firetruss/dist/firetruss.umd.js

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory(require('lodash'), require('vue')) :
  typeof null === 'function' && null.amd ? null(['lodash', 'vue'], factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.Truss = factory(global._, global.Vue));
}(this, (function (_, Vue) { 'use strict';

  _ = _ && Object.prototype.hasOwnProperty.call(_, 'default') ? _['default'] : _;
  Vue = Vue && Object.prototype.hasOwnProperty.call(Vue, 'default') ? Vue['default'] : Vue;

  var vue;
  var lastDigestRequest = 0, digestInProgress = false;
  var bareDigest = function() {
    if (vue.digestRequest > lastDigestRequest) { return; }
    vue.digestRequest = lastDigestRequest + 1;
  };

  var angularProxy = {
    active: typeof window !== 'undefined' && window.angular
  };

  if (angularProxy.active) {
    initAngular();
  } else {
    _.forEach(['digest', 'watch', 'defineModule', 'debounceDigest'], function (method) {
      angularProxy[method] = _.noop;
    });
  }

  function initAngular() {
    var module = window.angular.module('firetruss', []);
    angularProxy.digest = bareDigest;
    angularProxy.watch = function() {throw new Error('Angular watch proxy not yet initialized');};
    angularProxy.defineModule = function(Truss) {
      module.constant('Truss', Truss);
    };
    angularProxy.debounceDigest = function(wait) {
      if (wait) {
        var debouncedDigest = _.debounce(bareDigest, wait);
        angularProxy.digest = function() {
          if (vue.digestRequest > lastDigestRequest) { return; }
          if (digestInProgress) { bareDigest(); } else { debouncedDigest(); }
        };
      } else {
        angularProxy.digest = bareDigest;
      }
    };

    module.config(['$provide', function($provide) {
      $provide.decorator('$rootScope', ['$delegate', '$exceptionHandler',
        function($delegate, $exceptionHandler) {
          var rootScope = $delegate;
          angularProxy.watch = rootScope.$watch.bind(rootScope);
          var proto = Object.getPrototypeOf(rootScope);
          var angularDigest = proto.$digest;
          proto.$digest = bareDigest;
          proto.$digest.original = angularDigest;
          vue = new Vue({data: {digestRequest: 0}});
          vue.$watch(function () { return vue.digestRequest; }, function () {
            if (vue.digestRequest > lastDigestRequest) {
              // Make sure we execute the digest outside the Vue task queue, because otherwise if the
              // client replaced Promise with angular.$q all Truss.nextTick().then() functions will be
              // executed inside the Angular digest and hence inside the Vue task queue. But
              // Truss.nextTick() is used precisely to avoid that.  Note that it's OK to use
              // Vue.nextTick() here because even though it will schedule a flush via Promise.then()
              // it only uses the native Promise, before it could've been monkey-patched by the app.
              Vue.nextTick(function () {
                if (vue.digestRequest <= lastDigestRequest) { return; }
                digestInProgress = true;
                rootScope.$digest.original.call(rootScope);
                lastDigestRequest = vue.digestRequest = vue.digestRequest + 1;
              });
            } else {
              digestInProgress = false;
            }
          });
          var watcher = _.last(vue._watchers || vue._scope.effects);
          watcher.id = Infinity;  // make sure watcher is scheduled last
          patchRenderWatcherGet(Object.getPrototypeOf(watcher));
          return rootScope;
        }
      ]);
    }]);
  }

  // This is a kludge that catches errors that get through render watchers and end up killing the
  // entire Vue event loop (e.g., errors raised in transition callbacks).  The state of the DOM may
  // not be consistent after such an error is caught, but the global error handler should stop the
  // world anyway.  May be related to https://github.com/vuejs/vue/issues/7653.
  function patchRenderWatcherGet(prototype) {
    var originalGet = prototype.get;
    prototype.get = function get() {
      try {
        return originalGet.call(this);
      } catch (e) {
        if (this.vm._watcher === this && Vue.config.errorHandler) {
          Vue.config.errorHandler(e, this.vm, 'uncaught render error');
        } else {
          throw e;
        }
      }
    };
  }

  var LruCacheItem = function LruCacheItem(key, value) {
    this.key = key;
    this.value = value;
    this.touch();
  };

  LruCacheItem.prototype.touch = function touch () {
    this.timestamp = Date.now();
  };


  var LruCache = function LruCache(maxSize, pruningSize) {
    this._items = Object.create(null);
    this._size = 0;
    this._maxSize = maxSize;
    this._pruningSize = pruningSize || Math.ceil(maxSize * 0.10);
  };

  LruCache.prototype.has = function has (key) {
    return Boolean(this._items[key]);
  };

  LruCache.prototype.get = function get (key) {
    var item = this._items[key];
    if (!item) { return; }
    item.touch();
    return item.value;
  };

  LruCache.prototype.set = function set (key, value) {
    var item = this._items[key];
    if (item) {
      item.value = value;
    } else {
      if (this._size >= this._maxSize) { this._prune(); }
      this._items[key] = new LruCacheItem(key, value);
      this._size += 1;
    }
  };

  LruCache.prototype.delete = function delete$1 (key) {
    var item = this._items[key];
    if (!item) { return; }
    delete this._items[key];
    this._size -= 1;
  };

  LruCache.prototype._prune = function _prune () {
    var itemsToPrune =
      _(this._items).toArray().sortBy('timestamp').take(this._pruningSize).value();
    for (var i = 0, list = itemsToPrune; i < list.length; i += 1) {
        var item = list[i];

        this.delete(item.key);
      }
  };

  var pathSegments = new LruCache(1000);
  var pathMatchers = {};
  var maxNumPathMatchers = 1000;


  function escapeKey(key) {
    if (!key) { return key; }
    // eslint-disable-next-line no-control-regex
    return key.toString().replace(/[\x00-\x1f\\.$#[\]\x7f/]/g, function(char) {
      return '\\' + _.padStart(char.charCodeAt(0).toString(16), 2, '0');
    });
  }

  function unescapeKey(key) {
    if (!key) { return key; }
    return key.toString().replace(/\\[0-9a-f]{2}/gi, function(code) {
      return String.fromCharCode(parseInt(code.slice(1), 16));
    });
  }

  function escapeKeys(object) {
    // isExtensible check avoids trying to escape references to Firetruss internals.
    if (!(_.isObject(object) && Object.isExtensible(object))) { return object; }
    var result = object;
    for (var key in object) {
      if (!object.hasOwnProperty(key)) { continue; }
      var value = object[key];
      var escapedKey = escapeKey(key);
      var escapedValue = escapeKeys(value);
      if (escapedKey !== key || escapedValue !== value) {
        if (result === object) { result = _.clone(object); }
        result[escapedKey] = escapedValue;
        if (result[key] === value) { delete result[key]; }
      }
    }
    return result;
  }

  function joinPath() {
    var segments = [];
    for (var i = 0, list = arguments; i < list.length; i += 1) {
      var segment = list[i];

      if (!_.isString(segment)) { segment = '' + segment; }
      if (segment.charAt(0) === '/') { segments.splice(0, segments.length); }
      segments.push(segment);
    }
    if (segments[0] === '/') { segments[0] = ''; }
    return segments.join('/');
  }

  function splitPath(path, leaveSegmentsEscaped) {
    var key = (leaveSegmentsEscaped ? 'esc:' : '') + path;
    var segments = pathSegments.get(key);
    if (!segments) {
      segments = path.split('/');
      if (!leaveSegmentsEscaped) { segments = _.map(segments, unescapeKey); }
      pathSegments.set(key, segments);
    }
    return segments;
  }


  var PathMatcher = function PathMatcher(pattern) {
    var this$1 = this;

    this.variables = [];
    var prefixMatch = _.endsWith(pattern, '/$*');
    if (prefixMatch) { pattern = pattern.slice(0, -3); }
    var pathTemplate = pattern.replace(/\/\$[^/]*/g, function (match) {
      if (match.length > 1) { this$1.variables.push(match.slice(1)); }
      return '\u0001';
    });
    Object.freeze(this.variables);
    if (/[.$#[\]]|\\(?![0-9a-f][0-9a-f])/i.test(pathTemplate)) {
      throw new Error('Path pattern has unescaped keys: ' + pattern);
    }
    this._regex = new RegExp(
      // eslint-disable-next-line no-control-regex
      '^' + pathTemplate.replace(/\u0001/g, '/([^/]+)') + (prefixMatch ? '($|/)' : '$'));
  };

  PathMatcher.prototype.match = function match (path) {
    this._regex.lastIndex = 0;
    var match = this._regex.exec(path);
    if (!match) { return; }
    var bindings = {};
    for (var i = 0; i < this.variables.length; i++) {
      bindings[this.variables[i]] = unescapeKey(match[i + 1]);
    }
    return bindings;
  };

  PathMatcher.prototype.test = function test (path) {
    return this._regex.test(path);
  };

  PathMatcher.prototype.toString = function toString () {
    return this._regex.toString();
  };

  function makePathMatcher(pattern) {
    var matcher = pathMatchers[pattern];
    if (!matcher) {
      matcher = new PathMatcher(pattern);
      // Minimal pseudo-LRU behavior, since we don't expect to actually fill up the cache.
      if (_.size(pathMatchers) === maxNumPathMatchers) { delete pathMatchers[_.keys(pathMatchers)[0]]; }
      pathMatchers[pattern] = matcher;
    }
    return matcher;
  }

  var MIN_WORKER_VERSION = '2.3.0';


  var Snapshot = function Snapshot(ref) {
    var path = ref.path;
    var value = ref.value;
    var exists = ref.exists;
    var writeSerial = ref.writeSerial;

    this._path = path;
    this._value = value;
    this._exists = value === undefined ? exists || false : value !== null;
    this._writeSerial = writeSerial;
  };

  var prototypeAccessors = { path: { configurable: true },exists: { configurable: true },value: { configurable: true },key: { configurable: true },writeSerial: { configurable: true } };

  prototypeAccessors.path.get = function () {
    return this._path;
  };

  prototypeAccessors.exists.get = function () {
    return this._exists;
  };

  prototypeAccessors.value.get = function () {
    if (this._value === undefined) { throw new Error('Value omitted from snapshot'); }
    return this._value;
  };

  prototypeAccessors.key.get = function () {
    if (this._key === undefined) { this._key = unescapeKey(this._path.replace(/.*\//, '')); }
    return this._key;
  };

  prototypeAccessors.writeSerial.get = function () {
    return this._writeSerial;
  };

  Object.defineProperties( Snapshot.prototype, prototypeAccessors );


  var Bridge = function Bridge(webWorker) {
    var this$1 = this;

    this._idCounter = 0;
    this._deferreds = {};
    this._suspended = false;
    this._servers = {};
    this._callbacks = {};
    this._log = _.noop;
    this._inboundMessages = [];
    this._outboundMessages = [];
    this._flushMessageQueue = this._flushMessageQueue.bind(this);
    this._port = webWorker.port || webWorker;
    this._shared = !!webWorker.port;
    Object.seal(this);
    this._port.onmessage = this._receive.bind(this);
    window.addEventListener('unload', function () {this$1._send({msg: 'destroy'});});
  };

  Bridge.prototype.init = function init (webWorker, config) {
    var items = [];
    try {
      var storage = window.localStorage || window.sessionStorage;
      if (!storage) { throw new Error('localStorage and sessionStorage not available'); }
      for (var i = 0; i < storage.length; i++) {
        var key = storage.key(i);
        items.push({key: key, value: storage.getItem(key)});
      }
    } catch (e) {
      // Some browsers don't like us accessing local storage -- nothing we can do.
    }
    return this._send({msg: 'init', storage: items, config: config}).then(function (response) {
      var workerVersion = response.version.match(/^(\d+)\.(\d+)\.(\d+)(-.*)?$/);
      if (workerVersion) {
        var minVersion = MIN_WORKER_VERSION.match(/^(\d+)\.(\d+)\.(\d+)(-.*)?$/);
        // Major version must match precisely, minor and patch must be greater than or equal.
        var sufficient = workerVersion[1] === minVersion[1] && (
          workerVersion[2] > minVersion[2] ||
          workerVersion[2] === minVersion[2] && workerVersion[3] >= minVersion[3]
        );
        if (!sufficient) {
          return Promise.reject(new Error(
            "Incompatible Firetruss worker version: " + (response.version) + " " +
            "(" + MIN_WORKER_VERSION + " or better required)"
          ));
        }
      }
      return response;
    });
  };

  Bridge.prototype.suspend = function suspend (suspended) {
    if (suspended === undefined) { suspended = true; }
    if (this._suspended === suspended) { return; }
    this._suspended = suspended;
    if (!suspended) {
      this._receiveMessages(this._inboundMessages);
      this._inboundMessages = [];
      if (this._outboundMessages.length) { Promise.resolve().then(this._flushMessageQueue); }
    }
  };

  Bridge.prototype.enableLogging = function enableLogging (fn) {
    if (fn) {
      if (fn === true) {
        fn = console.log.bind(console);
        this._send({msg: 'enableFirebaseLogging', value: true});
      }
      this._log = fn;
    } else {
      this._send({msg: 'enableFirebaseLogging', value: false});
      this._log = _.noop;
    }
  };

  Bridge.prototype._send = function _send (message) {
      var this$1 = this;

    message.id = ++this._idCounter;
    var promise;
    if (message.oneWay) {
      promise = Promise.resolve();
    } else {
      promise = new Promise(function (resolve, reject) {
        this$1._deferreds[message.id] = {resolve: resolve, reject: reject};
      });
      var deferred = this._deferreds[message.id];
      deferred.promise = promise;
      promise.sent = new Promise(function (resolve) {
        deferred.resolveSent = resolve;
      });
      deferred.params = message;
    }
    if (!this._outboundMessages.length && !this._suspended) {
      Promise.resolve().then(this._flushMessageQueue);
    }
    this._log('send:', message);
    this._outboundMessages.push(message);
    return promise;
  };

  Bridge.prototype._flushMessageQueue = function _flushMessageQueue () {
    try {
      this._port.postMessage(this._outboundMessages);
      this._outboundMessages = [];
    } catch (e) {
      e.extra = {messages: this._outboundMessages};
      throw e;
    }
  };

  Bridge.prototype._receive = function _receive (event) {
    if (this._suspended) {
      this._inboundMessages = this._inboundMessages.concat(event.data);
    } else {
      this._receiveMessages(event.data);
    }
  };

  Bridge.prototype._receiveMessages = function _receiveMessages (messages) {
    for (var i = 0, list = messages; i < list.length; i += 1) {
      var message = list[i];

        this._log('recv:', message);
      var fn = this[message.msg];
      if (!_.isFunction(fn)) { throw new Error('Unknown message: ' + message.msg); }
      fn.call(this, message);
    }
  };

  Bridge.prototype.bindExposedFunction = function bindExposedFunction (name) {
    return (function() {
      return this._send({msg: 'call', name: name, args: Array.prototype.slice.call(arguments)});
    }).bind(this);
  };

  Bridge.prototype.resolve = function resolve (message) {
    var deferred = this._deferreds[message.id];
    if (!deferred) { throw new Error('Received resolution to inexistent Firebase call'); }
    delete this._deferreds[message.id];
    deferred.resolve(message.result);
  };

  Bridge.prototype.reject = function reject (message) {
    var deferred = this._deferreds[message.id];
    if (!deferred) { throw new Error('Received rejection of inexistent Firebase call'); }
    delete this._deferreds[message.id];
    deferred.reject(errorFromJson(message.error, deferred.params));
  };

  Bridge.prototype.updateLocalStorage = function updateLocalStorage (ref) {
      var items = ref.items;

    try {
      var storage = window.localStorage || window.sessionStorage;
      for (var i = 0, list = items; i < list.length; i += 1) {
        var item = list[i];

          if (item.value === null) {
          storage.removeItem(item.key);
        } else {
          storage.setItem(item.key, item.value);
        }
      }
    } catch (e) {
      // If we're denied access, there's nothing we can do.
    }
  };

  Bridge.prototype.trackServer = function trackServer (rootUrl) {
    if (this._servers.hasOwnProperty(rootUrl)) { return Promise.resolve(); }
    var server = this._servers[rootUrl] = {authListeners: []};
    var authCallbackId = this._registerCallback(this._authCallback.bind(this, server));
    this._send({msg: 'onAuth', url: rootUrl, callbackId: authCallbackId});
  };

  Bridge.prototype._authCallback = function _authCallback (server, auth) {
    server.auth = auth;
    for (var i = 0, list = server.authListeners; i < list.length; i += 1) {
        var listener = list[i];

        listener(auth);
      }
  };

  Bridge.prototype.onAuth = function onAuth (rootUrl, callback, context) {
    var listener = callback.bind(context);
    listener.callback = callback;
    listener.context = context;
    this._servers[rootUrl].authListeners.push(listener);
    listener(this.getAuth(rootUrl));
  };

  Bridge.prototype.offAuth = function offAuth (rootUrl, callback, context) {
    var authListeners = this._servers[rootUrl].authListeners;
    for (var i = 0; i < authListeners.length; i++) {
      var listener = authListeners[i];
      if (listener.callback === callback && listener.context === context) {
        authListeners.splice(i, 1);
        break;
      }
    }
  };

  Bridge.prototype.getAuth = function getAuth (rootUrl) {
    return this._servers[rootUrl].auth;
  };

  Bridge.prototype.authWithCustomToken = function authWithCustomToken (url, authToken) {
    return this._send({msg: 'authWithCustomToken', url: url, authToken: authToken});
  };

  Bridge.prototype.authAnonymously = function authAnonymously (url) {
    return this._send({msg: 'authAnonymously', url: url});
  };

  Bridge.prototype.unauth = function unauth (url) {
    return this._send({msg: 'unauth', url: url});
  };

  Bridge.prototype.set = function set (url, value, writeSerial) {return this._send({msg: 'set', url: url, value: value, writeSerial: writeSerial});};
  Bridge.prototype.update = function update (url, value, writeSerial) {return this._send({msg: 'update', url: url, value: value, writeSerial: writeSerial});};

  Bridge.prototype.once = function once (url, writeSerial) {
    return this._send({msg: 'once', url: url, writeSerial: writeSerial}).then(function (snapshot) { return new Snapshot(snapshot); });
  };

  Bridge.prototype.on = function on (listenerKey, url, spec, eventType, snapshotCallback, cancelCallback, context, options) {
    var handle = {
      listenerKey: listenerKey, eventType: eventType, snapshotCallback: snapshotCallback, cancelCallback: cancelCallback, context: context,
      params: {msg: 'on', listenerKey: listenerKey, url: url, spec: spec, eventType: eventType, options: options}
    };
    var callback = this._onCallback.bind(this, handle);
    this._registerCallback(callback, handle);
    // Keep multiple IDs to allow the same snapshotCallback to be reused.
    snapshotCallback.__callbackIds = snapshotCallback.__callbackIds || [];
    snapshotCallback.__callbackIds.push(handle.id);
    this._send({
      msg: 'on', listenerKey: listenerKey, url: url, spec: spec, eventType: eventType, callbackId: handle.id, options: options
    }).catch(function (error) {
      callback(error);
    });
  };

  Bridge.prototype.off = function off (listenerKey, url, spec, eventType, snapshotCallback, context) {
      var this$1 = this;

    var idsToDeregister = [];
    var callbackId;
    if (snapshotCallback) {
      callbackId = this._findAndRemoveCallbackId(
        snapshotCallback, function (handle) { return _.isMatch(handle, {listenerKey: listenerKey, eventType: eventType, context: context}); }
      );
      if (!callbackId) { return Promise.resolve(); }// no-op, never registered or already deregistered
      idsToDeregister.push(callbackId);
    } else {
      for (var i = 0, list = _.keys(this._callbacks); i < list.length; i += 1) {
        var id = list[i];

          var handle = this._callbacks[id];
        if (handle.listenerKey === listenerKey && (!eventType || handle.eventType === eventType)) {
          idsToDeregister.push(id);
        }
      }
    }
    // Nullify callbacks first, then deregister after off() is complete.We don't want any
    // callbacks in flight from the worker to be invoked while the off() is processing, but we don't
    // want them to throw an exception either.
    for (var i$1 = 0, list$1 = idsToDeregister; i$1 < list$1.length; i$1 += 1) {
        var id$1 = list$1[i$1];

        this._nullifyCallback(id$1);
      }
    return this._send({msg: 'off', listenerKey: listenerKey, url: url, spec: spec, eventType: eventType, callbackId: callbackId}).then(function () {
      for (var i = 0, list = idsToDeregister; i < list.length; i += 1) {
          var id = list[i];

          this$1._deregisterCallback(id);
        }
    });
  };

  Bridge.prototype._onCallback = function _onCallback (handle, error, snapshotJson) {
    if (error) {
      this._deregisterCallback(handle.id);
      var e = errorFromJson(error, handle.params);
      if (handle.cancelCallback) {
        handle.cancelCallback.call(handle.context, e);
      } else {
        console.error(e);
      }
    } else {
      handle.snapshotCallback.call(handle.context, new Snapshot(snapshotJson));
    }
  };

  Bridge.prototype.transaction = function transaction (url, oldValue, relativeUpdates, writeSerial) {
    return this._send(
      {msg: 'transaction', url: url, oldValue: oldValue, relativeUpdates: relativeUpdates, writeSerial: writeSerial}
    ).then(function (result) {
      if (result.snapshots) {
        result.snapshots = _.map(result.snapshots, function (jsonSnapshot) { return new Snapshot(jsonSnapshot); });
      }
      return result;
    });
  };

  Bridge.prototype.onDisconnect = function onDisconnect (url, method, value) {
    return this._send({msg: 'onDisconnect', url: url, method: method, value: value});
  };

  Bridge.prototype.bounceConnection = function bounceConnection () {
    return this._send({msg: 'bounceConnection'});
  };

  Bridge.prototype.callback = function callback (ref) {
      var id = ref.id;
      var args = ref.args;

    var handle = this._callbacks[id];
    if (!handle) { throw new Error('Unregistered callback: ' + id); }
    handle.callback.apply(null, args);
  };

  Bridge.prototype._registerCallback = function _registerCallback (callback, handle) {
    handle = handle || {};
    handle.callback = callback;
    handle.id = "cb" + (++this._idCounter);
    this._callbacks[handle.id] = handle;
    return handle.id;
  };

  Bridge.prototype._nullifyCallback = function _nullifyCallback (id) {
    this._callbacks[id].callback = _.noop;
  };

  Bridge.prototype._deregisterCallback = function _deregisterCallback (id) {
    delete this._callbacks[id];
  };

  Bridge.prototype._findAndRemoveCallbackId = function _findAndRemoveCallbackId (callback, predicate) {
    if (!callback.__callbackIds) { return; }
    var i = 0;
    while (i < callback.__callbackIds.length) {
      var id = callback.__callbackIds[i];
      var handle = this._callbacks[id];
      if (!handle) {
        callback.__callbackIds.splice(i, 1);
        continue;
      }
      if (predicate(handle)) {
        callback.__callbackIds.splice(i, 1);
        return id;
      }
      i += 1;
    }
  };


  function errorFromJson(json, params) {
    if (!json || _.isError(json)) { return json; }
    var error = new Error(json.message);
    error.params = params;
    for (var propertyName in json) {
      if (propertyName === 'message' || !json.hasOwnProperty(propertyName)) { continue; }
      try {
        error[propertyName] = json[propertyName];
      } catch (e) {
        error.extra = error.extra || {};
        error.extra[propertyName] = json[propertyName];
      }
    }
    return error;
  }

  /* eslint-disable no-use-before-define */

  var EMPTY_ANNOTATIONS = {};
  Object.freeze(EMPTY_ANNOTATIONS);


  var Handle = function Handle(tree, path, annotations) {
    this._tree = tree;
    this._path = path.replace(/^\/*/, '/').replace(/\/$/, '') || '/';
    if (annotations) {
      this._annotations = annotations;
      Object.freeze(annotations);
    }
  };

  var prototypeAccessors$1 = { $ref: { configurable: true },key: { configurable: true },path: { configurable: true },_pathPrefix: { configurable: true },parent: { configurable: true },annotations: { configurable: true } };

  prototypeAccessors$1.$ref.get = function () {return this;};
  prototypeAccessors$1.key.get = function () {
    if (!this._key) { this._key = unescapeKey(this._path.replace(/.*\//, '')); }
    return this._key;
  };
  prototypeAccessors$1.path.get = function () {return this._path;};
  prototypeAccessors$1._pathPrefix.get = function () {return this._path === '/' ? '' : this._path;};
  prototypeAccessors$1.parent.get = function () {
    return new Reference(this._tree, this._path.replace(/\/[^/]*$/, ''), this._annotations);
  };

  prototypeAccessors$1.annotations.get = function () {
    return this._annotations || EMPTY_ANNOTATIONS;
  };

  Handle.prototype.child = function child () {
    if (!arguments.length) { return this; }
    var segments = [];
    for (var i = 0, list = arguments; i < list.length; i += 1) {
      var key = list[i];

        if (_.isNil(key)) { return; }
      segments.push(escapeKey(key));
    }
    return new Reference(
      this._tree, ((this._pathPrefix) + "/" + (segments.join('/'))),
      this._annotations
    );
  };

  Handle.prototype.children = function children () {
      var arguments$1 = arguments;

    if (!arguments.length) { return this; }
    var escapedKeys = [];
    for (var i = 0; i < arguments.length; i++) {
      var arg = arguments$1[i];
      if (_.isArray(arg)) {
        var mapping = {};
        var subPath = this._pathPrefix + (escapedKeys.length ? ("/" + (escapedKeys.join('/'))) : '');
        var rest = _.slice(arguments$1, i + 1);
        for (var i$1 = 0, list = arg; i$1 < list.length; i$1 += 1) {
          var key = list[i$1];

            var subRef =
            new Reference(this._tree, (subPath + "/" + (escapeKey(key))), this._annotations);
          var subMapping = subRef.children.apply(subRef, rest);
          if (subMapping) { mapping[key] = subMapping; }
        }
        return mapping;
      }
      if (_.isNil(arg)) { return; }
      escapedKeys.push(escapeKey(arg));
    }
    return new Reference(
      this._tree, ((this._pathPrefix) + "/" + (escapedKeys.join('/'))), this._annotations);
  };

  Handle.prototype.peek = function peek (callback) {
    return this._tree.truss.peek(this, callback);
  };

  Handle.prototype.match = function match (pattern) {
    return makePathMatcher(pattern).match(this.path);
  };

  Handle.prototype.test = function test (pattern) {
    return makePathMatcher(pattern).test(this.path);
  };

  Handle.prototype.isEqual = function isEqual (that) {
    if (!(that instanceof Handle)) { return false; }
    return this._tree === that._tree && this.toString() === that.toString() &&
      _.isEqual(this._annotations, that._annotations);
  };

  Handle.prototype.belongsTo = function belongsTo (truss) {
    return this._tree.truss === truss;
  };

  Object.defineProperties( Handle.prototype, prototypeAccessors$1 );


  var Query = /*@__PURE__*/(function (Handle) {
    function Query(tree, path, spec, annotations) {
      Handle.call(this, tree, path, annotations);
      this._spec = this._copyAndValidateSpec(spec);
      var queryTerms = _(this._spec)
        .map(function (value, key) { return (key + "=" + (encodeURIComponent(JSON.stringify(value)))); })
        .sortBy()
        .join('&');
      this._string = (this._path) + "?" + queryTerms;
      Object.freeze(this);
    }

    if ( Handle ) Query.__proto__ = Handle;
    Query.prototype = Object.create( Handle && Handle.prototype );
    Query.prototype.constructor = Query;

    var prototypeAccessors$1 = { ready: { configurable: true },constraints: { configurable: true } };

    // Vue-bound
    prototypeAccessors$1.ready.get = function () {
      return this._tree.isQueryReady(this);
    };

    prototypeAccessors$1.constraints.get = function () {
      return this._spec;
    };

    Query.prototype.annotate = function annotate (annotations) {
      return new Query(
        this._tree, this._path, this._spec, _.assign({}, this._annotations, annotations));
    };

    Query.prototype._copyAndValidateSpec = function _copyAndValidateSpec (spec) {
      if (!spec.by) { throw new Error('Query needs "by" clause: ' + JSON.stringify(spec)); }
      if (('at' in spec) + ('from' in spec) + ('to' in spec) > 1) {
        throw new Error(
          'Query must contain at most one of "at", "from", or "to" clauses: ' + JSON.stringify(spec));
      }
      if (('first' in spec) + ('last' in spec) > 1) {
        throw new Error(
          'Query must contain at most one of "first" or "last" clauses: ' + JSON.stringify(spec));
      }
      if (!_.some(['at', 'from', 'to', 'first', 'last'], function (clause) { return clause in spec; })) {
        throw new Error(
          'Query must contain at least one of "at", "from", "to", "first", or "last" clauses: ' +
          JSON.stringify(spec));
      }
      spec = _.clone(spec);
      if (spec.by !== '$key' && spec.by !== '$value') {
        if (!(spec.by instanceof Reference)) {
          throw new Error('Query "by" value must be a reference: ' + spec.by);
        }
        var childPath = spec.by.toString();
        if (!_.startsWith(childPath, this._path)) {
          throw new Error(
            'Query "by" value must be a descendant of target reference: ' + spec.by);
        }
        childPath = childPath.slice(this._path.length).replace(/^\/?/, '');
        if (!_.includes(childPath, '/')) {
          throw new Error(
            'Query "by" value must not be a direct child of target reference: ' + spec.by);
        }
        spec.by = childPath.replace(/.*?\//, '');
      }
      Object.freeze(spec);
      return spec;
    };


    Query.prototype.toString = function toString () {
      return this._string;
    };

    Object.defineProperties( Query.prototype, prototypeAccessors$1 );

    return Query;
  }(Handle));


  var Reference = /*@__PURE__*/(function (Handle) {
    function Reference(tree, path, annotations) {
      Handle.call(this, tree, path, annotations);
      Object.freeze(this);
    }

    if ( Handle ) Reference.__proto__ = Handle;
    Reference.prototype = Object.create( Handle && Handle.prototype );
    Reference.prototype.constructor = Reference;

    var prototypeAccessors$2 = { ready: { configurable: true },value: { configurable: true } };

    prototypeAccessors$2.ready.get = function () {return this._tree.isReferenceReady(this);};  // Vue-bound
    prototypeAccessors$2.value.get = function () {return this._tree.getObject(this.path);};  // Vue-bound
    Reference.prototype.toString = function toString () {return this._path;};

    Reference.prototype.annotate = function annotate (annotations) {
      return new Reference(this._tree, this._path, _.assign({}, this._annotations, annotations));
    };

    Reference.prototype.query = function query (spec) {
      return new Query(this._tree, this._path, spec, this._annotations);
    };

    Reference.prototype.set = function set (value) {
      var obj;

      this._checkForUndefinedPath();
      return this._tree.update(this, 'set', ( obj = {}, obj[this.path] = value, obj ));
    };

    Reference.prototype.update = function update (values) {
      this._checkForUndefinedPath();
      return this._tree.update(this, 'update', values);
    };

    Reference.prototype.override = function override (value) {
      var obj;

      this._checkForUndefinedPath();
      return this._tree.update(this, 'override', ( obj = {}, obj[this.path] = value, obj ));
    };

    Reference.prototype.commit = function commit (updateFunction) {
      this._checkForUndefinedPath();
      return this._tree.commit(this, updateFunction);
    };

    Reference.prototype._checkForUndefinedPath = function _checkForUndefinedPath () {
      if (this.path === '/undefined') { throw new Error('Invalid path for operation: ' + this.path); }
    };

    Object.defineProperties( Reference.prototype, prototypeAccessors$2 );

    return Reference;
  }(Handle));

  var SERVER_TIMESTAMP = Object.freeze({'.sv': 'timestamp'});

  function isTrussEqual(a, b) {
    return _.isEqualWith(a, b, isTrussValueEqual);
  }

  function isTrussValueEqual(a, b) {
    if (a === b || a === undefined || a === null || b === undefined || b === null ||
        a.$truss || b.$truss) { return a === b; }
    if (a.isEqual) { return a.isEqual(b); }
  }

  function copyPrototype(a, b) {
    for (var i = 0, list = Object.getOwnPropertyNames(a.prototype); i < list.length; i += 1) {
      var prop = list[i];

      if (prop === 'constructor') { continue; }
      Object.defineProperty(b.prototype, prop, Object.getOwnPropertyDescriptor(a.prototype, prop));
    }
  }

  var commonjsGlobal = typeof globalThis !== 'undefined' ? globalThis : typeof window !== 'undefined' ? window : typeof global !== 'undefined' ? global : typeof self !== 'undefined' ? self : {};

  function createCommonjsModule(fn, basedir, module) {
  	return module = {
  	  path: basedir,
  	  exports: {},
  	  require: function (path, base) {
        return commonjsRequire(path, (base === undefined || base === null) ? module.path : base);
      }
  	}, fn(module, module.exports), module.exports;
  }

  function commonjsRequire () {
  	throw new Error('Dynamic requires are not currently supported by @rollup/plugin-commonjs');
  }

  var performanceNow = createCommonjsModule(function (module) {
  // Generated by CoffeeScript 1.12.2
  (function() {
    var getNanoSeconds, hrtime, loadTime, moduleLoadTime, nodeLoadTime, upTime;

    if ((typeof performance !== "undefined" && performance !== null) && performance.now) {
      module.exports = function() {
        return performance.now();
      };
    } else if ((typeof process !== "undefined" && process !== null) && process.hrtime) {
      module.exports = function() {
        return (getNanoSeconds() - nodeLoadTime) / 1e6;
      };
      hrtime = process.hrtime;
      getNanoSeconds = function() {
        var hr;
        hr = hrtime();
        return hr[0] * 1e9 + hr[1];
      };
      moduleLoadTime = getNanoSeconds();
      upTime = process.uptime() * 1e9;
      nodeLoadTime = moduleLoadTime - upTime;
    } else if (Date.now) {
      module.exports = function() {
        return Date.now() - loadTime;
      };
      loadTime = Date.now();
    } else {
      module.exports = function() {
        return new Date().getTime() - loadTime;
      };
      loadTime = new Date().getTime();
    }

  }).call(commonjsGlobal);


  });

  var StatItem = function StatItem(name) {
    _.assign(this, {name: name, numRecomputes: 0, numUpdates: 0, runtime: 0});
  };

  var prototypeAccessors$2 = { runtimePerRecompute: { configurable: true } };

  StatItem.prototype.add = function add (item) {
    this.runtime += item.runtime;
    this.numUpdates += item.numUpdates;
    this.numRecomputes += item.numRecomputes;
  };

  prototypeAccessors$2.runtimePerRecompute.get = function () {
    return this.numRecomputes ? this.runtime / this.numRecomputes : 0;
  };

  StatItem.prototype.toLogParts = function toLogParts (totals) {
    return [
      ((this.name) + ":"), (" " + ((this.runtime / 1000).toFixed(2)) + "s"),
      ("(" + ((this.runtime / totals.runtime * 100).toFixed(1)) + "%)"),
      (" " + (this.numUpdates) + " upd /"), ((this.numRecomputes) + " runs"),
      ("(" + ((this.numUpdates / this.numRecomputes * 100).toFixed(1)) + "%)"),
      (" " + (this.runtimePerRecompute.toFixed(2)) + "ms / run")
    ];
  };

  Object.defineProperties( StatItem.prototype, prototypeAccessors$2 );

  var Stats = function Stats() {
    this._items = {};
  };

  var prototypeAccessors$1$1 = { list: { configurable: true } };

  Stats.prototype.for = function for$1 (name) {
    if (!this._items[name]) { this._items[name] = new StatItem(name); }
    return this._items[name];
  };

  prototypeAccessors$1$1.list.get = function () {
    return _(this._items).values().sortBy(function (item) { return -item.runtime; }).value();
  };

  Stats.prototype.log = function log (n) {
      if ( n === void 0 ) n = 10;

    var stats = this.list;
    if (!stats.length) { return; }
    var totals = new StatItem('=== Total');
    _.forEach(stats, function (stat) {totals.add(stat);});
    stats = _.take(stats, n);
    var above = new StatItem('--- Above');
    _.forEach(stats, function (stat) {above.add(stat);});
    var lines = _.map(stats, function (item) { return item.toLogParts(totals); });
    lines.push(above.toLogParts(totals));
    lines.push(totals.toLogParts(totals));
    var widths = _.map(_.range(lines[0].length), function (i) { return _(lines).map(function (line) { return line[i].length; }).max(); });
    _.forEach(lines, function (line) {
      console.log(_.map(line, function (column, i) { return _.padStart(column, widths[i]); }).join(' '));
    });
  };

  Stats.prototype.wrap = function wrap (getter, className, propName) {
    var item = this.for((className + "." + propName));
    return function() {
      /* eslint-disable no-invalid-this */
      var startTime = performanceNow();
      var oldValue = this._computedWatchers && this._computedWatchers[propName].value;
      try {
        var newValue = getter.call(this);
        if (!isTrussEqual(oldValue, newValue)) { item.numUpdates += 1; }
        return newValue;
      } finally {
        item.runtime += performanceNow() - startTime;
        item.numRecomputes += 1;
      }
    };
  };

  Object.defineProperties( Stats.prototype, prototypeAccessors$1$1 );

  var stats = new Stats();

  var Connector = function Connector(scope, connections, tree, method, refs) {
    var this$1 = this;

    Object.freeze(connections);
    this._scope = scope;
    this._connections = connections;
    this._tree = tree;
    this._method = method;

    this._subConnectors = {};
    this._disconnects = {};
    this._angularUnwatches = undefined;
    this._data = {};
    this._vue = new Vue({data: {
      descriptors: {},
      refs: refs || {},
      values: _.mapValues(connections, _.constant(undefined))
    }});
    // allow instance-level overrides of destroy() method
    this.destroy = this.destroy;// eslint-disable-line no-self-assign
    Object.seal(this);

    this._linkScopeProperties();

    _.forEach(connections, function (descriptor, key) {
      if (_.isFunction(descriptor)) {
        this$1._bindComputedConnection(key, descriptor);
      } else {
        this$1._connect(key, descriptor);
      }
    });

    if (angularProxy.active && scope && scope.$on && scope.$id) {
      scope.$on('$destroy', function () {this$1.destroy();});
    }
  };

  var prototypeAccessors$3 = { ready: { configurable: true },at: { configurable: true },data: { configurable: true } };

  prototypeAccessors$3.ready.get = function () {
      var this$1 = this;

    return _.every(this._connections, function (ignored, key) {
      var descriptor = this$1._vue.descriptors[key];
      if (!descriptor) { return false; }
      if (descriptor instanceof Handle) { return descriptor.ready; }
      return this$1._subConnectors[key].ready;
    });
  };

  prototypeAccessors$3.at.get = function () {
    return this._vue.refs;
  };

  prototypeAccessors$3.data.get = function () {
    return this._data;
  };

  Connector.prototype.destroy = function destroy () {
      var this$1 = this;

    this._unlinkScopeProperties();
    _.forEach(this._angularUnwatches, function (unwatch) {unwatch();});
    _.forEach(this._connections, function (descriptor, key) {this$1._disconnect(key);});
    this._vue.$destroy();
  };

  Connector.prototype._linkScopeProperties = function _linkScopeProperties () {
      var this$1 = this;

    var dataProperties = _.mapValues(this._connections, function (unused, key) { return ({
      configurable: true, enumerable: false, get: function () {
        var descriptor = this$1._vue.descriptors[key];
        if (descriptor instanceof Reference) { return descriptor.value; }
        return this$1._vue.values[key];
      }
    }); });
    Object.defineProperties(this._data, dataProperties);
    if (this._scope) {
      for (var key in this._connections) {
        if (key in this._scope) {
          throw new Error(("Property already defined on connection target: " + key));
        }
      }
      Object.defineProperties(this._scope, dataProperties);
      if (this._scope.__ob__) { this._scope.__ob__.dep.notify(); }
    }
  };

  Connector.prototype._unlinkScopeProperties = function _unlinkScopeProperties () {
      var this$1 = this;

    if (!this._scope) { return; }
    _.forEach(this._connections, function (descriptor, key) {
      delete this$1._scope[key];
    });
  };

  Connector.prototype._bindComputedConnection = function _bindComputedConnection (key, fn) {
    var connectionStats = stats.for(("connection.at." + key));
    var getter = this._computeConnection.bind(this, fn, connectionStats);
    var update = this._updateComputedConnection.bind(this, key, fn, connectionStats);
    var angularWatch = angularProxy.active && !fn.angularWatchSuppressed;
    // Use this._vue.$watch instead of truss.observe here so that we can disable the immediate
    // callback if we'll get one from Angular anyway.
    this._vue.$watch(getter, update, {immediate: !angularWatch});
    if (angularWatch) {
      if (!this._angularUnwatches) { this._angularUnwatches = []; }
      this._angularUnwatches.push(angularProxy.watch(getter, update, true));
    }
  };

  Connector.prototype._computeConnection = function _computeConnection (fn, connectionStats) {
    var startTime = performanceNow();
    try {
      return flattenRefs(fn.call(this._scope));
    } finally {
      connectionStats.runtime += performanceNow() - startTime;
      connectionStats.numRecomputes += 1;
    }
  };

  Connector.prototype._updateComputedConnection = function _updateComputedConnection (key, value, connectionStats) {
    var newDescriptor = _.isFunction(value) ? value(this._scope) : value;
    var oldDescriptor = this._vue.descriptors[key];
    var descriptorChanged = !isTrussEqual(oldDescriptor, newDescriptor);
    if (!descriptorChanged) { return; }
    if (connectionStats && descriptorChanged) { connectionStats.numUpdates += 1; }
    if (!newDescriptor) {
      this._disconnect(key);
      return;
    }
    if (newDescriptor instanceof Handle || !_.has(this._subConnectors, key)) {
      this._disconnect(key);
      this._connect(key, newDescriptor);
    } else {
      this._subConnectors[key]._updateConnections(newDescriptor);
    }
    Vue.set(this._vue.descriptors, key, newDescriptor);
    angularProxy.digest();
  };

  Connector.prototype._updateConnections = function _updateConnections (connections) {
      var this$1 = this;

    _.forEach(connections, function (descriptor, key) {
      this$1._updateComputedConnection(key, descriptor);
    });
    _.forEach(this._connections, function (descriptor, key) {
      if (!_.has(connections, key)) { this$1._updateComputedConnection(key); }
    });
    this._connections = connections;
  };

  Connector.prototype._connect = function _connect (key, descriptor) {
      var this$1 = this;

    Vue.set(this._vue.descriptors, key, descriptor);
    angularProxy.digest();
    if (!descriptor) { return; }
    Vue.set(this._vue.values, key, undefined);
    if (descriptor instanceof Reference) {
      Vue.set(this._vue.refs, key, descriptor);
      this._disconnects[key] = this._tree.connectReference(descriptor, this._method);
    } else if (descriptor instanceof Query) {
      Vue.set(this._vue.refs, key, descriptor);
      var updateFn = this._updateQueryValue.bind(this, key);
      this._disconnects[key] = this._tree.connectQuery(descriptor, updateFn, this._method);
    } else {
      var subScope = {}, subRefs = {};
      Vue.set(this._vue.refs, key, subRefs);
      var subConnector = this._subConnectors[key] =
        new Connector(subScope, descriptor, this._tree, this._method, subRefs);
      // Use a truss.observe here instead of this._vue.$watch so that the "immediate" execution
      // actually takes place after we've captured the unwatch function, in case the subConnector
      // is ready immediately.
      var unobserve = this._disconnects[key] = this._tree.truss.observe(
        function () { return subConnector.ready; },
        function (subReady) {
          if (!subReady) { return; }
          unobserve();
          delete this$1._disconnects[key];
          Vue.set(this$1._vue.values, key, subScope);
          angularProxy.digest();
        }
      );
    }
  };

  Connector.prototype._disconnect = function _disconnect (key) {
    Vue.delete(this._vue.refs, key);
    this._updateRefValue(key, undefined);
    if (_.has(this._subConnectors, key)) {
      this._subConnectors[key].destroy();
      delete this._subConnectors[key];
    }
    if (this._disconnects[key]) { this._disconnects[key](); }
    delete this._disconnects[key];
    Vue.delete(this._vue.descriptors, key);
    angularProxy.digest();
  };

  Connector.prototype._updateRefValue = function _updateRefValue (key, value) {
    if (this._vue.values[key] !== value) {
      Vue.set(this._vue.values, key, value);
      angularProxy.digest();
    }
  };

  Connector.prototype._updateQueryValue = function _updateQueryValue (key, childKeys) {
    if (!this._vue.values[key]) {
      Vue.set(this._vue.values, key, {});
      angularProxy.digest();
    }
    var subScope = this._vue.values[key];
    for (var childKey in subScope) {
      if (!subScope.hasOwnProperty(childKey)) { continue; }
      if (!_.includes(childKeys, childKey)) {
        Vue.delete(subScope, childKey);
        angularProxy.digest();
      }
    }
    var object = this._tree.getObject(this._vue.descriptors[key].path);
    for (var i = 0, list = childKeys; i < list.length; i += 1) {
      var childKey$1 = list[i];

        if (subScope.hasOwnProperty(childKey$1)) { continue; }
      Vue.set(subScope, childKey$1, object[childKey$1]);
      angularProxy.digest();
    }
  };

  Object.defineProperties( Connector.prototype, prototypeAccessors$3 );

  function flattenRefs(refs) {
    if (!refs) { return; }
    if (refs instanceof Handle) { return refs.toString(); }
    return _.mapValues(refs, flattenRefs);
  }

  function wrapPromiseCallback(callback) {
    return function() {
      try {
        // eslint-disable-next-line no-invalid-this
        return Promise.resolve(callback.apply(this, arguments));
      } catch (e) {
        return Promise.reject(e);
      }
    };
  }

  function promiseCancel(promise, cancel) {
    promise = promiseFinally(promise, function () {cancel = null;});
    promise.cancel = function () {
      if (!cancel) { return; }
      cancel();
      cancel = null;
    };
    propagatePromiseProperty(promise, 'cancel');
    return promise;
  }

  function propagatePromiseProperty(promise, propertyName) {
    var originalThen = promise.then, originalCatch = promise.catch;
    promise.then = function (onResolved, onRejected) {
      var derivedPromise = originalThen.call(promise, onResolved, onRejected);
      derivedPromise[propertyName] = promise[propertyName];
      propagatePromiseProperty(derivedPromise, propertyName);
      return derivedPromise;
    };
    promise.catch = function (onRejected) {
      var derivedPromise = originalCatch.call(promise, onRejected);
      derivedPromise[propertyName] = promise[propertyName];
      propagatePromiseProperty(derivedPromise, propertyName);
      return derivedPromise;
    };
    return promise;
  }

  function promiseFinally(promise, onFinally) {
    if (!onFinally) { return promise; }
    onFinally = wrapPromiseCallback(onFinally);
    return promise.then(function (result) {
      return onFinally().then(function () { return result; });
    }, function (error) {
      return onFinally().then(function () { return Promise.reject(error); });
    });
  }

  var INTERCEPT_KEYS = [
    'read', 'write', 'auth', 'set', 'update', 'commit', 'connect', 'peek', 'authenticate',
    'unathenticate', 'certify', 'all'
  ];

  var EMPTY_ARRAY = [];


  var SlowHandle = function SlowHandle(operation, delay, callback) {
    this._operation = operation;
    this._delay = delay;
    this._callback = callback;
    this._fired = false;
  };

  SlowHandle.prototype.initiate = function initiate () {
      var this$1 = this;

    this.cancel();
    this._fired = false;
    var elapsed = Date.now() - this._operation._startTimestamp;
    this._timeoutId = setTimeout(function () {
      this$1._fired = true;
      this$1._callback(this$1._operation);
    }, this._delay - elapsed);
  };

  SlowHandle.prototype.cancel = function cancel () {
    if (this._fired) { this._callback(this._operation); }
    if (this._timeoutId) { clearTimeout(this._timeoutId); }
  };


  var Operation = function Operation(type, method, target, operand) {
    this._type = type;
    this._method = method;
    this._target = target;
    this._operand = operand;
    this._ready = false;
    this._running = false;
    this._ended = false;
    this._tries = 0;
    this._startTimestamp = Date.now();
    this._slowHandles = [];
  };

  var prototypeAccessors$4 = { type: { configurable: true },method: { configurable: true },target: { configurable: true },targets: { configurable: true },operand: { configurable: true },ready: { configurable: true },running: { configurable: true },ended: { configurable: true },tries: { configurable: true },error: { configurable: true } };

  prototypeAccessors$4.type.get = function () {return this._type;};
  prototypeAccessors$4.method.get = function () {return this._method;};
  prototypeAccessors$4.target.get = function () {return this._target;};
  prototypeAccessors$4.targets.get = function () {
      var this$1 = this;

    if (this._method !== 'update') { return [this._target]; }
    return _.map(this._operand, function (value, escapedPathFragment) {
      return new Reference(
        this$1._target._tree, joinPath(this$1._target.path, escapedPathFragment),
        this$1._target._annotations);
    });
  };
  prototypeAccessors$4.operand.get = function () {return this._operand;};
  prototypeAccessors$4.ready.get = function () {return this._ready;};
  prototypeAccessors$4.running.get = function () {return this._running;};
  prototypeAccessors$4.ended.get = function () {return this._ended;};
  prototypeAccessors$4.tries.get = function () {return this._tries;};
  prototypeAccessors$4.error.get = function () {return this._error;};

  Operation.prototype.onSlow = function onSlow (delay, callback) {
    var handle = new SlowHandle(this, delay, callback);
    this._slowHandles.push(handle);
    handle.initiate();
  };

  Operation.prototype._setRunning = function _setRunning (value) {
    this._running = value;
  };

  Operation.prototype._setEnded = function _setEnded (value) {
    this._ended = value;
  };

  Operation.prototype._markReady = function _markReady (ending) {
    this._ready = true;
    if (!ending) { this._tries = 0; }
    _.forEach(this._slowHandles, function (handle) { return handle.cancel(); });
  };

  Operation.prototype._clearReady = function _clearReady () {
    this._ready = false;
    this._startTimestamp = Date.now();
    _.forEach(this._slowHandles, function (handle) { return handle.initiate(); });
  };

  Operation.prototype._incrementTries = function _incrementTries () {
    this._tries++;
  };

  Object.defineProperties( Operation.prototype, prototypeAccessors$4 );


  var Dispatcher = function Dispatcher(bridge) {
    this._bridge = bridge;
    this._callbacks = {};
    Object.freeze(this);
  };

  Dispatcher.prototype.intercept = function intercept (interceptKey, callbacks) {
    if (!_.includes(INTERCEPT_KEYS, interceptKey)) {
      throw new Error('Unknown intercept operation type: ' + interceptKey);
    }
    var badCallbackKeys =
      _.difference(_.keys(callbacks), ['onBefore', 'onAfter', 'onError', 'onFailure']);
    if (badCallbackKeys.length) {
      throw new Error('Unknown intercept callback types: ' + badCallbackKeys.join(', '));
    }
    var wrappedCallbacks = {
      onBefore: this._addCallback('onBefore', interceptKey, callbacks.onBefore),
      onAfter: this._addCallback('onAfter', interceptKey, callbacks.onAfter),
      onError: this._addCallback('onError', interceptKey, callbacks.onError),
      onFailure: this._addCallback('onFailure', interceptKey, callbacks.onFailure)
    };
    return this._removeCallbacks.bind(this, interceptKey, wrappedCallbacks);
  };

  Dispatcher.prototype._addCallback = function _addCallback (stage, interceptKey, callback) {
    if (!callback) { return; }
    var key = this._getCallbacksKey(stage, interceptKey);
    var wrappedCallback = wrapPromiseCallback(callback);
    (this._callbacks[key] || (this._callbacks[key] = [])).push(wrappedCallback);
    return wrappedCallback;
  };

  Dispatcher.prototype._removeCallback = function _removeCallback (stage, interceptKey, wrappedCallback) {
    if (!wrappedCallback) { return; }
    var key = this._getCallbacksKey(stage, interceptKey);
    if (this._callbacks[key]) { _.pull(this._callbacks[key], wrappedCallback); }
  };

  Dispatcher.prototype._removeCallbacks = function _removeCallbacks (interceptKey, wrappedCallbacks) {
      var this$1 = this;

    _.forEach(wrappedCallbacks, function (wrappedCallback, stage) {
      this$1._removeCallback(stage, interceptKey, wrappedCallback);
    });
  };

  Dispatcher.prototype._getCallbacks = function _getCallbacks (stage, operationType, method) {
    return [].concat(
      this._callbacks[this._getCallbacksKey(stage, method)] || EMPTY_ARRAY,
      this._callbacks[this._getCallbacksKey(stage, operationType)] || EMPTY_ARRAY,
      this._callbacks[this._getCallbacksKey(stage, 'all')] || EMPTY_ARRAY
    );
  };

  Dispatcher.prototype._getCallbacksKey = function _getCallbacksKey (stage, interceptKey) {
    return (stage + "_" + interceptKey);
  };

  Dispatcher.prototype.execute = function execute (operationType, method, target, operand, executor) {
      var this$1 = this;

    executor = wrapPromiseCallback(executor);
    var operation = this.createOperation(operationType, method, target, operand);
    return this.begin(operation).then(function () {
      var executeWithRetries = function () {
        return executor().catch(function (e) { return this$1._retryOrEnd(operation, e).then(executeWithRetries); });
      };
      return executeWithRetries();
    }).then(function (result) { return this$1.end(operation).then(function () { return result; }); });
  };

  Dispatcher.prototype.createOperation = function createOperation (operationType, method, target, operand) {
    return new Operation(operationType, method, target, operand);
  };

  Dispatcher.prototype.begin = function begin (operation) {
      var this$1 = this;

    return Promise.all(_.map(
      this._getCallbacks('onBefore', operation.type, operation.method),
      function (onBefore) { return onBefore(operation); }
    )).then(function () {
      if (!operation.ended) { operation._setRunning(true); }
    }, function (e) { return this$1.end(operation, e); });
  };

  Dispatcher.prototype.markReady = function markReady (operation) {
    operation._markReady();
  };

  Dispatcher.prototype.clearReady = function clearReady (operation) {
    operation._clearReady();
  };

  Dispatcher.prototype.retry = function retry (operation, error) {
    operation._incrementTries();
    operation._error = error;
    return Promise.all(_.map(
      this._getCallbacks('onError', operation.type, operation.method),
      function (onError) { return onError(operation, error); }
    )).then(function (results) {
      // If the operation ended in the meantime, bail.This will cause the caller to attempt to
      // fail the operation, but since it's already ended the call to end() with an error will be a
      // no-op.
      if (operation.ended) { return; }
      var retrying = _.some(results);
      if (retrying) { delete operation._error; }
      return retrying;
    });
  };

  Dispatcher.prototype._retryOrEnd = function _retryOrEnd (operation, error) {
      var this$1 = this;

    return this.retry(operation, error).then(function (result) {
      if (!result) { return this$1.end(operation, error); }
    }, function (e) { return this$1.end(operation, e); });
  };

  Dispatcher.prototype.end = function end (operation, error) {
      var this$1 = this;

    if (operation.ended) { return Promise.resolve(); }
    operation._setRunning(false);
    operation._setEnded(true);
    if (error) {
      operation._error = error;
    } else {
      // In case we're racing with a retry(), wipe out the error.
      delete operation._error;
    }
    return Promise.all(_.map(
      this._getCallbacks('onAfter', operation.type, operation.method),
      function (onAfter) { return onAfter(operation); }
    )).then(
      function () { return this$1._afterEnd(operation); },
      function (e) {
        operation._error = e;
        return this$1._afterEnd(operation);
      }
    );
  };

  Dispatcher.prototype._afterEnd = function _afterEnd (operation) {
    operation._markReady(true);
    if (!operation.error) { return Promise.resolve(); }
    var onFailureCallbacks = this._getCallbacks('onFailure', operation.type, operation.method);
    if (onFailureCallbacks) {
      setTimeout(function () {
        _.forEach(onFailureCallbacks, function (onFailure) { return onFailure(operation); });
      }, 0);
    }
    return Promise.reject(operation.error);
  };

  var ALPHABET = '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';

  var getRandomValues = window.crypto && window.crypto.getRandomValues &&
    window.crypto.getRandomValues.bind(window.crypto);

  var KeyGenerator = function KeyGenerator() {
    this._lastUniqueKeyTime = 0;
    this._lastRandomValues = [];
  };

  KeyGenerator.prototype.generateUniqueKey = function generateUniqueKey (now) {
    now = now || Date.now();
    var chars = new Array(20);
    var prefix = now;
    for (var i = 7; i >= 0; i--) {
      chars[i] = ALPHABET.charAt(prefix & 0x3f);// eslint-disable-line no-bitwise
      prefix = Math.floor(prefix / 64);
    }
    if (now === this._lastUniqueKeyTime) {
      var i$1 = 11;
      while (i$1 >= 0 && this._lastRandomValues[i$1] === 63) {
        this._lastRandomValues[i$1] = 0;
        i$1 -= 1;
      }
      if (i$1 === -1) {
        throw new Error('Internal assertion failure: ran out of unique IDs for this millisecond');
      }
      this._lastRandomValues[i$1] += 1;
    } else {
      this._lastUniqueKeyTime = now;
      if (getRandomValues) {
        var array = new Uint8Array(12);
        getRandomValues(array);
        for (var i$2 = 0; i$2 < 12; i$2++) {
          // eslint-disable-next-line no-bitwise
          this._lastRandomValues[i$2] = array[i$2] & (i$2 ? 0x3f : 0x0f);
        }
      } else {
        for (var i$3 = 0; i$3 < 12; i$3++) {
          // Make sure to leave some space for incrementing in the top nibble.
          this._lastRandomValues[i$3] = Math.floor(Math.random() * (i$3 ? 64 : 16));
        }
      }
    }
    for (var i$4 = 0; i$4 < 12; i$4++) {
      chars[i$4 + 8] = ALPHABET[this._lastRandomValues[i$4]];
    }
    return chars.join('');
  };

  var MetaTree = function MetaTree(rootUrl, tree, bridge, dispatcher) {
    this._rootUrl = rootUrl;
    this._tree = tree;
    this._dispatcher = dispatcher;
    this._bridge = bridge;
    this._vue = new Vue({data: {$root: {
      connected: undefined, timeOffset: 0, user: undefined, userid: undefined,
      nowAtInterval: function nowAtInterval(intervalMillis) {
        var this$1 = this;

        var key = 'now' + intervalMillis;
        if (!this.hasOwnProperty(key)) {
          var update = function () {
            Vue.set(this$1, key, Date.now() + this$1.timeOffset);
            angularProxy.digest();
          };
          update();
          setInterval(update, intervalMillis);
        }
        return this[key];
      }
    }}});

    this._auth = {serial: 0, initialAuthChangeReceived: false};

    bridge.onAuth(rootUrl, this._handleAuthChange, this);

    this._connectInfoProperty('serverTimeOffset', 'timeOffset');
    this._connectInfoProperty('connected', 'connected');
    Object.freeze(this);
  };

  var prototypeAccessors$5 = { root: { configurable: true } };

  prototypeAccessors$5.root.get = function () {
    return this._vue.$data.$root;
  };

  MetaTree.prototype.destroy = function destroy () {
    this._bridge.offAuth(this._rootUrl, this._handleAuthChange, this);
    this._vue.$destroy();
  };

  MetaTree.prototype.authenticate = function authenticate (token) {
      var this$1 = this;

    this._auth.serial++;
    return this._dispatcher.execute(
      'auth', 'authenticate', new Reference(this._tree, '/'), token, function () {
        if (token) { return this$1._bridge.authWithCustomToken(this$1._rootUrl, token); }
        return this$1._bridge.authAnonymously(this$1._rootUrl);
      }
    );
  };

  MetaTree.prototype.unauthenticate = function unauthenticate () {
      var this$1 = this;

    // Signal user change to null pre-emptively.This is what the Firebase SDK does as well, since
    // it lets the app tear down user-required connections before the user is actually deauthed,
    // which can prevent spurious permission denied errors.
    this._auth.serial++;
    return this._handleAuthChange(null).then(function (approved) {
      // Bail if auth change callback initiated another authentication, since it will have already
      // sent the command to the bridge and sending our own now would incorrectly override it.
      if (!approved) { return; }
      return this$1._dispatcher.execute(
        'auth', 'unauthenticate', new Reference(this$1._tree, '/'), undefined, function () {
          return this$1._bridge.unauth(this$1._rootUrl);
        }
      );
    });
  };

  MetaTree.prototype._handleAuthChange = function _handleAuthChange (user) {
      var this$1 = this;

    var supersededChange = !this._auth.initialAuthChangeReceived && this._auth.serial;
    if (user !== undefined) { this._auth.initialAuthChangeReceived = true; }
    if (supersededChange) { return; }
    var authSerial = this._auth.serial;
    if (this.root.user === user) { return Promise.resolve(false); }
    return this._dispatcher.execute('auth', 'certify', new Reference(this._tree, '/'), user, function () {
      if (this$1.root.user === user || authSerial !== this$1._auth.serial) { return false; }
      if (user) { Object.freeze(user); }
      this$1.root.user = user;
      this$1.root.userid = user && user.uid;
      angularProxy.digest();
      return true;
    });
  };

  MetaTree.prototype._isAuthChangeStale = function _isAuthChangeStale (user) {
    return this.root.user === user;
  };

  MetaTree.prototype._connectInfoProperty = function _connectInfoProperty (property, attribute) {
      var this$1 = this;

    var propertyUrl = (this._rootUrl) + "/.info/" + property;
    this._bridge.on(propertyUrl, propertyUrl, null, 'value', function (snap) {
      this$1.root[attribute] = snap.value;
      angularProxy.digest();
    });
  };

  Object.defineProperties( MetaTree.prototype, prototypeAccessors$5 );

  // These are defined separately for each object so they're not included in Value below.
  var RESERVED_VALUE_PROPERTY_NAMES = {$$$trussCheck: true, __ob__: true};

  // Holds properties that we're going to set on a model object that's being created right now as soon
  // as it's been created, but that we'd like to be accessible in the constructor.  The object
  // prototype's getters will pick those up until they get overridden in the instance.
  var creatingObjectProperties;

  var currentPropertyFrozen;


  var BaseValue = function BaseValue () {};

  var prototypeAccessors$6 = { $meta: { configurable: true },$store: { configurable: true },$now: { configurable: true },$$finalizers: { configurable: true } };

  prototypeAccessors$6.$meta.get = function () {return this.$truss.meta;};
  prototypeAccessors$6.$store.get = function () {return this.$truss.store;};// access indirectly to leave dependency trace
  prototypeAccessors$6.$now.get = function () {return this.$truss.now;};

  BaseValue.prototype.$newKey = function $newKey () {return this.$truss.newKey();};

  BaseValue.prototype.$intercept = function $intercept (actionType, callbacks) {
      var this$1 = this;

    if (this.$destroyed) { throw new Error('Object already destroyed'); }
    var unintercept = this.$truss.intercept(actionType, callbacks);
    var uninterceptAndRemoveFinalizer = function () {
      unintercept();
      _.pull(this$1.$$finalizers, uninterceptAndRemoveFinalizer);
    };
    this.$$finalizers.push(uninterceptAndRemoveFinalizer);
    return uninterceptAndRemoveFinalizer;
  };

  BaseValue.prototype.$connect = function $connect (scope, connections) {
      var this$1 = this;

    if (this.$destroyed) { throw new Error('Object already destroyed'); }
    if (!connections) {
      connections = scope;
      scope = undefined;
    }
    var connector = this.$truss.connect(scope, wrapConnections(this, connections));
    var originalDestroy = connector.destroy;
    var destroy = function () {
      _.pull(this$1.$$finalizers, destroy);
      return originalDestroy.call(connector);
    };
    this.$$finalizers.push(destroy);
    connector.destroy = destroy;
    return connector;
  };

  BaseValue.prototype.$peek = function $peek (target, callback) {
      var this$1 = this;

    if (this.$destroyed) { throw new Error('Object already destroyed'); }
    var promise = promiseFinally(
      this.$truss.peek(target, callback), function () {_.pull(this$1.$$finalizers, promise.cancel);}
    );
    this.$$finalizers.push(promise.cancel);
    return promise;
  };

  BaseValue.prototype.$observe = function $observe (subjectFn, callbackFn, options) {
      var this$1 = this;

    if (this.$destroyed) { throw new Error('Object already destroyed'); }
    var unobserveAndRemoveFinalizer;

    var unobserve = this.$truss.observe(function () {
      this$1.$$touchThis();
      return subjectFn.call(this$1);
    }, callbackFn.bind(this), options);

    unobserveAndRemoveFinalizer = function () {// eslint-disable-line prefer-const
      unobserve();
      _.pull(this$1.$$finalizers, unobserveAndRemoveFinalizer);
    };
    this.$$finalizers.push(unobserveAndRemoveFinalizer);
    return unobserveAndRemoveFinalizer;
  };

  BaseValue.prototype.$when = function $when (expression, options) {
      var this$1 = this;

    if (this.$destroyed) { throw new Error('Object already destroyed'); }
    var promise = this.$truss.when(function () {
      this$1.$$touchThis();
      return expression.call(this$1);
    }, options);
    promiseFinally(promise, function () {_.pull(this$1.$$finalizers, promise.cancel);});
    this.$$finalizers.push(promise.cancel);
    return promise;
  };

  prototypeAccessors$6.$$finalizers.get = function () {
    Object.defineProperty(this, '$$finalizers', {
      value: [], writable: false, enumerable: false, configurable: false});
    return this.$$finalizers;
  };

  Object.defineProperties( BaseValue.prototype, prototypeAccessors$6 );


  var Value = function Value () {};

  var prototypeAccessors$1$2 = { $parent: { configurable: true },$path: { configurable: true },$truss: { configurable: true },$ref: { configurable: true },$refs: { configurable: true },$key: { configurable: true },$data: { configurable: true },$hidden: { configurable: true },$empty: { configurable: true },$keys: { configurable: true },$values: { configurable: true },$ready: { configurable: true },$overridden: { configurable: true },$$initializers: { configurable: true },$destroyed: { configurable: true } };

  prototypeAccessors$1$2.$parent.get = function () {return creatingObjectProperties.$parent.value;};
  prototypeAccessors$1$2.$path.get = function () {return creatingObjectProperties.$path.value;};
  prototypeAccessors$1$2.$truss.get = function () {
    Object.defineProperty(this, '$truss', {value: this.$parent.$truss});
    return this.$truss;
  };
  prototypeAccessors$1$2.$ref.get = function () {
    Object.defineProperty(this, '$ref', {value: new Reference(this.$truss._tree, this.$path)});
    return this.$ref;
  };
  prototypeAccessors$1$2.$refs.get = function () {return this.$ref;};
  prototypeAccessors$1$2.$key.get = function () {
    Object.defineProperty(
      this, '$key', {value: unescapeKey(this.$path.slice(this.$path.lastIndexOf('/') + 1))});
    return this.$key;
  };
  prototypeAccessors$1$2.$data.get = function () {return this;};
  prototypeAccessors$1$2.$hidden.get = function () {return false;};// eslint-disable-line lodash/prefer-constant
  prototypeAccessors$1$2.$empty.get = function () {return _.isEmpty(this.$data);};
  prototypeAccessors$1$2.$keys.get = function () {return _.keys(this.$data);};
  prototypeAccessors$1$2.$values.get = function () {return _.values(this.$data);};
  prototypeAccessors$1$2.$ready.get = function () {return this.$ref.ready;};
  prototypeAccessors$1$2.$overridden.get = function () {return false;};// eslint-disable-line lodash/prefer-constant

  Value.prototype.$nextTick = function $nextTick () {
      var this$1 = this;

    if (this.$destroyed) { throw new Error('Object already destroyed'); }
    var promise = this.$truss.nextTick();
    promiseFinally(promise, function () {_.pull(this$1.$$finalizers, promise.cancel);});
    this.$$finalizers.push(promise.cancel);
    return promise;
  };

  Value.prototype.$freezeComputedProperty = function $freezeComputedProperty () {
    if (!_.isBoolean(currentPropertyFrozen)) {
      throw new Error('Cannot freeze a computed property outside of its getter function');
    }
    currentPropertyFrozen = true;
  };

  Value.prototype.$set = function $set (value) {return this.$ref.set(value);};
  Value.prototype.$update = function $update (values) {return this.$ref.update(values);};
  Value.prototype.$override = function $override (values) {return this.$ref.override(values);};
  Value.prototype.$commit = function $commit (options, updateFn) {return this.$ref.commit(options, updateFn);};

  Value.prototype.$$touchThis = function $$touchThis () {
    /* eslint-disable no-unused-expressions */
    if (this.__ob__) {
      this.__ob__.dep.depend();
    } else if (this.$parent) {
      (this.$parent.hasOwnProperty('$data') ? this.$parent.$data : this.$parent)[this.$key];
    } else {
      this.$store;
    }
    /* eslint-enable no-unused-expressions */
  };

  prototypeAccessors$1$2.$$initializers.get = function () {
    Object.defineProperty(this, '$$initializers', {
      value: [], writable: false, enumerable: false, configurable: true});
    return this.$$initializers;
  };

  prototypeAccessors$1$2.$destroyed.get = function () {// eslint-disable-line lodash/prefer-constant
    return false;
  };

  Object.defineProperties( Value.prototype, prototypeAccessors$1$2 );

  copyPrototype(BaseValue, Value);

  _.forEach(Value.prototype, function (prop, name) {
    Object.defineProperty(
      Value.prototype, name, {value: prop, enumerable: false, configurable: false, writable: false});
  });


  var ErrorWrapper = function ErrorWrapper(error) {
    this.error = error;
  };


  var FrozenWrapper = function FrozenWrapper(value) {
    this.value = value;
  };


  var Modeler = function Modeler(debug) {
    this._trie = {Class: Value};
    this._debug = debug;
    Object.freeze(this);
  };

  Modeler.prototype.init = function init (classes, rootAcceptable) {
      var this$1 = this;

    if (_.isPlainObject(classes)) {
      _.forEach(classes, function (Class, path) {
        if (Class.$trussMount) { return; }
        Class.$$trussMount = Class.$$trussMount || [];
        Class.$$trussMount.push(path);
      });
      classes = _.values(classes);
      _.forEach(classes, function (Class) {
        if (!Class.$trussMount && Class.$$trussMount) {
          Class.$trussMount = Class.$$trussMount;
          delete Class.$$trussMount;
        }
      });
    }
    classes = _.uniq(classes);
    _.forEach(classes, function (Class) { return this$1._mountClass(Class, rootAcceptable); });
    this._decorateTrie(this._trie);
  };

  Modeler.prototype.destroy = function destroy () {// eslint-disable-line no-empty-function
  };

  Modeler.prototype._getMount = function _getMount (path, scaffold, predicate) {
    var segments = splitPath(path, true);
    var node;
    for (var i = 0, list = segments; i < list.length; i += 1) {
      var segment = list[i];

        var child = segment ?
        node.children && (node.children[segment] || !scaffold && node.children.$) : this._trie;
      if (!child) {
        if (!scaffold) { return; }
        node.children = node.children || {};
        child = node.children[segment] = {Class: Value};
      }
      node = child;
      if (predicate && predicate(node)) { break; }
    }
    return node;
  };

  Modeler.prototype._findMount = function _findMount (predicate, node) {
    if (!node) { node = this._trie; }
    if (predicate(node)) { return node; }
    for (var i = 0, list = _.keys(node.children); i < list.length; i += 1) {
      var childKey = list[i];

        var result = this._findMount(predicate, node.children[childKey]);
      if (result) { return result; }
    }
  };

  Modeler.prototype._decorateTrie = function _decorateTrie (node) {
      var this$1 = this;

    _.forEach(node.children, function (child) {
      this$1._decorateTrie(child);
      if (child.local || child.localDescendants) { node.localDescendants = true; }
    });
  };

  Modeler.prototype._augmentClass = function _augmentClass (Class) {
    var computedProperties;
    var proto = Class.prototype;
    while (proto && proto.constructor !== Object) {
      for (var i = 0, list = Object.getOwnPropertyNames(proto); i < list.length; i += 1) {
        var name = list[i];

          var descriptor = Object.getOwnPropertyDescriptor(proto, name);
        if (name.charAt(0) === '$') {
          if (name === '$finalize') { continue; }
          if (_.isEqual(descriptor, Object.getOwnPropertyDescriptor(Value.prototype, name))) {
            continue;
          }
          throw new Error(("Property names starting with \"$\" are reserved: " + (Class.name) + "." + name));
        }
        if (descriptor.get && !(computedProperties && computedProperties[name])) {
          (computedProperties || (computedProperties = {}))[name] = {
            name: name, fullName: ((proto.constructor.name) + "." + name), get: descriptor.get,
            set: descriptor.set
          };
        }
      }
      proto = Object.getPrototypeOf(proto);
    }
    for (var i$1 = 0, list$1 = Object.getOwnPropertyNames(Value.prototype); i$1 < list$1.length; i$1 += 1) {
      var name$1 = list$1[i$1];

        if (name$1 === 'constructor' || Class.prototype.hasOwnProperty(name$1)) { continue; }
      Object.defineProperty(
        Class.prototype, name$1, Object.getOwnPropertyDescriptor(Value.prototype, name$1));
    }
    return computedProperties;
  };

  Modeler.prototype._mountClass = function _mountClass (Class, rootAcceptable) {
      var this$1 = this;

    var computedProperties = this._augmentClass(Class);
    var allVariables = [];
    var mounts = Class.$trussMount;
    if (!mounts) { throw new Error(("Class " + (Class.name) + " lacks a $trussMount static property")); }
    if (!_.isArray(mounts)) { mounts = [mounts]; }
    _.forEach(mounts, function (mount) {
      if (_.isString(mount)) { mount = {path: mount}; }
      if (!rootAcceptable && mount.path === '/') {
        throw new Error('Data root already accessed, too late to mount class');
      }
      var matcher = makePathMatcher(mount.path);
      for (var i = 0, list = matcher.variables; i < list.length; i += 1) {
        var variable = list[i];

          if (variable === '$' || variable.charAt(1) === '$') {
          throw new Error(("Invalid variable name: " + variable));
        }
        if (variable.charAt(0) === '$' && (
          _.has(Value.prototype, variable) || RESERVED_VALUE_PROPERTY_NAMES[variable]
        )) {
          throw new Error(("Variable name conflicts with built-in property or method: " + variable));
        }
        allVariables.push(variable);
      }
      var escapedKey = mount.path.match(/\/([^/]*)$/)[1];
      if (escapedKey.charAt(0) === '$') {
        if (mount.placeholder) {
          throw new Error(
            ("Class " + (Class.name) + " mounted at wildcard " + escapedKey + " cannot be a placeholder"));
        }
      } else if (!_.has(mount, 'placeholder')) {
        mount.placeholder = {};
      }
      var targetMount = this$1._getMount(mount.path.replace(/\$[^/]*/g, '$'), true);
      if (targetMount.matcher && (
        targetMount.escapedKey === escapedKey ||
        targetMount.escapedKey.charAt(0) === '$' && escapedKey.charAt(0) === '$'
      )) {
        throw new Error(
          ("Multiple classes mounted at " + (mount.path) + ": " + (targetMount.Class.name) + ", " + (Class.name)));
      }
      _.assign(
        targetMount, {Class: Class, matcher: matcher, computedProperties: computedProperties, escapedKey: escapedKey},
        _.pick(mount, 'placeholder', 'local', 'keysUnsafe', 'hidden'));
    });
    _(allVariables).uniq().forEach(function (variable) {
      Object.defineProperty(Class.prototype, variable, {get: function get() {
        return creatingObjectProperties ?
          creatingObjectProperties[variable] && creatingObjectProperties[variable].value :
          undefined;
      }});
    });
  };

  /**
   * Creates a Truss object and sets all its basic properties: path segment variables, user-defined
   * properties, and computed properties.The latter two will be enumerable so that Vue will pick
   * them up and make the reactive.
   */
  Modeler.prototype.createObject = function createObject (path, properties) {
      var this$1 = this;

    var mount = this._getMount(path) || {Class: Value};
    try {
      if (mount.matcher) {
        var match = mount.matcher.match(path);
        for (var variable in match) {
          properties[variable] = {value: match[variable]};
        }
      }

      creatingObjectProperties = properties;
      var object = new mount.Class();
      creatingObjectProperties = null;

      if (angularProxy.active) { this._wrapProperties(object); }

      if (mount.keysUnsafe) {
        properties.$data = {value: Object.create(null), configurable: true, enumerable: true};
      }
      if (mount.hidden) { properties.$hidden = {value: true}; }
      if (mount.computedProperties) {
        _.forEach(mount.computedProperties, function (prop) {
          properties[prop.name] = this$1._buildComputedPropertyDescriptor(object, prop);
        });
      }

      return object;
    } catch (e) {
      e.extra = _.assign({mount: mount, properties: properties, className: mount.Class && mount.Class.name}, e.extra);
      throw e;
    }
  };

  Modeler.prototype._wrapProperties = function _wrapProperties (object) {
    _.forEach(object, function (value, key) {
        var obj;

      var valueKey = '$_' + key;
      Object.defineProperties(object, ( obj = {}, obj[valueKey] = {value: value, writable: true}, obj[key] = {
          get: function () { return object[valueKey]; },
          set: function (arg) {object[valueKey] = arg; angularProxy.digest();},
          enumerable: true, configurable: true
        }, obj ));
    });
  };

  Modeler.prototype._buildComputedPropertyDescriptor = function _buildComputedPropertyDescriptor (object, prop) {
      var this$1 = this;

    var propertyStats = stats.for(prop.fullName);

    var value, pendingPromise;
    var writeAllowed = false;

    object.$$initializers.push(function (vue) {
      var unwatchNow = false;
      var compute = computeValue.bind(object, prop, propertyStats);
      if (this$1._debug) { compute.toString = function () {return prop.fullName;}; }
      var unwatch = function () {unwatchNow = true;};
      unwatch = vue.$watch(compute, function (newValue) {
        if (object.$destroyed) {
          unwatch();
          return;
        }
        if (pendingPromise) {
          if (pendingPromise.cancel) { pendingPromise.cancel(); }
          pendingPromise = undefined;
        }
        if (_.isObject(newValue) && _.isFunction(newValue.then)) {
          var promise = newValue.then(function (finalValue) {
            if (promise === pendingPromise) { update(finalValue); }
            // No need to angular.digest() here, since if we're running under Angular then we expect
            // promises to be aliased to its $q service, which triggers digest itself.
          }, function (error) {
            if (promise === pendingPromise && update(new ErrorWrapper(error)) &&
                !error.trussExpectedException) { throw error; }
          });
          pendingPromise = promise;
        } else if (update(newValue)) {
          angularProxy.digest();
          if (newValue instanceof ErrorWrapper && !newValue.error.trussExpectedException) {
            throw newValue.error;
          }
        }
      }, {immediate: true});// use immediate:true since watcher will run computeValue anyway
      // Hack to change order of computed property watchers.By flipping their ids to be negative,
      // we ensure that they will settle before all other watchers, and also that children
      // properties will settle before their parents since values are often aggregated upwards.
      var watcher = _.last(vue._watchers || vue._scope.effects);
      watcher.id = -watcher.id;

      function update(newValue) {
        if (newValue instanceof FrozenWrapper) {
          newValue = newValue.value;
          unwatch();
          _.pull(object.$$finalizers, unwatch);
        }
        if (isTrussEqual(value, newValue)) { return; }
        // console.log('updating', object.$key, prop.fullName, 'from', value, 'to', newValue);
        propertyStats.numUpdates += 1;
        writeAllowed = true;
        object[prop.name] = newValue;
        writeAllowed = false;
        // Freeze the computed value so it can't be accidentally modified by a third party.Ideally
        // we'd freeze it before setting it so that Vue wouldn't instrument the object recursively
        // (since it can't change anyway), but we actually need the instrumentation in case a client
        // tries to access an inexistent property off a computed pointer to an unfrozen value (e.g.,
        // a $truss-ified object).When instrumented, Vue will add a dependency on the unfrozen
        // value in case the property is later added.If uninstrumented, the dependency won't be
        // added and we won't be notified.And Vue only instruments extensible objects...
        freeze(newValue);
        return true;
      }

      if (unwatchNow) {
        unwatch();
      } else {
        object.$$finalizers.push(unwatch);
      }
    });
    return {
      enumerable: true, configurable: true,
      get: function get() {
        if (!writeAllowed && value instanceof ErrorWrapper) { throw value.error; }
        return value;
      },
      set: function set(newValue) {
        if (writeAllowed) {
          value = newValue;
        } else if (prop.set) {
          prop.set.call(this, newValue);
        } else {
          throw new Error(("You cannot set a computed property: " + (prop.name)));
        }
      }
    };
  };

  Modeler.prototype.destroyObject = function destroyObject (object) {
    if (_.has(object, '$$finalizers')) {
      // Some finalizers remove themselves from the array, so clone it before iterating.
      for (var i = 0, list = _.clone(object.$$finalizers); i < list.length; i += 1) {
          var fn = list[i];

          fn();
        }
    }
    if (_.isFunction(object.$finalize)) { object.$finalize(); }
    Object.defineProperty(
      object, '$destroyed', {value: true, enumerable: false, configurable: false});
  };

  Modeler.prototype.isPlaceholder = function isPlaceholder (path) {
    var mount = this._getMount(path);
    return mount && mount.placeholder;
  };

  Modeler.prototype.isLocal = function isLocal (path, value) {
    // eslint-disable-next-line no-shadow
    var mount = this._getMount(path, false, function (mount) { return mount.local; });
    if (mount && mount.local) { return true; }
    if (this._hasLocalProperties(mount, value)) {
      throw new Error('Write on a mix of local and remote tree paths.');
    }
    return false;
  };

  Modeler.prototype._hasLocalProperties = function _hasLocalProperties (mount, value) {
    if (!mount) { return false; }
    if (mount.local) { return true; }
    if (!mount.localDescendants || !_.isObject(value)) { return false; }
    for (var key in value) {
      var local =
        this._hasLocalProperties(mount.children[escapeKey(key)] || mount.children.$, value[key]);
      if (local) { return true; }
    }
    return false;
  };

  Modeler.prototype.forEachPlaceholderChild = function forEachPlaceholderChild (path, iteratee) {
    var mount = this._getMount(path);
    _.forEach(mount && mount.children, function (child) {
      if (child.placeholder) { iteratee(child); }
    });
  };

  Modeler.prototype.checkVueObject = function checkVueObject (object, path, checkedObjects) {
    var top = !checkedObjects;
    if (top) { checkedObjects = []; }
    try {
      for (var i = 0, list = Object.getOwnPropertyNames(object); i < list.length; i += 1) {
        var key = list[i];

          if (RESERVED_VALUE_PROPERTY_NAMES[key] || Value.prototype.hasOwnProperty(key) ||
            /^\$_/.test(key)) { continue; }
        // eslint-disable-next-line no-shadow
        var mount = this._findMount(function (mount) { return mount.Class === object.constructor; });
        if (mount && mount.matcher && _.includes(mount.matcher.variables, key)) { continue; }
        var value = (void 0);
        try {
          value = object[key];
        } catch (e) {
          // Ignore any values that hold exceptions, or otherwise throw on access -- we won't be
          // able to check them anyway.
          continue;
        }
        if (!(_.isArray(object) && (/\d+/.test(key) || key === 'length'))) {
          var descriptor = Object.getOwnPropertyDescriptor(object, key);
          if ('value' in descriptor || !descriptor.get) {
            throw new Error(
              ("Value at " + path + ", contained in a Firetruss object, has a rogue property: " + key));
          }
          if (object.$truss && descriptor.enumerable) {
            try {
              object[key] = value;
              throw new Error(
                ("Firetruss object at " + path + " has an enumerable non-Firebase property: " + key));
            } catch (e$1) {
              if (e$1.trussCode !== 'firebase_overwrite') { throw e$1; }
            }
          }
        }
        if (_.isObject(value) && !value.$$$trussCheck && Object.isExtensible(value) &&
            !(_.isFunction(value) || value instanceof Promise)) {
          value.$$$trussCheck = true;
          checkedObjects.push(value);
          this.checkVueObject(value, joinPath(path, escapeKey(key)), checkedObjects);
        }
      }
    } finally {
      if (top) {
        for (var i$1 = 0, list$1 = checkedObjects; i$1 < list$1.length; i$1 += 1) {
            var item = list$1[i$1];

            delete item.$$$trussCheck;
          }
      }
    }
  };


  function computeValue(prop, propertyStats) {
    /* eslint-disable no-invalid-this */
    if (this.$destroyed) { return; }
    // Touch this object, since a failed access to a missing property doesn't get captured as a
    // dependency.
    this.$$touchThis();

    var oldPropertyFrozen = currentPropertyFrozen;
    currentPropertyFrozen = false;
    var startTime = performanceNow();
    var value;
    try {
      try {
        value = prop.get.call(this);
      } catch (e) {
        value = new ErrorWrapper(e);
      } finally {
        propertyStats.runtime += performanceNow() - startTime;
        propertyStats.numRecomputes += 1;
      }
      if (currentPropertyFrozen) { value = new FrozenWrapper(value); }
      return value;
    } finally {
      currentPropertyFrozen = oldPropertyFrozen;
    }
    /* eslint-enable no-invalid-this */
  }

  function wrapConnections(object, connections) {
    if (!connections || connections instanceof Handle) { return connections; }
    return _.mapValues(connections, function (descriptor) {
      if (descriptor instanceof Handle) { return descriptor; }
      if (_.isFunction(descriptor)) {
        var fn = function() {
          /* eslint-disable no-invalid-this */
          object.$$touchThis();
          return wrapConnections(object, descriptor.call(this));
          /* eslint-enable no-invalid-this */
        };
        fn.angularWatchSuppressed = true;
        return fn;
      }
      return wrapConnections(object, descriptor);
    });
  }

  function freeze(object) {
    if (_.isNil(object) || !_.isObject(object) || Object.isFrozen(object) || object.$truss) {
      return object;
    }
    object = Object.freeze(object);
    if (_.isArray(object)) { return _.map(object, function (value) { return freeze(value); }); }
    return _.mapValues(object, function (value) { return freeze(value); });
  }

  var QueryHandler = function QueryHandler(coupler, query) {
    this._coupler = coupler;
    this._query = query;
    this._listeners = [];
    this._keys = [];
    this._url = this._coupler._rootUrl + query.path;
    this._segments = splitPath(query.path, true);
    this._listening = false;
    this.ready = false;
  };

  QueryHandler.prototype.attach = function attach (operation, keysCallback) {
    this._listen();
    this._listeners.push({operation: operation, keysCallback: keysCallback});
    if (this.ready) {
      this._coupler._dispatcher.markReady(operation);
      if (keysCallback) { keysCallback(this._keys); }
    }
  };

  QueryHandler.prototype.detach = function detach (operation) {
    var k = _.findIndex(this._listeners, {operation: operation});
    if (k >= 0) { this._listeners.splice(k, 1); }
    return this._listeners.length;
  };

  QueryHandler.prototype._listen = function _listen () {
    if (this._listening) { return; }
    this._coupler._bridge.on(
      this._query.toString(), this._url, this._query.constraints, 'value',
      this._handleSnapshot, this._handleError, this, {sync: true});
    this._listening = true;
  };

  QueryHandler.prototype.destroy = function destroy () {
    this._coupler._bridge.off(
      this._query.toString(), this._url, this._query.constraints, 'value', this._handleSnapshot,
      this);
    this._listening = false;
    this.ready = false;
    angularProxy.digest();
    for (var i = 0, list = this._keys; i < list.length; i += 1) {
      var key = list[i];

        this._coupler._decoupleSegments(this._segments.concat(key));
    }
  };

  QueryHandler.prototype._handleSnapshot = function _handleSnapshot (snap) {
      var this$1 = this;

    this._coupler._queueSnapshotCallback(function () {
      // Order is important here: first couple any new subpaths so _handleSnapshot will update the
      // tree, then tell the client to update its keys, pulling values from the tree.
      if (!this$1._listeners.length || !this$1._listening) { return; }
      var updatedKeys = this$1._updateKeysAndApplySnapshot(snap);
      if (!this$1.ready) {
        this$1.ready = true;
        angularProxy.digest();
        for (var i = 0, list = this$1._listeners; i < list.length; i += 1) {
          var listener = list[i];

            this$1._coupler._dispatcher.markReady(listener.operation);
        }
      }
      if (updatedKeys) {
        for (var i$1 = 0, list$1 = this$1._listeners; i$1 < list$1.length; i$1 += 1) {
          var listener$1 = list$1[i$1];

            if (listener$1.keysCallback) { listener$1.keysCallback(updatedKeys); }
        }
      }
    });
  };

  QueryHandler.prototype._updateKeysAndApplySnapshot = function _updateKeysAndApplySnapshot (snap) {
    var updatedKeys;
    if (snap.path === this._query.path) {
      updatedKeys = _.keys(snap.value);
      updatedKeys.sort();
      if (_.isEqual(this._keys, updatedKeys)) {
        updatedKeys = null;
      } else {
        for (var i = 0, list = _.difference(updatedKeys, this._keys); i < list.length; i += 1) {
          var key = list[i];

            this._coupler._coupleSegments(this._segments.concat(key));
        }
        for (var i$1 = 0, list$1 = _.difference(this._keys, updatedKeys); i$1 < list$1.length; i$1 += 1) {
          // Decoupling a segment will prune the tree at that location is there are no other
          // listeners.
          var key$1 = list$1[i$1];

            this._coupler._decoupleSegments(this._segments.concat(key$1));
        }
        this._keys = updatedKeys;
      }
      // The snapshot may be partial, so create synthetic snapshots for subpaths and apply those to
      // update / insert values.(Deleted ones got pruned above.)
      if (snap.exists) {
        var rootValue = snap.value;
        var rootPath = snap.path;
        for (var i$2 = 0, list$2 = this._keys; i$2 < list$2.length; i$2 += 1) {
          var key$2 = list$2[i$2];

            snap._path = rootPath + '/' + key$2;
          snap._key = undefined;
          snap._value = rootValue[key$2];
          this._coupler._applySnapshot(snap);
        }
        // Restore original properties, just in case.
        snap._path = rootPath;
        snap._key = undefined;
        snap._value = rootValue;
      }
    } else if (snap.path.replace(/\/[^/]+/, '') === this._query.path) {
      var hasKey = _.includes(this._keys, snap.key);
      if (snap.value) {
        if (!hasKey) {
          this._coupler._coupleSegments(this._segments.concat(snap.key));
          this._keys.push(snap.key);
          this._keys.sort();
          updatedKeys = this._keys;
        }
      } else if (hasKey) {
        this._coupler._decoupleSegments(this._segments.concat(snap.key));
        _.pull(this._keys, snap.key);
        this._keys.sort();
        updatedKeys = this._keys;
      }
      // A snapshot under the query's level is guaranteed to be a full snapshot, so we can apply it
      // directly.
      this._coupler._applySnapshot(snap);
    }
    return updatedKeys;
  };

  QueryHandler.prototype._handleError = function _handleError (error) {
      var this$1 = this;

    if (!this._listeners.length || !this._listening) { return; }
    this._listening = false;
    this.ready = false;
    angularProxy.digest();
    Promise.all(_.map(this._listeners, function (listener) {
      this$1._coupler._dispatcher.clearReady(listener.operation);
      return this$1._coupler._dispatcher.retry(listener.operation, error).catch(function (e) {
        listener.operation._disconnect(e);
        return false;
      });
    })).then(function (results) {
      if (_.some(results)) {
        if (this$1._listeners.length) { this$1._listen(); }
      } else {
        for (var i = 0, list = this$1._listeners; i < list.length; i += 1) {
            var listener = list[i];

            listener.operation._disconnect(error);
          }
      }
    });
  };


  var Node = function Node(coupler, path, parent) {
    this._coupler = coupler;
    this.path = path;
    this.parent = parent;
    this.url = this._coupler._rootUrl + path;
    this.operations = [];
    this.queryCount = 0;
    this.listening = false;
    this.ready = false;
    this.children = {};
  };

  var prototypeAccessors$7 = { active: { configurable: true },count: { configurable: true } };

  prototypeAccessors$7.active.get = function () {
    return this.count || this.queryCount;
  };

  prototypeAccessors$7.count.get = function () {
    return this.operations.length;
  };

  Node.prototype.listen = function listen (skip) {
      var this$1 = this;

    if (!skip && this.count) {
      if (this.listening) { return; }
      _.forEach(this.operations, function (op) {this$1._coupler._dispatcher.clearReady(op);});
      this._coupler._bridge.on(
        this.url, this.url, null, 'value', this._handleSnapshot, this._handleError, this,
        {sync: true});
      this.listening = true;
    } else {
      _.forEach(this.children, function (child) {child.listen();});
    }
  };

  Node.prototype.unlisten = function unlisten (skip) {
    if (!skip && this.listening) {
      this._coupler._bridge.off(this.url, this.url, null, 'value', this._handleSnapshot, this);
      this.listening = false;
      this._forAllDescendants(function (node) {
        if (node.listening) { return false; }
        if (node.ready) {
          node.ready = false;
          angularProxy.digest();
        }
      });
    } else {
      _.forEach(this.children, function (child) {child.unlisten();});
    }
  };

  Node.prototype._handleSnapshot = function _handleSnapshot (snap) {
      var this$1 = this;

    this._coupler._queueSnapshotCallback(function () {
      if (!this$1.listening || !this$1._coupler.isTrunkCoupled(snap.path)) { return; }
      this$1._coupler._applySnapshot(snap);
      if (!this$1.ready && snap.path === this$1.path) {
        this$1.ready = true;
        angularProxy.digest();
        this$1.unlisten(true);
        this$1._forAllDescendants(function (node) {
          for (var i = 0, list = node.operations; i < list.length; i += 1) {
              var op = list[i];

              this$1._coupler._dispatcher.markReady(op);
            }
        });
      }
    });
  };

  Node.prototype._handleError = function _handleError (error) {
      var this$1 = this;

    if (!this.count || !this.listening) { return; }
    this.listening = false;
    this._forAllDescendants(function (node) {
      if (node.listening) { return false; }
      if (node.ready) {
        node.ready = false;
        angularProxy.digest();
      }
      for (var i = 0, list = node.operations; i < list.length; i += 1) {
          var op = list[i];

          this$1._coupler._dispatcher.clearReady(op);
        }
    });
    return Promise.all(_.map(this.operations, function (op) {
      return this$1._coupler._dispatcher.retry(op, error).catch(function (e) {
        op._disconnect(e);
        return false;
      });
    })).then(function (results) {
      if (_.some(results)) {
        if (this$1.count) { this$1.listen(); }
      } else {
        for (var i = 0, list = this$1.operations; i < list.length; i += 1) {
            var op = list[i];

            op._disconnect(error);
          }
        // Pulling all the operations will automatically get us listening on descendants.
      }
    });
  };

  Node.prototype._forAllDescendants = function _forAllDescendants (iteratee) {
    if (iteratee(this) === false) { return; }
    _.forEach(this.children, function (child) { return child._forAllDescendants(iteratee); });
  };

  Node.prototype.collectCoupledDescendantPaths = function collectCoupledDescendantPaths (paths) {
    if (!paths) { paths = {}; }
    paths[this.path] = this.active;
    if (!this.active) {
      _.forEach(this.children, function (child) {child.collectCoupledDescendantPaths(paths);});
    }
    return paths;
  };

  Object.defineProperties( Node.prototype, prototypeAccessors$7 );


  var Coupler = function Coupler(rootUrl, bridge, dispatcher, applySnapshot, prunePath) {
    this._rootUrl = rootUrl;
    this._bridge = bridge;
    this._dispatcher = dispatcher;
    this._applySnapshot = applySnapshot;
    this._pendingSnapshotCallbacks = [];
    this._throttled = {processPendingSnapshots: this._processPendingSnapshots};
    this._prunePath = prunePath;
    this._vue = new Vue({data: {root: undefined, queryHandlers: {}}});
    // Prevent Vue from instrumenting rendering since there's actually nothing to render, and the
    // warnings cause false positives from Lodash primitives when running tests.
    this._vue._renderProxy = this._vue;
    this._nodeIndex = Object.create(null);
    Object.freeze(this);
    // Set root node after freezing Coupler, otherwise it gets vue-ified too.
    this._vue.$data.root = new Node(this, '/');
    this._nodeIndex['/'] = this._root;
  };

  var prototypeAccessors$1$3 = { _root: { configurable: true },_queryHandlers: { configurable: true } };

  prototypeAccessors$1$3._root.get = function () {
    return this._vue.$data.root;
  };

  prototypeAccessors$1$3._queryHandlers.get = function () {
    return this._vue.$data.queryHandlers;
  };

  Coupler.prototype.destroy = function destroy () {
    _.forEach(this._queryHandlers, function (queryHandler) {queryHandler.destroy();});
    this._root.unlisten();
    this._vue.$destroy();
  };

  Coupler.prototype.couple = function couple (path, operation) {
    return this._coupleSegments(splitPath(path, true), operation);
  };

  Coupler.prototype._coupleSegments = function _coupleSegments (segments, operation) {
    var node;
    var superseded = !operation;
    var ready = false;
    for (var i = 0, list = segments; i < list.length; i += 1) {
      var segment = list[i];

        var child = segment ? node.children && node.children[segment] : this._root;
      if (!child) {
        child = new Node(this, ((node.path === '/' ? '' : node.path) + "/" + segment), node);
        Vue.set(node.children, segment, child);
        this._nodeIndex[child.path] = child;
      }
      superseded = superseded || child.listening;
      ready = ready || child.ready;
      node = child;
    }
    if (operation) {
      node.operations.push(operation);
    } else {
      node.queryCount++;
    }
    if (superseded) {
      if (operation && ready) { this._dispatcher.markReady(operation); }
    } else {
      node.listen();// node will call unlisten() on descendants when ready
    }
  };

  Coupler.prototype.decouple = function decouple (path, operation) {
    return this._decoupleSegments(splitPath(path, true), operation);
  };

  Coupler.prototype._decoupleSegments = function _decoupleSegments (segments, operation) {
    var ancestors = [];
    var node;
    for (var i$1 = 0, list = segments; i$1 < list.length; i$1 += 1) {
      var segment = list[i$1];

        node = segment ? node.children && node.children[segment] : this._root;
      if (!node) { break; }
      ancestors.push(node);
    }
    if (!node || !(operation ? node.count : node.queryCount)) {
      throw new Error(("Path not coupled: " + (segments.join('/') || '/')));
    }
    if (operation) {
      _.pull(node.operations, operation);
    } else {
      node.queryCount--;
    }
    if (operation && !node.count) {
      // Ideally, we wouldn't resync the full values here since we probably already have the current
      // value for all children.But making sure that's true is tricky in an async system (what if
      // the node's value changes and the update crosses the 'off' call in transit?) and this
      // situation should be sufficiently rare that the optimization is probably not worth it right
      // now.
      node.listen();
      if (node.listening) { node.unlisten(); }
    }
    if (!node.active) {
      for (var i = ancestors.length - 1; i > 0; i--) {
        node = ancestors[i];
        if (node === this._root || node.active || !_.isEmpty(node.children)) { break; }
        Vue.delete(ancestors[i - 1].children, segments[i]);
        node.ready = undefined;
        delete this._nodeIndex[node.path];
      }
      var path = segments.join('/') || '/';
      this._prunePath(path, this.findCoupledDescendantPaths(path));
    }
  };

  Coupler.prototype.subscribe = function subscribe (query, operation, keysCallback) {
    var queryHandler = this._queryHandlers[query.toString()];
    if (!queryHandler) {
      queryHandler = new QueryHandler(this, query);
      Vue.set(this._queryHandlers, query.toString(), queryHandler);
    }
    queryHandler.attach(operation, keysCallback);
  };

  Coupler.prototype.unsubscribe = function unsubscribe (query, operation) {
    var queryHandler = this._queryHandlers[query.toString()];
    if (queryHandler && !queryHandler.detach(operation)) {
      queryHandler.destroy();
      Vue.delete(this._queryHandlers, query.toString());
    }
  };

  // Return whether the node at path or any ancestors are coupled.
  Coupler.prototype.isTrunkCoupled = function isTrunkCoupled (path) {
    var segments = splitPath(path, true);
    var node;
    for (var i = 0, list = segments; i < list.length; i += 1) {
      var segment = list[i];

        node = segment ? node.children && node.children[segment] : this._root;
      if (!node) { return false; }
      if (node.active) { return true; }
    }
    return false;
  };

  Coupler.prototype.findCoupledDescendantPaths = function findCoupledDescendantPaths (path) {
      var obj;

    var node;
    for (var i = 0, list = splitPath(path, true); i < list.length; i += 1) {
      var segment = list[i];

        node = segment ? node.children && node.children[segment] : this._root;
      if (node && node.active) { return ( obj = {}, obj[path] = node.active, obj ); }
      if (!node) { break; }
    }
    return node && node.collectCoupledDescendantPaths();
  };

  Coupler.prototype.isSubtreeReady = function isSubtreeReady (path) {
    var node, childSegment;
    function extractChildSegment(match) {
      childSegment = match.slice(1);
      return '';
    }
    while (!(node = this._nodeIndex[path])) {
      path = path.replace(/\/[^/]*$/, extractChildSegment) || '/';
    }
    if (childSegment) { void node.children; }// state an interest in the closest ancestor's children
    while (node) {
      if (node.ready) { return true; }
      node = node.parent;
    }
    return false;
  };

  Coupler.prototype.isQueryReady = function isQueryReady (query) {
    var queryHandler = this._queryHandlers[query.toString()];
    return queryHandler && queryHandler.ready;
  };

  Coupler.prototype._queueSnapshotCallback = function _queueSnapshotCallback (callback) {
    this._pendingSnapshotCallbacks.push(callback);
    this._throttled.processPendingSnapshots.call(this);
  };

  Coupler.prototype._processPendingSnapshots = function _processPendingSnapshots () {
    for (var i = 0, list = this._pendingSnapshotCallbacks; i < list.length; i += 1) {
        var callback = list[i];

        callback();
      }
    // Property is frozen, so we need to splice to empty the array.
    this._pendingSnapshotCallbacks.splice(0, Infinity);
  };

  Coupler.prototype.throttleSnapshots = function throttleSnapshots (delay) {
    if (delay) {
      this._throttled.processPendingSnapshots =
        _.debounce(_.throttle(this._processPendingSnapshots, delay));
    } else {
      this._throttled.processPendingSnapshots = this._processPendingSnapshots;
    }
  };

  Object.defineProperties( Coupler.prototype, prototypeAccessors$1$3 );

  var Transaction = function Transaction(ref) {
    this._ref = ref;
    this._outcome = undefined;
    this._values = undefined;
  };

  var prototypeAccessors$8 = { currentValue: { configurable: true },outcome: { configurable: true },values: { configurable: true } };

  prototypeAccessors$8.currentValue.get = function () {return this._ref.value;};
  prototypeAccessors$8.outcome.get = function () {return this._outcome;};
  prototypeAccessors$8.values.get = function () {return this._values;};

  Transaction.prototype._setOutcome = function _setOutcome (value) {
    if (this._outcome) { throw new Error('Transaction already resolved with ' + this._outcome); }
    this._outcome = value;
  };

  Transaction.prototype.abort = function abort () {
    this._setOutcome('abort');
  };

  Transaction.prototype.cancel = function cancel () {
    this._setOutcome('cancel');
  };

  Transaction.prototype.set = function set (value) {
    if (value === undefined) { throw new Error('Invalid argument: undefined'); }
    this._setOutcome('set');
    this._values = {'': value};
  };

  Transaction.prototype.update = function update (values) {
    if (values === undefined) { throw new Error('Invalid argument: undefined'); }
    if (_.isEmpty(values)) { return this.cancel(); }
    this._setOutcome('update');
    this._values = values;
  };

  Object.defineProperties( Transaction.prototype, prototypeAccessors$8 );


  var Tree = function Tree(truss, rootUrl, bridge, dispatcher) {
    this._truss = truss;
    this._rootUrl = rootUrl;
    this._bridge = bridge;
    this._dispatcher = dispatcher;
    this._firebasePropertyEditAllowed = false;
    this._writeSerial = 0;
    this._localWrites = {};
    this._localWriteTimestamp = null;
    this._initialized = false;
    this._modeler = new Modeler(truss.constructor.VERSION === 'dev');
    this._coupler = new Coupler(
      rootUrl, bridge, dispatcher, this._integrateSnapshot.bind(this), this._prune.bind(this));
    this._vue = new Vue({data: {$root: undefined}});
    Object.seal(this);
    // Call this.init(classes) to complete initialization; we need two phases so that truss can bind
    // the tree into its own accessors prior to defining computed functions, which may try to
    // access the tree root via truss.
  };

  var prototypeAccessors$1$4 = { root: { configurable: true },truss: { configurable: true } };

  prototypeAccessors$1$4.root.get = function () {
    if (!this._vue.$data.$root) {
      this._vue.$data.$root = this._createObject('/');
      this._fixObject(this._vue.$data.$root);
      this._completeCreateObject(this._vue.$data.$root);
      angularProxy.digest();
    }
    return this._vue.$data.$root;
  };

  prototypeAccessors$1$4.truss.get = function () {
    return this._truss;
  };

  Tree.prototype.init = function init (classes) {
    if (this._initialized) {
      throw new Error('Data objects already created, too late to mount classes');
    }
    this._initialized = true;
    this._modeler.init(classes, !this._vue.$data.$root);
    var createdObjects = [];
    this._plantPlaceholders(this.root, '/', undefined, createdObjects);
    for (var i = 0, list = createdObjects; i < list.length; i += 1) {
        var object = list[i];

        this._completeCreateObject(object);
      }
  };

  Tree.prototype.destroy = function destroy () {
    this._coupler.destroy();
    if (this._modeler) { this._modeler.destroy(); }
    this._vue.$destroy();
  };

  Tree.prototype.connectReference = function connectReference (ref, method) {
      var this$1 = this;

    this._checkHandle(ref);
    var operation = this._dispatcher.createOperation('read', method, ref);
    var unwatch;
    operation._disconnect = this._disconnectReference.bind(this, ref, operation, unwatch);
    this._dispatcher.begin(operation).then(function () {
      if (operation.running && !operation._disconnected) {
        this$1._coupler.couple(ref.path, operation);
        operation._coupled = true;
      }
    }).catch(_.noop);// ignore exception, let onFailure handlers deal with it
    return operation._disconnect;
  };

  Tree.prototype._disconnectReference = function _disconnectReference (ref, operation, unwatch, error) {
    if (operation._disconnected) { return; }
    operation._disconnected = true;
    if (unwatch) { unwatch(); }
    if (operation._coupled) {
      this._coupler.decouple(ref.path, operation);// will call back to _prune if necessary
      operation._coupled = false;
    }
    this._dispatcher.end(operation, error).catch(_.noop);
  };

  Tree.prototype.isReferenceReady = function isReferenceReady (ref) {
    this._checkHandle(ref);
    return this._coupler.isSubtreeReady(ref.path);
  };

  Tree.prototype.connectQuery = function connectQuery (query, keysCallback, method) {
      var this$1 = this;

    this._checkHandle(query);
    var operation = this._dispatcher.createOperation('read', method, query);
    operation._disconnect = this._disconnectQuery.bind(this, query, operation);
    this._dispatcher.begin(operation).then(function () {
      if (operation.running && !operation._disconnected) {
        this$1._coupler.subscribe(query, operation, keysCallback);
        operation._coupled = true;
      }
    }).catch(_.noop);// ignore exception, let onFailure handlers deal with it
    return operation._disconnect;
  };

  Tree.prototype._disconnectQuery = function _disconnectQuery (query, operation, error) {
    if (operation._disconnected) { return; }
    operation._disconnected = true;
    if (operation._coupled) {
      this._coupler.unsubscribe(query, operation);// will call back to _prune if necessary
      operation._coupled = false;
    }
    this._dispatcher.end(operation, error).catch(_.noop);
  };

  Tree.prototype.isQueryReady = function isQueryReady (query) {
    return this._coupler.isQueryReady(query);
  };

  Tree.prototype._checkHandle = function _checkHandle (handle) {
    if (!handle.belongsTo(this._truss)) {
      throw new Error('Reference belongs to another Truss instance');
    }
  };

  Tree.prototype.throttleRemoteDataUpdates = function throttleRemoteDataUpdates (delay) {
    this._coupler.throttleSnapshots(delay);
  };

  Tree.prototype.update = function update (ref, method, values) {
      var this$1 = this;

    values = _.mapValues(values, function (value) { return escapeKeys(value); });
    var numValues = _.size(values);
    if (!numValues) { return Promise.resolve(); }
    if (method === 'update' || method === 'override') {
      checkUpdateHasOnlyDescendantsWithNoOverlap(ref.path, values);
    }
    if (this._applyLocalWrite(values, method === 'override')) { return Promise.resolve(); }
    var pathPrefix = extractCommonPathPrefix(values);
    relativizePaths(pathPrefix, values);
    if (pathPrefix !== ref.path) { ref = new Reference(ref._tree, pathPrefix, ref._annotations); }
    var url = this._rootUrl + pathPrefix;
    var writeSerial = this._writeSerial;
    var set = numValues === 1;
    var operand = set ? values[''] : values;
    return this._dispatcher.execute('write', set ? 'set' : 'update', ref, operand, function () {
      var promise = this$1._bridge[set ? 'set' : 'update'](url, operand, writeSerial);
      return promise.catch(function (e) {
        if (!e.immediateFailure) { return Promise.reject(e); }
        return promiseFinally(this$1._repair(ref, values), function () { return Promise.reject(e); });
      });
    });
  };

  Tree.prototype.commit = function commit (ref, updateFunction) {
      var this$1 = this;

    var tries = 0;
    updateFunction = wrapPromiseCallback(updateFunction);

    var attemptTransaction = function () {
      if (tries++ >= 25) {
        return Promise.reject(new Error('Transaction needed too many retries, giving up'));
      }
      var txn = new Transaction(ref);
      var oldValue;
      // Ensure that Vue's watcher queue gets emptied and computed properties are up to date before
      // running the updateFunction.
      return Vue.nextTick().then(function () {
        oldValue = toFirebaseJson(txn.currentValue);
        return updateFunction(txn);
      }).then(function () {
          var obj;

        if (!_.isEqual(oldValue, toFirebaseJson(txn.currentValue))) { return attemptTransaction(); }
        if (txn.outcome === 'abort') { return txn; }// early return to save time
        var values = _.mapValues(txn.values, function (value) { return escapeKeys(value); });
        switch (txn.outcome) {
          case 'cancel':
            break;
          case 'set':
            if (this$1._applyLocalWrite(( obj = {}, obj[ref.path] = values[''], obj ))) { return Promise.resolve(); }
            break;
          case 'update':
            checkUpdateHasOnlyDescendantsWithNoOverlap(ref.path, values);
            if (this$1._applyLocalWrite(values)) { return Promise.resolve(); }
            relativizePaths(ref.path, values);
            break;
          default:
            throw new Error('Invalid transaction outcome: ' + (txn.outcome || 'none'));
        }
        return this$1._bridge.transaction(
          this$1._rootUrl + ref.path, oldValue, values, this$1._writeSerial
        ).then(function (result) {
          _.forEach(result.snapshots, function (snapshot) { return this$1._integrateSnapshot(snapshot); });
          return result.committed ? txn : attemptTransaction();
        }, function (e) {
          if (e.immediateFailure && (txn.outcome === 'set' || txn.outcome === 'update')) {
            return promiseFinally(this$1._repair(ref, values), function () { return Promise.reject(e); });
          }
          return Promise.reject(e);
        });
      });
    };

    return this._truss.peek(ref, function () {
      return this$1._dispatcher.execute('write', 'commit', ref, undefined, attemptTransaction);
    });
  };

  Tree.prototype._repair = function _repair (ref, values) {
      var this$1 = this;

    // If a write fails early -- that is, before it gets applied to the Firebase client's local
    // tree -- then we need to repair our own local tree manually since Firebase won't send events
    // to unwind the change.This should be very rare since it's always due to a developer mistake
    // so we don't need to be particularly efficient.
    var basePath = ref.path;
    var paths = _(values).keys().flatMap(function (key) {
      var path = basePath;
      if (key) { path = joinPath(path, key); }
      return _.keys(this$1._coupler.findCoupledDescendantPaths(path));
    }).value();
    return Promise.all(_.map(paths, function (path) {
      return this$1._bridge.once(this$1._rootUrl + path).then(function (snap) {
        this$1._integrateSnapshot(snap);
      });
    }));
  };

  Tree.prototype._applyLocalWrite = function _applyLocalWrite (values, override) {
      var this$1 = this;

    // TODO: correctly apply local writes that impact queries.Currently, a local write will update
    // any objects currently selected by a query, but won't add or remove results.
    this._writeSerial++;
    this._localWriteTimestamp = this._truss.now;
    var createdObjects = [];
    var numLocal = 0;
    _.forEach(values, function (value, path) {
        var obj;

      var local = this$1._modeler.isLocal(path, value);
      if (local) { numLocal++; }
      var coupledDescendantPaths =
        local ? ( obj = {}, obj[path] = true, obj ) : this$1._coupler.findCoupledDescendantPaths(path);
      if (_.isEmpty(coupledDescendantPaths)) { return; }
      var offset = (path === '/' ? 0 : path.length) + 1;
      for (var descendantPath in coupledDescendantPaths) {
        var subPath = descendantPath.slice(offset);
        var subValue = value;
        if (subPath && value !== null && value !== undefined) {
          for (var i = 0, list = splitPath(subPath); i < list.length; i += 1) {
            var segment = list[i];

              subValue = subValue.$data[segment];
            if (subValue === undefined) { break; }
          }
        }
        if (_.isNil(subValue)) {
          this$1._prune(descendantPath);
        } else {
          var key = _.last(splitPath(descendantPath));
          this$1._plantValue(
            descendantPath, key, subValue,
            this$1._scaffoldAncestors(descendantPath, false, createdObjects), false, override, local,
            createdObjects
          );
        }
        if (!override && !local) { this$1._localWrites[descendantPath] = this$1._writeSerial; }
      }
    });
    for (var i = 0, list = createdObjects; i < list.length; i += 1) {
        var object = list[i];

        this._completeCreateObject(object);
      }
    if (numLocal && numLocal < _.size(values)) {
      throw new Error('Write on a mix of local and remote tree paths.');
    }
    return override || !!numLocal;
  };

  /**
   * Creates a Truss object and sets all its basic properties: path segment variables, user-defined
   * properties, and computed properties.The latter two will be enumerable so that Vue will pick
   * them up and make the reactive, so you should call _completeCreateObject once it's done so and
   * before any Firebase properties are added.
   */
  Tree.prototype._createObject = function _createObject (path, parent) {
    if (!this._initialized && path !== '/') { this.init(); }
    var properties = {
      // We want Vue to wrap this; we'll make it non-enumerable in _fixObject.
      $parent: {value: parent, configurable: true, enumerable: true},
      $path: {value: path}
    };
    if (path === '/') { properties.$truss = {value: this._truss}; }

    var object = this._modeler.createObject(path, properties);
    Object.defineProperties(object, properties);
    return object;
  };

  // To be called on the result of _createObject after it's been inserted into the _vue hierarchy
  // and Vue has had a chance to initialize it.
  Tree.prototype._fixObject = function _fixObject (object) {
    for (var i = 0, list = Object.getOwnPropertyNames(object); i < list.length; i += 1) {
      var name = list[i];

        var descriptor = Object.getOwnPropertyDescriptor(object, name);
      if (descriptor.configurable && descriptor.enumerable) {
        descriptor.enumerable = false;
        if (_.startsWith(name, '$')) { descriptor.configurable = false; }
        Object.defineProperty(object, name, descriptor);
      }
    }
  };

  // To be called on the result of _createObject after _fixObject, and after any additional Firebase
  // properties have been set, to run initialiers.
  Tree.prototype._completeCreateObject = function _completeCreateObject (object) {
    if (object.hasOwnProperty('$$initializers')) {
      for (var i = 0, list = object.$$initializers; i < list.length; i += 1) {
          var fn = list[i];

          fn(this._vue);
        }
      delete object.$$initializers;
    }
  };

  Tree.prototype._destroyObject = function _destroyObject (object) {
    if (!(object && object.$truss) || object.$destroyed) { return; }
    this._modeler.destroyObject(object);
    // Normally we'd only destroy enumerable children, which are the Firebase properties.However,
    // clients have the option of creating hidden placeholders, so we need to scan non-enumerable
    // properties as well.To distinguish such placeholders from the myriad other non-enumerable
    // properties (that lead all over tree, e.g. $parent), we check that the property's parent is
    // ourselves before destroying.
    for (var i = 0, list = Object.getOwnPropertyNames(object.$data); i < list.length; i += 1) {
      var key = list[i];

        var child = object.$data[key];
      if (child && child.$parent === object) { this._destroyObject(child); }
    }
  };

  Tree.prototype._integrateSnapshot = function _integrateSnapshot (snap) {
      var this$1 = this;

    _.forEach(this._localWrites, function (writeSerial, path) {
      if (snap.writeSerial >= writeSerial) { delete this$1._localWrites[path]; }
    });
    if (snap.exists) {
      var createdObjects = [];
      var parent = this._scaffoldAncestors(snap.path, true, createdObjects);
      if (parent) {
        this._plantValue(
          snap.path, snap.key, snap.value, parent, true, false, false, createdObjects);
      }
      for (var i = 0, list = createdObjects; i < list.length; i += 1) {
          var object = list[i];

          this._completeCreateObject(object);
        }
    } else {
      this._prune(snap.path, null, true);
    }
  };

  Tree.prototype._scaffoldAncestors = function _scaffoldAncestors (path, remoteWrite, createdObjects) {
    var object;
    var segments = _.dropRight(splitPath(path, true));
    var ancestorPath = '/';
    for (var i = 0; i < segments.length; i++) {
      var segment = segments[i];
      var key = unescapeKey(segment);
      var child = segment ? object.$data[key] : this.root;
      if (segment) { ancestorPath += (ancestorPath === '/' ? '' : '/') + segment; }
      if (child) {
        if (remoteWrite && this._localWrites[ancestorPath]) { return; }
      } else {
        child = this._plantValue(
          ancestorPath, key, {}, object, remoteWrite, false, false, createdObjects);
        if (!child) { return; }
      }
      object = child;
    }
    return object;
  };

  Tree.prototype._plantValue = function _plantValue (path, key, value, parent, remoteWrite, override, local, createdObjects) {
      var this$1 = this;

    if (remoteWrite && _.isNil(value)) {
      throw new Error(("Snapshot includes invalid value at " + path + ": " + value));
    }
    if (remoteWrite && this._localWrites[path || '/']) { return; }
    if (_.isEqual(value, SERVER_TIMESTAMP)) { value = this._localWriteTimestamp; }
    var object = parent.$data[key];
    if (!_.isArray(value) && !(local ? _.isPlainObject(value) : _.isObject(value))) {
      this._destroyObject(object);
      if (!local && _.isNil(value)) {
        this._deleteFirebaseProperty(parent, key);
      } else {
        this._setFirebaseProperty(parent, key, value);
      }
      return;
    }
    var objectCreated = false;
    if (!_.isObject(object)) {
      // Need to pre-set the property, so that if the child object attempts to watch any of its own
      // properties while being created the $$touchThis method has something to add a dependency on
      // as the object's own properties won't be made reactive until *after* it's been created.
      this._setFirebaseProperty(parent, key, null);
      object = this._createObject(path, parent);
      this._setFirebaseProperty(parent, key, object, object.$hidden);
      this._fixObject(object);
      createdObjects.push(object);
      objectCreated = true;
    }
    if (override) {
      Object.defineProperty(object, '$overridden', {get: _.constant(true), configurable: true});
    } else if (object.$overridden) {
      delete object.$overridden;
    }
    // Plant hidden placeholders first, so their computed watchers will have a similar precedence to
    // the parent object, and the parent object's other children will get computed first.This can
    // optimize updates when parts of a complex model are broken out into hidden sub-models, and
    // shouldn't risk being overwritten by actual Firebase data since that will rarely (never?) be
    // hidden.
    if (objectCreated) { this._plantPlaceholders(object, path, true, createdObjects); }
    _.forEach(value, function (item, escapedChildKey) {
      this$1._plantValue(
        joinPath(path, escapedChildKey), unescapeKey(escapedChildKey), item, object, remoteWrite,
        override, local, createdObjects
      );
    });
    if (objectCreated) {
      this._plantPlaceholders(object, path, false, createdObjects);
    } else {
      _.forEach(object.$data, function (item, childKey) {
        var escapedChildKey = escapeKey(childKey);
        if (!value.hasOwnProperty(escapedChildKey)) {
          this$1._prune(joinPath(path, escapedChildKey), null, remoteWrite);
        }
      });
    }
    return object;
  };

  Tree.prototype._plantPlaceholders = function _plantPlaceholders (object, path, hidden, createdObjects) {
      var this$1 = this;

    this._modeler.forEachPlaceholderChild(path, function (mount) {
      if (hidden !== undefined && hidden !== !!mount.hidden) { return; }
      var key = unescapeKey(mount.escapedKey);
      if (!object.$data.hasOwnProperty(key)) {
        this$1._plantValue(
          joinPath(path, mount.escapedKey), key, mount.placeholder, object, false, false, false,
          createdObjects);
      }
    });
  };

  Tree.prototype._prune = function _prune (path, lockedDescendantPaths, remoteWrite) {
    lockedDescendantPaths = lockedDescendantPaths || {};
    var object = this.getObject(path);
    if (object === undefined) { return; }
    if (remoteWrite && this._avoidLocalWritePaths(path, lockedDescendantPaths)) { return; }
    if (!(_.isEmpty(lockedDescendantPaths) && this._pruneAncestors(path, object)) &&
        _.isObject(object)) {
      // The target object is a placeholder, and all ancestors are placeholders or otherwise needed
      // as well, so we can't delete it.Instead, dive into its descendants to delete what we can.
      this._pruneDescendants(object, lockedDescendantPaths);
    }
  };

  Tree.prototype._avoidLocalWritePaths = function _avoidLocalWritePaths (path, lockedDescendantPaths) {
    for (var localWritePath in this._localWrites) {
      if (!this._localWrites.hasOwnProperty(localWritePath)) { continue; }
      if (path === localWritePath || localWritePath === '/' ||
          _.startsWith(path, localWritePath + '/')) { return true; }
      if (path === '/' || _.startsWith(localWritePath, path + '/')) {
        var segments = splitPath(localWritePath, true);
        for (var i = segments.length; i > 0; i--) {
          var subPath = segments.slice(0, i).join('/');
          var active = i === segments.length;
          if (lockedDescendantPaths[subPath] || lockedDescendantPaths[subPath] === active) { break; }
          lockedDescendantPaths[subPath] = active;
          if (subPath === path) { break; }
        }
      }
    }
  };

  Tree.prototype._pruneAncestors = function _pruneAncestors (targetPath, targetObject) {
    // Destroy the child (unless it's a placeholder that's still needed) and any ancestors that
    // are no longer needed to keep this child rooted, and have no other reason to exist.
    var deleted = false;
    var object = targetObject;
    // The target object may be a primitive, in which case it won't have $path, $parent and $key
    // properties.In that case, use the target path to figure those out instead.Note that all
    // ancestors of the target object will necessarily not be primitives and will have those
    // properties.
    var targetKey;
    var targetParentPath = targetPath.replace(/\/[^/]+$/, function (match) {
      targetKey = unescapeKey(match.slice(1));
      return '';
    });
    while (object !== undefined && object !== this.root) {
      var parent =
        object && object.$parent || object === targetObject && this.getObject(targetParentPath);
      if (!this._modeler.isPlaceholder(object && object.$path || targetPath)) {
        var ghostObjects = deleted ? null : [targetObject];
        if (!this._holdsConcreteData(object, ghostObjects)) {
          deleted = true;
          this._deleteFirebaseProperty(
            parent, object && object.$key || object === targetObject && targetKey);
        }
      }
      object = parent;
    }
    return deleted;
  };

  Tree.prototype._holdsConcreteData = function _holdsConcreteData (object, ghostObjects) {
      var this$1 = this;

    if (_.isNil(object)) { return false; }
    if (ghostObjects && _.includes(ghostObjects, object)) { return false; }
    if (!_.isObject(object) || !object.$truss) { return true; }
    return _.some(object.$data, function (value) { return this$1._holdsConcreteData(value, ghostObjects); });
  };

  Tree.prototype._pruneDescendants = function _pruneDescendants (object, lockedDescendantPaths) {
      var this$1 = this;

    if (lockedDescendantPaths[object.$path]) { return true; }
    if (object.$overridden) { delete object.$overridden; }
    var coupledDescendantFound = false;
    _.forEach(object.$data, function (value, key) {
      var shouldDelete = true;
      var valueLocked;
      if (lockedDescendantPaths[joinPath(object.$path, escapeKey(key))]) {
        shouldDelete = false;
        valueLocked = true;
      } else if (!_.isNil(value) && value.$truss) {
        var placeholder = this$1._modeler.isPlaceholder(value.$path);
        if (placeholder || _.has(lockedDescendantPaths, value.$path)) {
          valueLocked = this$1._pruneDescendants(value, lockedDescendantPaths);
          shouldDelete = !placeholder && !valueLocked;
        }
      }
      if (shouldDelete) { this$1._deleteFirebaseProperty(object, key); }
      coupledDescendantFound = coupledDescendantFound || valueLocked;
    });
    return coupledDescendantFound;
  };

  Tree.prototype.getObject = function getObject (path) {
    var segments = splitPath(path);
    var object;
    for (var i = 0, list = segments; i < list.length; i += 1) {
      var segment = list[i];

        object = segment ? object.$data[segment] : this.root;
      if (object === undefined) { return; }
    }
    return object;
  };

  Tree.prototype._getFirebasePropertyDescriptor = function _getFirebasePropertyDescriptor (object, data, key) {
    var descriptor = Object.getOwnPropertyDescriptor(data, key);
    if (descriptor) {
      if (!descriptor.enumerable) {
        var child = data[key];
        if (!child || child.$parent !== object) {
          throw new Error(
            "Key conflict between Firebase and instance or computed properties at " +
            (object.$path) + ": " + key);
        }
      }
      if (!descriptor.get || !descriptor.set) {
        throw new Error(("Unbound property at " + (object.$path) + ": " + key));
      }
    } else if (key in data) {
      throw new Error(
        ("Key conflict between Firebase and inherited property at " + (object.$path) + ": " + key));
    }
    return descriptor;
  };

  Tree.prototype._setFirebaseProperty = function _setFirebaseProperty (object, key, value, hidden) {
    var data = object.hasOwnProperty('$data') ? object.$data : object;
    var descriptor = this._getFirebasePropertyDescriptor(object, data, key);
    if (descriptor) {
      if (hidden) {
        // Redefine property as hidden after it's been created, since we usually don't know whether
        // it should be hidden until too late.This is a one-way deal -- you can't unhide a
        // property later, but that's fine for our purposes.
        Object.defineProperty(data, key, {
          get: descriptor.get, set: descriptor.set, configurable: true, enumerable: false
        });
      }
      if (data[key] === value) { return; }
      this._firebasePropertyEditAllowed = true;
      data[key] = value;
      this._firebasePropertyEditAllowed = false;
    } else {
      Vue.set(data, key, value);
      descriptor = Object.getOwnPropertyDescriptor(data, key);
      Object.defineProperty(data, key, {
        get: descriptor.get, set: this._overwriteFirebaseProperty.bind(this, descriptor, key),
        configurable: true, enumerable: !hidden
      });
    }
    angularProxy.digest();
  };

  Tree.prototype._overwriteFirebaseProperty = function _overwriteFirebaseProperty (descriptor, key, newValue) {
    if (!this._firebasePropertyEditAllowed) {
      var e = new Error(("Firebase data cannot be mutated directly: " + key));
      e.trussCode = 'firebase_overwrite';
      throw e;
    }
    descriptor.set.call(this, newValue);
  };

  Tree.prototype._deleteFirebaseProperty = function _deleteFirebaseProperty (object, key) {
    var data = object.hasOwnProperty('$data') ? object.$data : object;
    // Make sure it's actually a Firebase property.
    this._getFirebasePropertyDescriptor(object, data, key);
    this._destroyObject(data[key]);
    Vue.delete(data, key);
    angularProxy.digest();
  };

  Tree.prototype.checkVueObject = function checkVueObject (object, path) {
    this._modeler.checkVueObject(object, path);
  };

  Object.defineProperties( Tree.prototype, prototypeAccessors$1$4 );


  function checkUpdateHasOnlyDescendantsWithNoOverlap(rootPath, values) {
    // First, check all paths for correctness and absolutize them, since there could be a mix of
    // absolute paths and relative keys.
    _.forEach(_.keys(values), function (path) {
      if (path.charAt(0) === '/') {
        if (!(path === rootPath || rootPath === '/' ||
              _.startsWith(path, rootPath + '/') && path.length > rootPath.length + 1)) {
          throw new Error(("Update item is not a descendant of target ref: " + path));
        }
      } else {
        if (_.includes(path, '/')) {
          throw new Error(("Update item deep path must be absolute, taken from a reference: " + path));
        }
        var absolutePath = joinPath(rootPath, escapeKey(path));
        if (values.hasOwnProperty(absolutePath)) {
          throw new Error(("Update items overlap: " + path + " and " + absolutePath));
        }
        values[absolutePath] = values[path];
        delete values[path];
      }
    });
    // Then check for overlaps;
    var allPaths = _(values).keys().map(function (path) { return joinPath(path, ''); }).sortBy('length').value();
    _.forEach(values, function (value, path) {
      for (var i = 0, list = allPaths; i < list.length; i += 1) {
        var otherPath = list[i];

        if (otherPath.length > path.length) { break; }
        if (path !== otherPath && _.startsWith(path, otherPath)) {
          throw new Error(("Update items overlap: " + otherPath + " and " + path));
        }
      }
    });
  }

  function extractCommonPathPrefix(values) {
    var prefixSegments;
    _.forEach(values, function (value, path) {
      var segments = path === '/' ? [''] : splitPath(path, true);
      if (prefixSegments) {
        var firstMismatchIndex = 0;
        var maxIndex = Math.min(prefixSegments.length, segments.length);
        while (firstMismatchIndex < maxIndex &&
               prefixSegments[firstMismatchIndex] === segments[firstMismatchIndex]) {
          firstMismatchIndex++;
        }
        prefixSegments = prefixSegments.slice(0, firstMismatchIndex);
        if (!prefixSegments.length) { return false; }
      } else {
        prefixSegments = segments;
      }
    });
    return prefixSegments.length === 1 ? '/' : prefixSegments.join('/');
  }

  function relativizePaths(rootPath, values) {
    var offset = rootPath === '/' ? 1 : rootPath.length + 1;
    _.forEach(_.keys(values), function (path) {
      values[path.slice(offset)] = values[path];
      delete values[path];
    });
  }

  function toFirebaseJson(object) {
    if (!_.isObject(object)) { return object; }
    var result = {};
    var data = object.$data;
    for (var key in data) {
      if (data.hasOwnProperty(key)) { result[escapeKey(key)] = toFirebaseJson(data[key]); }
    }
    return result;
  }

  var bridge, logging;
  var workerFunctions = {};
  // This version is filled in by the build, don't reformat the line.
  var VERSION = '4.2.2';


  var Truss = function Truss(rootUrl) {
    // TODO: allow rootUrl to be a test database object for testing
    if (!bridge) {
      throw new Error('Truss worker not connected, please call Truss.connectWorker first');
    }
    this._rootUrl = rootUrl.replace(/\/$/, '');
    this._keyGenerator = new KeyGenerator();
    this._dispatcher = new Dispatcher(bridge);
    this._vue = new Vue();

    bridge.trackServer(this._rootUrl);
    this._tree = new Tree(this, this._rootUrl, bridge, this._dispatcher);
    this._metaTree = new MetaTree(this._rootUrl, this._tree, bridge, this._dispatcher);

    Object.freeze(this);
  };

  var prototypeAccessors$9 = { meta: { configurable: true },store: { configurable: true },now: { configurable: true },SERVER_TIMESTAMP: { configurable: true },VERSION: { configurable: true },FIREBASE_SDK_VERSION: { configurable: true } };
  var staticAccessors = { computedPropertyStats: { configurable: true },worker: { configurable: true } };

  prototypeAccessors$9.meta.get = function () {return this._metaTree.root;};
  prototypeAccessors$9.store.get = function () {return this._tree.root;};

  /**
   * Mount a set of classes against the datastore structure.Must be called at most once, and
   * cannot be called once any data has been loaded into the tree.
   * @param classes {Array<Function> | Object<Function>} A list of the classes to map onto the
   *  datastore structure.Each class must have a static $trussMount property that is a
   *  (wildcarded) unescaped datastore path, or an options object
   *  {path: string, placeholder: object}, or an array of either.If the list is an object then
   *  the keys serve as default option-less $trussMount paths for classes that don't define an
   *  explicit $trussMount.
   */
  Truss.prototype.mount = function mount (classes) {
    this._tree.init(classes);
  };

  Truss.prototype.destroy = function destroy () {
    this._vue.$destroy();
    this._tree.destroy();
    this._metaTree.destroy();
  };

  prototypeAccessors$9.now.get = function () {return Date.now() + this.meta.timeOffset;};
  Truss.prototype.newKey = function newKey () {return this._keyGenerator.generateUniqueKey(this.now);};

  Truss.prototype.authenticate = function authenticate (token) {
    return this._metaTree.authenticate(token);
  };

  Truss.prototype.unauthenticate = function unauthenticate () {
    return this._metaTree.unauthenticate();
  };

  Truss.prototype.intercept = function intercept (actionType, callbacks) {
    return this._dispatcher.intercept(actionType, callbacks);
  };

  // connections are {key: Query | Object | fn() -> (Query | Object)}
  Truss.prototype.connect = function connect (scope, connections) {
    if (!connections) {
      connections = scope;
      scope = undefined;
    }
    if (connections instanceof Handle) { connections = {_: connections}; }
    return new Connector(scope, connections, this._tree, 'connect');
  };

  // target is Reference, Query, or connection Object like above
  Truss.prototype.peek = function peek (target, callback) {
      var this$1 = this;

    callback = wrapPromiseCallback(callback || _.identity);
    var cleanup, cancel;
    var promise = Promise.resolve().then(function () { return new Promise(function (resolve, reject) {
      var scope = {};
      var callbackPromise;

      var connector = new Connector(scope, {result: target}, this$1._tree, 'peek');

      var unintercept = this$1.intercept('peek', {onFailure: function (op) {
        function match(descriptor) {
          if (!descriptor) { return; }
          if (descriptor instanceof Handle) { return op.target.isEqual(descriptor); }
          return _.some(descriptor, function (value) { return match(value); });
        }
        if (match(connector.at)) {
          reject(op.error);
          cleanup();
        }
      }});

      var unobserve = this$1.observe(function () { return connector.ready; }, function (ready) {
        if (!ready) { return; }
        unobserve();
        unobserve = null;
        callbackPromise = promiseFinally(
          callback(scope.result), function () {angularProxy.digest(); callbackPromise = null; cleanup();}
        ).then(function (result) {resolve(result);}, function (error) {reject(error);});
      });

      cleanup = function () {
        if (unobserve) {unobserve(); unobserve = null;}
        if (unintercept) {unintercept(); unintercept = null;}
        if (connector) {connector.destroy(); connector = null;}
        if (callbackPromise && callbackPromise.cancel) { callbackPromise.cancel(); }
      };

      cancel = function () {
        reject(new Error('Canceled'));
        cleanup();
      };
    }); });
    return promiseCancel(promise, cancel);
  };

  Truss.prototype.observe = function observe (subjectFn, callbackFn, options) {
    var usePreciseDefaults = _.isObject(options && options.precise);
    var numCallbacks = 0;
    var oldValueClone;
    if (usePreciseDefaults) {
      oldValueClone = options.deep ? _.cloneDeep(options.precise) : _.clone(options.precise);
    }

    var unwatch = this._vue.$watch(subjectFn, function (newValue, oldValue) {
      if (options && options.precise) {
        var newValueClone = usePreciseDefaults ?
          (options.deep ?
            _.defaultsDeep({}, newValue, options.precise) :
            _.defaults({}, newValue, options.precise)) :
          (options.deep ? _.cloneDeep(newValue) : _.clone(newValue));
        if (_.isEqual(newValueClone, oldValueClone)) { return; }
        oldValueClone = newValueClone;
      }
      numCallbacks++;
      if (!unwatch) {
        // Delay the immediate callback until we've had a chance to return the unwatch function.
        Promise.resolve().then(function () {
          if (numCallbacks > 1) { return; }
          callbackFn(newValue, oldValue);
          // No need to digest since under Angular we'll be using $q as Promise.
        });
      } else {
        callbackFn(newValue, oldValue);
        angularProxy.digest();
      }
    }, {immediate: true, deep: options && options.deep});

    if (options && options.scope) { options.scope.$on('$destroy', unwatch); }
    return unwatch;
  };

  Truss.prototype.when = function when (expression, options) {
      var this$1 = this;

    var cleanup, timeoutHandle;
    var promise = new Promise(function (resolve, reject) {
      var unobserve = this$1.observe(expression, function (value) {
        if (!value) { return; }
        // Wait for computed properties to settle and double-check.
        Vue.nextTick(function () {
          value = expression();
          if (!value) { return; }
          resolve(value);
          cleanup();
        });
      });
      if (_.has(options, 'timeout')) {
        timeoutHandle = setTimeout(function () {
          timeoutHandle = null;
          reject(new Error(options.timeoutMessage || 'Timeout'));
          cleanup();
        }, options.timeout);
      }
      cleanup = function () {
        if (unobserve) {unobserve(); unobserve = null;}
        if (timeoutHandle) {clearTimeout(timeoutHandle); timeoutHandle = null;}
        reject(new Error('Canceled'));
      };
    });
    promise = promiseCancel(promiseFinally(promise, cleanup), cleanup);
    if (options && options.scope) { options.scope.$on('$destroy', function () {promise.cancel();}); }
    return promise;
  };

  Truss.prototype.nextTick = function nextTick () {
    var cleanup;
    var promise = new Promise(function (resolve, reject) {
      Vue.nextTick(resolve);
      cleanup = function () {
        reject(new Error('Canceled'));
      };
    });
    promise = promiseCancel(promise, cleanup);
    return promise;
  };

  Truss.prototype.throttleRemoteDataUpdates = function throttleRemoteDataUpdates (delay) {
    this._tree.throttleRemoteDataUpdates(delay);
  };

  Truss.prototype.checkObjectsForRogueProperties = function checkObjectsForRogueProperties () {
    this._tree.checkVueObject(this._tree.root, '/');
  };

  staticAccessors.computedPropertyStats.get = function () {
    return stats;
  };

  Truss.connectWorker = function connectWorker (webWorker, config) {
    if (bridge) { throw new Error('Worker already connected'); }
    if (_.isString(webWorker)) {
      var Worker = window.SharedWorker || window.Worker;
      if (!Worker) { throw new Error('Browser does not implement Web Workers'); }
      webWorker = new Worker(webWorker);
    }
    bridge = new Bridge(webWorker);
    if (logging) { bridge.enableLogging(logging); }
    return bridge.init(webWorker, config).then(
      function (ref) {
          var exposedFunctionNames = ref.exposedFunctionNames;
          var firebaseSdkVersion = ref.firebaseSdkVersion;

        Object.defineProperty(Truss, 'FIREBASE_SDK_VERSION', {value: firebaseSdkVersion});
        for (var i = 0, list = exposedFunctionNames; i < list.length; i += 1) {
          var name = list[i];

            Truss.worker[name] = bridge.bindExposedFunction(name);
        }
      }
    );
  };

  staticAccessors.worker.get = function () {return workerFunctions;};
  Truss.preExpose = function preExpose (functionName) {
    Truss.worker[functionName] = bridge.bindExposedFunction(functionName);
  };

  Truss.bounceConnection = function bounceConnection () {return bridge.bounceConnection();};
  Truss.suspend = function suspend () {return bridge.suspend();};
  Truss.debugPermissionDeniedErrors = function debugPermissionDeniedErrors (simulatedTokenGenerator, maxSimulationDuration, callFilter) {
    return bridge.debugPermissionDeniedErrors(
      simulatedTokenGenerator, maxSimulationDuration, callFilter);
  };

  Truss.debounceAngularDigest = function debounceAngularDigest (wait) {
    angularProxy.debounceDigest(wait);
  };

  Truss.escapeKey = function escapeKey$1 (key) {return escapeKey(key);};
  Truss.unescapeKey = function unescapeKey$1 (escapedKey) {return unescapeKey(escapedKey);};

  Truss.enableLogging = function enableLogging (fn) {
    logging = fn;
    if (bridge) { bridge.enableLogging(fn); }
  };

  // Duplicate static constants on instance for convenience.
  prototypeAccessors$9.SERVER_TIMESTAMP.get = function () {return Truss.SERVER_TIMESTAMP;};
  prototypeAccessors$9.VERSION.get = function () {return Truss.VERSION;};
  prototypeAccessors$9.FIREBASE_SDK_VERSION.get = function () {return Truss.FIREBASE_SDK_VERSION;};

  Object.defineProperties( Truss.prototype, prototypeAccessors$9 );
  Object.defineProperties( Truss, staticAccessors );

  Object.defineProperties(Truss, {
    SERVER_TIMESTAMP: {value: SERVER_TIMESTAMP},
    VERSION: {value: VERSION},

    ComponentPlugin: {value: {
      install: function install(Vue2, pluginOptions) {
        if (Vue !== Vue2) { throw new Error('Multiple versions of Vue detected'); }
        if (!pluginOptions.truss) {
          throw new Error('Need to pass `truss` instance as an option to use the ComponentPlugin');
        }
        var prototypeExtension = {
          $truss: {value: pluginOptions.truss},
          $destroyed: {get: function get() {return this._isBeingDestroyed || this._isDestroyed;}},
          $$touchThis: {value: function value() {if (this.__ob__) { this.__ob__.dep.depend(); }}}
        };
        var conflictingKeys = _(prototypeExtension).keys()
          .union(_.keys(BaseValue.prototype)).intersection(_.keys(Vue.prototype)).value();
        if (conflictingKeys.length) {
          throw new Error(
            'Truss extension properties conflict with Vue properties: ' + conflictingKeys.join(', '));
        }
        Object.defineProperties(Vue.prototype, prototypeExtension);
        copyPrototype(BaseValue, Vue);
        Vue.mixin({
          destroyed: function destroyed() {
            if (_.has(this, '$$finalizers')) {
              // Some finalizers remove themselves from the array, so clone it before iterating.
              for (var i = 0, list = _.clone(this.$$finalizers); i < list.length; i += 1) {
                var fn = list[i];

                fn();
              }
            }
          }
        });
      }
    }}
  });

  angularProxy.defineModule(Truss);

  return Truss;

})));

//# sourceMappingURL=firetruss.umd.js.map