting) {
      var fieldName = getKey(sorting);
      var parsedField = parseField(fieldName);
      var docFieldValue = getFieldFromDoc(doc, parsedField);
      return docFieldValue;
    });
  }

  return function (aRow, bRow) {
    var aFieldValues = getFieldValuesAsArray(aRow.doc);
    var bFieldValues = getFieldValuesAsArray(bRow.doc);
    var collation = collate(aFieldValues, bFieldValues);
    if (collation !== 0) {
      return collation;
    }
    // this is what mango seems to do
    return compare(aRow.doc._id, bRow.doc._id);
  };
}

function filterInMemoryFields(rows, requestDef, inMemoryFields) {
  rows = rows.filter(function (row) {
    return rowFilter(row.doc, requestDef.selector, inMemoryFields);
  });

  if (requestDef.sort) {
    // in-memory sort
    var fieldSorter = createFieldSorter(requestDef.sort);
    rows = rows.sort(fieldSorter);
    if (typeof requestDef.sort[0] !== 'string' &&
        getValue(requestDef.sort[0]) === 'desc') {
      rows = rows.reverse();
    }
  }

  if ('limit' in requestDef || 'skip' in requestDef) {
    // have to do the limit in-memory
    var skip = requestDef.skip || 0;
    var limit = ('limit' in requestDef ? requestDef.limit : rows.length) + skip;
    rows = rows.slice(skip, limit);
  }
  return rows;
}

function rowFilter(doc, selector, inMemoryFields) {
  return inMemoryFields.every(function (field) {
    var matcher = selector[field];
    var parsedField = parseField(field);
    var docFieldValue = getFieldFromDoc(doc, parsedField);
    if (isCombinationalField(field)) {
      return matchCominationalSelector(field, matcher, doc);
    }

    return matchSelector(matcher, doc, parsedField, docFieldValue);
  });
}

function matchSelector(matcher, doc, parsedField, docFieldValue) {
  if (!matcher) {
    // no filtering necessary; this field is just needed for sorting
    return true;
  }

  // is matcher an object, if so continue recursion
  if (typeof matcher === 'object') {
    return Object.keys(matcher).every(function (maybeUserOperator) {
      var userValue = matcher[ maybeUserOperator ];
      // explicit operator
      if (maybeUserOperator.indexOf("$") === 0) {
        return match(maybeUserOperator, doc, userValue, parsedField, docFieldValue);
      } else {
        var subParsedField = parseField(maybeUserOperator);

        if (
          docFieldValue === undefined &&
          typeof userValue !== "object" &&
          subParsedField.length > 0
        ) {
          // the field does not exist, return or getFieldFromDoc will throw
          return false;
        }

        var subDocFieldValue = getFieldFromDoc(docFieldValue, subParsedField);

        if (typeof userValue === "object") {
          // field value is an object that might contain more operators
          return matchSelector(userValue, doc, parsedField, subDocFieldValue);
        }

        // implicit operator
        return match("$eq", doc, userValue, subParsedField, subDocFieldValue);
      }
    });
  }

  // no more depth, No need to recurse further
  return matcher === docFieldValue;
}

function matchCominationalSelector(field, matcher, doc) {

  if (field === '$or') {
    return matcher.some(function (orMatchers) {
      return rowFilter(doc, orMatchers, Object.keys(orMatchers));
    });
  }

  if (field === '$not') {
    return !rowFilter(doc, matcher, Object.keys(matcher));
  }

  //`$nor`
  return !matcher.find(function (orMatchers) {
    return rowFilter(doc, orMatchers, Object.keys(orMatchers));
  });

}

function match(userOperator, doc, userValue, parsedField, docFieldValue) {
  if (!matchers[userOperator]) {
    /* istanbul ignore next */
    throw new Error('unknown operator "' + userOperator +
      '" - should be one of $eq, $lte, $lt, $gt, $gte, $exists, $ne, $in, ' +
      '$nin, $size, $mod, $regex, $elemMatch, $type, $allMatch or $all');
  }
  return matchers[userOperator](doc, userValue, parsedField, docFieldValue);
}

function fieldExists(docFieldValue) {
  return typeof docFieldValue !== 'undefined' && docFieldValue !== null;
}

function fieldIsNotUndefined(docFieldValue) {
  return typeof docFieldValue !== 'undefined';
}

function modField(docFieldValue, userValue) {
  if (typeof docFieldValue !== "number" ||
    parseInt(docFieldValue, 10) !== docFieldValue) {
    return false;
  }

  var divisor = userValue[0];
  var mod = userValue[1];

  return docFieldValue % divisor === mod;
}

function arrayContainsValue(docFieldValue, userValue) {
  return userValue.some(function (val) {
    if (docFieldValue instanceof Array) {
      return docFieldValue.some(function (docFieldValueItem) {
        return collate(val, docFieldValueItem) === 0;
      });
    }

    return collate(val, docFieldValue) === 0;
  });
}

function arrayContainsAllValues(docFieldValue, userValue) {
  return userValue.every(function (val) {
    return docFieldValue.some(function (docFieldValueItem) {
      return collate(val, docFieldValueItem) === 0;
    });
  });
}

function arraySize(docFieldValue, userValue) {
  return docFieldValue.length === userValue;
}

function regexMatch(docFieldValue, userValue) {
  var re = new RegExp(userValue);

  return re.test(docFieldValue);
}

function typeMatch(docFieldValue, userValue) {

  switch (userValue) {
    case 'null':
      return docFieldValue === null;
    case 'boolean':
      return typeof (docFieldValue) === 'boolean';
    case 'number':
      return typeof (docFieldValue) === 'number';
    case 'string':
      return typeof (docFieldValue) === 'string';
    case 'array':
      return docFieldValue instanceof Array;
    case 'object':
      return ({}).toString.call(docFieldValue) === '[object Object]';
  }
}

var matchers = {

  '$elemMatch': function (doc, userValue, parsedField, docFieldValue) {
    if (!Array.isArray(docFieldValue)) {
      return false;
    }

    if (docFieldValue.length === 0) {
      return false;
    }

    if (typeof docFieldValue[0] === 'object' &&  docFieldValue[0] !== null) {
      return docFieldValue.some(function (val) {
        return rowFilter(val, userValue, Object.keys(userValue));
      });
    }

    return docFieldValue.some(function (val) {
      return matchSelector(userValue, doc, parsedField, val);
    });
  },

  '$allMatch': function (doc, userValue, parsedField, docFieldValue) {
    if (!Array.isArray(docFieldValue)) {
      return false;
    }

    /* istanbul ignore next */
    if (docFieldValue.length === 0) {
      return false;
    }

    if (typeof docFieldValue[0] === 'object' &&  docFieldValue[0] !== null) {
      return docFieldValue.every(function (val) {
        return rowFilter(val, userValue, Object.keys(userValue));
      });
    }

    return docFieldValue.every(function (val) {
      return matchSelector(userValue, doc, parsedField, val);
    });
  },

  '$eq': function (doc, userValue, parsedField, docFieldValue) {
    return fieldIsNotUndefined(docFieldValue) && collate(docFieldValue, userValue) === 0;
  },

  '$gte': function (doc, userValue, parsedField, docFieldValue) {
    return fieldIsNotUndefined(docFieldValue) && collate(docFieldValue, userValue) >= 0;
  },

  '$gt': function (doc, userValue, parsedField, docFieldValue) {
    return fieldIsNotUndefined(docFieldValue) && collate(docFieldValue, userValue) > 0;
  },

  '$lte': function (doc, userValue, parsedField, docFieldValue) {
    return fieldIsNotUndefined(docFieldValue) && collate(docFieldValue, userValue) <= 0;
  },

  '$lt': function (doc, userValue, parsedField, docFieldValue) {
    return fieldIsNotUndefined(docFieldValue) && collate(docFieldValue, userValue) < 0;
  },

  '$exists': function (doc, userValue, parsedField, docFieldValue) {
    //a field that is null is still considered to exist
    if (userValue) {
      return fieldIsNotUndefined(docFieldValue);
    }

    return !fieldIsNotUndefined(docFieldValue);
  },

  '$mod': function (doc, userValue, parsedField, docFieldValue) {
    return fieldExists(docFieldValue) && modField(docFieldValue, userValue);
  },

  '$ne': function (doc, userValue, parsedField, docFieldValue) {
    return userValue.every(function (neValue) {
      return collate(docFieldValue, neValue) !== 0;
    });
  },
  '$in': function (doc, userValue, parsedField, docFieldValue) {
    return fieldExists(docFieldValue) && arrayContainsValue(docFieldValue, userValue);
  },

  '$nin': function (doc, userValue, parsedField, docFieldValue) {
    return fieldExists(docFieldValue) && !arrayContainsValue(docFieldValue, userValue);
  },

  '$size': function (doc, userValue, parsedField, docFieldValue) {
    return fieldExists(docFieldValue) &&
      Array.isArray(docFieldValue) &&
      arraySize(docFieldValue, userValue);
  },

  '$all': function (doc, userValue, parsedField, docFieldValue) {
    return Array.isArray(docFieldValue) && arrayContainsAllValues(docFieldValue, userValue);
  },

  '$regex': function (doc, userValue, parsedField, docFieldValue) {
    return fieldExists(docFieldValue) &&
      typeof docFieldValue == "string" &&
      userValue.every(function (regexValue) {
        return regexMatch(docFieldValue, regexValue);
      });
  },

  '$type': function (doc, userValue, parsedField, docFieldValue) {
    return typeMatch(docFieldValue, userValue);
  }
};

// return true if the given doc matches the supplied selector
function matchesSelector(doc, selector) {
  /* istanbul ignore if */
  if (typeof selector !== 'object') {
    // match the CouchDB error message
    throw new Error('Selector error: expected a JSON object');
  }

  selector = massageSelector(selector);
  var row = {
    doc
  };

  var rowsMatched = filterInMemoryFields([row], { selector }, Object.keys(selector));
  return rowsMatched && rowsMatched.length === 1;
}

const nativeFlat = (...args) => args.flat(Infinity);

const polyFlat = (...args) => {
  let res = [];
  for (const subArr of args) {
    if (Array.isArray(subArr)) {
      res = res.concat(polyFlat(...subArr));
    } else {
      res.push(subArr);
    }
  }
  return res;
};

const flatten = typeof Array.prototype.flat === 'function'
  ? nativeFlat
  : polyFlat;

function mergeObjects(arr) {
  const res = {};
  for (const element of arr) {
    Object.assign(res, element);
  }
  return res;
}

// Selects a list of fields defined in dot notation from one doc
// and copies them to a new doc. Like underscore _.pick but supports nesting.
function pick$1(obj, arr) {
  const res = {};
  for (const field of arr) {
    const parsedField = parseField(field);
    const value = getFieldFromDoc(obj, parsedField);
    if (typeof value !== 'undefined') {
      setFieldInDoc(res, parsedField, value);
    }
  }
  return res;
}

// e.g. ['a'], ['a', 'b'] is true, but ['b'], ['a', 'b'] is false
function oneArrayIsSubArrayOfOther(left, right) {
  for (let i = 0, len = Math.min(left.length, right.length); i < len; i++) {
    if (left[i] !== right[i]) {
      return false;
    }
  }
  return true;
}

// e.g.['a', 'b', 'c'], ['a', 'b'] is false
function oneArrayIsStrictSubArrayOfOther(left, right) {
  if (left.length > right.length) {
    return false;
  }

  return oneArrayIsSubArrayOfOther(left, right);
}

// same as above, but treat the left array as an unordered set
// e.g. ['b', 'a'], ['a', 'b', 'c'] is true, but ['c'], ['a', 'b', 'c'] is false
function oneSetIsSubArrayOfOther(left, right) {
  left = left.slice();
  for (const field of right) {
    if (!left.length) {
      break;
    }
    const leftIdx = left.indexOf(field);
    if (leftIdx === -1) {
      return false;
    } else {
      left.splice(leftIdx, 1);
    }
  }
  return true;
}

function arrayToObject(arr) {
  const res = {};
  for (const field of arr) {
    res[field] = true;
  }
  return res;
}

function max(arr, fun) {
  let max = null;
  let maxScore = -1;
  for (const element of arr) {
    const score = fun(element);
    if (score > maxScore) {
      maxScore = score;
      max = element;
    }
  }
  return max;
}

function arrayEquals(arr1, arr2) {
  if (arr1.length !== arr2.length) {
    return false;
  }
  for (let i = 0, len = arr1.length; i < len; i++) {
    if (arr1[i] !== arr2[i]) {
      return false;
    }
  }
  return true;
}

function uniq(arr) {
  return Array.from(new Set(arr));
}

/**
 * Callbackifyable wrapper for async functions
 *
 * @template T, Args
 * @param {(...args: Args) => Promise<T>} fun
 * @returns {<CBArgs = [...Args, (err: any, value: T) => void], InnerArgs extends Args | CBArgs>(...innerArgs: InnerArgs) => InnerArgs extends CBArgs ? void : Promise<T>}
 *
 * @example
 * const fn = resolveToCallback(async () => { return 42; })
 * // with callback:
 * fn((err, value) => { ... })
 * // with await:
 * const value = await fn()
 */
function resolveToCallback(fun) {
  return function (...args) {
    const maybeCallback = args[args.length - 1];
    if (typeof maybeCallback === "function") {
      const fulfilled = maybeCallback.bind(null, null);
      const rejected = maybeCallback.bind(null);
      fun.apply(this, args.slice(0, -1)).then(fulfilled, rejected);
    } else {
      return fun.apply(this, args);
    }
  };
}

var h = Headers;

// we restructure the supplied JSON considerably, because the official
// Mango API is very particular about a lot of this stuff, but we like
// to be liberal with what we accept in order to prevent mental
// breakdowns in our users
function massageCreateIndexRequest(requestDef) {
  requestDef = clone(requestDef);

  if (!requestDef.index) {
    requestDef.index = {};
  }

  for (const key of ['type', 'name', 'ddoc']) {
    if (requestDef.index[key]) {
      requestDef[key] = requestDef.index[key];
      delete requestDef.index[key];
    }
  }

  if (requestDef.fields) {
    requestDef.index.fields = requestDef.fields;
    delete requestDef.fields;
  }

  if (!requestDef.type) {
    requestDef.type = 'json';
  }
  return requestDef;
}

function isNonNullObject(value) {
  return typeof value === 'object' && value !== null;
}

// throws if the user is using the wrong query field value type
function checkFieldValueType(name, value, isHttp) {
  let message = '';
  let received = value;
  let addReceived = true;
  if (['$in', '$nin', '$or', '$and', '$mod', '$nor', '$all'].indexOf(name) !== -1) {
    if (!Array.isArray(value)) {
      message = 'Query operator ' + name + ' must be an array.';

    }
  }

  if (['$not', '$elemMatch', '$allMatch'].indexOf(name) !== -1) {
    if (!(!Array.isArray(value) && isNonNullObject(value))) {
      message = 'Query operator ' + name + ' must be an object.';
    }
  }

  if (name === '$mod' && Array.isArray(value)) {
    if (value.length !== 2) {
      message = 'Query operator $mod must be in the format [divisor, remainder], ' +
        'where divisor and remainder are both integers.';
    } else {
      const divisor = value[0];
      const mod = value[1];
      if (divisor === 0) {
        message = 'Query operator $mod\'s divisor cannot be 0, cannot divide by zero.';
        addReceived = false;
      }
      if (typeof divisor !== 'number' || parseInt(divisor, 10) !== divisor) {
        message = 'Query operator $mod\'s divisor is not an integer.';
        received = divisor;
      }
      if (parseInt(mod, 10) !== mod) {
        message = 'Query operator $mod\'s remainder is not an integer.';
        received = mod;
      }
    }
  }
  if (name === '$exists') {
    if (typeof value !== 'boolean') {
      message = 'Query operator $exists must be a boolean.';
    }
  }

  if (name === '$type') {
    const allowed = ['null', 'boolean', 'number', 'string', 'array', 'object'];
    const allowedStr = '"' + allowed.slice(0, allowed.length - 1).join('", "') + '", or "' + allowed[allowed.length - 1] + '"';
    if (typeof value !== 'string') {
      message = 'Query operator $type must be a string. Supported values: ' + allowedStr + '.';
    } else if (allowed.indexOf(value) == -1) {
      message = 'Query operator $type must be a string. Supported values: ' + allowedStr + '.';
    }
  }

  if (name === '$size') {
    if (parseInt(value, 10) !== value) {
      message = 'Query operator $size must be a integer.';
    }
  }

  if (name === '$regex') {
    if (typeof value !== 'string') {
      if (isHttp) {
        message = 'Query operator $regex must be a string.';
      } else if (!(value instanceof RegExp)) {
        message = 'Query operator $regex must be a string or an instance ' +
          'of a javascript regular expression.';
      }
    }
  }

  if (message) {
    if (addReceived) {
      const type = received === null
        ? ' '
        : Array.isArray(received)
          ? ' array'
          : ' ' + typeof received;
      const receivedStr = isNonNullObject(received)
        ? JSON.stringify(received, null, '\t')
        : received;

      message += ' Received' + type + ': ' + receivedStr;
    }
    throw new Error(message);
  }
}

const requireValidation = ['$all', '$allMatch', '$and', '$elemMatch', '$exists', '$in', '$mod', '$nin', '$nor', '$not', '$or', '$regex', '$size', '$type'];
const arrayTypeComparisonOperators = ['$in', '$nin', '$mod', '$all'];
const equalityOperators = ['$eq', '$gt', '$gte', '$lt', '$lte'];

// recursively walks down the a query selector validating any operators
function validateSelector(input, isHttp) {
  if (Array.isArray(input)) {
    for (const entry of input) {
      if (isNonNullObject(entry)) {
        validateSelector(entry, isHttp);
      }
    }
  }
  else {
    for (const [key, value] of Object.entries(input)) {
      if (requireValidation.indexOf(key) !== -1) {
        checkFieldValueType(key, value, isHttp);
      }
      if (equalityOperators.indexOf(key) !== -1) {
        // skip, explicit comparison operators can be anything
        continue;
      }
      if (arrayTypeComparisonOperators.indexOf(key) !== -1) {
        // skip, their values are already valid
        continue;
      }
      if (isNonNullObject(value)) {
        validateSelector(value, isHttp);
      }
    }
  }
}

async function dbFetch(db, path, opts) {
  if (opts.body) {
    opts.body = JSON.stringify(opts.body);
    opts.headers = new h({ 'Content-type': 'application/json' });
  }

  const response = await db.fetch(path, opts);
  const json = await response.json();
  if (!response.ok) {
    json.status = response.status;
    const pouchError = createError(json);
    throw generateErrorFromResponse(pouchError);
  }
  return json;
}

async function createIndex(db, requestDef) {
  return await dbFetch(db, '_index', {
    method: 'POST',
    body: massageCreateIndexRequest(requestDef)
  });
}

async function find(db, requestDef) {
  validateSelector(requestDef.selector, true);
  return await dbFetch(db, '_find', {
    method: 'POST',
    body: requestDef
  });
}

async function explain(db, requestDef) {
  return await dbFetch(db, '_explain', {
    method: 'POST',
    body: requestDef
  });
}

async function getIndexes(db) {
  return await dbFetch(db, '_index', {
    method: 'GET'
  });
}

async function deleteIndex(db, indexDef) {
  const ddoc = indexDef.ddoc;
  const type = indexDef.type || 'json';
  const name = indexDef.name;

  if (!ddoc) {
    throw new Error('you must provide an index\'s ddoc');
  }

  if (!name) {
    throw new Error('you must provide an index\'s name');
  }

  const url = '_index/' + [ddoc, type, name].map(encodeURIComponent).join('/');

  return await dbFetch(db, url, { method: 'DELETE' });
}

/*
 * Simple task queue to sequentialize actions. Assumes
 * callbacks will eventually fire (once).
 */

class TaskQueue {
  constructor() {
    this.promise = Promise.resolve();
  }

  add(promiseFactory) {
    this.promise = this.promise
      // just recover
      .catch(() => { })
      .then(() => promiseFactory());
    return this.promise;
  }

  finish() {
    return this.promise;
  }
}

function stringify(input) {
  if (!input) {
    return 'undefined'; // backwards compat for empty reduce
  }
  // for backwards compat with mapreduce, functions/strings are stringified
  // as-is. everything else is JSON-stringified.
  switch (typeof input) {
    case 'function':
      // e.g. a mapreduce map
      return input.toString();
    case 'string':
      // e.g. a mapreduce built-in _reduce function
      return input.toString();
    default:
      // e.g. a JSON object in the case of mango queries
      return JSON.stringify(input);
  }
}

/* create a string signature for a view so we can cache it and uniq it */
function createViewSignature(mapFun, reduceFun) {
  // the "undefined" part is for backwards compatibility
  return stringify(mapFun) + stringify(reduceFun) + 'undefined';
}

async function createView(sourceDB, viewName, mapFun, reduceFun, temporary, localDocName) {
  const viewSignature = createViewSignature(mapFun, reduceFun);

  let cachedViews;
  if (!temporary) {
    // cache this to ensure we don't try to update the same view twice
    cachedViews = sourceDB._cachedViews = sourceDB._cachedViews || {};
    if (cachedViews[viewSignature]) {
      return cachedViews[viewSignature];
    }
  }

  const promiseForView = sourceDB.info().then(async function (info) {
    const depDbName = info.db_name + '-mrview-' +
    (temporary ? 'temp' : stringMd5(viewSignature));

    // save the view name in the source db so it can be cleaned up if necessary
    // (e.g. when the _design doc is deleted, remove all associated view data)
    function diffFunction(doc) {
      doc.views = doc.views || {};
      let fullViewName = viewName;
      if (fullViewName.indexOf('/') === -1) {
        fullViewName = viewName + '/' + viewName;
      }
      const depDbs = doc.views[fullViewName] = doc.views[fullViewName] || {};
      /* istanbul ignore if */
      if (depDbs[depDbName]) {
        return; // no update necessary
      }
      depDbs[depDbName] = true;
      return doc;
    }
    await upsert(sourceDB, '_local/' + localDocName, diffFunction);
    const res = await sourceDB.registerDependentDatabase(depDbName);
    const db = res.db;
    db.auto_compaction = true;
    const view = {
      name: depDbName,
      db,
      sourceDB,
      adapter: sourceDB.adapter,
      mapFun,
      reduceFun
    };

    let lastSeqDoc;
    try {
      lastSeqDoc = await view.db.get('_local/lastSeq');
    } catch (err) {
        /* istanbul ignore if */
      if (err.status !== 404) {
        throw err;
      }
    }

    view.seq = lastSeqDoc ? lastSeqDoc.seq : 0;
    if (cachedViews) {
      view.db.once('destroyed', function () {
        delete cachedViews[viewSignature];
      });
    }
    return view;
  });

  if (cachedViews) {
    cachedViews[viewSignature] = promiseForView;
  }
  return promiseForView;
}

class QueryParseError extends Error {
  constructor(message) {
    super();
    this.status = 400;
    this.name = 'query_parse_error';
    this.message = message;
    this.error = true;
    try {
      Error.captureStackTrace(this, QueryParseError);
    } catch (e) {}
  }
}

class NotFoundError extends Error {
  constructor(message) {
    super();
    this.status = 404;
    this.name = 'not_found';
    this.message = message;
    this.error = true;
    try {
      Error.captureStackTrace(this, NotFoundError);
    } catch (e) {}
  }
}

class BuiltInError extends Error {
  constructor(message) {
    super();
    this.status = 500;
    this.name = 'invalid_value';
    this.message = message;
    this.error = true;
    try {
      Error.captureStackTrace(this, BuiltInError);
    } catch (e) {}
  }
}

function promisedCallback(promise, callback) {
  if (callback) {
    promise.then(function (res) {
      nextTick(function () {
        callback(null, res);
      });
    }, function (reason) {
      nextTick(function () {
        callback(reason);
      });
    });
  }
  return promise;
}

function callbackify(fun) {
  return function (...args) {
    var cb = args.pop();
    var promise = fun.apply(this, args);
    if (typeof cb === 'function') {
      promisedCallback(promise, cb);
    }
    return promise;
  };
}

// Promise finally util similar to Q.finally
function fin(promise, finalPromiseFactory) {
  return promise.then(function (res) {
    return finalPromiseFactory().then(function () {
      return res;
    });
  }, function (reason) {
    return finalPromiseFactory().then(function () {
      throw reason;
    });
  });
}

function sequentialize(queue, promiseFactory) {
  return function () {
    var args = arguments;
    var that = this;
    return queue.add(function () {
      return promiseFactory.apply(that, args);
    });
  };
}

// uniq an array of strings, order not guaranteed
// similar to underscore/lodash _.uniq
function uniq$1(arr) {
  var theSet = new Set(arr);
  var result = new Array(theSet.size);
  var index = -1;
  theSet.forEach(function (value) {
    result[++index] = value;
  });
  return result;
}

function mapToKeysArray(map) {
  var result = new Array(map.size);
  var index = -1;
  map.forEach(function (value, key) {
    result[++index] = key;
  });
  return result;
}

const persistentQueues = {};
const tempViewQueue = new TaskQueue();
const CHANGES_BATCH_SIZE = 50;

function parseViewName(name) {
  // can be either 'ddocname/viewname' or just 'viewname'
  // (where the ddoc name is the same)
  return name.indexOf('/') === -1 ? [name, name] : name.split('/');
}

function isGenOne(changes) {
  // only return true if the current change is 1-
  // and there are no other leafs
  return changes.length === 1 && /^1-/.test(changes[0].rev);
}

function emitError(db, e, data) {
  try {
    db.emit('error', e);
  } catch (err) {
    guardedConsole('error',
      'The user\'s map/reduce function threw an uncaught error.\n' +
      'You can debug this error by doing:\n' +
      'myDatabase.on(\'error\', function (err) { debugger; });\n' +
      'Please double-check your map/reduce function.');
    guardedConsole('error', e, data);
  }
}

/**
 * Returns an "abstract" mapreduce object of the form:
 *
 *   {
 *     query: queryFun,
 *     viewCleanup: viewCleanupFun
 *   }
 *
 * Arguments are:
 *
 * localDoc: string
 *   This is for the local doc that gets saved in order to track the
 *   "dependent" DBs and clean them up for viewCleanup. It should be
 *   unique, so that indexer plugins don't collide with each other.
 * mapper: function (mapFunDef, emit)
 *   Returns a map function based on the mapFunDef, which in the case of
 *   normal map/reduce is just the de-stringified function, but may be
 *   something else, such as an object in the case of pouchdb-find.
 * reducer: function (reduceFunDef)
 *   Ditto, but for reducing. Modules don't have to support reducing
 *   (e.g. pouchdb-find).
 * ddocValidator: function (ddoc, viewName)
 *   Throws an error if the ddoc or viewName is not valid.
 *   This could be a way to communicate to the user that the configuration for the
 *   indexer is invalid.
 */
function createAbstractMapReduce(localDocName, mapper, reducer, ddocValidator) {

  function tryMap(db, fun, doc) {
    // emit an event if there was an error thrown by a map function.
    // putting try/catches in a single function also avoids deoptimizations.
    try {
      fun(doc);
    } catch (e) {
      emitError(db, e, {fun, doc});
    }
  }

  function tryReduce(db, fun, keys, values, rereduce) {
    // same as above, but returning the result or an error. there are two separate
    // functions to avoid extra memory allocations since the tryCode() case is used
    // for custom map functions (common) vs this function, which is only used for
    // custom reduce functions (rare)
    try {
      return {output : fun(keys, values, rereduce)};
    } catch (e) {
      emitError(db, e, {fun, keys, values, rereduce});
      return {error: e};
    }
  }

  function sortByKeyThenValue(x, y) {
    const keyCompare = collate(x.key, y.key);
    return keyCompare !== 0 ? keyCompare : collate(x.value, y.value);
  }

  function sliceResults(results, limit, skip) {
    skip = skip || 0;
    if (typeof limit === 'number') {
      return results.slice(skip, limit + skip);
    } else if (skip > 0) {
      return results.slice(skip);
    }
    return results;
  }

  function rowToDocId(row) {
    const val = row.value;
    // Users can explicitly specify a joined doc _id, or it
    // defaults to the doc _id that emitted the key/value.
    const docId = (val && typeof val === 'object' && val._id) || row.id;
    return docId;
  }

  function readAttachmentsAsBlobOrBuffer(res) {
    for (const row of res.rows) {
      const atts = row.doc && row.doc._attachments;
      if (!atts) {
        continue;
      }
      for (const filename of Object.keys(atts)) {
        const att = atts[filename];
        atts[filename].data = b64ToBluffer(att.data, att.content_type);
      }
    }
  }

  function postprocessAttachments(opts) {
    return function (res) {
      if (opts.include_docs && opts.attachments && opts.binary) {
        readAttachmentsAsBlobOrBuffer(res);
      }
      return res;
    };
  }

  function addHttpParam(paramName, opts, params, asJson) {
    // add an http param from opts to params, optionally json-encoded
    let val = opts[paramName];
    if (typeof val !== 'undefined') {
      if (asJson) {
        val = encodeURIComponent(JSON.stringify(val));
      }
      params.push(paramName + '=' + val);
    }
  }

  function coerceInteger(integerCandidate) {
    if (typeof integerCandidate !== 'undefined') {
      const asNumber = Number(integerCandidate);
      // prevents e.g. '1foo' or '1.1' being coerced to 1
      if (!isNaN(asNumber) && asNumber === parseInt(integerCandidate, 10)) {
        return asNumber;
      } else {
        return integerCandidate;
      }
    }
  }

  function coerceOptions(opts) {
    opts.group_level = coerceInteger(opts.group_level);
    opts.limit = coerceInteger(opts.limit);
    opts.skip = coerceInteger(opts.skip);
    return opts;
  }

  function checkPositiveInteger(number) {
    if (number) {
      if (typeof number !== 'number') {
        return  new QueryParseError(`Invalid value for integer: "${number}"`);
      }
      if (number < 0) {
        return new QueryParseError(`Invalid value for positive integer: "${number}"`);
      }
    }
  }

  function checkQueryParseError(options, fun) {
    const startkeyName = options.descending ? 'endkey' : 'startkey';
    const endkeyName = options.descending ? 'startkey' : 'endkey';

    if (typeof options[startkeyName] !== 'undefined' &&
      typeof options[endkeyName] !== 'undefined' &&
      collate(options[startkeyName], options[endkeyName]) > 0) {
      throw new QueryParseError('No rows can match your key range, ' +
        'reverse your start_key and end_key or set {descending : true}');
    } else if (fun.reduce && options.reduce !== false) {
      if (options.include_docs) {
        throw new QueryParseError('{include_docs:true} is invalid for reduce');
      } else if (options.keys && options.keys.length > 1 &&
        !options.group && !options.group_level) {
        throw new QueryParseError('Multi-key fetches for reduce views must use ' +
          '{group: true}');
      }
    }
    for (const optionName of ['group_level', 'limit', 'skip']) {
      const error = checkPositiveInteger(options[optionName]);
      if (error) {
        throw error;
      }
    }
  }

  async function httpQuery(db, fun, opts) {
    // List of parameters to add to the PUT request
    let params = [];
    let body;
    let method = 'GET';
    let ok;

    // If opts.reduce exists and is defined, then add it to the list
    // of parameters.
    // If reduce=false then the results are that of only the map function
    // not the final result of map and reduce.
    addHttpParam('reduce', opts, params);
    addHttpParam('include_docs', opts, params);
    addHttpParam('attachments', opts, params);
    addHttpParam('limit', opts, params);
    addHttpParam('descending', opts, params);
    addHttpParam('group', opts, params);
    addHttpParam('group_level', opts, params);
    addHttpParam('skip', opts, params);
    addHttpParam('stale', opts, params);
    addHttpParam('conflicts', opts, params);
    addHttpParam('startkey', opts, params, true);
    addHttpParam('start_key', opts, params, true);
    addHttpParam('endkey', opts, params, true);
    addHttpParam('end_key', opts, params, true);
    addHttpParam('inclusive_end', opts, params);
    addHttpParam('key', opts, params, true);
    addHttpParam('update_seq', opts, params);

    // Format the list of parameters into a valid URI query string
    params = params.join('&');
    params = params === '' ? '' : '?' + params;

    // If keys are supplied, issue a POST to circumvent GET query string limits
    // see http://wiki.apache.org/couchdb/HTTP_view_API#Querying_Options
    if (typeof opts.keys !== 'undefined') {
      const MAX_URL_LENGTH = 2000;
      // according to http://stackoverflow.com/a/417184/680742,
      // the de facto URL length limit is 2000 characters

      const keysAsString = `keys=${encodeURIComponent(JSON.stringify(opts.keys))}`;
      if (keysAsString.length + params.length + 1 <= MAX_URL_LENGTH) {
        // If the keys are short enough, do a GET. we do this to work around
        // Safari not understanding 304s on POSTs (see pouchdb/pouchdb#1239)
        params += (params[0] === '?' ? '&' : '?') + keysAsString;
      } else {
        method = 'POST';
        if (typeof fun === 'string') {
          body = {keys: opts.keys};
        } else { // fun is {map : mapfun}, so append to this
          fun.keys = opts.keys;
        }
      }
    }

    // We are referencing a query defined in the design doc
    if (typeof fun === 'string') {
      const parts = parseViewName(fun);

      const response = await db.fetch('_design/' + parts[0] + '/_view/' + parts[1] + params, {
        headers: new h({'Content-Type': 'application/json'}),
        method,
        body: JSON.stringify(body)
      });
      ok = response.ok;
      // status = response.status;
      const result = await response.json();

      if (!ok) {
        result.status = response.status;
        throw generateErrorFromResponse(result);
      }

      // fail the entire request if the result contains an error
      for (const row of result.rows) {
        /* istanbul ignore if */
        if (row.value && row.value.error && row.value.error === "builtin_reduce_error") {
          throw new Error(row.reason);
        }
      }

      return new Promise(function (resolve) {
        resolve(result);
      }).then(postprocessAttachments(opts));
    }

    // We are using a temporary view, terrible for performance, good for testing
    body = body || {};
    for (const key of Object.keys(fun)) {
      if (Array.isArray(fun[key])) {
        body[key] = fun[key];
      } else {
        body[key] = fun[key].toString();
      }
    }

    const response = await db.fetch('_temp_view' + params, {
      headers: new h({'Content-Type': 'application/json'}),
      method: 'POST',
      body: JSON.stringify(body)
    });

    ok = response.ok;
    // status = response.status;
    const result = await response.json();
    if (!ok) {
      result.status = response.status;
      throw generateErrorFromResponse(result);
    }

    return new Promise(function (resolve) {
      resolve(result);
    }).then(postprocessAttachments(opts));
  }

  // custom adapters can define their own api._query
  // and override the default behavior
  /* istanbul ignore next */
  function customQuery(db, fun, opts) {
    return new Promise(function (resolve, reject) {
      db._query(fun, opts, function (err, res) {
        if (err) {
          return reject(err);
        }
        resolve(res);
      });
    });
  }

  // custom adapters can define their own api._viewCleanup
  // and override the default behavior
  /* istanbul ignore next */
  function customViewCleanup(db) {
    return new Promise(function (resolve, reject) {
      db._viewCleanup(function (err, res) {
        if (err) {
          return reject(err);
        }
        resolve(res);
      });
    });
  }

  function defaultsTo(value) {
    return function (reason) {
      /* istanbul ignore else */
      if (reason.status === 404) {
        return value;
      } else {
        throw reason;
      }
    };
  }

  // returns a promise for a list of docs to update, based on the input docId.
  // the order doesn't matter, because post-3.2.0, bulkDocs
  // is an atomic operation in all three adapters.
  async function getDocsToPersist(docId, view, docIdsToChangesAndEmits) {
    const metaDocId = '_local/doc_' + docId;
    const defaultMetaDoc = {_id: metaDocId, keys: []};
    const docData = docIdsToChangesAndEmits.get(docId);
    const indexableKeysToKeyValues = docData[0];
    const changes = docData[1];

    function getMetaDoc() {
      if (isGenOne(changes)) {
        // generation 1, so we can safely assume initial state
        // for performance reasons (avoids unnecessary GETs)
        return Promise.resolve(defaultMetaDoc);
      }
      return view.db.get(metaDocId).catch(defaultsTo(defaultMetaDoc));
    }

    function getKeyValueDocs(metaDoc) {
      if (!metaDoc.keys.length) {
        // no keys, no need for a lookup
        return Promise.resolve({rows: []});
      }
      return view.db.allDocs({
        keys: metaDoc.keys,
        include_docs: true
      });
    }

    function processKeyValueDocs(metaDoc, kvDocsRes) {
      const kvDocs = [];
      const oldKeys = new Set();

      for (const row of kvDocsRes.rows) {
        const doc = row.doc;
        if (!doc) { // deleted
          continue;
        }
        kvDocs.push(doc);
        oldKeys.add(doc._id);
        doc._deleted = !indexableKeysToKeyValues.has(doc._id);
        if (!doc._deleted) {
          const keyValue = indexableKeysToKeyValues.get(doc._id);
          if ('value' in keyValue) {
            doc.value = keyValue.value;
          }
        }
      }
      const newKeys = mapToKeysArray(indexableKeysToKeyValues);
      for (const key of newKeys) {
        if (!oldKeys.has(key)) {
          // new doc
          const kvDoc = {
            _id: key
          };
          const keyValue = indexableKeysToKeyValues.get(key);
          if ('value' in keyValue) {
            kvDoc.value = keyValue.value;
          }
          kvDocs.push(kvDoc);
        }
      }
      metaDoc.keys = uniq$1(newKeys.concat(metaDoc.keys));
      kvDocs.push(metaDoc);

      return kvDocs;
    }

    const metaDoc = await getMetaDoc();
    const keyValueDocs = await getKeyValueDocs(metaDoc);
    return processKeyValueDocs(metaDoc, keyValueDocs);
  }

  function updatePurgeSeq(view) {
    // with this approach, we just assume to have processed all missing purges and write the latest
    // purgeSeq into the _local/purgeSeq doc.
    return view.sourceDB.get('_local/purges').then(function (res) {
      const purgeSeq = res.purgeSeq;
      return view.db.get('_local/purgeSeq').then(function (res) {
        return res._rev;
      })
      .catch(defaultsTo(undefined))
      .then(function (rev$$1) {
        return view.db.put({
          _id: '_local/purgeSeq',
          _rev: rev$$1,
          purgeSeq,
        });
      });
    }).catch(function (err) {
      if (err.status !== 404) {
        throw err;
      }
    });
  }

  // updates all emitted key/value docs and metaDocs in the mrview database
  // for the given batch of documents from the source database
  function saveKeyValues(view, docIdsToChangesAndEmits, seq) {
    var seqDocId = '_local/lastSeq';
    return view.db.get(seqDocId)
      .catch(defaultsTo({_id: seqDocId, seq: 0}))
      .then(function (lastSeqDoc) {
        var docIds = mapToKeysArray(docIdsToChangesAndEmits);
        return Promise.all(docIds.map(function (docId) {
          return getDocsToPersist(docId, view, docIdsToChangesAndEmits);
        })).then(function (listOfDocsToPersist) {
          var docsToPersist = listOfDocsToPersist.flat();
          lastSeqDoc.seq = seq;
          docsToPersist.push(lastSeqDoc);
          // write all docs in a single operation, update the seq once
          return view.db.bulkDocs({docs : docsToPersist});
        })
          // TODO: this should be placed somewhere else, probably? we're querying both docs twice
          //   (first time when getting the actual purges).
          .then(() => updatePurgeSeq(view));
      });
  }

  function getQueue(view) {
    const viewName = typeof view === 'string' ? view : view.name;
    let queue = persistentQueues[viewName];
    if (!queue) {
      queue = persistentQueues[viewName] = new TaskQueue();
    }
    return queue;
  }

  async function updateView(view, opts) {
    return sequentialize(getQueue(view), function () {
      return updateViewInQueue(view, opts);
    })();
  }

  async function updateViewInQueue(view, opts) {
    // bind the emit function once
    let mapResults;
    let doc;
    let taskId;

    function emit(key, value) {
      const output = {id: doc._id, key: normalizeKey(key)};
      // Don't explicitly store the value unless it's defined and non-null.
      // This saves on storage space, because often people don't use it.
      if (typeof value !== 'undefined' && value !== null) {
        output.value = normalizeKey(value);
      }
      mapResults.push(output);
    }

    const mapFun = mapper(view.mapFun, emit);

    let currentSeq = view.seq || 0;

    function createTask() {
      return view.sourceDB.info().then(function (info) {
        taskId = view.sourceDB.activeTasks.add({
          name: 'view_indexing',
          total_items: info.update_seq - currentSeq,
        });
      });
    }

    function processChange(docIdsToChangesAndEmits, seq) {
      return function () {
        return saveKeyValues(view, docIdsToChangesAndEmits, seq);
      };
    }

    let indexed_docs = 0;
    const progress = {
      view: view.name,
      indexed_docs
    };
    view.sourceDB.emit('indexing', progress);

    const queue = new TaskQueue();

    async function processNextBatch() {
      const response = await view.sourceDB.changes({
        return_docs: true,
        conflicts: true,
        include_docs: true,
        style: 'all_docs',
        since: currentSeq,
        limit: opts.changes_batch_size
      });
      const purges = await getRecentPurges();
      return processBatch(response, purges);
    }

    function getRecentPurges() {
      return view.db.get('_local/purgeSeq').then(function (res) {
        return res.purgeSeq;
      })
      .catch(defaultsTo(-1))
      .then(function (purgeSeq) {
        return view.sourceDB.get('_local/purges').then(function (res) {
          const recentPurges = res.purges.filter(function (purge, index) {
            return index > purgeSeq;
          }).map((purge) => purge.docId);

          const uniquePurges = recentPurges.filter(function (docId, index) {
            return recentPurges.indexOf(docId) === index;
          });

          return Promise.all(uniquePurges.map(function (docId) {
            return view.sourceDB.get(docId).then(function (doc) {
              return { docId, doc };
            })
            .catch(defaultsTo({ docId }));
          }));
        })
        .catch(defaultsTo([]));
      });
    }

    function processBatch(response, purges) {
      const results = response.results;
      if (!results.length && !purges.length) {
        return;
      }

      for (const purge of purges) {
        const index = results.findIndex(function (change) {
          return change.id === purge.docId;
        });
        if (index < 0) {
          // mimic a db.remove() on the changes feed
          const entry = {
            _id: purge.docId,
            doc: {
              _id: purge.docId,
              _deleted: 1,
            },
            changes: [],
          };

          if (purge.doc) {
            // update with new winning rev after purge
            entry.doc = purge.doc;
            entry.changes.push({ rev: purge.doc._rev });
          }

          results.push(entry);
        }
      }

      const docIdsToChangesAndEmits = createDocIdsToChangesAndEmits(results);

      queue.add(processChange(docIdsToChangesAndEmits, currentSeq));

      indexed_docs = indexed_docs + results.length;
      const progress = {
        view: view.name,
        last_seq: response.last_seq,
        results_count: results.length,
        indexed_docs
      };
      view.sourceDB.emit('indexing', progress);
      view.sourceDB.activeTasks.update(taskId, {completed_items: indexed_docs});

      if (results.length < opts.changes_batch_size) {
        return;
      }
      return processNextBatch();
    }

    function createDocIdsToChangesAndEmits(results) {
      const docIdsToChangesAndEmits = new Map();
      for (const change of results) {
        if (change.doc._id[0] !== '_') {
          mapResults = [];
          doc = change.doc;

          if (!doc._deleted) {
            tryMap(view.sourceDB, mapFun, doc);
          }
          mapResults.sort(sortByKeyThenValue);

          const indexableKeysToKeyValues = createIndexableKeysToKeyValues(mapResults);
          docIdsToChangesAndEmits.set(change.doc._id, [
            indexableKeysToKeyValues,
            change.changes
          ]);
        }
        currentSeq = change.seq;
      }
      return docIdsToChangesAndEmits;
    }

    function createIndexableKeysToKeyValues(mapResults) {
      const indexableKeysToKeyValues = new Map();
      let lastKey;
      for (let i = 0, len = mapResults.length; i < len; i++) {
        const emittedKeyValue = mapResults[i];
        const complexKey = [emittedKeyValue.key, emittedKeyValue.id];
        if (i > 0 && collate(emittedKeyValue.key, lastKey) === 0) {
          complexKey.push(i); // dup key+id, so make it unique
        }
        indexableKeysToKeyValues.set(toIndexableString(complexKey), emittedKeyValue);
        lastKey = emittedKeyValue.key;
      }
      return indexableKeysToKeyValues;
    }

    try {
      await createTask();
      await processNextBatch();
      await queue.finish();
      view.seq = currentSeq;
      view.sourceDB.activeTasks.remove(taskId);
    } catch (error) {
      view.sourceDB.activeTasks.remove(taskId, error);
    }
  }

  function reduceView(view, results, options) {
    if (options.group_level === 0) {
      delete options.group_level;
    }

    const shouldGroup = options.group || options.group_level;
    const reduceFun = reducer(view.reduceFun);
    const groups = [];
    const lvl = isNaN(options.group_level)
      ? Number.POSITIVE_INFINITY
      : options.group_level;

    for (const result of results) {
      const last = groups[groups.length - 1];
      let groupKey = shouldGroup ? result.key : null;

      // only set group_level for array keys
      if (shouldGroup && Array.isArray(groupKey)) {
        groupKey = groupKey.slice(0, lvl);
      }

      if (last && collate(last.groupKey, groupKey) === 0) {
        last.keys.push([result.key, result.id]);
        last.values.push(result.value);
        continue;
      }
      groups.push({
        keys: [[result.key, result.id]],
        values: [result.value],
        groupKey
      });
    }

    results = [];
    for (const group of groups) {
      const reduceTry = tryReduce(view.sourceDB, reduceFun, group.keys, group.values, false);
      if (reduceTry.error && reduceTry.error instanceof BuiltInError) {
        // CouchDB returns an error if a built-in errors out
        throw reduceTry.error;
      }
      results.push({
        // CouchDB just sets the value to null if a non-built-in errors out
        value: reduceTry.error ? null : reduceTry.output,
        key: group.groupKey
      });
    }
    // no total_rows/offset when reducing
    return { rows: sliceResults(results, options.limit, options.skip) };
  }

  function queryView(view, opts) {
    return sequentialize(getQueue(view), function () {
      return queryViewInQueue(view, opts);
    })();
  }

  async function queryViewInQueue(view, opts) {
    let totalRows;
    const shouldReduce = view.reduceFun && opts.reduce !== false;
    const skip = opts.skip || 0;
    if (typeof opts.keys !== 'undefined' && !opts.keys.length) {
      // equivalent query
      opts.limit = 0;
      delete opts.keys;
    }

    async function fetchFromView(viewOpts) {
      viewOpts.include_docs = true;
      const res = await view.db.allDocs(viewOpts);
      totalRows = res.total_rows;

      return res.rows.map(function (result) {
        // implicit migration - in older versions of PouchDB,
        // we explicitly stored the doc as {id: ..., key: ..., value: ...}
        // this is tested in a migration test
        /* istanbul ignore next */
        if ('value' in result.doc && typeof result.doc.value === 'object' &&
          result.doc.value !== null) {
          const keys = Object.keys(result.doc.value).sort();
          // this detection method is not perfect, but it's unlikely the user
          // emitted a value which was an object with these 3 exact keys
          const expectedKeys = ['id', 'key', 'value'];
          if (!(keys < expectedKeys || keys > expectedKeys)) {
            return result.doc.value;
          }
        }

        const parsedKeyAndDocId = parseIndexableString(result.doc._id);
        return {
          key: parsedKeyAndDocId[0],
          id: parsedKeyAndDocId[1],
          value: ('value' in result.doc ? result.doc.value : null)
        };
      });
    }

    async function onMapResultsReady(rows) {
      let finalResults;
      if (shouldReduce) {
        finalResults = reduceView(view, rows, opts);
      } else if (typeof opts.keys === 'undefined') {
        finalResults = {
          total_rows: totalRows,
          offset: skip,
          rows
        };
      } else {
        // support limit, skip for keys query
        finalResults = {
          total_rows: totalRows,
          offset: skip,
          rows: sliceResults(rows,opts.limit,opts.skip)
        };
      }
      /* istanbul ignore if */
      if (opts.update_seq) {
        finalResults.update_seq = view.seq;
      }
      if (opts.include_docs) {
        const docIds = uniq$1(rows.map(rowToDocId));

        const allDocsRes = await view.sourceDB.allDocs({
          keys: docIds,
          include_docs: true,
          conflicts: opts.conflicts,
          attachments: opts.attachments,
          binary: opts.binary
        });
        const docIdsToDocs = new Map();
        for (const row of allDocsRes.rows) {
          docIdsToDocs.set(row.id, row.doc);
        }
        for (const row of rows) {
          const docId = rowToDocId(row);
          const doc = docIdsToDocs.get(docId);
          if (doc) {
            row.doc = doc;
          }
        }
      }
      return finalResults;
    }

    if (typeof opts.keys !== 'undefined') {
      const keys = opts.keys;
      const fetchPromises = keys.map(function (key) {
        const viewOpts = {
          startkey : toIndexableString([key]),
          endkey   : toIndexableString([key, {}])
        };
        /* istanbul ignore if */
        if (opts.update_seq) {
          viewOpts.update_seq = true;
        }
        return fetchFromView(viewOpts);
      });
      const result = await Promise.all(fetchPromises);
      const flattenedResult = result.flat();
      return onMapResultsReady(flattenedResult);
    } else { // normal query, no 'keys'
      const viewOpts = {
        descending : opts.descending
      };
      /* istanbul ignore if */
      if (opts.update_seq) {
        viewOpts.update_seq = true;
      }
      let startkey;
      let endkey;
      if ('start_key' in opts) {
        startkey = opts.start_key;
      }
      if ('startkey' in opts) {
        startkey = opts.startkey;
      }
      if ('end_key' in opts) {
        endkey = opts.end_key;
      }
      if ('endkey' in opts) {
        endkey = opts.endkey;
      }
      if (typeof startkey !== 'undefined') {
        viewOpts.startkey = opts.descending ?
          toIndexableString([startkey, {}]) :
          toIndexableString([startkey]);
      }
      if (typeof endkey !== 'undefined') {
        let inclusiveEnd = opts.inclusive_end !== false;
        if (opts.descending) {
          inclusiveEnd = !inclusiveEnd;
        }

        viewOpts.endkey = toIndexableString(
          inclusiveEnd ? [endkey, {}] : [endkey]);
      }
      if (typeof opts.key !== 'undefined') {
        const keyStart = toIndexableString([opts.key]);
        const keyEnd = toIndexableString([opts.key, {}]);
        if (viewOpts.descending) {
          viewOpts.endkey = keyStart;
          viewOpts.startkey = keyEnd;
        } else {
          viewOpts.startkey = keyStart;
          viewOpts.endkey = keyEnd;
        }
      }
      if (!shouldReduce) {
        if (typeof opts.limit === 'number') {
          viewOpts.limit = opts.limit;
        }
        viewOpts.skip = skip;
      }

      const result = await fetchFromView(viewOpts);
      return onMapResultsReady(result);
    }
  }

  async function httpViewCleanup(db) {
    const response = await db.fetch('_view_cleanup', {
      headers: new h({'Content-Type': 'application/json'}),
      method: 'POST'
    });
    return response.json();
  }

  async function localViewCleanup(db) {
    try {
      const metaDoc = await db.get('_local/' + localDocName);
      const docsToViews = new Map();

      for (const fullViewName of Object.keys(metaDoc.views)) {
        const parts = parseViewName(fullViewName);
        const designDocName = '_design/' + parts[0];
        const viewName = parts[1];
        let views = docsToViews.get(designDocName);
        if (!views) {
          views = new Set();
          docsToViews.set(designDocName, views);
        }
        views.add(viewName);
      }
      const opts = {
        keys : mapToKeysArray(docsToViews),
        include_docs : true
      };

      const res = await db.allDocs(opts);
      const viewsToStatus = {};
      for (const row of res.rows) {
        const ddocName = row.key.substring(8); // cuts off '_design/'
        for (const viewName of docsToViews.get(row.key)) {
          let fullViewName = ddocName + '/' + viewName;
          /* istanbul ignore if */
          if (!metaDoc.views[fullViewName]) {
            // new format, without slashes, to support PouchDB 2.2.0
            // migration test in pouchdb's browser.migration.js verifies this
            fullViewName = viewName;
          }
          const viewDBNames = Object.keys(metaDoc.views[fullViewName]);
          // design doc deleted, or view function nonexistent
          const statusIsGood = row.doc && row.doc.views &&
            row.doc.views[viewName];
          for (const viewDBName of viewDBNames) {
            viewsToStatus[viewDBName] = viewsToStatus[viewDBName] || statusIsGood;
          }
        }
      }

      const dbsToDelete = Object.keys(viewsToStatus)
        .filter(function (viewDBName) { return !viewsToStatus[viewDBName]; });

      const destroyPromises = dbsToDelete.map(function (viewDBName) {
        return sequentialize(getQueue(viewDBName), function () {
          return new db.constructor(viewDBName, db.__opts).destroy();
        })();
      });

      return Promise.all(destroyPromises).then(function () {
        return {ok: true};
      });
    } catch (err) {
      if (err.status === 404) {
        return {ok: true};
      } else {
        throw err;
      }
    }
  }

  async function queryPromised(db, fun, opts) {
    /* istanbul ignore next */
    if (typeof db._query === 'function') {
      return customQuery(db, fun, opts);
    }
    if (isRemote(db)) {
      return httpQuery(db, fun, opts);
    }

    const updateViewOpts = {
      changes_batch_size: db.__opts.view_update_changes_batch_size || CHANGES_BATCH_SIZE
    };

    if (typeof fun !== 'string') {
      // temp_view
      checkQueryParseError(opts, fun);

      tempViewQueue.add(async function () {
        const view = await createView(
          /* sourceDB */ db,
          /* viewName */ 'temp_view/temp_view',
          /* mapFun */ fun.map,
          /* reduceFun */ fun.reduce,
          /* temporary */ true,
          /* localDocName */ localDocName);

        return fin(updateView(view, updateViewOpts).then(
          function () { return queryView(view, opts); }),
          function () { return view.db.destroy(); }
        );
      });
      return tempViewQueue.finish();
    } else {
      // persistent view
      const fullViewName = fun;
      const parts = parseViewName(fullViewName);
      const designDocName = parts[0];
      const viewName = parts[1];

      const doc = await db.get('_design/' + designDocName);
      fun = doc.views && doc.views[viewName];

      if (!fun) {
        // basic validator; it's assumed that every subclass would want this
        throw new NotFoundError(`ddoc ${doc._id} has no view named ${viewName}`);
      }

      ddocValidator(doc, viewName);
      checkQueryParseError(opts, fun);

      const view = await createView(
        /* sourceDB */ db,
        /* viewName */ fullViewName,
        /* mapFun */ fun.map,
        /* reduceFun */ fun.reduce,
        /* temporary */ false,
        /* localDocName */ localDocName);

      if (opts.stale === 'ok' || opts.stale === 'update_after') {
        if (opts.stale === 'update_after') {
          nextTick(function () {
            updateView(view, updateViewOpts);
          });
        }
        return queryView(view, opts);
      } else { // stale not ok
        await updateView(view, updateViewOpts);
        return queryView(view, opts);
      }
    }
  }

  function abstractQuery(fun, opts, callback) {
    const db = this;
    if (typeof opts === 'function') {
      callback = opts;
      opts = {};
    }
    opts = opts ? coerceOptions(opts) : {};

    if (typeof fun === 'function') {
      fun = {map : fun};
    }

    const promise = Promise.resolve().then(function () {
      return queryPromised(db, fun, opts);
    });
    promisedCallback(promise, callback);
    return promise;
  }

  const abstractViewCleanup = callbackify(function () {
    const db = this;
    /* istanbul ignore next */
    if (typeof db._viewCleanup === 'function') {
      return customViewCleanup(db);
    }
    if (isRemote(db)) {
      return httpViewCleanup(db);
    }
    return localViewCleanup(db);
  });

  return {
    query: abstractQuery,
    viewCleanup: abstractViewCleanup
  };
}

//
// One thing about these mappers:
//
// Per the advice of John-David Dalton (http://youtu.be/NthmeLEhDDM),
// what you want to do in this case is optimize for the smallest possible
// function, since that's the thing that gets run over and over again.
//
// This code would be a lot simpler if all the if/elses were inside
// the function, but it would also be a lot less performant.
//

function getDeepValue(value, path) {
  for (const key of path) {
    value = value[key];
    if (value === undefined) {
      return undefined;
    }
  }
  return value;
}

function createDeepMultiMapper(fields, emit, selector) {
  return function (doc) {
    if (selector && !matchesSelector(doc, selector)) { return; }

    const toEmit = [];
    for (const field of fields) {
      const value = getDeepValue(doc, parseField(field));
      if (value === undefined) {
        return;
      }
      toEmit.push(value);
    }
    emit(toEmit);
  };
}

function createDeepSingleMapper(field, emit, selector) {
  const parsedField = parseField(field);
  return function (doc) {
    if (selector && !matchesSelector(doc, selector)) { return; }

    const value = getDeepValue(doc, parsedField);
    if (value !== undefined) {
      emit(value);
    }
  };
}

function createShallowSingleMapper(field, emit, selector) {
  return function (doc) {
    if (selector && !matchesSelector(doc, selector)) { return; }
    emit(doc[field]);
  };
}

function createShallowMultiMapper(fields, emit, selector) {
  return function (doc) {
    if (selector && !matchesSelector(doc, selector)) { return; }
    const toEmit = fields.map(field => doc[field]);
    emit(toEmit);
  };
}

function checkShallow(fields) {
  return fields.every((field) => field.indexOf('.') === -1);
}

function createMapper(fields, emit, selector) {
  const isShallow = checkShallow(fields);
  const isSingle = fields.length === 1;

  // notice we try to optimize for the most common case,
  // i.e. single shallow indexes
  if (isShallow) {
    if (isSingle) {
      return createShallowSingleMapper(fields[0], emit, selector);
    } else { // multi
      return createShallowMultiMapper(fields, emit, selector);
    }
  } else { // deep
    if (isSingle) {
      return createDeepSingleMapper(fields[0], emit, selector);
    } else { // multi
      return createDeepMultiMapper(fields, emit, selector);
    }
  }
}

function mapper(mapFunDef, emit) {
  // mapFunDef is a list of fields

  const fields = Object.keys(mapFunDef.fields);
  const partialSelector = mapFunDef.partial_filter_selector;

  return createMapper(fields, emit, partialSelector);
}

/* istanbul ignore next */
function reducer(/*reduceFunDef*/) {
  throw new Error('reduce not supported');
}

function ddocValidator(ddoc, viewName) {
  const view = ddoc.views[viewName];
  // This doesn't actually need to be here apparently, but
  // I feel safer keeping it.
  /* istanbul ignore if */
  if (!view.map || !view.map.fields) {
    throw new Error('ddoc ' + ddoc._id + ' with view ' + viewName +
      ' doesn\'t have map.fields defined. ' +
      'maybe it wasn\'t created by this plugin?');
  }
}

const abstractMapper = createAbstractMapReduce(
  /* localDocName */ 'indexes',
  mapper,
  reducer,
  ddocValidator
);

function abstractMapper$1 (db) {
  if (db._customFindAbstractMapper) {
    return {
      // Calls the _customFindAbstractMapper, but with a third argument:
      // the standard findAbstractMapper query/viewCleanup.
      // This allows the indexeddb adapter to support partial_filter_selector.
      query: function addQueryFallback(signature, opts) {
        const fallback = abstractMapper.query.bind(this);
        return db._customFindAbstractMapper.query.call(this, signature, opts, fallback);
      },
      viewCleanup: function addViewCleanupFallback() {
        const fallback = abstractMapper.viewCleanup.bind(this);
        return db._customFindAbstractMapper.viewCleanup.call(this, fallback);
      }
    };
  }
  return abstractMapper;
}

// normalize the "sort" value
function massageSort(sort) {
  if (!Array.isArray(sort)) {
    throw new Error('invalid sort json - should be an array');
  }
  return sort.map(function (sorting) {
    if (typeof sorting === 'string') {
      const obj = {};
      obj[sorting] = 'asc';
      return obj;
    } else {
      return sorting;
    }
  });
}

const ddocIdPrefix = /^_design\//;
function massageUseIndex(useIndex) {
  let cleanedUseIndex = [];
  if (typeof useIndex === 'string') {
    cleanedUseIndex.push(useIndex);
  } else {
    cleanedUseIndex = useIndex;
  }

  return cleanedUseIndex.map(function (name) {
    return name.replace(ddocIdPrefix, '');
  });
}

function massageIndexDef(indexDef) {
  indexDef.fields = indexDef.fields.map(function (field) {
    if (typeof field === 'string') {
      const obj = {};
      obj[field] = 'asc';
      return obj;
    }
    return field;
  });
  if (indexDef.partial_filter_selector) {
    indexDef.partial_filter_selector = massageSelector(
      indexDef.partial_filter_selector
    );
  }
  return indexDef;
}

function getKeyFromDoc(doc, index) {
  return index.def.fields.map((obj) => {
    const field = getKey(obj);
    return getFieldFromDoc(doc, parseField(field));
  });
}

// have to do this manually because REASONS. I don't know why
// CouchDB didn't implement inclusive_start
function filterInclusiveStart(rows, targetValue, index) {
  const indexFields = index.def.fields;
  let startAt = 0;
  for (const row of rows) {
    // shave off any docs at the beginning that are <= the
    // target value

    let docKey = getKeyFromDoc(row.doc, index);
    if (indexFields.length === 1) {
      docKey = docKey[0]; // only one field, not multi-field
    } else { // more than one field in index
      // in the case where e.g. the user is searching {$gt: {a: 1}}
      // but the index is [a, b], then we need to shorten the doc key
      while (docKey.length > targetValue.length) {
        docKey.pop();
      }
    }
    //ABS as we just looking for values that don't match
    if (Math.abs(collate(docKey, targetValue)) > 0) {
      // no need to filter any further; we're past the key
      break;
    }
    ++startAt;
  }
  return startAt > 0 ? rows.slice(startAt) : rows;
}

function reverseOptions(opts) {
  const newOpts = clone(opts);
  delete newOpts.startkey;
  delete newOpts.endkey;
  delete newOpts.inclusive_start;
  delete newOpts.inclusive_end;

  if ('endkey' in opts) {
    newOpts.startkey = opts.endkey;
  }
  if ('startkey' in opts) {
    newOpts.endkey = opts.startkey;
  }
  if ('inclusive_start' in opts) {
    newOpts.inclusive_end = opts.inclusive_start;
  }
  if ('inclusive_end' in opts) {
    newOpts.inclusive_start = opts.inclusive_end;
  }
  return newOpts;
}

function validateIndex(index) {
  const ascFields = index.fields.filter(function (field) {
    return getValue(field) === 'asc';
  });
  if (ascFields.length !== 0 && ascFields.length !== index.fields.length) {
    throw new Error('unsupported mixed sorting');
  }
}

function validateSort(requestDef, index) {
  if (index.defaultUsed && requestDef.sort) {
    const noneIdSorts = requestDef.sort.filter(function (sortItem) {
      return Object.keys(sortItem)[0] !== '_id';
    }).map(function (sortItem) {
      return Object.keys(sortItem)[0];
    });

    if (noneIdSorts.length > 0) {
      throw new Error('Cannot sort on field(s) "' + noneIdSorts.join(',') +
        '" when using the default index');
    }
  }

  if (index.defaultUsed) {
    return;
  }
}

function validateFindRequest(requestDef) {
  if (typeof requestDef.selector !== 'object') {
    throw new Error('you must provide a selector when you find()');
  }

  /*var selectors = requestDef.selector['$and'] || [requestDef.selector];
  for (var i = 0; i < selectors.length; i++) {
    var selector = selectors[i];
    var keys = Object.keys(selector);
    if (keys.length === 0) {
      throw new Error('invalid empty selector');
    }
    //var selection = selector[keys[0]];
    /*if (Object.keys(selection).length !== 1) {
      throw new Error('invalid selector: ' + JSON.stringify(selection) +
        ' - it must have exactly one key/value');
    }
  }*/
}

// determine the maximum number of fields
// we're going to need to query, e.g. if the user
// has selection ['a'] and sorting ['a', 'b'], then we
// need to use the longer of the two: ['a', 'b']
function getUserFields(selector, sort) {
  const selectorFields = Object.keys(selector);
  const sortFields = sort ? sort.map(getKey) : [];
  let userFields;
  if (selectorFields.length >= sortFields.length) {
    userFields = selectorFields;
  } else {
    userFields = sortFields;
  }

  if (sortFields.length === 0) {
    return {
      fields: userFields
    };
  }

  // sort according to the user's preferred sorting
  userFields = userFields.sort(function (left, right) {
    let leftIdx = sortFields.indexOf(left);
    if (leftIdx === -1) {
      leftIdx = Number.MAX_VALUE;
    }
    let rightIdx = sortFields.indexOf(right);
    if (rightIdx === -1) {
      rightIdx = Number.MAX_VALUE;
    }
    return leftIdx < rightIdx ? -1 : leftIdx > rightIdx ? 1 : 0;
  });

  return {
    fields: userFields,
    sortOrder: sort.map(getKey)
  };
}

async function createIndex$1(db, requestDef) {
  requestDef = massageCreateIndexRequest(requestDef);
  const originalIndexDef = clone(requestDef.index);
  requestDef.index = massageIndexDef(requestDef.index);

  validateIndex(requestDef.index);

  // calculating md5 is expensive - memoize and only
  // run if required
  let md5;
  function getMd5() {
    return md5 || (md5 = stringMd5(JSON.stringify(requestDef)));
  }

  const viewName = requestDef.name || ('idx-' + getMd5());

  const ddocName = requestDef.ddoc || ('idx-' + getMd5());
  const ddocId = '_design/' + ddocName;

  let hasInvalidLanguage = false;
  let viewExists = false;

  function updateDdoc(doc) {
    if (doc._rev && doc.language !== 'query') {
      hasInvalidLanguage = true;
    }
    doc.language = 'query';
    doc.views = doc.views || {};

    viewExists = !!doc.views[viewName];

    if (viewExists) {
      return false;
    }

    doc.views[viewName] = {
      map: {
        fields: mergeObjects(requestDef.index.fields),
        partial_filter_selector: requestDef.index.partial_filter_selector
      },
      reduce: '_count',
      options: {
        def: originalIndexDef
      }
    };

    return doc;
  }

  db.constructor.emit('debug', ['find', 'creating index', ddocId]);

  await upsert(db, ddocId, updateDdoc);

  if (hasInvalidLanguage) {
    throw new Error('invalid language for ddoc with id "' +
      ddocId +
      '" (should be "query")');
  }

  // kick off a build
  // TODO: abstract-pouchdb-mapreduce should support auto-updating
  // TODO: should also use update_after, but pouchdb/pouchdb#3415 blocks me
  const signature = ddocName + '/' + viewName;
  await abstractMapper$1(db).query.call(db, signature, {
    limit: 0,
    reduce: false
  });
  return {
    id: ddocId,
    name: viewName,
    result: viewExists ? 'exists' : 'created'
  };
}

async function getIndexes$1(db) {
  // just search through all the design docs and filter in-memory.
  // hopefully there aren't that many ddocs.
  const allDocsRes = await db.allDocs({
    startkey: '_design/',
    endkey: '_design/\uffff',
    include_docs: true
  });
  const res = {
    indexes: [{
      ddoc: null,
      name: '_all_docs',
      type: 'special',
      def: {
        fields: [{ _id: 'asc' }]
      }
    }]
  };

  res.indexes = flatten(res.indexes, allDocsRes.rows.filter(function (row) {
    return row.doc.language === 'query';
  }).map(function (row) {
    const viewNames = row.doc.views !== undefined ? Object.keys(row.doc.views) : [];

    return viewNames.map(function (viewName) {
      const view = row.doc.views[viewName];
      return {
        ddoc: row.id,
        name: viewName,
        type: 'json',
        def: massageIndexDef(view.options.def)
      };
    });
  }));

  // these are sorted by view name for some reason
  res.indexes.sort(function (left, right) {
    return compare(left.name, right.name);
  });
  res.total_rows = res.indexes.length;
  return res;
}

// couchdb lowest collation value
const COLLATE_LO = null;

// couchdb highest collation value (TODO: well not really, but close enough amirite)
const COLLATE_HI = { "\uffff": {} };

const SHORT_CIRCUIT_QUERY = {
  queryOpts: { limit: 0, startkey: COLLATE_HI, endkey: COLLATE_LO },
  inMemoryFields: [],
};

// couchdb second-lowest collation value

function checkFieldInIndex(index, field) {
  return index.def.fields
    .some((key) => getKey(key) === field);
}

// so when you do e.g. $eq/$eq, we can do it entirely in the database.
// but when you do e.g. $gt/$eq, the first part can be done
// in the database, but the second part has to be done in-memory,
// because $gt has forced us to lose precision.
// so that's what this determines
function userOperatorLosesPrecision(selector, field) {
  const matcher = selector[field];
  const userOperator = getKey(matcher);

  return userOperator !== '$eq';
}

// sort the user fields by their position in the index,
// if they're in the index
function sortFieldsByIndex(userFields, index) {
  const indexFields = index.def.fields.map(getKey);

  return userFields.slice().sort(function (a, b) {
    let aIdx = indexFields.indexOf(a);
    let bIdx = indexFields.indexOf(b);
    if (aIdx === -1) {
      aIdx = Number.MAX_VALUE;
    }
    if (bIdx === -1) {
      bIdx = Number.MAX_VALUE;
    }
    return compare(aIdx, bIdx);
  });
}

// first pass to try to find fields that will need to be sorted in-memory
function getBasicInMemoryFields(index, selector, userFields) {
  userFields = sortFieldsByIndex(userFields, index);

  // check if any of the user selectors lose precision
  let needToFilterInMemory = false;
  for (let i = 0, len = userFields.length; i < len; i++) {
    const field = userFields[i];
    if (needToFilterInMemory || !checkFieldInIndex(index, field)) {
      return userFields.slice(i);
    }
    if (i < len - 1 && userOperatorLosesPrecision(selector, field)) {
      needToFilterInMemory = true;
    }
  }
  return [];
}

function getInMemoryFieldsFromNe(selector) {
  const fields = [];
  for (const [field, matcher] of Object.entries(selector)) {
    for (const operator of Object.keys(matcher)) {
      if (operator === '$ne') {
        fields.push(field);
      }
    }
  }
  return fields;
}

function getInMemoryFields(coreInMemoryFields, index, selector, userFields) {
  const result = flatten(
    // in-memory fields reported as necessary by the query planner
    coreInMemoryFields,
    // combine with another pass that checks for any we may have missed
    getBasicInMemoryFields(index, selector, userFields),
    // combine with another pass that checks for $ne's
    getInMemoryFieldsFromNe(selector)
  );

  return sortFieldsByIndex(uniq(result), index);
}

// check that at least one field in the user's query is represented
// in the index. order matters in the case of sorts
function checkIndexFieldsMatch(indexFields, sortOrder, fields) {
  if (sortOrder) {
    // array has to be a strict subarray of index array. furthermore,
    // the sortOrder fields need to all be represented in the index
    const sortMatches = oneArrayIsStrictSubArrayOfOther(sortOrder, indexFields);
    const selectorMatches = oneArrayIsSubArrayOfOther(fields, indexFields);

    return sortMatches && selectorMatches;
  }

  // all of the user's specified fields still need to be
  // on the left side of the index array, although the order
  // doesn't matter
  return oneSetIsSubArrayOfOther(fields, indexFields);
}

const logicalMatchers = ['$eq', '$gt', '$gte', '$lt', '$lte'];
function isNonLogicalMatcher(matcher) {
  return logicalMatchers.indexOf(matcher) === -1;
}

// check all the index fields for usages of '$ne'
// e.g. if the user queries {foo: {$ne: 'foo'}, bar: {$eq: 'bar'}},
// then we can neither use an index on ['foo'] nor an index on
// ['foo', 'bar'], but we can use an index on ['bar'] or ['bar', 'foo']
function checkFieldsLogicallySound(indexFields, selector) {
  const firstField = indexFields[0];
  const matcher = selector[firstField];

  if (typeof matcher === 'undefined') {
    /* istanbul ignore next */
    return true;
  }

  const isInvalidNe = Object.keys(matcher).length === 1 &&
    getKey(matcher) === '$ne';

  return !isInvalidNe;
}

function checkIndexMatches(index, sortOrder, fields, selector) {
  const indexFields = index.def.fields.map(getKey);
  const fieldsMatch = checkIndexFieldsMatch(indexFields, sortOrder, fields);

  if (!fieldsMatch) {
    return false;
  }

  return checkFieldsLogicallySound(indexFields, selector);
}

//
// the algorithm is very simple:
// take all the fields the user supplies, and if those fields
// are a strict subset of the fields in some index,
// then use that index
//
function findMatchingIndexes(selector, userFields, sortOrder, indexes) {
  return indexes.filter(function (index) {
    return checkIndexMatches(index, sortOrder, userFields, selector);
  });
}

// find the best index, i.e. the one that matches the most fields
// in the user's query
function findBestMatchingIndex(selector, userFields, sortOrder, indexes, useIndex) {
  const matchingIndexes = findMatchingIndexes(selector, userFields, sortOrder, indexes);

  if (matchingIndexes.length === 0) {
    if (useIndex) {
      throw {
        error: "no_usable_index",
        message: "There is no index available for this selector."
      };
    }
    // return `all_docs` as a default index;
    // I'm assuming that _all_docs is always first
    const defaultIndex = indexes[0];
    defaultIndex.defaultUsed = true;
    return defaultIndex;
  }
  if (matchingIndexes.length === 1 && !useIndex) {
    return matchingIndexes[0];
  }

  const userFieldsMap = arrayToObject(userFields);

  function scoreIndex(index) {
    const indexFields = index.def.fields.map(getKey);
    let score = 0;
    for (const indexField of indexFields) {
      if (userFieldsMap[indexField]) {
        score++;
      }
    }
    return score;
  }

  if (useIndex) {
    const useIndexDdoc = '_design/' + useIndex[0];
    const useIndexName = useIndex.length === 2 ? useIndex[1] : false;
    const index = matchingIndexes.find(function (index) {
      if (useIndexName && index.ddoc === useIndexDdoc && useIndexName === index.name) {
        return true;
      }

      if (index.ddoc === useIndexDdoc) {
        /* istanbul ignore next */
        return true;
      }

      return false;
    });

    if (!index) {
      throw {
        error: "unknown_error",
        message: "Could not find that index or could not use that index for the query"
      };
    }
    return index;
  }

  return max(matchingIndexes, scoreIndex);
}

function getSingleFieldQueryOptsFor(userOperator, userValue) {
  switch (userOperator) {
    case '$eq':
      return { key: userValue };
    case '$lte':
      return { endkey: userValue };
    case '$gte':
      return { startkey: userValue };
    case '$lt':
      return {
        endkey: userValue,
        inclusive_end: false
      };
    case '$gt':
      return {
        startkey: userValue,
        inclusive_start: false
      };
  }

  return {
    startkey: COLLATE_LO
  };
}

function getSingleFieldCoreQueryPlan(selector, index) {
  const field = getKey(index.def.fields[0]);
  //ignoring this because the test to exercise the branch is skipped at the moment
  /* istanbul ignore next */
  const matcher = selector[field] || {};
  const inMemoryFields = [];
  const userOperators = Object.keys(matcher);

  let combinedOpts;

  for (const userOperator of userOperators) {
    if (isNonLogicalMatcher(userOperator)) {
      inMemoryFields.push(field);
    }

    const userValue = matcher[userOperator];
    const newQueryOpts = getSingleFieldQueryOptsFor(userOperator, userValue);

    if (combinedOpts) {
      combinedOpts = mergeObjects([combinedOpts, newQueryOpts]);
    } else {
      combinedOpts = newQueryOpts;
    }
  }

  return {
    queryOpts: combinedOpts,
    inMemoryFields
  };
}

function getMultiFieldCoreQueryPlan(userOperator, userValue) {
  switch (userOperator) {
    case '$eq':
      return {
        startkey: userValue,
        endkey: userValue
      };
    case '$lte':
      return {
        endkey: userValue
      };
    case '$gte':
      return {
        startkey: userValue
      };
    case '$lt':
      return {
        endkey: userValue,
        inclusive_end: false
      };
    case '$gt':
      return {
        startkey: userValue,
        inclusive_start: false
      };
  }
}

function getMultiFieldQueryOpts(selector, index) {
  const indexFields = index.def.fields.map(getKey);

  let inMemoryFields = [];
  const startkey = [];
  const endkey = [];
  let inclusiveStart;
  let inclusiveEnd;

  function finish(i) {

    if (inclusiveStart !== false) {
      startkey.push(COLLATE_LO);
    }
    if (inclusiveEnd !== false) {
      endkey.push(COLLATE_HI);
    }
    // keep track of the fields where we lost specificity,
    // and therefore need to filter in-memory
    inMemoryFields = indexFields.slice(i);
  }

  for (let i = 0, len = indexFields.length; i < len; i++) {
    const indexField = indexFields[i];
    const matcher = selector[indexField];

    if (!matcher || !Object.keys(matcher).length) { // fewer fields in user query than in index
      finish(i);
      break;
    } else if (Object.keys(matcher).some(isNonLogicalMatcher)) { // non-logical are ignored
      finish(i);
      break;
    } else if (i > 0) {
      const usingGtlt = (
        '$gt' in matcher || '$gte' in matcher ||
        '$lt' in matcher || '$lte' in matcher);
      const previousKeys = Object.keys(selector[indexFields[i - 1]]);
      const previousWasEq = arrayEquals(previousKeys, ['$eq']);
      const previousWasSame = arrayEquals(previousKeys, Object.keys(matcher));
      const gtltLostSpecificity = usingGtlt && !previousWasEq && !previousWasSame;
      if (gtltLostSpecificity) {
        finish(i);
        break;
      }
    }

    const userOperators = Object.keys(matcher);
    let combinedOpts = null;

    for (const userOperator of userOperators) {
      const userValue = matcher[userOperator];
      const newOpts = getMultiFieldCoreQueryPlan(userOperator, userValue);

      if (combinedOpts) {
        combinedOpts = mergeObjects([combinedOpts, newOpts]);
      } else {
        combinedOpts = newOpts;
      }
    }

    startkey.push('startkey' in combinedOpts ? combinedOpts.startkey : COLLATE_LO);
    endkey.push('endkey' in combinedOpts ? combinedOpts.endkey : COLLATE_HI);
    if ('inclusive_start' in combinedOpts) {
      inclusiveStart = combinedOpts.inclusive_start;
    }
    if ('inclusive_end' in combinedOpts) {
      inclusiveEnd = combinedOpts.inclusive_end;
    }
  }

  const res = {
    startkey,
    endkey
  };

  if (typeof inclusiveStart !== 'undefined') {
    res.inclusive_start = inclusiveStart;
  }
  if (typeof inclusiveEnd !== 'undefined') {
    res.inclusive_end = inclusiveEnd;
  }

  return {
    queryOpts: res,
    inMemoryFields
  };
}

function shouldShortCircuit(selector) {
  // We have a field to select from, but not a valid value
  // this should result in a short circuited query
  // just like the http adapter (couchdb) and mongodb
  // see tests for issue #7810

  // @todo Use 'Object.values' when Node.js v6 support is dropped.
  const values = Object.keys(selector).map(function (key) {
    return selector[key];
  });
  return values.some(function (val) {
    return typeof val === 'object' && Object.keys(val).length === 0;
  });
}

function getDefaultQueryPlan(selector) {
  //using default index, so all fields need to be done in memory
  return {
    queryOpts: { startkey: null },
    inMemoryFields: [Object.keys(selector)]
  };
}

function getCoreQueryPlan(selector, index) {
  if (index.defaultUsed) {
    return getDefaultQueryPlan(selector, index);
  }

  if (index.def.fields.length === 1) {
    // one field in index, so the value was indexed as a singleton
    return getSingleFieldCoreQueryPlan(selector, index);
  }
  // else index has multiple fields, so the value was indexed as an array
  return getMultiFieldQueryOpts(selector, index);
}

function planQuery(request, indexes) {
  const selector = request.selector;
  const sort = request.sort;

  if (shouldShortCircuit(selector)) {
    return Object.assign({}, SHORT_CIRCUIT_QUERY, { index: indexes[0] });
  }

  const userFieldsRes = getUserFields(selector, sort);

  const userFields = userFieldsRes.fields;
  const sortOrder = userFieldsRes.sortOrder;
  const index = findBestMatchingIndex(selector, userFields, sortOrder, indexes, request.use_index);

  const coreQueryPlan = getCoreQueryPlan(selector, index);
  const queryOpts = coreQueryPlan.queryOpts;
  const coreInMemoryFields = coreQueryPlan.inMemoryFields;

  const inMemoryFields = getInMemoryFields(coreInMemoryFields, index, selector, userFields);

  return {
    queryOpts,
    index,
    inMemoryFields
  };
}

function indexToSignature(index) {
  // remove '_design/'
  return index.ddoc.substring(8) + '/' + index.name;
}

async function doAllDocs(db, originalOpts) {
  const opts = clone(originalOpts);

  // CouchDB responds in weird ways when you provide a non-string to _id;
  // we mimic the behavior for consistency. See issue66 tests for details.
  if (opts.descending) {
    if ('endkey' in opts && typeof opts.endkey !== 'string') {
      opts.endkey = '';
    }
    if ('startkey' in opts && typeof opts.startkey !== 'string') {
      opts.limit = 0;
    }
  } else {
    if ('startkey' in opts && typeof opts.startkey !== 'string') {
      opts.startkey = '';
    }
    if ('endkey' in opts && typeof opts.endkey !== 'string') {
      opts.limit = 0;
    }
  }
  if ('key' in opts && typeof opts.key !== 'string') {
    opts.limit = 0;
  }

  if (opts.limit > 0 && opts.indexes_count) {
    // brute force and quite naive impl.
    // amp up the limit with the amount of (indexes) design docs
    // or is this too naive? How about skip?
    opts.original_limit = opts.limit;
    opts.limit += opts.indexes_count;
  }

  const res = await db.allDocs(opts);
  // filter out any design docs that _all_docs might return
  res.rows = res.rows.filter(function (row) {
    return !/^_design\//.test(row.id);
  });
  // put back original limit
  if (opts.original_limit) {
    opts.limit = opts.original_limit;
  }
  // enforce the rows to respect the given limit
  res.rows = res.rows.slice(0, opts.limit);
  return res;
}

async function queryAllOrIndex(db, opts, indexToUse) {
  if (indexToUse.name === '_all_docs') {
    return doAllDocs(db, opts);
  }
  return abstractMapper$1(db).query.call(db, indexToSignature(indexToUse), opts);
}

async function find$1(db, requestDef, explain) {
  if (requestDef.selector) {
    // must be validated before massaging
    validateSelector(requestDef.selector, false);
    requestDef.selector = massageSelector(requestDef.selector);
  }

  if (requestDef.sort) {
    requestDef.sort = massageSort(requestDef.sort);
  }

  if (requestDef.use_index) {
    requestDef.use_index = massageUseIndex(requestDef.use_index);
  }

  if (!('limit' in requestDef)) {
    // Match the default limit of CouchDB
    requestDef.limit = 25;
  }

  validateFindRequest(requestDef);

  const getIndexesRes = await getIndexes$1(db);

  db.constructor.emit('debug', ['find', 'planning query', requestDef]);
  const queryPlan = planQuery(requestDef, getIndexesRes.indexes);
  db.constructor.emit('debug', ['find', 'query plan', queryPlan]);

  const indexToUse = queryPlan.index;

  validateSort(requestDef, indexToUse);

  let opts = Object.assign({
    include_docs: true,
    reduce: false,
    // Add amount of index for doAllDocs to use (related to issue #7810)
    indexes_count: getIndexesRes.total_rows,
  }, queryPlan.queryOpts);

  if ('startkey' in opts && 'endkey' in opts &&
    collate(opts.startkey, opts.endkey) > 0) {
    // can't possibly return any results, startkey > endkey
    /* istanbul ignore next */
    return { docs: [] };
  }

  const isDescending = requestDef.sort &&
    typeof requestDef.sort[0] !== 'string' &&
    getValue(requestDef.sort[0]) === 'desc';

  if (isDescending) {
    // either all descending or all ascending
    opts.descending = true;
    opts = reverseOptions(opts);
  }

  if (!queryPlan.inMemoryFields.length) {
    // no in-memory filtering necessary, so we can let the
    // database do the limit/skip for us
    opts.limit = requestDef.limit;
    if ('skip' in requestDef) {
      opts.skip = requestDef.skip;
    }
  }

  if (explain) {
    return Promise.resolve(queryPlan, opts);
  }

  const res = await queryAllOrIndex(db, opts, indexToUse);


  if (opts.inclusive_start === false) {
    // may have to manually filter the first one,
    // since couchdb has no true inclusive_start option
    res.rows = filterInclusiveStart(res.rows, opts.startkey, indexToUse);
  }

  if (queryPlan.inMemoryFields.length) {
    // need to filter some stuff in-memory
    res.rows = filterInMemoryFields(res.rows, requestDef, queryPlan.inMemoryFields);
  }

  const resp = {
    docs: res.rows.map(function (row) {
      const doc = row.doc;
      if (requestDef.fields) {
        return pick$1(doc, requestDef.fields);
      }
      return doc;
    })
  };

  if (indexToUse.defaultUsed) {
    resp.warning = 'No matching index found, create an index to optimize query time.';
  }

  return resp;
}

async function explain$1(db, requestDef) {
  const queryPlan = await find$1(db, requestDef, true);

  return {
    dbname: db.name,
    index: queryPlan.index,
    selector: requestDef.selector,
    range: {
      start_key: queryPlan.queryOpts.startkey,
      end_key: queryPlan.queryOpts.endkey,
    },
    opts: {
      use_index: requestDef.use_index || [],
      bookmark: "nil", //hardcoded to match CouchDB since its not supported,
      limit: requestDef.limit,
      skip: requestDef.skip,
      sort: requestDef.sort || {},
      fields: requestDef.fields,
      conflicts: false, //hardcoded to match CouchDB since its not supported,
      r: [49], // hardcoded to match CouchDB since its not support
    },
    limit: requestDef.limit,
    skip: requestDef.skip || 0,
    fields: requestDef.fields,
  };
}

async function deleteIndex$1(db, index) {

  if (!index.ddoc) {
    throw new Error('you must supply an index.ddoc when deleting');
  }

  if (!index.name) {
    throw new Error('you must supply an index.name when deleting');
  }

  const docId = index.ddoc;
  const viewName = index.name;

  function deltaFun(doc) {
    if (Object.keys(doc.views).length === 1 && doc.views[viewName]) {
      // only one view in this ddoc, delete the whole ddoc
      return {_id: docId, _deleted: true};
    }
    // more than one view here, just remove the view
    delete doc.views[viewName];
    return doc;
  }

  await upsert(db, docId, deltaFun);
  await abstractMapper$1(db).viewCleanup.apply(db);
  return { ok: true };
}

const plugin = {};
plugin.createIndex = resolveToCallback(async function (requestDef) {
  if (typeof requestDef !== 'object') {
    throw new Error('you must provide an index to create');
  }

  const createIndex$$1 = isRemote(this) ?
    createIndex : createIndex$1;
  return createIndex$$1(this, requestDef);
});

plugin.find = resolveToCallback(async function (requestDef) {
  if (typeof requestDef !== 'object') {
    throw new Error('you must provide search parameters to find()');
  }

  const find$$1 = isRemote(this) ? find : find$1;
  return find$$1(this, requestDef);
});

plugin.explain = resolveToCallback(async function (requestDef) {
  if (typeof requestDef !== 'object') {
    throw new Error('you must provide search parameters to explain()');
  }

  const find$$1 = isRemote(this) ? explain : explain$1;
  return find$$1(this, requestDef);
});

plugin.getIndexes = resolveToCallback(async function () {
  const getIndexes$$1 = isRemote(this) ? getIndexes : getIndexes$1;
  return getIndexes$$1(this);
});

plugin.deleteIndex = resolveToCallback(async function (indexDef) {
  if (typeof indexDef !== 'object') {
    throw new Error('you must provide an index to delete');
  }

  const deleteIndex$$1 = isRemote(this) ?
    deleteIndex : deleteIndex$1;
  return deleteIndex$$1(this, indexDef);
});

// this code only runs in the browser, as its own dist/ script

if (typeof PouchDB === 'undefined') {
  guardedConsole('error', 'pouchdb-find plugin error: ' +
    'Cannot find global "PouchDB" object! ' +
    'Did you remember to include pouchdb.js?');
} else {
  PouchDB.plugin(plugin);
}

},{"events":1,"spark-md5":2,"uuid":3}]},{},[18]);