pouchdb/dist/pouchdb.indexeddb.js

// PouchDB indexeddb plugin 9.0.0
(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; }

var EventEmitter = _interopDefault(_dereq_('events'));
var uuid = _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()
function pick(obj, arr) {
  var res = {};
  for (var i = 0, len = arr.length; i < len; i++) {
    var prop = arr[i];
    if (prop in obj) {
      res[prop] = obj[prop];
    }
  }
  return res;
}

var hasLocal;

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

function hasLocalStorage() {
  return hasLocal;
}

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

class Changes extends EventEmitter {
  constructor() {
    super();

    this._listeners = {};

    if (hasLocalStorage()) {
      addEventListener("storage", (e) => {
        this.emit(e.key);
      });
    }
  }

  addListener(dbName, id, db, opts) {
    if (this._listeners[id]) {
      return;
    }
    var inprogress = false;
    var self = this;
    function eventFunction() {
      if (!self._listeners[id]) {
        return;
      }
      if (inprogress) {
        inprogress = 'waiting';
        return;
      }
      inprogress = true;
      var changesOpts = pick(opts, [
        'style', 'include_docs', 'attachments', 'conflicts', 'filter',
        'doc_ids', 'view', 'since', 'query_params', 'binary', 'return_docs'
      ]);

      function onError() {
        inprogress = false;
      }

      db.changes(changesOpts).on('change', function (c) {
        if (c.seq > opts.since && !opts.cancelled) {
          opts.since = c.seq;
          opts.onChange(c);
        }
      }).on('complete', function () {
        if (inprogress === 'waiting') {
          nextTick(eventFunction);
        }
        inprogress = false;
      }).on('error', onError);
    }
    this._listeners[id] = eventFunction;
    this.on(dbName, eventFunction);
  }

  removeListener(dbName, id) {
    if (!(id in this._listeners)) {
      return;
    }
    super.removeListener(dbName, this._listeners[id]);
    delete this._listeners[id];
  }

  notifyLocalWindows(dbName) {
    //do a useless change on a storage thing
    //in order to get other windows's listeners to activate
    if (hasLocalStorage()) {
      localStorage[dbName] = (localStorage[dbName] === "a") ? "b" : "a";
    }
  }

  notify(dbName) {
    this.emit(dbName);
    this.notifyLocalWindows(dbName);
  }
}

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 tryFilter(filter, doc, req) {
  try {
    return !filter(doc, req);
  } catch (err) {
    var msg = 'Filter function threw: ' + err.toString();
    return createError(BAD_REQUEST, msg);
  }
}

function filterChange(opts) {
  var req = {};
  var hasFilter = opts.filter && typeof opts.filter === 'function';
  req.query = opts.query_params;

  return function filter(change) {
    if (!change.doc) {
      // CSG sends events on the changes feed that don't have documents,
      // this hack makes a whole lot of existing code robust.
      change.doc = {};
    }

    var filterReturn = hasFilter && tryFilter(opts.filter, change.doc, req);

    if (typeof filterReturn === 'object') {
      return filterReturn;
    }

    if (filterReturn) {
      return false;
    }

    if (!opts.include_docs) {
      delete change.doc;
    } else if (!opts.attachments) {
      for (var att in change.doc._attachments) {
        /* istanbul ignore else */
        if (Object.prototype.hasOwnProperty.call(change.doc._attachments, att)) {
          change.doc._attachments[att].stub = true;
        }
      }
    }
    return true;
  };
}

// shim for Function.prototype.name,

// Determine id an ID is valid
//   - invalid IDs begin with an underescore that does not begin '_design' or
//     '_local'
//   - any other string value is a valid id
// Returns the specific error object for each case
function invalidIdError(id) {
  var err;
  if (!id) {
    err = createError(MISSING_ID);
  } else if (typeof id !== 'string') {
    err = createError(INVALID_ID);
  } else if (/^_/.test(id) && !(/^_(design|local)/).test(id)) {
    err = createError(RESERVED_ID);
  }
  if (err) {
    throw err;
  }
}

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

// originally parseUri 1.2.2, now patched by us

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

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

var thisBtoa = function (str) {
  return btoa(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
//http://stackoverflow.com/questions/6965107/ (continues on next line)
//converting-between-strings-and-arraybuffers
function arrayBufferToBinaryString(buffer) {
  var binary = '';
  var bytes = new Uint8Array(buffer);
  var length = bytes.byteLength;
  for (var i = 0; i < length; i++) {
    binary += String.fromCharCode(bytes[i]);
  }
  return binary;
}

// shim for browsers that don't support it
function readAsBinaryString(blob, callback) {
  var reader = new FileReader();
  var hasBinaryString = typeof reader.readAsBinaryString === 'function';
  reader.onloadend = function (e) {
    var result = e.target.result || '';
    if (hasBinaryString) {
      return callback(result);
    }
    callback(arrayBufferToBinaryString(result));
  };
  if (hasBinaryString) {
    reader.readAsBinaryString(blob);
  } else {
    reader.readAsArrayBuffer(blob);
  }
}

function blobToBinaryString(blobOrBuffer, callback) {
  readAsBinaryString(blobOrBuffer, function (bin) {
    callback(bin);
  });
}

function blobToBase64(blobOrBuffer, callback) {
  blobToBinaryString(blobOrBuffer, function (base64) {
    callback(thisBtoa(base64));
  });
}

// simplified API. universal browser support is assumed
function readAsArrayBuffer(blob, callback) {
  var reader = new FileReader();
  reader.onloadend = function (e) {
    var result = e.target.result || new ArrayBuffer(0);
    callback(result);
  };
  reader.readAsArrayBuffer(blob);
}

// this is not used in the browser

var setImmediateShim = self.setImmediate || self.setTimeout;
var MD5_CHUNK_SIZE = 32768;

function rawToBase64(raw) {
  return thisBtoa(raw);
}

function appendBlob(buffer, blob, start, end, callback) {
  if (start > 0 || end < blob.size) {
    // only slice blob if we really need to
    blob = blob.slice(start, end);
  }
  readAsArrayBuffer(blob, function (arrayBuffer) {
    buffer.append(arrayBuffer);
    callback();
  });
}

function appendString(buffer, string, start, end, callback) {
  if (start > 0 || end < string.length) {
    // only create a substring if we really need to
    string = string.substring(start, end);
  }
  buffer.appendBinary(string);
  callback();
}

function binaryMd5(data, callback) {
  var inputIsString = typeof data === 'string';
  var len = inputIsString ? data.length : data.size;
  var chunkSize = Math.min(MD5_CHUNK_SIZE, len);
  var chunks = Math.ceil(len / chunkSize);
  var currentChunk = 0;
  var buffer = inputIsString ? new Md5() : new Md5.ArrayBuffer();

  var append = inputIsString ? appendString : appendBlob;

  function next() {
    setImmediateShim(loadNextChunk);
  }

  function done() {
    var raw = buffer.end(true);
    var base64 = rawToBase64(raw);
    callback(base64);
    buffer.destroy();
  }

  function loadNextChunk() {
    var start = currentChunk * chunkSize;
    var end = start + chunkSize;
    currentChunk++;
    if (currentChunk < chunks) {
      append(buffer, data, start, end, next);
    } else {
      append(buffer, data, start, end, done);
    }
  }
  loadNextChunk();
}

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

/**
 * Creates a new revision string that does NOT include the revision height
 * For example '56649f1b0506c6ca9fda0746eb0cacdf'
 */
function rev(doc, deterministic_revs) {
  if (!deterministic_revs) {
    return uuid.v4().replace(/-/g, '').toLowerCase();
  }

  var mutateableDoc = Object.assign({}, doc);
  delete mutateableDoc._rev_tree;
  return stringMd5(JSON.stringify(mutateableDoc));
}

var uuid$1 = uuid.v4; // mimic old import, only v4 is ever used elsewhere

//
// Blobs are not supported in all versions of IndexedDB, notably
// Chrome <37, Android <5 and (some?) webkit-based browsers.
// In those versions, storing a blob will throw.
//
// Example Webkit error:
// > DataCloneError: Failed to store record in an IDBObjectStore: BlobURLs are not yet supported.
//
// Various other blob bugs exist in Chrome v37-42 (inclusive).
// Detecting them is expensive and confusing to users, and Chrome 37-42
// is at very low usage worldwide, so we do a hacky userAgent check instead.
//
// content-type bug: https://code.google.com/p/chromium/issues/detail?id=408120
// 404 bug: https://code.google.com/p/chromium/issues/detail?id=447916
// FileReader bug: https://code.google.com/p/chromium/issues/detail?id=447836
//
function checkBlobSupport(txn, store, docIdOrCreateDoc) {
  return new Promise(function (resolve) {
    var blob$$1 = createBlob(['']);

    let req;
    if (typeof docIdOrCreateDoc === 'function') {
      // Store may require a specific key path, in which case we can't store the
      // blob directly in the store.
      const createDoc = docIdOrCreateDoc;
      const doc = createDoc(blob$$1);
      req = txn.objectStore(store).put(doc);
    } else {
      const docId = docIdOrCreateDoc;
      req = txn.objectStore(store).put(blob$$1, docId);
    }

    req.onsuccess = function () {
      var matchedChrome = navigator.userAgent.match(/Chrome\/(\d+)/);
      var matchedEdge = navigator.userAgent.match(/Edge\//);
      // MS Edge pretends to be Chrome 42:
      // https://msdn.microsoft.com/en-us/library/hh869301%28v=vs.85%29.aspx
      resolve(matchedEdge || !matchedChrome ||
        parseInt(matchedChrome[1], 10) >= 43);
    };

    req.onerror = txn.onabort = function (e) {
      // If the transaction aborts now its due to not being able to
      // write to the database, likely due to the disk being full
      e.preventDefault();
      e.stopPropagation();
      resolve(false);
    };
  }).catch(function () {
    return false; // error, so assume unsupported
  });
}

function toObject(array) {
  return array.reduce(function (obj, item) {
    obj[item] = true;
    return obj;
  }, {});
}
// List of top level reserved words for doc
var reservedWords = toObject([
  '_id',
  '_rev',
  '_access',
  '_attachments',
  '_deleted',
  '_revisions',
  '_revs_info',
  '_conflicts',
  '_deleted_conflicts',
  '_local_seq',
  '_rev_tree',
  // replication documents
  '_replication_id',
  '_replication_state',
  '_replication_state_time',
  '_replication_state_reason',
  '_replication_stats',
  // Specific to Couchbase Sync Gateway
  '_removed'
]);

// List of reserved words that should end up in the document
var dataWords = toObject([
  '_access',
  '_attachments',
  // replication documents
  '_replication_id',
  '_replication_state',
  '_replication_state_time',
  '_replication_state_reason',
  '_replication_stats'
]);

function parseRevisionInfo(rev$$1) {
  if (!/^\d+-/.test(rev$$1)) {
    return createError(INVALID_REV);
  }
  var idx = rev$$1.indexOf('-');
  var left = rev$$1.substring(0, idx);
  var right = rev$$1.substring(idx + 1);
  return {
    prefix: parseInt(left, 10),
    id: right
  };
}

function makeRevTreeFromRevisions(revisions, opts) {
  var pos = revisions.start - revisions.ids.length + 1;

  var revisionIds = revisions.ids;
  var ids = [revisionIds[0], opts, []];

  for (var i = 1, len = revisionIds.length; i < len; i++) {
    ids = [revisionIds[i], {status: 'missing'}, [ids]];
  }

  return [{
    pos,
    ids
  }];
}

// Preprocess documents, parse their revisions, assign an id and a
// revision for new writes that are missing them, etc
function parseDoc(doc, newEdits, dbOpts) {
  if (!dbOpts) {
    dbOpts = {
      deterministic_revs: true
    };
  }

  var nRevNum;
  var newRevId;
  var revInfo;
  var opts = {status: 'available'};
  if (doc._deleted) {
    opts.deleted = true;
  }

  if (newEdits) {
    if (!doc._id) {
      doc._id = uuid$1();
    }
    newRevId = rev(doc, dbOpts.deterministic_revs);
    if (doc._rev) {
      revInfo = parseRevisionInfo(doc._rev);
      if (revInfo.error) {
        return revInfo;
      }
      doc._rev_tree = [{
        pos: revInfo.prefix,
        ids: [revInfo.id, {status: 'missing'}, [[newRevId, opts, []]]]
      }];
      nRevNum = revInfo.prefix + 1;
    } else {
      doc._rev_tree = [{
        pos: 1,
        ids : [newRevId, opts, []]
      }];
      nRevNum = 1;
    }
  } else {
    if (doc._revisions) {
      doc._rev_tree = makeRevTreeFromRevisions(doc._revisions, opts);
      nRevNum = doc._revisions.start;
      newRevId = doc._revisions.ids[0];
    }
    if (!doc._rev_tree) {
      revInfo = parseRevisionInfo(doc._rev);
      if (revInfo.error) {
        return revInfo;
      }
      nRevNum = revInfo.prefix;
      newRevId = revInfo.id;
      doc._rev_tree = [{
        pos: nRevNum,
        ids: [newRevId, opts, []]
      }];
    }
  }

  invalidIdError(doc._id);

  doc._rev = nRevNum + '-' + newRevId;

  var result = {metadata : {}, data : {}};
  for (var key in doc) {
    /* istanbul ignore else */
    if (Object.prototype.hasOwnProperty.call(doc, key)) {
      var specialKey = key[0] === '_';
      if (specialKey && !reservedWords[key]) {
        var error = createError(DOC_VALIDATION, key);
        error.message = DOC_VALIDATION.message + ': ' + key;
        throw error;
      } else if (specialKey && !dataWords[key]) {
        result.metadata[key.slice(1)] = doc[key];
      } else {
        result.data[key] = doc[key];
      }
    }
  }
  return result;
}

// We fetch all leafs of the revision tree, and sort them based on tree length
// and whether they were deleted, undeleted documents with the longest revision
// tree (most edits) win
// The final sort algorithm is slightly documented in a sidebar here:
// http://guide.couchdb.org/draft/conflicts.html
function winningRev(metadata) {
  var winningId;
  var winningPos;
  var winningDeleted;
  var toVisit = metadata.rev_tree.slice();
  var node;
  while ((node = toVisit.pop())) {
    var tree = node.ids;
    var branches = tree[2];
    var pos = node.pos;
    if (branches.length) { // non-leaf
      for (var i = 0, len = branches.length; i < len; i++) {
        toVisit.push({pos: pos + 1, ids: branches[i]});
      }
      continue;
    }
    var deleted = !!tree[1].deleted;
    var id = tree[0];
    // sort by deleted, then pos, then id
    if (!winningId || (winningDeleted !== deleted ? winningDeleted :
        winningPos !== pos ? winningPos < pos : winningId < id)) {
      winningId = id;
      winningPos = pos;
      winningDeleted = deleted;
    }
  }

  return winningPos + '-' + winningId;
}

// Pretty much all below can be combined into a higher order function to
// traverse revisions
// The return value from the callback will be passed as context to all
// children of that node
function traverseRevTree(revs, callback) {
  var toVisit = revs.slice();

  var node;
  while ((node = toVisit.pop())) {
    var pos = node.pos;
    var tree = node.ids;
    var branches = tree[2];
    var newCtx =
      callback(branches.length === 0, pos, tree[0], node.ctx, tree[1]);
    for (var i = 0, len = branches.length; i < len; i++) {
      toVisit.push({pos: pos + 1, ids: branches[i], ctx: newCtx});
    }
  }
}

function sortByPos(a, b) {
  return a.pos - b.pos;
}

function collectLeaves(revs) {
  var leaves = [];
  traverseRevTree(revs, function (isLeaf, pos, id, acc, opts) {
    if (isLeaf) {
      leaves.push({rev: pos + "-" + id, pos, opts});
    }
  });
  leaves.sort(sortByPos).reverse();
  for (var i = 0, len = leaves.length; i < len; i++) {
    delete leaves[i].pos;
  }
  return leaves;
}

// returns revs of all conflicts that is leaves such that
// 1. are not deleted and
// 2. are different than winning revision
function collectConflicts(metadata) {
  var win = winningRev(metadata);
  var leaves = collectLeaves(metadata.rev_tree);
  var conflicts = [];
  for (var i = 0, len = leaves.length; i < len; i++) {
    var leaf = leaves[i];
    if (leaf.rev !== win && !leaf.opts.deleted) {
      conflicts.push(leaf.rev);
    }
  }
  return conflicts;
}

// compact a tree by marking its non-leafs as missing,
// and return a list of revs to delete
function compactTree(metadata) {
  var revs = [];
  traverseRevTree(metadata.rev_tree, function (isLeaf, pos,
                                               revHash, ctx, opts) {
    if (opts.status === 'available' && !isLeaf) {
      revs.push(pos + '-' + revHash);
      opts.status = 'missing';
    }
  });
  return revs;
}

// `findPathToLeaf()` returns an array of revs that goes from the specified

// build up a list of all the paths to the leafs in this revision tree
function rootToLeaf(revs) {
  var paths = [];
  var toVisit = revs.slice();
  var node;
  while ((node = toVisit.pop())) {
    var pos = node.pos;
    var tree = node.ids;
    var id = tree[0];
    var opts = tree[1];
    var branches = tree[2];
    var isLeaf = branches.length === 0;

    var history = node.history ? node.history.slice() : [];
    history.push({id, opts});
    if (isLeaf) {
      paths.push({pos: (pos + 1 - history.length), ids: history});
    }
    for (var i = 0, len = branches.length; i < len; i++) {
      toVisit.push({pos: pos + 1, ids: branches[i], history});
    }
  }
  return paths.reverse();
}

// for a better overview of what this is doing, read:

function sortByPos$1(a, b) {
  return a.pos - b.pos;
}

// classic binary search
function binarySearch(arr, item, comparator) {
  var low = 0;
  var high = arr.length;
  var mid;
  while (low < high) {
    mid = (low + high) >>> 1;
    if (comparator(arr[mid], item) < 0) {
      low = mid + 1;
    } else {
      high = mid;
    }
  }
  return low;
}

// assuming the arr is sorted, insert the item in the proper place
function insertSorted(arr, item, comparator) {
  var idx = binarySearch(arr, item, comparator);
  arr.splice(idx, 0, item);
}

// Turn a path as a flat array into a tree with a single branch.
// If any should be stemmed from the beginning of the array, that's passed
// in as the second argument
function pathToTree(path, numStemmed) {
  var root;
  var leaf;
  for (var i = numStemmed, len = path.length; i < len; i++) {
    var node = path[i];
    var currentLeaf = [node.id, node.opts, []];
    if (leaf) {
      leaf[2].push(currentLeaf);
      leaf = currentLeaf;
    } else {
      root = leaf = currentLeaf;
    }
  }
  return root;
}

// compare the IDs of two trees
function compareTree(a, b) {
  return a[0] < b[0] ? -1 : 1;
}

// Merge two trees together
// The roots of tree1 and tree2 must be the same revision
function mergeTree(in_tree1, in_tree2) {
  var queue = [{tree1: in_tree1, tree2: in_tree2}];
  var conflicts = false;
  while (queue.length > 0) {
    var item = queue.pop();
    var tree1 = item.tree1;
    var tree2 = item.tree2;

    if (tree1[1].status || tree2[1].status) {
      tree1[1].status =
        (tree1[1].status ===  'available' ||
        tree2[1].status === 'available') ? 'available' : 'missing';
    }

    for (var i = 0; i < tree2[2].length; i++) {
      if (!tree1[2][0]) {
        conflicts = 'new_leaf';
        tree1[2][0] = tree2[2][i];
        continue;
      }

      var merged = false;
      for (var j = 0; j < tree1[2].length; j++) {
        if (tree1[2][j][0] === tree2[2][i][0]) {
          queue.push({tree1: tree1[2][j], tree2: tree2[2][i]});
          merged = true;
        }
      }
      if (!merged) {
        conflicts = 'new_branch';
        insertSorted(tree1[2], tree2[2][i], compareTree);
      }
    }
  }
  return {conflicts, tree: in_tree1};
}

function doMerge(tree, path, dontExpand) {
  var restree = [];
  var conflicts = false;
  var merged = false;
  var res;

  if (!tree.length) {
    return {tree: [path], conflicts: 'new_leaf'};
  }

  for (var i = 0, len = tree.length; i < len; i++) {
    var branch = tree[i];
    if (branch.pos === path.pos && branch.ids[0] === path.ids[0]) {
      // Paths start at the same position and have the same root, so they need
      // merged
      res = mergeTree(branch.ids, path.ids);
      restree.push({pos: branch.pos, ids: res.tree});
      conflicts = conflicts || res.conflicts;
      merged = true;
    } else if (dontExpand !== true) {
      // The paths start at a different position, take the earliest path and
      // traverse up until it as at the same point from root as the path we
      // want to merge.  If the keys match we return the longer path with the
      // other merged After stemming we don't want to expand the trees

      var t1 = branch.pos < path.pos ? branch : path;
      var t2 = branch.pos < path.pos ? path : branch;
      var diff = t2.pos - t1.pos;

      var candidateParents = [];

      var trees = [];
      trees.push({ids: t1.ids, diff, parent: null, parentIdx: null});
      while (trees.length > 0) {
        var item = trees.pop();
        if (item.diff === 0) {
          if (item.ids[0] === t2.ids[0]) {
            candidateParents.push(item);
          }
          continue;
        }
        var elements = item.ids[2];
        for (var j = 0, elementsLen = elements.length; j < elementsLen; j++) {
          trees.push({
            ids: elements[j],
            diff: item.diff - 1,
            parent: item.ids,
            parentIdx: j
          });
        }
      }

      var el = candidateParents[0];

      if (!el) {
        restree.push(branch);
      } else {
        res = mergeTree(el.ids, t2.ids);
        el.parent[2][el.parentIdx] = res.tree;
        restree.push({pos: t1.pos, ids: t1.ids});
        conflicts = conflicts || res.conflicts;
        merged = true;
      }
    } else {
      restree.push(branch);
    }
  }

  // We didnt find
  if (!merged) {
    restree.push(path);
  }

  restree.sort(sortByPos$1);

  return {
    tree: restree,
    conflicts: conflicts || 'internal_node'
  };
}

// To ensure we don't grow the revision tree infinitely, we stem old revisions
function stem(tree, depth) {
  // First we break out the tree into a complete list of root to leaf paths
  var paths = rootToLeaf(tree);
  var stemmedRevs;

  var result;
  for (var i = 0, len = paths.length; i < len; i++) {
    // Then for each path, we cut off the start of the path based on the
    // `depth` to stem to, and generate a new set of flat trees
    var path = paths[i];
    var stemmed = path.ids;
    var node;
    if (stemmed.length > depth) {
      // only do the stemming work if we actually need to stem
      if (!stemmedRevs) {
        stemmedRevs = {}; // avoid allocating this object unnecessarily
      }
      var numStemmed = stemmed.length - depth;
      node = {
        pos: path.pos + numStemmed,
        ids: pathToTree(stemmed, numStemmed)
      };

      for (var s = 0; s < numStemmed; s++) {
        var rev = (path.pos + s) + '-' + stemmed[s].id;
        stemmedRevs[rev] = true;
      }
    } else { // no need to actually stem
      node = {
        pos: path.pos,
        ids: pathToTree(stemmed, 0)
      };
    }

    // Then we remerge all those flat trees together, ensuring that we don't
    // connect trees that would go beyond the depth limit
    if (result) {
      result = doMerge(result, node, true).tree;
    } else {
      result = [node];
    }
  }

  // this is memory-heavy per Chrome profiler, avoid unless we actually stemmed
  if (stemmedRevs) {
    traverseRevTree(result, function (isLeaf, pos, revHash) {
      // some revisions may have been removed in a branch but not in another
      delete stemmedRevs[pos + '-' + revHash];
    });
  }

  return {
    tree: result,
    revs: stemmedRevs ? Object.keys(stemmedRevs) : []
  };
}

function merge(tree, path, depth) {
  var newTree = doMerge(tree, path);
  var stemmed = stem(newTree.tree, depth);
  return {
    tree: stemmed.tree,
    stemmedRevs: stemmed.revs,
    conflicts: newTree.conflicts
  };
}

// this method removes a leaf from a rev tree, independent of its status.
// e.g., by removing an available leaf, it could leave its predecessor as
// a missing leaf and corrupting the tree.
function removeLeafFromRevTree(tree, leafRev) {
  return tree.flatMap((path) => {
    path = removeLeafFromPath(path, leafRev);
    return path ? [path] : [];
  });
}

function removeLeafFromPath(path, leafRev) {
  const tree = clone(path);
  const toVisit = [tree];
  let node;

  while ((node = toVisit.pop())) {
    const { pos, ids: [id, , branches], parent } = node;
    const isLeaf = branches.length === 0;
    const hash = `${pos}-${id}`;

    if (isLeaf && hash === leafRev) {
      if (!parent) {
        // FIXME: we're facing the root, and probably shouldn't just return an empty array (object? null?).
        return null;
      }

      parent.ids[2] = parent.ids[2].filter(function (branchNode) {
        return branchNode[0] !== id;
      });
      return tree;
    }

    for (let i = 0, len = branches.length; i < len; i++) {
      toVisit.push({ pos: pos + 1, ids: branches[i], parent: node });
    }
  }
  return tree;
}

// return true if a rev exists in the rev tree, false otherwise

function isLocalId(id) {
  return typeof id === 'string' && id.startsWith('_local/');
}

// returns the current leaf node for a given revision
function latest(rev, metadata) {
  var toVisit = metadata.rev_tree.slice();
  var node;
  while ((node = toVisit.pop())) {
    var pos = node.pos;
    var tree = node.ids;
    var id = tree[0];
    var opts = tree[1];
    var branches = tree[2];
    var isLeaf = branches.length === 0;

    var history = node.history ? node.history.slice() : [];
    history.push({id, pos, opts});

    if (isLeaf) {
      for (var i = 0, len = history.length; i < len; i++) {
        var historyNode = history[i];
        var historyRev = historyNode.pos + '-' + historyNode.id;

        if (historyRev === rev) {
          // return the rev of this leaf
          return pos + '-' + id;
        }
      }
    }

    for (var j = 0, l = branches.length; j < l; j++) {
      toVisit.push({pos: pos + 1, ids: branches[j], history});
    }
  }

  /* istanbul ignore next */
  throw new Error('Unable to resolve latest revision for id ' + metadata.id + ', rev ' + rev);
}

const IDB_NULL = Number.MIN_SAFE_INTEGER;
const IDB_FALSE = Number.MIN_SAFE_INTEGER + 1;
const IDB_TRUE = Number.MIN_SAFE_INTEGER + 2;

// These are the same as below but without the global flag
// we want to use RegExp.test because it's really fast, but the global flag
// makes the regex const stateful (seriously) as it walked through all instances
const TEST_KEY_INVALID = /^[^a-zA-Z$]|[^a-zA-Z0-9$]+/;
const TEST_PATH_INVALID = /\\.|(^|\.)[^a-zA-Z$]|[^a-zA-Z0-9$.]+/;
function needsSanitise(name, isPath) {
  if (isPath) {
    return TEST_PATH_INVALID.test(name);
  } else {
    return TEST_KEY_INVALID.test(name);
  }
}

//
// IndexedDB only allows valid JS names in its index paths, whereas JSON allows
// for any string at all. This converts invalid JS names to valid ones, to allow
// for them to be indexed.
//
// For example, "foo-bar" is a valid JSON key, but cannot be a valid JS name
// (because that would be read as foo minus bar).
//
// Very high level rules for valid JS names are:
//  - First character cannot start with a number
//  - Otherwise all characters must be be a-z, A-Z, 0-9, or $.
//  - Underscores (_) are encoded even though legal, to avoid collisions with
//    encoded illegal characters
//  - We allow . unless the name represents a single field, as that represents
//    a deep index path.
// See: https://www.w3.org/TR/IndexedDB/#key-path-construct
//
// This is more aggressive than it needs to be, but also simpler.
//
const KEY_INVALID = new RegExp(TEST_KEY_INVALID.source, 'g');
const PATH_INVALID = new RegExp(TEST_PATH_INVALID.source, 'g');
const SLASH = '\\'.charCodeAt(0);
const IS_DOT = '.'.charCodeAt(0);

function sanitise(name, isPath) {
  const correctCharacters = function (match) {
    let good = '';
    for (let i = 0; i < match.length; i++) {
      const code = match.charCodeAt(i);
      // If you're sanitising a path, a slash character is there to be interpreted
      // by whatever parses the path later as "escape the next thing".
      //
      // e.g., if you want to index THIS string:
      //   {"foo": {"bar.baz": "THIS"}}
      // Your index path would be "foo.bar\.baz".

      if (code === IS_DOT && isPath && i === 0) {
        good += '.';
      } else if (code === SLASH && isPath) {
        continue;
      } else {
        good += '_c' + code + '_';
      }
    }
    return good;
  };

  if (isPath) {
    return name.replace(PATH_INVALID, correctCharacters);
  } else {
    return name.replace(KEY_INVALID, correctCharacters);
  }
}

function needsRewrite(data) {
  for (const key of Object.keys(data)) {
    if (needsSanitise(key)) {
      return true;
    } else if (data[key] === null || typeof data[key] === 'boolean') {
      return true;
    } else if (typeof data[key] === 'object') {
      return needsRewrite(data[key]);
    }
  }
}

function rewrite(data) {
  if (!needsRewrite(data)) {
    return false;
  }

  const isArray = Array.isArray(data);
  const clone = isArray
    ? []
    : {};

  Object.keys(data).forEach(function (key) {
    const safeKey = isArray ? key : sanitise(key);

    if (data[key] === null) {
      clone[safeKey] = IDB_NULL;
    } else if (typeof data[key] === 'boolean') {
      clone[safeKey] = data[key] ? IDB_TRUE : IDB_FALSE;
    } else if (typeof data[key] === 'object') {
      clone[safeKey] = rewrite(data[key]);
    } else {
      clone[safeKey] = data[key];
    }
  });

  return clone;
}

const DOC_STORE = 'docs';
const META_LOCAL_STORE = 'meta';

function idbError(callback) {
  return function (evt) {
    let message = 'unknown_error';
    if (evt.target && evt.target.error) {
      message = evt.target.error.name || evt.target.error.message;
    }
    callback(createError(IDB_ERROR, message, evt.type));
  };
}

function processAttachment(name, src, doc, isBinary, attachmentFormat) {

  delete doc._attachments[name].stub;

  if (attachmentFormat === 'base64') {
    if (isBinary) {
      const att = src.attachments[doc._attachments[name].digest];
      doc._attachments[name].data = b64ToBluffer(att.data, att.content_type);
    } else {
      doc._attachments[name].data =
        src.attachments[doc._attachments[name].digest].data;
    }
    delete doc._attachments[name].length;
    return Promise.resolve();
  }

  if (isBinary) {
    doc._attachments[name].data =
      src.attachments[doc._attachments[name].digest].data;
    return Promise.resolve();
  }

  return new Promise(function (resolve) {
    const data = src.attachments[doc._attachments[name].digest].data;
    readAsBinaryString(data, function (binString) {
      doc._attachments[name].data = thisBtoa(binString);
      delete doc._attachments[name].length;
      resolve();
    });
  });
}

function rawIndexFields(ddoc, viewName) {
  // fields are an array of either the string name of the field, or a key value
  const fields = ddoc.views[viewName].options &&
                 ddoc.views[viewName].options.def &&
                 ddoc.views[viewName].options.def.fields || [];

  // Either ['foo'] or [{'foo': 'desc'}]
  return fields.map(function (field) {
    if (typeof field === 'string') {
      return field;
    } else {
      return Object.keys(field)[0];
    }
  });
}

/**
 * true if the view is has a "partial_filter_selector".
 */
function isPartialFilterView(ddoc, viewName) {
  return viewName in ddoc.views &&
    ddoc.views[viewName].options &&
    ddoc.views[viewName].options.def &&
    ddoc.views[viewName].options.def.partial_filter_selector;
}

function naturalIndexName(fields) {
  return '_find_idx/' + fields.join('/');
}

/**
 * Convert the fields the user gave us in the view and convert them to work for
 * indexeddb.
 *
 * fields is an array of field strings. A field string could be one field:
 *   'foo'
 * Or it could be a json path:
 *   'foo.bar'
 */
function correctIndexFields(fields) {
  // Every index has to have deleted at the front, because when we do a query
  // we need to filter out deleted documents.
  return ['deleted'].concat(
    fields.map(function (field) {
      if (['_id', '_rev', '_deleted', '_attachments'].includes(field)) {
        // These properties are stored at the top level without the underscore
        return field.substr(1);
      } else {
        // The custom document fields are inside the `data` property
        return 'data.' + sanitise(field, true);
      }
    })
  );
}

//
// Core PouchDB schema version. Increment this if we, as a library, want to make
// schema changes in indexeddb. See upgradePouchDbSchema()
//
const POUCHDB_IDB_VERSION = 2;

//
// Functions that manage a combinate indexeddb version, by combining the current
// time in millis that represents user migrations with a large multiplier that
// represents PouchDB system migrations.
//
// This lets us use the idb version number to both represent
// PouchDB-library-level migrations as well as "user migrations" required for
// when design documents trigger the addition or removal of native indexes.
//
// Given that Number.MAX_SAFE_INTEGER = 9007199254740991
//
// We can easily use the largest 2-3 digits and either allow:
//  - 900 system migrations up to 2198/02/18
//  - or 89 system migrations up to 5050/02/14
//
// This impl does the former. If this code still exists after 2198 someone send my
// descendants a Spacebook message congratulating them on their impressive genes.
//
// 9007199254740991 <- MAX_SAFE_INTEGER
//   10000000000000 <- 10^13
//    7199254740991 <- 2198-02-18T16:59:00.991Z
//
const versionMultiplier = Math.pow(10, 13);
function createIdbVersion() {
  return (versionMultiplier * POUCHDB_IDB_VERSION) + new Date().getTime();
}
function getPouchDbVersion(version) {
  return Math.floor(version / versionMultiplier);
}

function maintainNativeIndexes(openReq, reject) {
  const docStore = openReq.transaction.objectStore(DOC_STORE);
  const ddocsReq = docStore.getAll(IDBKeyRange.bound('_design/', '_design/\uffff'));

  ddocsReq.onsuccess = function (e) {
    const results = e.target.result;
    const existingIndexNames = Array.from(docStore.indexNames);

    // NB: the only thing we're supporting here is the declared indexing
    // fields nothing more.
    const expectedIndexes = results.filter(function (row) {
      return row.deleted === 0 && row.revs[row.rev].data.views;
    }).map(function (row) {
      return row.revs[row.rev].data;
    }).reduce(function (indexes, ddoc) {
      return Object.keys(ddoc.views).reduce(function (acc, viewName) {
        const fields = rawIndexFields(ddoc, viewName);

        if (fields && fields.length > 0) {
          acc[naturalIndexName(fields)] = correctIndexFields(fields);
        }

        return acc;
      }, indexes);
    }, {});

    const expectedIndexNames = Object.keys(expectedIndexes);

    // Delete any indexes that aren't system indexes or expected
    const systemIndexNames = ['seq', 'deleted,id'];
    existingIndexNames.forEach(function (index) {
      if (systemIndexNames.indexOf(index) === -1  && expectedIndexNames.indexOf(index) === -1) {
        docStore.deleteIndex(index);
      }
    });

    // Work out which indexes are missing and create them
    const newIndexNames = expectedIndexNames.filter(function (ei) {
      return existingIndexNames.indexOf(ei) === -1;
    });

    try {
      newIndexNames.forEach(function (indexName) {
        docStore.createIndex(indexName, expectedIndexes[indexName]);
      });
    } catch (err) {
      reject(err);
    }
  };
}

function upgradePouchDbSchema(dbName, db, tx, pouchdbVersion) {
  if (pouchdbVersion < 1) {
    const docStore = db.createObjectStore(DOC_STORE, {keyPath : 'id'});
    docStore.createIndex('seq', 'seq', {unique: true});

    db.createObjectStore(META_LOCAL_STORE, {keyPath: 'id'});
  }

  if (pouchdbVersion < 2) {
    const docStore = tx.objectStore(DOC_STORE);
    docStore.createIndex('deleted,id', [ 'deleted', 'id' ], {unique: true});
    if (dbName.includes('-mrview-')) {
      docStore.deleteIndex('seq');
    }
  }

  // Declare more PouchDB schema changes here
  // if (pouchdbVersion < 3) { .. }
}

function openDatabase(openDatabases, api, opts, resolve, reject) {
  const openReq = opts.versionChangedWhileOpen ?
    indexedDB.open(opts.name) :
    indexedDB.open(opts.name, createIdbVersion());

  openReq.onupgradeneeded = function (e) {
    if (e.oldVersion > 0 && e.oldVersion < versionMultiplier) {
      // This DB was created with the "idb" adapter, **not** this one.
      // For now we're going to just error out here: users must manually
      // migrate between the two. In the future, dependent on performance tests,
      // we might silently migrate
      throw new Error('Incorrect adapter: you should specify the "idb" adapter to open this DB');
    } else if (e.oldVersion === 0 && e.newVersion < versionMultiplier) {
      // Firefox still creates the database with version=1 even if we throw,
      // so we need to be sure to destroy the empty database before throwing
      indexedDB.deleteDatabase(opts.name);
      throw new Error('Database was deleted while open');
    }

    const tx = e.target.transaction;
    const db = e.target.result;

    const pouchdbVersion = getPouchDbVersion(e.oldVersion);
    upgradePouchDbSchema(opts.name, db, tx, pouchdbVersion);
    maintainNativeIndexes(openReq, reject);

    if (pouchdbVersion < 2) {
      const docStore = openReq.transaction.objectStore(DOC_STORE);
      const metaStore = openReq.transaction.objectStore(META_LOCAL_STORE);

      const allDocsReq = docStore.openCursor();
      allDocsReq.onsuccess = event => {
        const cursor = event.target.result;
        if (!cursor) {
          return;
        }

        const doc = cursor.value;

        if (!isLocalId(doc.id)) {
          return cursor.continue();
        }

        // Move _local/ docs to the META_LOCAL_STORE
        metaStore.put(doc).onsuccess = () => {
          cursor.delete(doc).onsuccess = () => {
            cursor.continue();
          };
        };
      };
    }
  };

  openReq.onblocked = function (e) {
      // AFAICT this only occurs if, after sending `onversionchange` events to
      // all other open DBs (ie in different tabs), there are still open
      // connections to the DB. In this code we should never see this because we
      // close our DBs on these events, and all DB interactions are wrapped in
      // safely re-opening the DB.
      console.error('onblocked, this should never happen', e);
  };

  openReq.onsuccess = function (e) {
    const idb = e.target.result;

    idb.onabort = function (e) {
      console.error('Database has a global failure', e.target.error);
      delete openDatabases[opts.name];
      idb.close();
    };

    // In IndexedDB you can only change the version, and thus the schema, when you are opening the database.
    // versionChangedWhileOpen means that something else outside of our control has likely updated the version.
    // One way this could happen is if you open multiple tabs, as the version number changes each time the database is opened.
    // If we suspect this we close the db and tag it, so that next time it's accessed it reopens the DB with the current version
    // as opposed to upping the version again
    // This avoids infinite loops of version updates if you have multiple tabs open
    idb.onversionchange = function () {
      console.log('Database was made stale, closing handle');
      openDatabases[opts.name].versionChangedWhileOpen = true;
      idb.close();
    };

    idb.onclose = function () {
      console.log('Database was made stale, closing handle');
      if (opts.name in openDatabases) {
        openDatabases[opts.name].versionChangedWhileOpen = true;
      }
    };

    let metadata = {id: META_LOCAL_STORE};
    const txn = idb.transaction([META_LOCAL_STORE], 'readwrite');

    txn.oncomplete = function () {
      resolve({idb, metadata});
    };

    const metaStore = txn.objectStore(META_LOCAL_STORE);
    metaStore.get(META_LOCAL_STORE).onsuccess = function (e) {
      metadata = e.target.result || metadata;
      let changed = false;

      if (!('doc_count' in metadata)) {
        changed = true;
        metadata.doc_count = 0;
      }

      if (!('seq' in metadata)) {
        changed = true;
        metadata.seq = 0;
      }

      if (!('db_uuid' in metadata)) {
        changed = true;
        metadata.db_uuid = uuid$1();
      }

      if (!('idb_attachment_format' in metadata)) {
        // There will be trouble if any browser _stops_ supporting blobs.

        const createBlobDoc = blob => ({ id:'blob-support', blob });

        checkBlobSupport(txn, META_LOCAL_STORE, createBlobDoc).then(blobSupport => {
          // Unfortunate that we have to track this in both the metadata and on
          // api, but sometimes we have access to one, sometimes the other (and
          // sometimes both).  We could change function signatures in index.js
          // to make this consistent.
          api.blobSupport = metadata.idb_attachment_format = blobSupport ? 'binary' : 'base64';
          metaStore.put(metadata);
        });
      } else if (changed) {
        api.blobSupport = metadata.idb_attachment_format;
        metaStore.put(metadata);
      }
    };
  };

  openReq.onerror = function (e) {
    reject(e.target.error);
  };
}

function setup (openDatabases, api, opts) {
  if (!openDatabases[opts.name] || openDatabases[opts.name].versionChangedWhileOpen) {
    opts.versionChangedWhileOpen = openDatabases[opts.name] &&
                          openDatabases[opts.name].versionChangedWhileOpen;

    openDatabases[opts.name] = new Promise(function (resolve, reject) {
      openDatabase(openDatabases, api, opts, resolve, reject);
    });
  }

  return openDatabases[opts.name];
}

function info (metadata, callback) {
  callback(null, {
    doc_count: metadata.doc_count,
    update_seq: metadata.seq
  });
}

function get (txn, id, opts, callback) {
  if (txn.error) {
    return callback(txn.error);
  }

  txn.txn.objectStore(DOC_STORE).get(id).onsuccess = function (e) {
    const doc = e.target.result;
    let rev;
    if (!opts.rev) {
      rev = (doc && doc.rev);
    } else {
      rev = opts.latest ? latest(opts.rev, doc) : opts.rev;
    }

    if (!doc || (doc.deleted && !opts.rev) || !(rev in doc.revs)) {
      callback(createError(MISSING_DOC, 'missing'));
      return;
    }

    const result = doc.revs[rev].data;
    result._id = doc.id;
    result._rev = rev;

    // WARNING: expecting possible old format
    // TODO: why are we passing the transaction in the context?
    //       It's not clear we ever thread these txns usefully
    callback(null, {
      doc: result,
      metadata: doc,
      ctx: txn
    });
  };
}

// _getLocal() doesn't know if opts.binary is set or not, so assume it's not.
const BINARY_ATTACHMENTS = false;

function getLocal (txn, id, api, callback) {
  if (txn.error) {
    return callback(txn.error);
  }

  txn.txn.objectStore(META_LOCAL_STORE).get(id).onsuccess = function (e) {
    const doc = e.target.result;

    if (!doc) {
      callback(createError(MISSING_DOC, 'missing'));
      return;
    }

    const result = doc.revs[doc.rev].data;
    result._id = doc.id;
    result._rev = doc.rev;

    if (result._attachments) {
      const processing = [];
      for (const name in result._attachments) {
        processing.push(processAttachment(name, doc, result, BINARY_ATTACHMENTS, api.blobSupport));
      }
      Promise.all(processing)
        .then(() => callback(null, result))
        .catch(callback);
    } else {
      callback(null, result);
    }
  };
}

function getAttachment(docId, attachId, attachment, opts, cb) {
  if (isLocalId(docId)) {
    cb(createError(MISSING_DOC, 'missing'));
    return;
  }

  const doc = opts.metadata;
  const data = doc.attachments[attachment.digest].data;

  if (typeof data === 'string') {
    if (opts.binary) {
      cb(null, b64ToBluffer(data, attachment.content_type));
    } else {
      cb(null, data);
    }
    return;
  }

  if (opts.binary) {
    return cb(null, data);
  } else {
    readAsBinaryString(data, function (binString) {
      cb(null, thisBtoa(binString));
    });
  }
}

function bulkDocs (api, req, opts, metadata, dbOpts, idbChanges, callback) {

  let txn;

  // TODO: I would prefer to get rid of these globals
  let error;
  const results = [];
  const docs = [];
  let lastWriteIndex;

  const revsLimit = dbOpts.revs_limit || 1000;
  const rewriteEnabled = dbOpts.name.indexOf("-mrview-") === -1;
  const autoCompaction = dbOpts.auto_compaction;

  // We only need to track 1 revision for local documents
  function docsRevsLimit(doc) {
    return isLocalId(doc.id) ? 1 : revsLimit;
  }

  function rootIsMissing(doc) {
    return doc.rev_tree[0].ids[1].status === 'missing';
  }

  // Reads the original doc from the store if available
  // As in allDocs with keys option using multiple get calls is the fastest way
  function fetchExistingDocs(txn, docs) {
    let fetched = 0;
    const oldDocs = {};

    function readDone(e) {
      if (e.target.result) {
        oldDocs[e.target.result.id] = e.target.result;
      }
      if (++fetched === docs.length) {
        processDocs$$1(txn, docs, oldDocs);
      }
    }

    docs.forEach(function (doc) {
      const docStore = isLocalId(doc.id) ? META_LOCAL_STORE : DOC_STORE;
      txn.objectStore(docStore).get(doc.id).onsuccess = readDone;
    });
  }

  function revHasAttachment(doc, rev, digest) {
    return doc.revs[rev] &&
      doc.revs[rev].data._attachments &&
      Object.values(doc.revs[rev].data._attachments).find(function (att) {
        return att.digest === digest;
      });
  }

  function processDocs$$1(txn, docs, oldDocs) {

    docs.forEach(function (doc, i) {
      let newDoc;

      // The first document write cannot be a deletion
      if ('was_delete' in opts && !(Object.prototype.hasOwnProperty.call(oldDocs, doc.id))) {
        newDoc = createError(MISSING_DOC, 'deleted');

      // The first write of a document cannot specify a revision
      } else if (opts.new_edits &&
                 !Object.prototype.hasOwnProperty.call(oldDocs, doc.id) &&
                 rootIsMissing(doc)) {
        newDoc = createError(REV_CONFLICT);

      // Update the existing document
      } else if (Object.prototype.hasOwnProperty.call(oldDocs, doc.id)) {
        newDoc = update(txn, doc, oldDocs[doc.id]);
        // The update can be rejected if it is an update to an existing
        // revision, if so skip it
        if (newDoc == false) {
          return;
        }

      // New document
      } else {
        // Ensure new documents are also stemmed
        const merged = merge([], doc.rev_tree[0], docsRevsLimit(doc));
        doc.rev_tree = merged.tree;
        doc.stemmedRevs = merged.stemmedRevs;
        newDoc = doc;
        newDoc.isNewDoc = true;
        newDoc.wasDeleted = doc.revs[doc.rev].deleted ? 1 : 0;
      }

      if (newDoc.error) {
        results[i] = newDoc;
      } else {
        oldDocs[newDoc.id] = newDoc;
        lastWriteIndex = i;
        write(txn, newDoc, i);
      }
    });
  }

  // Converts from the format returned by parseDoc into the new format
  // we use to store
  function convertDocFormat(doc) {

    const newDoc = {
      id: doc.metadata.id,
      rev: doc.metadata.rev,
      rev_tree: doc.metadata.rev_tree,
      revs: doc.metadata.revs || {}
    };

    newDoc.revs[newDoc.rev] = {
      data: doc.data,
      deleted: doc.metadata.deleted
    };

    return newDoc;
  }

  function update(txn, doc, oldDoc) {

    // Ignore updates to existing revisions
    if ((doc.rev in oldDoc.revs) && !opts.new_edits) {
      return false;
    }

    const isRoot = /^1-/.test(doc.rev);

    // Reattach first writes after a deletion to last deleted tree
    if (oldDoc.deleted && !doc.deleted && opts.new_edits && isRoot) {
      const tmp = doc.revs[doc.rev].data;
      tmp._rev = oldDoc.rev;
      tmp._id = oldDoc.id;
      doc = convertDocFormat(parseDoc(tmp, opts.new_edits, dbOpts));
    }

    const merged = merge(oldDoc.rev_tree, doc.rev_tree[0], docsRevsLimit(doc));
    doc.stemmedRevs = merged.stemmedRevs;
    doc.rev_tree = merged.tree;

    // Merge the old and new rev data
    const revs = oldDoc.revs;
    revs[doc.rev] = doc.revs[doc.rev];
    doc.revs = revs;

    doc.attachments = oldDoc.attachments;

    const inConflict = opts.new_edits && (((oldDoc.deleted && doc.deleted) ||
       (!oldDoc.deleted && merged.conflicts !== 'new_leaf') ||
       (oldDoc.deleted && !doc.deleted && merged.conflicts === 'new_branch') ||
       (oldDoc.rev === doc.rev)));

    if (inConflict) {
      return createError(REV_CONFLICT);
    }

    doc.wasDeleted = oldDoc.deleted;

    return doc;
  }

  function write(txn, doc, i) {

    // We copy the data from the winning revision into the root
    // of the document so that it can be indexed
    const winningRev$$1 = winningRev(doc);
    // rev of new doc for attachments and to return it
    const writtenRev = doc.rev;
    const isLocal = isLocalId(doc.id);

    const theDoc = doc.revs[winningRev$$1].data;

    const isNewDoc = doc.isNewDoc;

    if (rewriteEnabled) {
      // doc.data is what we index, so we need to clone and rewrite it, and clean
      // it up for indexability
      const result = rewrite(theDoc);
      if (result) {
        doc.data = result;
        delete doc.data._attachments;
      } else {
        doc.data = theDoc;
      }
    } else {
      doc.data = theDoc;
    }

    doc.rev = winningRev$$1;
    // .deleted needs to be an int for indexing
    doc.deleted = doc.revs[winningRev$$1].deleted ? 1 : 0;

    // Bump the seq for every new (non local) revision written
    if (!isLocal) {
      doc.seq = ++metadata.seq;

      let delta = 0;
      // If its a new document, we wont decrement if deleted
      if (doc.isNewDoc) {
        delta = doc.deleted ? 0 : 1;
      } else if (doc.wasDeleted !== doc.deleted) {
        delta = doc.deleted ? -1 : 1;
      }
      metadata.doc_count += delta;
    }
    delete doc.isNewDoc;
    delete doc.wasDeleted;

    // If there have been revisions stemmed when merging trees,
    // delete their data
    let revsToDelete = doc.stemmedRevs || [];

    if (autoCompaction && !isNewDoc) {
      const result = compactTree(doc);
      if (result.length) {
        revsToDelete = revsToDelete.concat(result);
      }
    }

    if (revsToDelete.length) {
      revsToDelete.forEach(function (rev) { delete doc.revs[rev]; });
    }

    delete doc.stemmedRevs;

    if (!('attachments' in doc)) {
      doc.attachments = {};
    }

    if (theDoc._attachments) {
      for (const k in theDoc._attachments) {
        const attachment = theDoc._attachments[k];
        if (attachment.stub) {
          if (!(attachment.digest in doc.attachments)) {
            error = createError(MISSING_STUB);
            // TODO: Not sure how safe this manual abort is, seeing
            // console issues
            txn.abort();
            return;
          }

          if (revHasAttachment(doc, writtenRev, attachment.digest)) {
            doc.attachments[attachment.digest].revs[writtenRev] = true;
          }

        } else {

          doc.attachments[attachment.digest] = attachment;
          doc.attachments[attachment.digest].revs = {};
          doc.attachments[attachment.digest].revs[writtenRev] = true;

          theDoc._attachments[k] = {
            stub: true,
            digest: attachment.digest,
            content_type: attachment.content_type,
            length: attachment.length,
            revpos: parseInt(writtenRev, 10)
          };
        }
      }
    }

    // Local documents have different revision handling
    if (isLocal && doc.deleted) {
      txn.objectStore(META_LOCAL_STORE).delete(doc.id).onsuccess = function () {
        results[i] = {
          ok: true,
          id: doc.id,
          rev: '0-0'
        };
      };
      updateSeq(i);
      return;
    }

    const docStore = isLocal ? META_LOCAL_STORE : DOC_STORE;
    txn.objectStore(docStore).put(doc).onsuccess = function () {
      results[i] = {
        ok: true,
        id: doc.id,
        rev: writtenRev
      };
      updateSeq(i);
    };
  }

  function updateSeq(i) {
    if (i === lastWriteIndex) {
      txn.objectStore(META_LOCAL_STORE).put(metadata);
    }
  }

  function preProcessAttachment(attachment) {
    if (attachment.stub) {
      return Promise.resolve(attachment);
    }

    let binData;
    if (typeof attachment.data === 'string') {
      try {
        binData = thisAtob(attachment.data);
      } catch (e) {
        return Promise.reject(createError(BAD_ARG, 'Attachment is not a valid base64 string'));
      }
      if (metadata.idb_attachment_format === 'binary') {
        attachment.data = binStringToBluffer(binData, attachment.content_type);
      }
    } else {
      binData = attachment.data;
      if (metadata.idb_attachment_format === 'base64') {
        // TODO could run these in parallel, if we cared
        return new Promise(resolve => {
          blobToBase64(attachment.data, function (b64) {
            attachment.data = b64;
            binaryMd5(binData, function (result) {
              attachment.digest = 'md5-' + result;
              attachment.length = binData.size || binData.length || 0;
              resolve(attachment);
            });
          });
        });
      }
    }

    return new Promise(function (resolve) {
      binaryMd5(binData, function (result) {
        attachment.digest = 'md5-' + result;
        attachment.length = binData.size || binData.length || 0;
        resolve(attachment);
      });
    });
  }

  function preProcessAttachments() {
    const promises = docs.map(function (doc) {
      const data = doc.revs[doc.rev].data;
      if (!data._attachments) {
        return Promise.resolve(data);
      }
      const attachments = Object.keys(data._attachments).map(function (k) {
        data._attachments[k].name = k;
        return preProcessAttachment(data._attachments[k]);
      });

      return Promise.all(attachments).then(function (newAttachments) {
        const processed = {};
        newAttachments.forEach(function (attachment) {
          processed[attachment.name] = attachment;
          delete attachment.name;
        });
        data._attachments = processed;
        return data;
      });
    });
    return Promise.all(promises);
  }

  for (let i = 0, len = req.docs.length; i < len; i++) {
    let result;
    // TODO: We should get rid of throwing for invalid docs, also not sure
    // why this is needed in idb-next and not idb
    try {
      result = parseDoc(req.docs[i], opts.new_edits, dbOpts);
    } catch (err) {
      result = err;
    }
    if (result.error) {
      return callback(result);
    }

    // Ideally parseDoc would return data in this format, but it is currently
    // shared so we need to convert
    docs.push(convertDocFormat(result));
  }

  preProcessAttachments().then(function () {
    // We _could_ check doc ids here, and skip opening DOC_STORE if all docs are local.
    // This may marginally slow things down for local docs.  It seems pragmatic to keep
    // the code simple and optimise for calls to bulkDocs() which include non-local docs.
    api._openTransactionSafely([DOC_STORE, META_LOCAL_STORE], 'readwrite', function (err, _txn) {
      if (err) {
        return callback(err);
      }

      txn = _txn;

      txn.onabort = function () {
        callback(error || createError(UNKNOWN_ERROR, 'transaction was aborted'));
      };
      txn.ontimeout = idbError(callback);

      txn.oncomplete = function () {
        idbChanges.notify(dbOpts.name);
        callback(null, results);
      };

      // We would like to use promises here, but idb sucks
      fetchExistingDocs(txn, docs);
    });
  }).catch(function (err) {
    callback(err);
  });
}

function allDocsKeys(keys, docStore, allDocsInner) {
  // It's not guaranteed to be returned in right order
  const valuesBatch = new Array(keys.length);
  let count = 0;
  keys.forEach(function (key, index) {
    docStore.get(key).onsuccess = function (event) {
      if (event.target.result) {
      valuesBatch[index] = event.target.result;
      } else {
        valuesBatch[index] = {key, error: 'not_found'};
      }
      count++;
      if (count === keys.length) {
        valuesBatch.forEach(function (doc) {
            allDocsInner(doc);
        });
      }
    };
  });
}

function createKeyRange(start, end, inclusiveStart, inclusiveEnd, key, descending) {
  try {
    if (key) {
      return IDBKeyRange.only([0, key]);
    } else if (descending) {
      return IDBKeyRange.bound(end, start, !inclusiveEnd, !inclusiveStart);
    } else {
      return IDBKeyRange.bound(start, end, !inclusiveStart, !inclusiveEnd);
    }
  } catch (e) {
    return {error: e};
  }
}

function handleKeyRangeError(opts, metadata, err, callback) {
  if (err.name === "DataError" && err.code === 0) {
    // data error, start is less than end
    const returnVal = {
      total_rows: metadata.doc_count,
      offset: opts.skip,
      rows: []
    };
    /* istanbul ignore if */
    if (opts.update_seq) {
      returnVal.update_seq = metadata.seq;
    }
    return callback(null, returnVal);
  }
  callback(createError(IDB_ERROR, err.name, err.message));
}

function allDocs (txn, metadata, opts, callback) {
  if (txn.error) {
    return callback(txn.error);
  }

  // TODO: Weird hack, I don't like it
  if (opts.limit === 0) {
    const returnVal = {
      total_rows: metadata.doc_count,
      offset: opts.skip,
      rows: []
    };

    /* istanbul ignore if */
    if (opts.update_seq) {
      returnVal.update_seq = metadata.seq;
    }
    return callback(null, returnVal);
  }

  const results = [];
  const processing = [];

  const key = 'key' in opts ? opts.key : false;
  const keys = 'keys' in opts ? opts.keys : false;
  let skip = opts.skip || 0;
  let limit = typeof opts.limit === 'number' ? opts.limit : undefined;
  const inclusiveEnd = opts.inclusive_end !== false;
  const descending = 'descending' in opts && opts.descending ? 'prev' : null;
  const start = 'startkey' in opts ? opts.startkey : (descending ?  '\uffff' : '');
  const end   = 'endkey'   in opts ? opts.endkey   : (descending ? '' :  '\uffff');

  const docStore = txn.txn.objectStore(DOC_STORE);

  if (keys) {
    txn.txn.oncomplete = onTxnComplete;
    const allDocsInner = doc => {
      if (doc.error) {
        return results.push(doc);
      }

      const row = { id:doc.id, key:doc.id, value:{ rev:doc.rev } };

      if (doc.deleted) {
        row.value.deleted = true;
        row.doc = null;
      } else if (opts.include_docs) {
        include_doc(row, doc);
      }

      results.push(row);
    };
    return allDocsKeys(keys, docStore, allDocsInner);
  }

  let keyRange = createKeyRange([0, start], [0, end], true, inclusiveEnd, key, descending);
  if (keyRange.error) {
    return handleKeyRangeError(opts, metadata, keyRange.error, callback);
  }

  // txn.oncomplete must be set AFTER key-range-error is generated
  txn.txn.oncomplete = onTxnComplete;

  function include_doc(row, doc) {
    const docData = doc.revs[doc.rev].data;

    row.doc = docData;
    row.doc._id = doc.id;
    row.doc._rev = doc.rev;
    if (opts.conflicts) {
      const conflicts = collectConflicts(doc);
      if (conflicts.length) {
        row.doc._conflicts = conflicts;
      }
    }
    if (opts.attachments && docData._attachments) {
      for (const name in docData._attachments) {
        processing.push(processAttachment(name, doc, row.doc, opts.binary,
            metadata.idb_attachment_format));
      }
    }
  }

  function onTxnComplete() {
    const returnVal = {
      total_rows: metadata.doc_count,
      offset: 0,
      rows: results
    };
    /* istanbul ignore if */
    if (opts.update_seq) {
      returnVal.update_seq = metadata.seq;
    }

    if (processing.length) {
      Promise.all(processing).then(function () {
        callback(null, returnVal);
      });
    } else {
      callback(null, returnVal);
    }
  }

  const dbIndex = docStore.index('deleted,id');

  if (!skip && !limit) {
    fetchResults();
  } else {
    let firstKey;
    let limitKey = limit > 0;

    dbIndex.openKeyCursor(keyRange, descending || 'next').onsuccess = (e) => {
      const cursor = e.target.result;

      if (skip) {
        if (!cursor) { return txn.txn.commit(); }
        cursor.advance(skip);
        skip = 0;
        return;
      }

      if (firstKey === undefined) {
        firstKey = cursor && cursor.key;
        if (!firstKey) { return txn.txn.commit(); }
      }

      if (limit) {
        if (limit > 1 && cursor) {
          cursor.advance(limit - 1);
          limit = undefined;
          return;
        }
        limit = undefined;
      }


      if (limitKey) {
        limitKey = cursor && cursor.key;
      }
      if (!limitKey) {
        limitKey = descending ? keyRange.lower : keyRange.upper;
      }

      keyRange = createKeyRange(firstKey, limitKey, true, inclusiveEnd, key, descending);
      if (keyRange.error) {
        txn.txn.abort();
        return handleKeyRangeError(opts, metadata, keyRange.error, callback);
      }

      fetchResults();
    };
  }

  async function fetchResults() {
    // There is a risk here with getting all results into memory - if they have multiple
    // revs, then we risk loading loads of extra data which is then discarded.  This is
    // reduced by batching.  This also loads unused data when include_docs is false.
    //
    // Current batch size is quite arbitrary, but seems like (1) more than a typical
    // result size, and (2) not so big it's likely to cause issues.
    const batchSize = 100;

    let kr = keyRange;
    do {
      kr = await fetchNextBatch(kr);
    } while (kr);
    if (descending) {
      results.reverse();
    }
    return txn.txn.commit();

    function fetchNextBatch(kr) {
      return new Promise((resolve) => {
        dbIndex.getAll(kr, batchSize).onsuccess = (e) => {
          const batch = e.target.result;
          for (let i=0; i<batch.length; ++i) {
            const doc = batch[i];
            const row = { id:doc.id, key:doc.id, value:{ rev:doc.rev } };
            if (opts.include_docs) {
              include_doc(row, doc);
            }
            results.push(row);
          }

          if (batch.length >= batchSize) {
            const lastSeenKey = [ 0, batch[batch.length-1].id ];
            const startKey = descending ? kr.upper : lastSeenKey;
            const endKey = descending ? lastSeenKey : kr.upper;
            if (startKey[1] !== endKey[1]) {
              const incEnd = descending ? false : inclusiveEnd;
              const incStart = descending ? true : false;
              return resolve(createKeyRange(startKey, endKey, incStart, incEnd, key, descending));
            }
          }
          return resolve();
        };
      });
    }
  }
}

function changes (txn, idbChanges, api, dbOpts, opts) {
  if (txn.error) {
    return opts.complete(txn.error);
  }

  if (opts.continuous) {
    const id = dbOpts.name + ':' + uuid$1();
    idbChanges.addListener(dbOpts.name, id, api, opts);
    idbChanges.notify(dbOpts.name);
    return {
      cancel: function () {
        idbChanges.removeListener(dbOpts.name, id);
      }
    };
  }

  let limit = 'limit' in opts ? opts.limit : -1;
  if (limit === 0) {
    limit = 1;
  }

  const store = txn.txn.objectStore(DOC_STORE).index('seq');

  const filter = filterChange(opts);
  let received = 0;

  let lastSeq = opts.since || 0;
  const results = [];

  const processing = [];

  function onReqSuccess(e) {
    if (!e.target.result) { return; }
    const cursor = e.target.result;
    const doc = cursor.value;
    // Overwrite doc.data, which may have been rewritten (see rewrite.js) with
    // the clean version for that rev
    doc.data = doc.revs[doc.rev].data;
    doc.data._id = doc.id;
    doc.data._rev = doc.rev;
    if (doc.deleted) {
      doc.data._deleted = true;
    }

    if (opts.doc_ids && opts.doc_ids.indexOf(doc.id) === -1) {
      return cursor.continue();
    }

    // WARNING: expecting possible old format
    const change = opts.processChange(doc.data, doc, opts);
    change.seq = doc.seq;
    lastSeq = doc.seq;
    const filtered = filter(change);

    // If its an error
    if (typeof filtered === 'object') {
      return opts.complete(filtered);
    }

    if (filtered) {
      received++;
      if (opts.return_docs) {
        results.push(change);
      }

      if (opts.include_docs && opts.attachments && doc.data._attachments) {
        const promises = [];
        for (const name in doc.data._attachments) {
          const p = processAttachment(name, doc, change.doc, opts.binary, api.blobSupport);
          // We add the processing promise to 2 arrays, one tracks all
          // the promises needed before we fire onChange, the other
          // ensure we process all attachments before onComplete
          promises.push(p);
          processing.push(p);
        }

        Promise.all(promises).then(function () {
          opts.onChange(change);
        });
      } else {
        opts.onChange(change);
      }
    }
    if (received !== limit) {
      cursor.continue();
    }
  }

  function onTxnComplete() {
    Promise.all(processing).then(function () {
      opts.complete(null, {
        results,
        last_seq: lastSeq
      });
    });
  }

  let req;
  if (opts.descending) {
    req = store.openCursor(null, 'prev');
  } else {
    req = store.openCursor(IDBKeyRange.lowerBound(opts.since, true));
  }

  txn.txn.oncomplete = onTxnComplete;
  req.onsuccess = onReqSuccess;
}

function getRevisionTree (txn, id, callback) {
  if (txn.error) {
    return callback(txn.error);
  }

  const req = txn.txn.objectStore(DOC_STORE).get(id);
  req.onsuccess = function (e) {
    if (!e.target.result) {
      callback(createError(MISSING_DOC));
    } else {
      callback(null, e.target.result.rev_tree);
    }
  };
}

function doCompaction (txn, id, revs, callback) {
  if (txn.error) {
    return callback(txn.error);
  }

  const docStore = txn.txn.objectStore(DOC_STORE);

  docStore.get(id).onsuccess = function (e) {
    const doc = e.target.result;

    traverseRevTree(doc.rev_tree, function (isLeaf, pos, revHash, ctx, opts) {
      const rev = pos + '-' + revHash;
      if (revs.indexOf(rev) !== -1) {
        opts.status = 'missing';
      }
    });

    const attachments = [];

    revs.forEach(function (rev) {
      if (rev in doc.revs) {
        // Make a list of attachments that are used by the revisions being
        // deleted
        if (doc.revs[rev].data._attachments) {
          for (const k in doc.revs[rev].data._attachments) {
            attachments.push(doc.revs[rev].data._attachments[k].digest);
          }
        }
        delete doc.revs[rev];
      }
    });

    // Attachments have a list of revisions that are using them, when
    // that list becomes empty we can delete the attachment.
    attachments.forEach(function (digest) {
      revs.forEach(function (rev) {
        delete doc.attachments[digest].revs[rev];
      });
      if (!Object.keys(doc.attachments[digest].revs).length) {
        delete doc.attachments[digest];
      }
    });

    docStore.put(doc);
  };

  txn.txn.oncomplete = function () {
    callback();
  };
}

function destroy (dbOpts, openDatabases, idbChanges, callback) {

  idbChanges.removeAllListeners(dbOpts.name);

  function doDestroy() {
    const req = indexedDB.deleteDatabase(dbOpts.name);
    req.onsuccess = function () {
      delete openDatabases[dbOpts.name];
      callback(null, {ok: true});
    };
  }

  // If the database is open we need to close it
  if (dbOpts.name in openDatabases) {
    openDatabases[dbOpts.name].then(function (res) {
      res.idb.close();
      doDestroy();
    });
  } else {
    doDestroy();
  }

}

// Adapted from
// https://github.com/pouchdb/pouchdb/blob/master/packages/node_modules/pouchdb-find/src/adapters/local/find/query-planner.js#L20-L24
// This could change / improve in the future?
const COUCH_COLLATE_LO = null;
const COUCH_COLLATE_HI = '\uffff'; // actually used as {"\uffff": {}}

// Adapted from: https://www.w3.org/TR/IndexedDB/#compare-two-keys
// Importantly, *there is no upper bound possible* in idb. The ideal data
// structure an infinitely deep array:
//   const IDB_COLLATE_HI = []; IDB_COLLATE_HI.push(IDB_COLLATE_HI)
// But IDBKeyRange is not a fan of shenanigans, so I've just gone with 12 layers
// because it looks nice and surely that's enough!
const IDB_COLLATE_LO = Number.NEGATIVE_INFINITY;
const IDB_COLLATE_HI = [[[[[[[[[[[[]]]]]]]]]]]];

//
// TODO: this should be made offical somewhere and used by AllDocs / get /
// changes etc as well.
//
function externaliseRecord(idbDoc) {
  const doc = idbDoc.revs[idbDoc.rev].data;
  doc._id = idbDoc.id;
  doc._rev = idbDoc.rev;
  if (idbDoc.deleted) {
    doc._deleted = true;
  }

  return doc;
}

/**
 * Generates a keyrange based on the opts passed to query
 *
 * The first key is always 0, as that's how we're filtering out deleted entries.
 */
function generateKeyRange(opts) {
  function defined(obj, k) {
    return obj[k] !== void 0;
  }

  // Converts a valid CouchDB key into a valid IndexedDB one
  function convert(key, exact) {
    // The first item in every native index is doc.deleted, and we always want
    // to only search documents that are not deleted.
    // "foo" -> [0, "foo"]
    const filterDeleted = [0].concat(key);

    return filterDeleted.map(function (k) {
      // null, true and false are not indexable by indexeddb. When we write
      // these values we convert them to these constants, and so when we
      // query for them we need to convert the query also.
      if (k === null && exact) {
        // for non-exact queries we treat null as a collate property
        // see `if (!exact)` block below
        return IDB_NULL;
      } else if (k === true) {
        return IDB_TRUE;
      } else if (k === false) {
        return IDB_FALSE;
      }

      if (!exact) {
        // We get passed CouchDB's collate low and high values, so for non-exact
        // ranged queries we're going to convert them to our IDB equivalents
        if (k === COUCH_COLLATE_LO) {
          return IDB_COLLATE_LO;
        } else if (Object.prototype.hasOwnProperty.call(k, COUCH_COLLATE_HI)) {
          return IDB_COLLATE_HI;
        }
      }

      return k;
    });
  }

  // CouchDB and so PouchdB defaults to true. We need to make this explicit as
  // we invert these later for IndexedDB.
  if (!defined(opts, 'inclusive_end')) {
    opts.inclusive_end = true;
  }
  if (!defined(opts, 'inclusive_start')) {
    opts.inclusive_start = true;
  }

  if (opts.descending) {
    // Flip before generating. We'll check descending again later when performing
    // an index request
    const realEndkey = opts.startkey,
        realInclusiveEnd = opts.inclusive_start;

    opts.startkey = opts.endkey;
    opts.endkey = realEndkey;
    opts.inclusive_start = opts.inclusive_end;
    opts.inclusive_end = realInclusiveEnd;
  }

  try {
    if (defined(opts, 'key')) {
      return IDBKeyRange.only(convert(opts.key, true));
    }

    if (defined(opts, 'startkey') && !defined(opts, 'endkey')) {
      // lowerBound, but without the deleted docs.
      // [1] is the start of the deleted doc range, and we don't want to include then.
      return IDBKeyRange.bound(
        convert(opts.startkey), [1],
        !opts.inclusive_start, true
      );
    }

    if (!defined(opts, 'startkey') && defined(opts, 'endkey')) {
      return IDBKeyRange.upperBound(convert(opts.endkey), !opts.inclusive_end);
    }

    if (defined(opts, 'startkey') && defined(opts, 'endkey')) {
      return IDBKeyRange.bound(
        convert(opts.startkey),    convert(opts.endkey),
        !opts.inclusive_start, !opts.inclusive_end
      );
    }

    return IDBKeyRange.only([0]);
  } catch (err) {
    console.error('Could not generate keyRange', err, opts);
    throw Error('Could not generate key range with ' + JSON.stringify(opts));
  }
}

function getIndexHandle(pdb, fields, reject) {
  const indexName = naturalIndexName(fields);

  return new Promise(function (resolve) {
    pdb._openTransactionSafely([DOC_STORE], 'readonly', function (err, txn) {
      if (err) {
        return idbError(reject)(err);
      }

      txn.onabort = idbError(reject);
      txn.ontimeout = idbError(reject);

      const existingIndexNames = Array.from(txn.objectStore(DOC_STORE).indexNames);

      if (existingIndexNames.indexOf(indexName) === -1) {
        // The index is missing, force a db restart and try again
        pdb._freshen()
          .then(function () { return getIndexHandle(pdb, fields, reject); })
          .then(resolve);
      } else {
        resolve(txn.objectStore(DOC_STORE).index(indexName));
      }
    });
  });
}

// In theory we should return something like the doc example below, but find
// only needs rows: [{doc: {...}}], so I think we can just not bother for now
// {
//   "offset" : 0,
//   "rows": [{
//     "id": "doc3",
//     "key": "Lisa Says",
//     "value": null,
//     "doc": {
//       "_id": "doc3",
//       "_rev": "1-z",
//       "title": "Lisa Says"
//     }
//   }],
//   "total_rows" : 4
// }
function query(idb, signature, opts, fallback) {
  // At this stage, in the current implementation, find has already gone through
  // and determined if the index already exists from PouchDB's perspective (eg
  // there is a design doc for it).
  //
  // If we find that the index doesn't exist this means we have to close and
  // re-open the DB to correct indexes before proceeding, at which point the
  // index should exist.

  const pdb = this;

  // Assumption, there will be only one /, between the design document name
  // and the view name.
  const parts = signature.split('/');

  return new Promise(function (resolve, reject) {
    pdb.get('_design/' + parts[0]).then(function (ddoc) {
      if (isPartialFilterView(ddoc, parts[1])) {
        // Fix for #8522
        // An IndexedDB index is always over all entries. And there is no way to filter them.
        // Therefore the normal findAbstractMapper will be used
        // for indexes with partial_filter_selector.
        return fallback(signature, opts).then(resolve, reject);
      }

      const fields = rawIndexFields(ddoc, parts[1]);
      if (!fields) {
        throw new Error('ddoc ' + ddoc._id +' with view ' + parts[1] +
          ' does not have map.options.def.fields defined.');
      }

      let skip = opts.skip;
      let limit = Number.isInteger(opts.limit) && opts.limit;

      return getIndexHandle(pdb, fields, reject)
        .then(function (indexHandle) {
          const keyRange = generateKeyRange(opts);
          const req = indexHandle.openCursor(keyRange, opts.descending ? 'prev' : 'next');

          const rows = [];
          req.onerror = idbError(reject);
          req.onsuccess = function (e) {
            const cursor = e.target.result;

            if (!cursor || limit === 0) {
              return resolve({
                rows
              });
            }

            if (skip) {
              cursor.advance(skip);
              skip = false;
              return;
            }

            if (limit) {
              limit = limit - 1;
            }

            rows.push({doc: externaliseRecord(cursor.value)});
            cursor.continue();
          };
        });
      })
      .catch(reject);
  });

}

function viewCleanup(idb, fallback) {
  // I'm not sure we have to do anything here.
  //
  // One option is to just close and re-open the DB, which performs the same
  // action. The only reason you'd want to call this is if you deleted a bunch
  // of indexes and wanted the space back immediately.
  //
  // Otherwise index cleanup happens when:
  //  - A DB is opened
  //  - A find query is performed against an index that doesn't exist but should

  // Fix for #8522
  // On views with partial_filter_selector the standard find-abstract-mapper is used.
  // Its indexes must be cleaned up.
  // Fallback is the standard viewCleanup.
  return fallback();
}

function purgeAttachments(doc, revs) {
  if (!doc.attachments) {
    // If there are no attachments, doc.attachments is an empty object
    return {};
  }

  // Iterate over all attachments and remove the respective revs
  for (let key in doc.attachments) {
    const attachment = doc.attachments[key];

    for (let rev of revs) {
      if (attachment.revs[rev]) {
        delete attachment.revs[rev];
      }
    }

    if (Object.keys(attachment.revs).length === 0) {
      delete doc.attachments[key];
    }
  }

  return doc.attachments;
}

// `purge()` expects a path of revisions in its revs argument that:
// - starts with a leaf rev
// - continues sequentially with the remaining revs of that leaf’s branch
//
// eg. for this rev tree:
// 1-9692 ▶ 2-37aa ▶ 3-df22 ▶ 4-6e94 ▶ 5-df4a ▶ 6-6a3a ▶ 7-57e5
//          ┃                 ┗━━━━━━▶ 5-8d8c ▶ 6-65e0
//          ┗━━━━━━▶ 3-43f6 ▶ 4-a3b4
//
// …if you wanted to purge '7-57e5', you would provide ['7-57e5', '6-6a3a', '5-df4a']
//
// The purge adapter implementation in `pouchdb-core` uses the helper function `findPathToLeaf`
// from `pouchdb-merge` to construct this array correctly. Since this purge implementation is
// only ever called from there, we do no additional checks here as to whether `revs` actually
// fulfills the criteria above, since `findPathToLeaf` already does these.
function purge(txn, docId, revs, callback) {
  if (txn.error) {
    return callback(txn.error);
  }

  const docStore = txn.txn.objectStore(DOC_STORE);
  const deletedRevs = [];
  let documentWasRemovedCompletely = false;
  docStore.get(docId).onsuccess = (e) => {
    const doc = e.target.result;

    // we could do a dry run here to check if revs is a proper path towards a leaf in the rev tree

    for (const rev of revs) {
      // purge rev from tree
      doc.rev_tree = removeLeafFromRevTree(doc.rev_tree, rev);

      // assign new revs
      delete doc.revs[rev];
      deletedRevs.push(rev);
    }

    if (doc.rev_tree.length === 0) {
      // if the rev tree is empty, we can delete the entire document
      docStore.delete(doc.id);
      documentWasRemovedCompletely = true;
      return;
    }

    // find new winning rev
    doc.rev = winningRev(doc);
    doc.data = doc.revs[doc.rev].data;
    doc.attachments = purgeAttachments(doc, revs);

    // finally, write the purged doc
    docStore.put(doc);
  };

  txn.txn.oncomplete = function () {
    callback(null, {
      ok: true,
      deletedRevs,
      documentWasRemovedCompletely
    });
  };
}

const ADAPTER_NAME = 'indexeddb';

// TODO: Constructor should be capitalised
const idbChanges = new Changes();

// A shared list of database handles
const openDatabases = {};

function IndexeddbPouch(dbOpts, callback) {

  if (dbOpts.view_adapter) {
    console.log('Please note that the indexeddb adapter manages _find indexes itself, therefore it is not using your specified view_adapter');
  }

  const api = this;
  let metadata = {};

  // Wrapper that gives you an active DB handle. You probably want $t.
  const $ = function (fun) {
    return function () {
      const args = Array.prototype.slice.call(arguments);
      setup(openDatabases, api, dbOpts).then(function (res) {
        metadata = res.metadata;
        args.unshift(res.idb);
        fun.apply(api, args);
      }).catch(function (err) {
        const last = args.pop();
        if (typeof last === 'function') {
          last(err);
        } else {
          console.error(err);
        }
      });
    };
  };
  // the promise version of $
  const $p = function (fun) {
    return function () {
      const args = Array.prototype.slice.call(arguments);

      return setup(openDatabases, api, dbOpts).then(function (res) {
        metadata = res.metadata;
        args.unshift(res.idb);

        return fun.apply(api, args);
      });
    };
  };
  // Wrapper that gives you a safe transaction handle. It's important to use
  // this instead of opening your own transaction from a db handle got from $,
  // because in the time between getting the db handle and opening the
  // transaction it may have been invalidated by index changes.
  const $t = function (fun, stores, mode) {
    mode = mode || 'readonly';

    return function () {
      const args = Array.prototype.slice.call(arguments);
      const txn = {};
      setup(openDatabases, api, dbOpts).then(function (res) {
        metadata = res.metadata;
        txn.txn = res.idb.transaction(stores, mode);
      }).catch(function (err) {
        console.error('Failed to establish transaction safely');
        console.error(err);
        txn.error = err;
      }).then(function () {
        args.unshift(txn);
        fun.apply(api, args);
      });
    };
  };

  api._openTransactionSafely = function (stores, mode, callback) {
    $t(function (txn, callback) {
      callback(txn.error, txn.txn);
    }, stores, mode)(callback);
  };

  api._remote = false;
  api.type = function () { return ADAPTER_NAME; };

  api._id = $(function (_, cb) {
    cb(null, metadata.db_uuid);
  });

  api._info = $(function (_, cb) {
    return info(metadata, cb);
  });

  api._get = $t(get, [DOC_STORE]);
  api._getLocal = $t(function (txn, id, callback) {
    return getLocal(txn, id, api, callback);
  }, [META_LOCAL_STORE]);

  api._bulkDocs = $(function (_, req, opts, callback) {
    bulkDocs(api, req, opts, metadata, dbOpts, idbChanges, callback);
  });

  api._allDocs = $t(function (txn, opts, cb) {
    allDocs(txn, metadata, opts, cb);
  }, [DOC_STORE]);

  api._getAttachment = getAttachment;

  api._changes = $t(function (txn, opts) {
    changes(txn, idbChanges, api, dbOpts, opts);
  }, [DOC_STORE]);

  api._getRevisionTree = $t(getRevisionTree, [DOC_STORE]);
  api._doCompaction = $t(doCompaction, [DOC_STORE], 'readwrite');

  api._customFindAbstractMapper = {
    query: $p(query),
    viewCleanup: $p(viewCleanup)
  };

  api._destroy = function (opts, callback) {
    return destroy(dbOpts, openDatabases, idbChanges, callback);
  };

  api._close = $(function (db, cb) {
    delete openDatabases[dbOpts.name];
    db.close();
    cb();
  });

  // Closing and re-opening the DB re-generates native indexes
  api._freshen = function () {
    return new Promise(function (resolve) {
      api._close(function () {
        $(resolve)();
      });
    });
  };

  api._purge = $t(purge, [DOC_STORE], 'readwrite');

  // TODO: this setTimeout seems nasty, if its needed lets
  // figure out / explain why
  setTimeout(function () {
    callback(null, api);
  });
}

// TODO: this isnt really valid permanently, just being lazy to start
IndexeddbPouch.valid = function () {
  return true;
};

function IndexeddbPouchPlugin (PouchDB) {
  PouchDB.adapter(ADAPTER_NAME, IndexeddbPouch, true);
}

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

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

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