Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2643 insertions, 0 deletions

diff --git a/services/common/kinto-offline-client.js b/services/common/kinto-offline-client.js
new file mode 100644
index 0000000000..9996e89854
--- /dev/null
+++ b/services/common/kinto-offline-client.js
@@ -0,0 +1,2643 @@
+/*
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+"use strict";
+
+/*
+ * This file is generated from kinto.js - do not modify directly.
+ */
+
+// This is required because with Babel compiles ES2015 modules into a
+// require() form that tries to keep its modules on "this", but
+// doesn't specify "this", leaving it to default to the global
+// object. However, in strict mode, "this" no longer defaults to the
+// global object, so expose the global object explicitly. Babel's
+// compiled output will use a variable called "global" if one is
+// present.
+//
+// See https://bugzilla.mozilla.org/show_bug.cgi?id=1394556#c3 for
+// more details.
+const global = this;
+
+var EXPORTED_SYMBOLS = ["Kinto"];
+
+/*
+ * Version 13.0.0 - 7fbf95d
+ */
+
+(function (global, factory) {
+  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
+  typeof define === 'function' && define.amd ? define(factory) :
+  (global = global || self, global.Kinto = factory());
+}(this, (function () { 'use strict';
+
+  /**
+   * Base db adapter.
+   *
+   * @abstract
+   */
+  class BaseAdapter {
+      /**
+       * Deletes every records present in the database.
+       *
+       * @abstract
+       * @return {Promise}
+       */
+      clear() {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Executes a batch of operations within a single transaction.
+       *
+       * @abstract
+       * @param  {Function} callback The operation callback.
+       * @param  {Object}   options  The options object.
+       * @return {Promise}
+       */
+      execute(callback, options = { preload: [] }) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Retrieve a record by its primary key from the database.
+       *
+       * @abstract
+       * @param  {String} id The record id.
+       * @return {Promise}
+       */
+      get(id) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Lists all records from the database.
+       *
+       * @abstract
+       * @param  {Object} params  The filters and order to apply to the results.
+       * @return {Promise}
+       */
+      list(params = { filters: {}, order: "" }) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Store the lastModified value.
+       *
+       * @abstract
+       * @param  {Number}  lastModified
+       * @return {Promise}
+       */
+      saveLastModified(lastModified) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Retrieve saved lastModified value.
+       *
+       * @abstract
+       * @return {Promise}
+       */
+      getLastModified() {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Load records in bulk that were exported from a server.
+       *
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      importBulk(records) {
+          throw new Error("Not Implemented.");
+      }
+      /**
+       * Load a dump of records exported from a server.
+       *
+       * @deprecated Use {@link importBulk} instead.
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      loadDump(records) {
+          throw new Error("Not Implemented.");
+      }
+      saveMetadata(metadata) {
+          throw new Error("Not Implemented.");
+      }
+      getMetadata() {
+          throw new Error("Not Implemented.");
+      }
+  }
+
+  const RE_RECORD_ID = /^[a-zA-Z0-9][a-zA-Z0-9_-]*$/;
+  /**
+   * Checks if a value is undefined.
+   * @param  {Any}  value
+   * @return {Boolean}
+   */
+  function _isUndefined(value) {
+      return typeof value === "undefined";
+  }
+  /**
+   * Sorts records in a list according to a given ordering.
+   *
+   * @param  {String} order The ordering, eg. `-last_modified`.
+   * @param  {Array}  list  The collection to order.
+   * @return {Array}
+   */
+  function sortObjects(order, list) {
+      const hasDash = order[0] === "-";
+      const field = hasDash ? order.slice(1) : order;
+      const direction = hasDash ? -1 : 1;
+      return list.slice().sort((a, b) => {
+          if (a[field] && _isUndefined(b[field])) {
+              return direction;
+          }
+          if (b[field] && _isUndefined(a[field])) {
+              return -direction;
+          }
+          if (_isUndefined(a[field]) && _isUndefined(b[field])) {
+              return 0;
+          }
+          return a[field] > b[field] ? direction : -direction;
+      });
+  }
+  /**
+   * Test if a single object matches all given filters.
+   *
+   * @param  {Object} filters  The filters object.
+   * @param  {Object} entry    The object to filter.
+   * @return {Boolean}
+   */
+  function filterObject(filters, entry) {
+      return Object.keys(filters).every(filter => {
+          const value = filters[filter];
+          if (Array.isArray(value)) {
+              return value.some(candidate => candidate === entry[filter]);
+          }
+          else if (typeof value === "object") {
+              return filterObject(value, entry[filter]);
+          }
+          else if (!Object.prototype.hasOwnProperty.call(entry, filter)) {
+              console.error(`The property ${filter} does not exist`);
+              return false;
+          }
+          return entry[filter] === value;
+      });
+  }
+  /**
+   * Resolves a list of functions sequentially, which can be sync or async; in
+   * case of async, functions must return a promise.
+   *
+   * @param  {Array} fns  The list of functions.
+   * @param  {Any}   init The initial value.
+   * @return {Promise}
+   */
+  function waterfall(fns, init) {
+      if (!fns.length) {
+          return Promise.resolve(init);
+      }
+      return fns.reduce((promise, nextFn) => {
+          return promise.then(nextFn);
+      }, Promise.resolve(init));
+  }
+  /**
+   * Simple deep object comparison function. This only supports comparison of
+   * serializable JavaScript objects.
+   *
+   * @param  {Object} a The source object.
+   * @param  {Object} b The compared object.
+   * @return {Boolean}
+   */
+  function deepEqual(a, b) {
+      if (a === b) {
+          return true;
+      }
+      if (typeof a !== typeof b) {
+          return false;
+      }
+      if (!(a && typeof a == "object") || !(b && typeof b == "object")) {
+          return false;
+      }
+      if (Object.keys(a).length !== Object.keys(b).length) {
+          return false;
+      }
+      for (const k in a) {
+          if (!deepEqual(a[k], b[k])) {
+              return false;
+          }
+      }
+      return true;
+  }
+  /**
+   * Return an object without the specified keys.
+   *
+   * @param  {Object} obj        The original object.
+   * @param  {Array}  keys       The list of keys to exclude.
+   * @return {Object}            A copy without the specified keys.
+   */
+  function omitKeys(obj, keys = []) {
+      const result = Object.assign({}, obj);
+      for (const key of keys) {
+          delete result[key];
+      }
+      return result;
+  }
+  function arrayEqual(a, b) {
+      if (a.length !== b.length) {
+          return false;
+      }
+      for (let i = a.length; i--;) {
+          if (a[i] !== b[i]) {
+              return false;
+          }
+      }
+      return true;
+  }
+  function makeNestedObjectFromArr(arr, val, nestedFiltersObj) {
+      const last = arr.length - 1;
+      return arr.reduce((acc, cv, i) => {
+          if (i === last) {
+              return (acc[cv] = val);
+          }
+          else if (Object.prototype.hasOwnProperty.call(acc, cv)) {
+              return acc[cv];
+          }
+          else {
+              return (acc[cv] = {});
+          }
+      }, nestedFiltersObj);
+  }
+  function transformSubObjectFilters(filtersObj) {
+      const transformedFilters = {};
+      for (const key in filtersObj) {
+          const keysArr = key.split(".");
+          const val = filtersObj[key];
+          makeNestedObjectFromArr(keysArr, val, transformedFilters);
+      }
+      return transformedFilters;
+  }
+
+  const INDEXED_FIELDS = ["id", "_status", "last_modified"];
+  /**
+   * Small helper that wraps the opening of an IndexedDB into a Promise.
+   *
+   * @param dbname          {String}   The database name.
+   * @param version         {Integer}  Schema version
+   * @param onupgradeneeded {Function} The callback to execute if schema is
+   *                                   missing or different.
+   * @return {Promise<IDBDatabase>}
+   */
+  async function open(dbname, { version, onupgradeneeded }) {
+      return new Promise((resolve, reject) => {
+          const request = indexedDB.open(dbname, version);
+          request.onupgradeneeded = event => {
+              const db = event.target.result;
+              db.onerror = event => reject(event.target.error);
+              // When an upgrade is needed, a transaction is started.
+              const transaction = event.target.transaction;
+              transaction.onabort = event => {
+                  const error = event.target.error ||
+                      transaction.error ||
+                      new DOMException("The operation has been aborted", "AbortError");
+                  reject(error);
+              };
+              // Callback for store creation etc.
+              return onupgradeneeded(event);
+          };
+          request.onerror = event => {
+              reject(event.target.error);
+          };
+          request.onsuccess = event => {
+              const db = event.target.result;
+              resolve(db);
+          };
+      });
+  }
+  /**
+   * Helper to run the specified callback in a single transaction on the
+   * specified store.
+   * The helper focuses on transaction wrapping into a promise.
+   *
+   * @param db           {IDBDatabase} The database instance.
+   * @param name         {String}      The store name.
+   * @param callback     {Function}    The piece of code to execute in the transaction.
+   * @param options      {Object}      Options.
+   * @param options.mode {String}      Transaction mode (default: read).
+   * @return {Promise} any value returned by the callback.
+   */
+  async function execute(db, name, callback, options = {}) {
+      const { mode } = options;
+      return new Promise((resolve, reject) => {
+          // On Safari, calling IDBDatabase.transaction with mode == undefined raises
+          // a TypeError.
+          const transaction = mode
+              ? db.transaction([name], mode)
+              : db.transaction([name]);
+          const store = transaction.objectStore(name);
+          // Let the callback abort this transaction.
+          const abort = e => {
+              transaction.abort();
+              reject(e);
+          };
+          // Execute the specified callback **synchronously**.
+          let result;
+          try {
+              result = callback(store, abort);
+          }
+          catch (e) {
+              abort(e);
+          }
+          transaction.onerror = event => reject(event.target.error);
+          transaction.oncomplete = event => resolve(result);
+          transaction.onabort = event => {
+              const error = event.target.error ||
+                  transaction.error ||
+                  new DOMException("The operation has been aborted", "AbortError");
+              reject(error);
+          };
+      });
+  }
+  /**
+   * Helper to wrap the deletion of an IndexedDB database into a promise.
+   *
+   * @param dbName {String} the database to delete
+   * @return {Promise}
+   */
+  async function deleteDatabase(dbName) {
+      return new Promise((resolve, reject) => {
+          const request = indexedDB.deleteDatabase(dbName);
+          request.onsuccess = event => resolve(event.target);
+          request.onerror = event => reject(event.target.error);
+      });
+  }
+  /**
+   * IDB cursor handlers.
+   * @type {Object}
+   */
+  const cursorHandlers = {
+      all(filters, done) {
+          const results = [];
+          return event => {
+              const cursor = event.target.result;
+              if (cursor) {
+                  const { value } = cursor;
+                  if (filterObject(filters, value)) {
+                      results.push(value);
+                  }
+                  cursor.continue();
+              }
+              else {
+                  done(results);
+              }
+          };
+      },
+      in(values, filters, done) {
+          const results = [];
+          let i = 0;
+          return function (event) {
+              const cursor = event.target.result;
+              if (!cursor) {
+                  done(results);
+                  return;
+              }
+              const { key, value } = cursor;
+              // `key` can be an array of two values (see `keyPath` in indices definitions).
+              // `values` can be an array of arrays if we filter using an index whose key path
+              // is an array (eg. `cursorHandlers.in([["bid/cid", 42], ["bid/cid", 43]], ...)`)
+              while (key > values[i]) {
+                  // The cursor has passed beyond this key. Check next.
+                  ++i;
+                  if (i === values.length) {
+                      done(results); // There is no next. Stop searching.
+                      return;
+                  }
+              }
+              const isEqual = Array.isArray(key)
+                  ? arrayEqual(key, values[i])
+                  : key === values[i];
+              if (isEqual) {
+                  if (filterObject(filters, value)) {
+                      results.push(value);
+                  }
+                  cursor.continue();
+              }
+              else {
+                  cursor.continue(values[i]);
+              }
+          };
+      },
+  };
+  /**
+   * Creates an IDB request and attach it the appropriate cursor event handler to
+   * perform a list query.
+   *
+   * Multiple matching values are handled by passing an array.
+   *
+   * @param  {String}           cid        The collection id (ie. `{bid}/{cid}`)
+   * @param  {IDBStore}         store      The IDB store.
+   * @param  {Object}           filters    Filter the records by field.
+   * @param  {Function}         done       The operation completion handler.
+   * @return {IDBRequest}
+   */
+  function createListRequest(cid, store, filters, done) {
+      const filterFields = Object.keys(filters);
+      // If no filters, get all results in one bulk.
+      if (filterFields.length == 0) {
+          const request = store.index("cid").getAll(IDBKeyRange.only(cid));
+          request.onsuccess = event => done(event.target.result);
+          return request;
+      }
+      // Introspect filters and check if they leverage an indexed field.
+      const indexField = filterFields.find(field => {
+          return INDEXED_FIELDS.includes(field);
+      });
+      if (!indexField) {
+          // Iterate on all records for this collection (ie. cid)
+          const isSubQuery = Object.keys(filters).some(key => key.includes(".")); // (ie. filters: {"article.title": "hello"})
+          if (isSubQuery) {
+              const newFilter = transformSubObjectFilters(filters);
+              const request = store.index("cid").openCursor(IDBKeyRange.only(cid));
+              request.onsuccess = cursorHandlers.all(newFilter, done);
+              return request;
+          }
+          const request = store.index("cid").openCursor(IDBKeyRange.only(cid));
+          request.onsuccess = cursorHandlers.all(filters, done);
+          return request;
+      }
+      // If `indexField` was used already, don't filter again.
+      const remainingFilters = omitKeys(filters, [indexField]);
+      // value specified in the filter (eg. `filters: { _status: ["created", "updated"] }`)
+      const value = filters[indexField];
+      // For the "id" field, use the primary key.
+      const indexStore = indexField == "id" ? store : store.index(indexField);
+      // WHERE IN equivalent clause
+      if (Array.isArray(value)) {
+          if (value.length === 0) {
+              return done([]);
+          }
+          const values = value.map(i => [cid, i]).sort();
+          const range = IDBKeyRange.bound(values[0], values[values.length - 1]);
+          const request = indexStore.openCursor(range);
+          request.onsuccess = cursorHandlers.in(values, remainingFilters, done);
+          return request;
+      }
+      // If no filters on custom attribute, get all results in one bulk.
+      if (remainingFilters.length == 0) {
+          const request = indexStore.getAll(IDBKeyRange.only([cid, value]));
+          request.onsuccess = event => done(event.target.result);
+          return request;
+      }
+      // WHERE field = value clause
+      const request = indexStore.openCursor(IDBKeyRange.only([cid, value]));
+      request.onsuccess = cursorHandlers.all(remainingFilters, done);
+      return request;
+  }
+  class IDBError extends Error {
+      constructor(method, err) {
+          super(`IndexedDB ${method}() ${err.message}`);
+          this.name = err.name;
+          this.stack = err.stack;
+      }
+  }
+  /**
+   * IndexedDB adapter.
+   *
+   * This adapter doesn't support any options.
+   */
+  class IDB extends BaseAdapter {
+      /* Expose the IDBError class publicly */
+      static get IDBError() {
+          return IDBError;
+      }
+      /**
+       * Constructor.
+       *
+       * @param  {String} cid  The key base for this collection (eg. `bid/cid`)
+       * @param  {Object} options
+       * @param  {String} options.dbName         The IndexedDB name (default: `"KintoDB"`)
+       * @param  {String} options.migrateOldData Whether old database data should be migrated (default: `false`)
+       */
+      constructor(cid, options = {}) {
+          super();
+          this.cid = cid;
+          this.dbName = options.dbName || "KintoDB";
+          this._options = options;
+          this._db = null;
+      }
+      _handleError(method, err) {
+          throw new IDBError(method, err);
+      }
+      /**
+       * Ensures a connection to the IndexedDB database has been opened.
+       *
+       * @override
+       * @return {Promise}
+       */
+      async open() {
+          if (this._db) {
+              return this;
+          }
+          // In previous versions, we used to have a database with name `${bid}/${cid}`.
+          // Check if it exists, and migrate data once new schema is in place.
+          // Note: the built-in migrations from IndexedDB can only be used if the
+          // database name does not change.
+          const dataToMigrate = this._options.migrateOldData
+              ? await migrationRequired(this.cid)
+              : null;
+          this._db = await open(this.dbName, {
+              version: 2,
+              onupgradeneeded: event => {
+                  const db = event.target.result;
+                  if (event.oldVersion < 1) {
+                      // Records store
+                      const recordsStore = db.createObjectStore("records", {
+                          keyPath: ["_cid", "id"],
+                      });
+                      // An index to obtain all the records in a collection.
+                      recordsStore.createIndex("cid", "_cid");
+                      // Here we create indices for every known field in records by collection.
+                      // Local record status ("synced", "created", "updated", "deleted")
+                      recordsStore.createIndex("_status", ["_cid", "_status"]);
+                      // Last modified field
+                      recordsStore.createIndex("last_modified", ["_cid", "last_modified"]);
+                      // Timestamps store
+                      db.createObjectStore("timestamps", {
+                          keyPath: "cid",
+                      });
+                  }
+                  if (event.oldVersion < 2) {
+                      // Collections store
+                      db.createObjectStore("collections", {
+                          keyPath: "cid",
+                      });
+                  }
+              },
+          });
+          if (dataToMigrate) {
+              const { records, timestamp } = dataToMigrate;
+              await this.importBulk(records);
+              await this.saveLastModified(timestamp);
+              console.log(`${this.cid}: data was migrated successfully.`);
+              // Delete the old database.
+              await deleteDatabase(this.cid);
+              console.warn(`${this.cid}: old database was deleted.`);
+          }
+          return this;
+      }
+      /**
+       * Closes current connection to the database.
+       *
+       * @override
+       * @return {Promise}
+       */
+      close() {
+          if (this._db) {
+              this._db.close(); // indexedDB.close is synchronous
+              this._db = null;
+          }
+          return Promise.resolve();
+      }
+      /**
+       * Returns a transaction and an object store for a store name.
+       *
+       * To determine if a transaction has completed successfully, we should rather
+       * listen to the transaction’s complete event rather than the IDBObjectStore
+       * request’s success event, because the transaction may still fail after the
+       * success event fires.
+       *
+       * @param  {String}      name  Store name
+       * @param  {Function}    callback to execute
+       * @param  {Object}      options Options
+       * @param  {String}      options.mode  Transaction mode ("readwrite" or undefined)
+       * @return {Object}
+       */
+      async prepare(name, callback, options) {
+          await this.open();
+          await execute(this._db, name, callback, options);
+      }
+      /**
+       * Deletes every records in the current collection.
+       *
+       * @override
+       * @return {Promise}
+       */
+      async clear() {
+          try {
+              await this.prepare("records", store => {
+                  const range = IDBKeyRange.only(this.cid);
+                  const request = store.index("cid").openKeyCursor(range);
+                  request.onsuccess = event => {
+                      const cursor = event.target.result;
+                      if (cursor) {
+                          store.delete(cursor.primaryKey);
+                          cursor.continue();
+                      }
+                  };
+                  return request;
+              }, { mode: "readwrite" });
+          }
+          catch (e) {
+              this._handleError("clear", e);
+          }
+      }
+      /**
+       * Executes the set of synchronous CRUD operations described in the provided
+       * callback within an IndexedDB transaction, for current db store.
+       *
+       * The callback will be provided an object exposing the following synchronous
+       * CRUD operation methods: get, create, update, delete.
+       *
+       * Important note: because limitations in IndexedDB implementations, no
+       * asynchronous code should be performed within the provided callback; the
+       * promise will therefore be rejected if the callback returns a Promise.
+       *
+       * Options:
+       * - {Array} preload: The list of record IDs to fetch and make available to
+       *   the transaction object get() method (default: [])
+       *
+       * @example
+       * const db = new IDB("example");
+       * const result = await db.execute(transaction => {
+       *   transaction.create({id: 1, title: "foo"});
+       *   transaction.update({id: 2, title: "bar"});
+       *   transaction.delete(3);
+       *   return "foo";
+       * });
+       *
+       * @override
+       * @param  {Function} callback The operation description callback.
+       * @param  {Object}   options  The options object.
+       * @return {Promise}
+       */
+      async execute(callback, options = { preload: [] }) {
+          // Transactions in IndexedDB are autocommited when a callback does not
+          // perform any additional operation.
+          // The way Promises are implemented in Firefox (see https://bugzilla.mozilla.org/show_bug.cgi?id=1193394)
+          // prevents using within an opened transaction.
+          // To avoid managing asynchronocity in the specified `callback`, we preload
+          // a list of record in order to execute the `callback` synchronously.
+          // See also:
+          // - http://stackoverflow.com/a/28388805/330911
+          // - http://stackoverflow.com/a/10405196
+          // - https://jakearchibald.com/2015/tasks-microtasks-queues-and-schedules/
+          let result;
+          await this.prepare("records", (store, abort) => {
+              const runCallback = (preloaded = []) => {
+                  // Expose a consistent API for every adapter instead of raw store methods.
+                  const proxy = transactionProxy(this, store, preloaded);
+                  // The callback is executed synchronously within the same transaction.
+                  try {
+                      const returned = callback(proxy);
+                      if (returned instanceof Promise) {
+                          // XXX: investigate how to provide documentation details in error.
+                          throw new Error("execute() callback should not return a Promise.");
+                      }
+                      // Bring to scope that will be returned (once promise awaited).
+                      result = returned;
+                  }
+                  catch (e) {
+                      // The callback has thrown an error explicitly. Abort transaction cleanly.
+                      abort(e);
+                  }
+              };
+              // No option to preload records, go straight to `callback`.
+              if (!options.preload.length) {
+                  return runCallback();
+              }
+              // Preload specified records using a list request.
+              const filters = { id: options.preload };
+              createListRequest(this.cid, store, filters, records => {
+                  // Store obtained records by id.
+                  const preloaded = {};
+                  for (const record of records) {
+                      delete record["_cid"];
+                      preloaded[record.id] = record;
+                  }
+                  runCallback(preloaded);
+              });
+          }, { mode: "readwrite" });
+          return result;
+      }
+      /**
+       * Retrieve a record by its primary key from the IndexedDB database.
+       *
+       * @override
+       * @param  {String} id The record id.
+       * @return {Promise}
+       */
+      async get(id) {
+          try {
+              let record;
+              await this.prepare("records", store => {
+                  store.get([this.cid, id]).onsuccess = e => (record = e.target.result);
+              });
+              return record;
+          }
+          catch (e) {
+              this._handleError("get", e);
+          }
+      }
+      /**
+       * Lists all records from the IndexedDB database.
+       *
+       * @override
+       * @param  {Object} params  The filters and order to apply to the results.
+       * @return {Promise}
+       */
+      async list(params = { filters: {} }) {
+          const { filters } = params;
+          try {
+              let results = [];
+              await this.prepare("records", store => {
+                  createListRequest(this.cid, store, filters, _results => {
+                      // we have received all requested records that match the filters,
+                      // we now park them within current scope and hide the `_cid` attribute.
+                      for (const result of _results) {
+                          delete result["_cid"];
+                      }
+                      results = _results;
+                  });
+              });
+              // The resulting list of records is sorted.
+              // XXX: with some efforts, this could be fully implemented using IDB API.
+              return params.order ? sortObjects(params.order, results) : results;
+          }
+          catch (e) {
+              this._handleError("list", e);
+          }
+      }
+      /**
+       * Store the lastModified value into metadata store.
+       *
+       * @override
+       * @param  {Number}  lastModified
+       * @return {Promise}
+       */
+      async saveLastModified(lastModified) {
+          const value = parseInt(lastModified, 10) || null;
+          try {
+              await this.prepare("timestamps", store => {
+                  if (value === null) {
+                      store.delete(this.cid);
+                  }
+                  else {
+                      store.put({ cid: this.cid, value });
+                  }
+              }, { mode: "readwrite" });
+              return value;
+          }
+          catch (e) {
+              this._handleError("saveLastModified", e);
+          }
+      }
+      /**
+       * Retrieve saved lastModified value.
+       *
+       * @override
+       * @return {Promise}
+       */
+      async getLastModified() {
+          try {
+              let entry = null;
+              await this.prepare("timestamps", store => {
+                  store.get(this.cid).onsuccess = e => (entry = e.target.result);
+              });
+              return entry ? entry.value : null;
+          }
+          catch (e) {
+              this._handleError("getLastModified", e);
+          }
+      }
+      /**
+       * Load a dump of records exported from a server.
+       *
+       * @deprecated Use {@link importBulk} instead.
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      async loadDump(records) {
+          return this.importBulk(records);
+      }
+      /**
+       * Load records in bulk that were exported from a server.
+       *
+       * @abstract
+       * @param  {Array} records The records to load.
+       * @return {Promise}
+       */
+      async importBulk(records) {
+          try {
+              await this.execute(transaction => {
+                  // Since the put operations are asynchronous, we chain
+                  // them together. The last one will be waited for the
+                  // `transaction.oncomplete` callback. (see #execute())
+                  let i = 0;
+                  putNext();
+                  function putNext() {
+                      if (i == records.length) {
+                          return;
+                      }
+                      // On error, `transaction.onerror` is called.
+                      transaction.update(records[i]).onsuccess = putNext;
+                      ++i;
+                  }
+              });
+              const previousLastModified = await this.getLastModified();
+              const lastModified = Math.max(...records.map(record => record.last_modified));
+              if (lastModified > previousLastModified) {
+                  await this.saveLastModified(lastModified);
+              }
+              return records;
+          }
+          catch (e) {
+              this._handleError("importBulk", e);
+          }
+      }
+      async saveMetadata(metadata) {
+          try {
+              await this.prepare("collections", store => store.put({ cid: this.cid, metadata }), { mode: "readwrite" });
+              return metadata;
+          }
+          catch (e) {
+              this._handleError("saveMetadata", e);
+          }
+      }
+      async getMetadata() {
+          try {
+              let entry = null;
+              await this.prepare("collections", store => {
+                  store.get(this.cid).onsuccess = e => (entry = e.target.result);
+              });
+              return entry ? entry.metadata : null;
+          }
+          catch (e) {
+              this._handleError("getMetadata", e);
+          }
+      }
+  }
+  /**
+   * IDB transaction proxy.
+   *
+   * @param  {IDB} adapter        The call IDB adapter
+   * @param  {IDBStore} store     The IndexedDB database store.
+   * @param  {Array}    preloaded The list of records to make available to
+   *                              get() (default: []).
+   * @return {Object}
+   */
+  function transactionProxy(adapter, store, preloaded = []) {
+      const _cid = adapter.cid;
+      return {
+          create(record) {
+              store.add(Object.assign(Object.assign({}, record), { _cid }));
+          },
+          update(record) {
+              return store.put(Object.assign(Object.assign({}, record), { _cid }));
+          },
+          delete(id) {
+              store.delete([_cid, id]);
+          },
+          get(id) {
+              return preloaded[id];
+          },
+      };
+  }
+  /**
+   * Up to version 10.X of kinto.js, each collection had its own collection.
+   * The database name was `${bid}/${cid}` (eg. `"blocklists/certificates"`)
+   * and contained only one store with the same name.
+   */
+  async function migrationRequired(dbName) {
+      let exists = true;
+      const db = await open(dbName, {
+          version: 1,
+          onupgradeneeded: event => {
+              exists = false;
+          },
+      });
+      // Check that the DB we're looking at is really a legacy one,
+      // and not some remainder of the open() operation above.
+      exists &=
+          db.objectStoreNames.contains("__meta__") &&
+              db.objectStoreNames.contains(dbName);
+      if (!exists) {
+          db.close();
+          // Testing the existence creates it, so delete it :)
+          await deleteDatabase(dbName);
+          return null;
+      }
+      console.warn(`${dbName}: old IndexedDB database found.`);
+      try {
+          // Scan all records.
+          let records;
+          await execute(db, dbName, store => {
+              store.openCursor().onsuccess = cursorHandlers.all({}, res => (records = res));
+          });
+          console.log(`${dbName}: found ${records.length} records.`);
+          // Check if there's a entry for this.
+          let timestamp = null;
+          await execute(db, "__meta__", store => {
+              store.get(`${dbName}-lastModified`).onsuccess = e => {
+                  timestamp = e.target.result ? e.target.result.value : null;
+              };
+          });
+          // Some previous versions, also used to store the timestamps without prefix.
+          if (!timestamp) {
+              await execute(db, "__meta__", store => {
+                  store.get("lastModified").onsuccess = e => {
+                      timestamp = e.target.result ? e.target.result.value : null;
+                  };
+              });
+          }
+          console.log(`${dbName}: ${timestamp ? "found" : "no"} timestamp.`);
+          // Those will be inserted in the new database/schema.
+          return { records, timestamp };
+      }
+      catch (e) {
+          console.error("Error occured during migration", e);
+          return null;
+      }
+      finally {
+          db.close();
+      }
+  }
+
+  var uuid4 = {};
+
+  const RECORD_FIELDS_TO_CLEAN = ["_status"];
+  const AVAILABLE_HOOKS = ["incoming-changes"];
+  const IMPORT_CHUNK_SIZE = 200;
+  /**
+   * Compare two records omitting local fields and synchronization
+   * attributes (like _status and last_modified)
+   * @param {Object} a    A record to compare.
+   * @param {Object} b    A record to compare.
+   * @param {Array} localFields Additional fields to ignore during the comparison
+   * @return {boolean}
+   */
+  function recordsEqual(a, b, localFields = []) {
+      const fieldsToClean = RECORD_FIELDS_TO_CLEAN.concat(["last_modified"]).concat(localFields);
+      const cleanLocal = r => omitKeys(r, fieldsToClean);
+      return deepEqual(cleanLocal(a), cleanLocal(b));
+  }
+  /**
+   * Synchronization result object.
+   */
+  class SyncResultObject {
+      /**
+       * Public constructor.
+       */
+      constructor() {
+          /**
+           * Current synchronization result status; becomes `false` when conflicts or
+           * errors are registered.
+           * @type {Boolean}
+           */
+          this.lastModified = null;
+          this._lists = {};
+          [
+              "errors",
+              "created",
+              "updated",
+              "deleted",
+              "published",
+              "conflicts",
+              "skipped",
+              "resolved",
+              "void",
+          ].forEach(l => (this._lists[l] = []));
+          this._cached = {};
+      }
+      /**
+       * Adds entries for a given result type.
+       *
+       * @param {String} type    The result type.
+       * @param {Array}  entries The result entries.
+       * @return {SyncResultObject}
+       */
+      add(type, entries) {
+          if (!Array.isArray(this._lists[type])) {
+              console.warn(`Unknown type "${type}"`);
+              return;
+          }
+          if (!Array.isArray(entries)) {
+              entries = [entries];
+          }
+          this._lists[type] = this._lists[type].concat(entries);
+          delete this._cached[type];
+          return this;
+      }
+      get ok() {
+          return this.errors.length + this.conflicts.length === 0;
+      }
+      get errors() {
+          return this._lists["errors"];
+      }
+      get conflicts() {
+          return this._lists["conflicts"];
+      }
+      get skipped() {
+          return this._deduplicate("skipped");
+      }
+      get resolved() {
+          return this._deduplicate("resolved");
+      }
+      get created() {
+          return this._deduplicate("created");
+      }
+      get updated() {
+          return this._deduplicate("updated");
+      }
+      get deleted() {
+          return this._deduplicate("deleted");
+      }
+      get published() {
+          return this._deduplicate("published");
+      }
+      _deduplicate(list) {
+          if (!(list in this._cached)) {
+              // Deduplicate entries by id. If the values don't have `id` attribute, just
+              // keep all.
+              const recordsWithoutId = new Set();
+              const recordsById = new Map();
+              this._lists[list].forEach(record => {
+                  if (!record.id) {
+                      recordsWithoutId.add(record);
+                  }
+                  else {
+                      recordsById.set(record.id, record);
+                  }
+              });
+              this._cached[list] = Array.from(recordsById.values()).concat(Array.from(recordsWithoutId));
+          }
+          return this._cached[list];
+      }
+      /**
+       * Reinitializes result entries for a given result type.
+       *
+       * @param  {String} type The result type.
+       * @return {SyncResultObject}
+       */
+      reset(type) {
+          this._lists[type] = [];
+          delete this._cached[type];
+          return this;
+      }
+      toObject() {
+          // Only used in tests.
+          return {
+              ok: this.ok,
+              lastModified: this.lastModified,
+              errors: this.errors,
+              created: this.created,
+              updated: this.updated,
+              deleted: this.deleted,
+              skipped: this.skipped,
+              published: this.published,
+              conflicts: this.conflicts,
+              resolved: this.resolved,
+          };
+      }
+  }
+  class ServerWasFlushedError extends Error {
+      constructor(clientTimestamp, serverTimestamp, message) {
+          super(message);
+          if (Error.captureStackTrace) {
+              Error.captureStackTrace(this, ServerWasFlushedError);
+          }
+          this.clientTimestamp = clientTimestamp;
+          this.serverTimestamp = serverTimestamp;
+      }
+  }
+  function createUUIDSchema() {
+      return {
+          generate() {
+              return uuid4();
+          },
+          validate(id) {
+              return typeof id == "string" && RE_RECORD_ID.test(id);
+          },
+      };
+  }
+  function markStatus(record, status) {
+      return Object.assign(Object.assign({}, record), { _status: status });
+  }
+  function markDeleted(record) {
+      return markStatus(record, "deleted");
+  }
+  function markSynced(record) {
+      return markStatus(record, "synced");
+  }
+  /**
+   * Import a remote change into the local database.
+   *
+   * @param  {IDBTransactionProxy} transaction The transaction handler.
+   * @param  {Object}              remote      The remote change object to import.
+   * @param  {Array<String>}       localFields The list of fields that remain local.
+   * @param  {String}              strategy    The {@link Collection.strategy}.
+   * @return {Object}
+   */
+  function importChange(transaction, remote, localFields, strategy) {
+      const local = transaction.get(remote.id);
+      if (!local) {
+          // Not found locally but remote change is marked as deleted; skip to
+          // avoid recreation.
+          if (remote.deleted) {
+              return { type: "skipped", data: remote };
+          }
+          const synced = markSynced(remote);
+          transaction.create(synced);
+          return { type: "created", data: synced };
+      }
+      // Apply remote changes on local record.
+      const synced = Object.assign(Object.assign({}, local), markSynced(remote));
+      // With pull only, we don't need to compare records since we override them.
+      if (strategy === Collection.strategy.PULL_ONLY) {
+          if (remote.deleted) {
+              transaction.delete(remote.id);
+              return { type: "deleted", data: local };
+          }
+          transaction.update(synced);
+          return { type: "updated", data: { old: local, new: synced } };
+      }
+      // With other sync strategies, we detect conflicts,
+      // by comparing local and remote, ignoring local fields.
+      const isIdentical = recordsEqual(local, remote, localFields);
+      // Detect or ignore conflicts if record has also been modified locally.
+      if (local._status !== "synced") {
+          // Locally deleted, unsynced: scheduled for remote deletion.
+          if (local._status === "deleted") {
+              return { type: "skipped", data: local };
+          }
+          if (isIdentical) {
+              // If records are identical, import anyway, so we bump the
+              // local last_modified value from the server and set record
+              // status to "synced".
+              transaction.update(synced);
+              return { type: "updated", data: { old: local, new: synced } };
+          }
+          if (local.last_modified !== undefined &&
+              local.last_modified === remote.last_modified) {
+              // If our local version has the same last_modified as the remote
+              // one, this represents an object that corresponds to a resolved
+              // conflict. Our local version represents the final output, so
+              // we keep that one. (No transaction operation to do.)
+              // But if our last_modified is undefined,
+              // that means we've created the same object locally as one on
+              // the server, which *must* be a conflict.
+              return { type: "void" };
+          }
+          return {
+              type: "conflicts",
+              data: { type: "incoming", local: local, remote: remote },
+          };
+      }
+      // Local record was synced.
+      if (remote.deleted) {
+          transaction.delete(remote.id);
+          return { type: "deleted", data: local };
+      }
+      // Import locally.
+      transaction.update(synced);
+      // if identical, simply exclude it from all SyncResultObject lists
+      const type = isIdentical ? "void" : "updated";
+      return { type, data: { old: local, new: synced } };
+  }
+  /**
+   * Abstracts a collection of records stored in the local database, providing
+   * CRUD operations and synchronization helpers.
+   */
+  class Collection {
+      /**
+       * Constructor.
+       *
+       * Options:
+       * - `{BaseAdapter} adapter` The DB adapter (default: `IDB`)
+       *
+       * @param  {String}    bucket  The bucket identifier.
+       * @param  {String}    name    The collection name.
+       * @param  {KintoBase} kinto   The Kinto instance.
+       * @param  {Object}    options The options object.
+       */
+      constructor(bucket, name, kinto, options = {}) {
+          this._bucket = bucket;
+          this._name = name;
+          this._lastModified = null;
+          const DBAdapter = options.adapter || IDB;
+          if (!DBAdapter) {
+              throw new Error("No adapter provided");
+          }
+          const db = new DBAdapter(`${bucket}/${name}`, options.adapterOptions);
+          if (!(db instanceof BaseAdapter)) {
+              throw new Error("Unsupported adapter.");
+          }
+          // public properties
+          /**
+           * The db adapter instance
+           * @type {BaseAdapter}
+           */
+          this.db = db;
+          /**
+           * The KintoBase instance.
+           * @type {KintoBase}
+           */
+          this.kinto = kinto;
+          /**
+           * The event emitter instance.
+           * @type {EventEmitter}
+           */
+          this.events = options.events;
+          /**
+           * The IdSchema instance.
+           * @type {Object}
+           */
+          this.idSchema = this._validateIdSchema(options.idSchema);
+          /**
+           * The list of remote transformers.
+           * @type {Array}
+           */
+          this.remoteTransformers = this._validateRemoteTransformers(options.remoteTransformers);
+          /**
+           * The list of hooks.
+           * @type {Object}
+           */
+          this.hooks = this._validateHooks(options.hooks);
+          /**
+           * The list of fields names that will remain local.
+           * @type {Array}
+           */
+          this.localFields = options.localFields || [];
+      }
+      /**
+       * The HTTP client.
+       * @type {KintoClient}
+       */
+      get api() {
+          return this.kinto.api;
+      }
+      /**
+       * The collection name.
+       * @type {String}
+       */
+      get name() {
+          return this._name;
+      }
+      /**
+       * The bucket name.
+       * @type {String}
+       */
+      get bucket() {
+          return this._bucket;
+      }
+      /**
+       * The last modified timestamp.
+       * @type {Number}
+       */
+      get lastModified() {
+          return this._lastModified;
+      }
+      /**
+       * Synchronization strategies. Available strategies are:
+       *
+       * - `MANUAL`: Conflicts will be reported in a dedicated array.
+       * - `SERVER_WINS`: Conflicts are resolved using remote data.
+       * - `CLIENT_WINS`: Conflicts are resolved using local data.
+       *
+       * @type {Object}
+       */
+      static get strategy() {
+          return {
+              CLIENT_WINS: "client_wins",
+              SERVER_WINS: "server_wins",
+              PULL_ONLY: "pull_only",
+              MANUAL: "manual",
+          };
+      }
+      /**
+       * Validates an idSchema.
+       *
+       * @param  {Object|undefined} idSchema
+       * @return {Object}
+       */
+      _validateIdSchema(idSchema) {
+          if (typeof idSchema === "undefined") {
+              return createUUIDSchema();
+          }
+          if (typeof idSchema !== "object") {
+              throw new Error("idSchema must be an object.");
+          }
+          else if (typeof idSchema.generate !== "function") {
+              throw new Error("idSchema must provide a generate function.");
+          }
+          else if (typeof idSchema.validate !== "function") {
+              throw new Error("idSchema must provide a validate function.");
+          }
+          return idSchema;
+      }
+      /**
+       * Validates a list of remote transformers.
+       *
+       * @param  {Array|undefined} remoteTransformers
+       * @return {Array}
+       */
+      _validateRemoteTransformers(remoteTransformers) {
+          if (typeof remoteTransformers === "undefined") {
+              return [];
+          }
+          if (!Array.isArray(remoteTransformers)) {
+              throw new Error("remoteTransformers should be an array.");
+          }
+          return remoteTransformers.map(transformer => {
+              if (typeof transformer !== "object") {
+                  throw new Error("A transformer must be an object.");
+              }
+              else if (typeof transformer.encode !== "function") {
+                  throw new Error("A transformer must provide an encode function.");
+              }
+              else if (typeof transformer.decode !== "function") {
+                  throw new Error("A transformer must provide a decode function.");
+              }
+              return transformer;
+          });
+      }
+      /**
+       * Validate the passed hook is correct.
+       *
+       * @param {Array|undefined} hook.
+       * @return {Array}
+       **/
+      _validateHook(hook) {
+          if (!Array.isArray(hook)) {
+              throw new Error("A hook definition should be an array of functions.");
+          }
+          return hook.map(fn => {
+              if (typeof fn !== "function") {
+                  throw new Error("A hook definition should be an array of functions.");
+              }
+              return fn;
+          });
+      }
+      /**
+       * Validates a list of hooks.
+       *
+       * @param  {Object|undefined} hooks
+       * @return {Object}
+       */
+      _validateHooks(hooks) {
+          if (typeof hooks === "undefined") {
+              return {};
+          }
+          if (Array.isArray(hooks)) {
+              throw new Error("hooks should be an object, not an array.");
+          }
+          if (typeof hooks !== "object") {
+              throw new Error("hooks should be an object.");
+          }
+          const validatedHooks = {};
+          for (const hook in hooks) {
+              if (!AVAILABLE_HOOKS.includes(hook)) {
+                  throw new Error("The hook should be one of " + AVAILABLE_HOOKS.join(", "));
+              }
+              validatedHooks[hook] = this._validateHook(hooks[hook]);
+          }
+          return validatedHooks;
+      }
+      /**
+       * Deletes every records in the current collection and marks the collection as
+       * never synced.
+       *
+       * @return {Promise}
+       */
+      async clear() {
+          await this.db.clear();
+          await this.db.saveMetadata(null);
+          await this.db.saveLastModified(null);
+          return { data: [], permissions: {} };
+      }
+      /**
+       * Encodes a record.
+       *
+       * @param  {String} type   Either "remote" or "local".
+       * @param  {Object} record The record object to encode.
+       * @return {Promise}
+       */
+      _encodeRecord(type, record) {
+          if (!this[`${type}Transformers`].length) {
+              return Promise.resolve(record);
+          }
+          return waterfall(this[`${type}Transformers`].map(transformer => {
+              return record => transformer.encode(record);
+          }), record);
+      }
+      /**
+       * Decodes a record.
+       *
+       * @param  {String} type   Either "remote" or "local".
+       * @param  {Object} record The record object to decode.
+       * @return {Promise}
+       */
+      _decodeRecord(type, record) {
+          if (!this[`${type}Transformers`].length) {
+              return Promise.resolve(record);
+          }
+          return waterfall(this[`${type}Transformers`].reverse().map(transformer => {
+              return record => transformer.decode(record);
+          }), record);
+      }
+      /**
+       * Adds a record to the local database, asserting that none
+       * already exist with this ID.
+       *
+       * Note: If either the `useRecordId` or `synced` options are true, then the
+       * record object must contain the id field to be validated. If none of these
+       * options are true, an id is generated using the current IdSchema; in this
+       * case, the record passed must not have an id.
+       *
+       * Options:
+       * - {Boolean} synced       Sets record status to "synced" (default: `false`).
+       * - {Boolean} useRecordId  Forces the `id` field from the record to be used,
+       *                          instead of one that is generated automatically
+       *                          (default: `false`).
+       *
+       * @param  {Object} record
+       * @param  {Object} options
+       * @return {Promise}
+       */
+      create(record, options = { useRecordId: false, synced: false }) {
+          // Validate the record and its ID (if any), even though this
+          // validation is also done in the CollectionTransaction method,
+          // because we need to pass the ID to preloadIds.
+          const reject = msg => Promise.reject(new Error(msg));
+          if (typeof record !== "object") {
+              return reject("Record is not an object.");
+          }
+          if ((options.synced || options.useRecordId) &&
+              !Object.prototype.hasOwnProperty.call(record, "id")) {
+              return reject("Missing required Id; synced and useRecordId options require one");
+          }
+          if (!options.synced &&
+              !options.useRecordId &&
+              Object.prototype.hasOwnProperty.call(record, "id")) {
+              return reject("Extraneous Id; can't create a record having one set.");
+          }
+          const newRecord = Object.assign(Object.assign({}, record), { id: options.synced || options.useRecordId
+                  ? record.id
+                  : this.idSchema.generate(record), _status: options.synced ? "synced" : "created" });
+          if (!this.idSchema.validate(newRecord.id)) {
+              return reject(`Invalid Id: ${newRecord.id}`);
+          }
+          return this.execute(txn => txn.create(newRecord), {
+              preloadIds: [newRecord.id],
+          }).catch(err => {
+              if (options.useRecordId) {
+                  throw new Error("Couldn't create record. It may have been virtually deleted.");
+              }
+              throw err;
+          });
+      }
+      /**
+       * Like {@link CollectionTransaction#update}, but wrapped in its own transaction.
+       *
+       * Options:
+       * - {Boolean} synced: Sets record status to "synced" (default: false)
+       * - {Boolean} patch:  Extends the existing record instead of overwriting it
+       *   (default: false)
+       *
+       * @param  {Object} record
+       * @param  {Object} options
+       * @return {Promise}
+       */
+      update(record, options = { synced: false, patch: false }) {
+          // Validate the record and its ID, even though this validation is
+          // also done in the CollectionTransaction method, because we need
+          // to pass the ID to preloadIds.
+          if (typeof record !== "object") {
+              return Promise.reject(new Error("Record is not an object."));
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              return Promise.reject(new Error("Cannot update a record missing id."));
+          }
+          if (!this.idSchema.validate(record.id)) {
+              return Promise.reject(new Error(`Invalid Id: ${record.id}`));
+          }
+          return this.execute(txn => txn.update(record, options), {
+              preloadIds: [record.id],
+          });
+      }
+      /**
+       * Like {@link CollectionTransaction#upsert}, but wrapped in its own transaction.
+       *
+       * @param  {Object} record
+       * @return {Promise}
+       */
+      upsert(record) {
+          // Validate the record and its ID, even though this validation is
+          // also done in the CollectionTransaction method, because we need
+          // to pass the ID to preloadIds.
+          if (typeof record !== "object") {
+              return Promise.reject(new Error("Record is not an object."));
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              return Promise.reject(new Error("Cannot update a record missing id."));
+          }
+          if (!this.idSchema.validate(record.id)) {
+              return Promise.reject(new Error(`Invalid Id: ${record.id}`));
+          }
+          return this.execute(txn => txn.upsert(record), { preloadIds: [record.id] });
+      }
+      /**
+       * Like {@link CollectionTransaction#get}, but wrapped in its own transaction.
+       *
+       * Options:
+       * - {Boolean} includeDeleted: Include virtually deleted records.
+       *
+       * @param  {String} id
+       * @param  {Object} options
+       * @return {Promise}
+       */
+      get(id, options = { includeDeleted: false }) {
+          return this.execute(txn => txn.get(id, options), { preloadIds: [id] });
+      }
+      /**
+       * Like {@link CollectionTransaction#getAny}, but wrapped in its own transaction.
+       *
+       * @param  {String} id
+       * @return {Promise}
+       */
+      getAny(id) {
+          return this.execute(txn => txn.getAny(id), { preloadIds: [id] });
+      }
+      /**
+       * Same as {@link Collection#delete}, but wrapped in its own transaction.
+       *
+       * Options:
+       * - {Boolean} virtual: When set to `true`, doesn't actually delete the record,
+       *   update its `_status` attribute to `deleted` instead (default: true)
+       *
+       * @param  {String} id       The record's Id.
+       * @param  {Object} options  The options object.
+       * @return {Promise}
+       */
+      delete(id, options = { virtual: true }) {
+          return this.execute(transaction => {
+              return transaction.delete(id, options);
+          }, { preloadIds: [id] });
+      }
+      /**
+       * Same as {@link Collection#deleteAll}, but wrapped in its own transaction, execulding the parameter.
+       *
+       * @return {Promise}
+       */
+      async deleteAll() {
+          const { data } = await this.list({}, { includeDeleted: false });
+          const recordIds = data.map(record => record.id);
+          return this.execute(transaction => {
+              return transaction.deleteAll(recordIds);
+          }, { preloadIds: recordIds });
+      }
+      /**
+       * The same as {@link CollectionTransaction#deleteAny}, but wrapped
+       * in its own transaction.
+       *
+       * @param  {String} id       The record's Id.
+       * @return {Promise}
+       */
+      deleteAny(id) {
+          return this.execute(txn => txn.deleteAny(id), { preloadIds: [id] });
+      }
+      /**
+       * Lists records from the local database.
+       *
+       * Params:
+       * - {Object} filters Filter the results (default: `{}`).
+       * - {String} order   The order to apply   (default: `-last_modified`).
+       *
+       * Options:
+       * - {Boolean} includeDeleted: Include virtually deleted records.
+       *
+       * @param  {Object} params  The filters and order to apply to the results.
+       * @param  {Object} options The options object.
+       * @return {Promise}
+       */
+      async list(params = {}, options = { includeDeleted: false }) {
+          params = Object.assign({ order: "-last_modified", filters: {} }, params);
+          const results = await this.db.list(params);
+          let data = results;
+          if (!options.includeDeleted) {
+              data = results.filter(record => record._status !== "deleted");
+          }
+          return { data, permissions: {} };
+      }
+      /**
+       * Imports remote changes into the local database.
+       * This method is in charge of detecting the conflicts, and resolve them
+       * according to the specified strategy.
+       * @param  {SyncResultObject} syncResultObject The sync result object.
+       * @param  {Array}            decodedChanges   The list of changes to import in the local database.
+       * @param  {String}           strategy         The {@link Collection.strategy} (default: MANUAL)
+       * @return {Promise}
+       */
+      async importChanges(syncResultObject, decodedChanges, strategy = Collection.strategy.MANUAL) {
+          // Retrieve records matching change ids.
+          try {
+              for (let i = 0; i < decodedChanges.length; i += IMPORT_CHUNK_SIZE) {
+                  const slice = decodedChanges.slice(i, i + IMPORT_CHUNK_SIZE);
+                  const { imports, resolved } = await this.db.execute(transaction => {
+                      const imports = slice.map(remote => {
+                          // Store remote change into local database.
+                          return importChange(transaction, remote, this.localFields, strategy);
+                      });
+                      const conflicts = imports
+                          .filter(i => i.type === "conflicts")
+                          .map(i => i.data);
+                      const resolved = this._handleConflicts(transaction, conflicts, strategy);
+                      return { imports, resolved };
+                  }, { preload: slice.map(record => record.id) });
+                  // Lists of created/updated/deleted records
+                  imports.forEach(({ type, data }) => syncResultObject.add(type, data));
+                  // Automatically resolved conflicts (if not manual)
+                  if (resolved.length > 0) {
+                      syncResultObject.reset("conflicts").add("resolved", resolved);
+                  }
+              }
+          }
+          catch (err) {
+              const data = {
+                  type: "incoming",
+                  message: err.message,
+                  stack: err.stack,
+              };
+              // XXX one error of the whole transaction instead of per atomic op
+              syncResultObject.add("errors", data);
+          }
+          return syncResultObject;
+      }
+      /**
+       * Imports the responses of pushed changes into the local database.
+       * Basically it stores the timestamp assigned by the server into the local
+       * database.
+       * @param  {SyncResultObject} syncResultObject The sync result object.
+       * @param  {Array}            toApplyLocally   The list of changes to import in the local database.
+       * @param  {Array}            conflicts        The list of conflicts that have to be resolved.
+       * @param  {String}           strategy         The {@link Collection.strategy}.
+       * @return {Promise}
+       */
+      async _applyPushedResults(syncResultObject, toApplyLocally, conflicts, strategy = Collection.strategy.MANUAL) {
+          const toDeleteLocally = toApplyLocally.filter(r => r.deleted);
+          const toUpdateLocally = toApplyLocally.filter(r => !r.deleted);
+          const { published, resolved } = await this.db.execute(transaction => {
+              const updated = toUpdateLocally.map(record => {
+                  const synced = markSynced(record);
+                  transaction.update(synced);
+                  return synced;
+              });
+              const deleted = toDeleteLocally.map(record => {
+                  transaction.delete(record.id);
+                  // Amend result data with the deleted attribute set
+                  return { id: record.id, deleted: true };
+              });
+              const published = updated.concat(deleted);
+              // Handle conflicts, if any
+              const resolved = this._handleConflicts(transaction, conflicts, strategy);
+              return { published, resolved };
+          });
+          syncResultObject.add("published", published);
+          if (resolved.length > 0) {
+              syncResultObject
+                  .reset("conflicts")
+                  .reset("resolved")
+                  .add("resolved", resolved);
+          }
+          return syncResultObject;
+      }
+      /**
+       * Handles synchronization conflicts according to specified strategy.
+       *
+       * @param  {SyncResultObject} result    The sync result object.
+       * @param  {String}           strategy  The {@link Collection.strategy}.
+       * @return {Promise<Array<Object>>} The resolved conflicts, as an
+       *    array of {accepted, rejected} objects
+       */
+      _handleConflicts(transaction, conflicts, strategy) {
+          if (strategy === Collection.strategy.MANUAL) {
+              return [];
+          }
+          return conflicts.map(conflict => {
+              const resolution = strategy === Collection.strategy.CLIENT_WINS
+                  ? conflict.local
+                  : conflict.remote;
+              const rejected = strategy === Collection.strategy.CLIENT_WINS
+                  ? conflict.remote
+                  : conflict.local;
+              let accepted, status, id;
+              if (resolution === null) {
+                  // We "resolved" with the server-side deletion. Delete locally.
+                  // This only happens during SERVER_WINS because the local
+                  // version of a record can never be null.
+                  // We can get "null" from the remote side if we got a conflict
+                  // and there is no remote version available; see kinto-http.js
+                  // batch.js:aggregate.
+                  transaction.delete(conflict.local.id);
+                  accepted = null;
+                  // The record was deleted, but that status is "synced" with
+                  // the server, so we don't need to push the change.
+                  status = "synced";
+                  id = conflict.local.id;
+              }
+              else {
+                  const updated = this._resolveRaw(conflict, resolution);
+                  transaction.update(updated);
+                  accepted = updated;
+                  status = updated._status;
+                  id = updated.id;
+              }
+              return { rejected, accepted, id, _status: status };
+          });
+      }
+      /**
+       * Execute a bunch of operations in a transaction.
+       *
+       * This transaction should be atomic -- either all of its operations
+       * will succeed, or none will.
+       *
+       * The argument to this function is itself a function which will be
+       * called with a {@link CollectionTransaction}. Collection methods
+       * are available on this transaction, but instead of returning
+       * promises, they are synchronous. execute() returns a Promise whose
+       * value will be the return value of the provided function.
+       *
+       * Most operations will require access to the record itself, which
+       * must be preloaded by passing its ID in the preloadIds option.
+       *
+       * Options:
+       * - {Array} preloadIds: list of IDs to fetch at the beginning of
+       *   the transaction
+       *
+       * @return {Promise} Resolves with the result of the given function
+       *    when the transaction commits.
+       */
+      execute(doOperations, { preloadIds = [] } = {}) {
+          for (const id of preloadIds) {
+              if (!this.idSchema.validate(id)) {
+                  return Promise.reject(Error(`Invalid Id: ${id}`));
+              }
+          }
+          return this.db.execute(transaction => {
+              const txn = new CollectionTransaction(this, transaction);
+              const result = doOperations(txn);
+              txn.emitEvents();
+              return result;
+          }, { preload: preloadIds });
+      }
+      /**
+       * Resets the local records as if they were never synced; existing records are
+       * marked as newly created, deleted records are dropped.
+       *
+       * A next call to {@link Collection.sync} will thus republish the whole
+       * content of the local collection to the server.
+       *
+       * @return {Promise} Resolves with the number of processed records.
+       */
+      async resetSyncStatus() {
+          const unsynced = await this.list({ filters: { _status: ["deleted", "synced"] }, order: "" }, { includeDeleted: true });
+          await this.db.execute(transaction => {
+              unsynced.data.forEach(record => {
+                  if (record._status === "deleted") {
+                      // Garbage collect deleted records.
+                      transaction.delete(record.id);
+                  }
+                  else {
+                      // Records that were synced become «created».
+                      transaction.update(Object.assign(Object.assign({}, record), { last_modified: undefined, _status: "created" }));
+                  }
+              });
+          });
+          this._lastModified = null;
+          await this.db.saveLastModified(null);
+          return unsynced.data.length;
+      }
+      /**
+       * Returns an object containing two lists:
+       *
+       * - `toDelete`: unsynced deleted records we can safely delete;
+       * - `toSync`: local updates to send to the server.
+       *
+       * @return {Promise}
+       */
+      async gatherLocalChanges() {
+          const unsynced = await this.list({
+              filters: { _status: ["created", "updated"] },
+              order: "",
+          });
+          const deleted = await this.list({ filters: { _status: "deleted" }, order: "" }, { includeDeleted: true });
+          return await Promise.all(unsynced.data
+              .concat(deleted.data)
+              .map(this._encodeRecord.bind(this, "remote")));
+      }
+      /**
+       * Fetch remote changes, import them to the local database, and handle
+       * conflicts according to `options.strategy`. Then, updates the passed
+       * {@link SyncResultObject} with import results.
+       *
+       * Options:
+       * - {String} strategy: The selected sync strategy.
+       * - {String} expectedTimestamp: A timestamp to use as a "cache busting" query parameter.
+       * - {Array<String>} exclude: A list of record ids to exclude from pull.
+       * - {Object} headers: The HTTP headers to use in the request.
+       * - {int} retry: The number of retries to do if the HTTP request fails.
+       * - {int} lastModified: The timestamp to use in `?_since` query.
+       *
+       * @param  {KintoClient.Collection} client           Kinto client Collection instance.
+       * @param  {SyncResultObject}       syncResultObject The sync result object.
+       * @param  {Object}                 options          The options object.
+       * @return {Promise}
+       */
+      async pullChanges(client, syncResultObject, options = {}) {
+          if (!syncResultObject.ok) {
+              return syncResultObject;
+          }
+          const since = this.lastModified
+              ? this.lastModified
+              : await this.db.getLastModified();
+          options = Object.assign({ strategy: Collection.strategy.MANUAL, lastModified: since, headers: {} }, options);
+          // Optionally ignore some records when pulling for changes.
+          // (avoid redownloading our own changes on last step of #sync())
+          let filters;
+          if (options.exclude) {
+              // Limit the list of excluded records to the first 50 records in order
+              // to remain under de-facto URL size limit (~2000 chars).
+              // http://stackoverflow.com/questions/417142/what-is-the-maximum-length-of-a-url-in-different-browsers/417184#417184
+              const exclude_id = options.exclude
+                  .slice(0, 50)
+                  .map(r => r.id)
+                  .join(",");
+              filters = { exclude_id };
+          }
+          if (options.expectedTimestamp) {
+              filters = Object.assign(Object.assign({}, filters), { _expected: options.expectedTimestamp });
+          }
+          // First fetch remote changes from the server
+          const { data, last_modified } = await client.listRecords({
+              // Since should be ETag (see https://github.com/Kinto/kinto.js/issues/356)
+              since: options.lastModified ? `${options.lastModified}` : undefined,
+              headers: options.headers,
+              retry: options.retry,
+              // Fetch every page by default (FIXME: option to limit pages, see #277)
+              pages: Infinity,
+              filters,
+          });
+          // last_modified is the ETag header value (string).
+          // For retro-compatibility with first kinto.js versions
+          // parse it to integer.
+          const unquoted = last_modified ? parseInt(last_modified, 10) : undefined;
+          // Check if server was flushed.
+          // This is relevant for the Kinto demo server
+          // (and thus for many new comers).
+          const localSynced = options.lastModified;
+          const serverChanged = unquoted > options.lastModified;
+          const emptyCollection = data.length === 0;
+          if (!options.exclude && localSynced && serverChanged && emptyCollection) {
+              const e = new ServerWasFlushedError(localSynced, unquoted, "Server has been flushed. Client Side Timestamp: " +
+                  localSynced +
+                  " Server Side Timestamp: " +
+                  unquoted);
+              throw e;
+          }
+          // Atomic updates are not sensible here because unquoted is not
+          // computed as a function of syncResultObject.lastModified.
+          // eslint-disable-next-line require-atomic-updates
+          syncResultObject.lastModified = unquoted;
+          // Decode incoming changes.
+          const decodedChanges = await Promise.all(data.map(change => {
+              return this._decodeRecord("remote", change);
+          }));
+          // Hook receives decoded records.
+          const payload = { lastModified: unquoted, changes: decodedChanges };
+          const afterHooks = await this.applyHook("incoming-changes", payload);
+          // No change, nothing to import.
+          if (afterHooks.changes.length > 0) {
+              // Reflect these changes locally
+              await this.importChanges(syncResultObject, afterHooks.changes, options.strategy);
+          }
+          return syncResultObject;
+      }
+      applyHook(hookName, payload) {
+          if (typeof this.hooks[hookName] == "undefined") {
+              return Promise.resolve(payload);
+          }
+          return waterfall(this.hooks[hookName].map(hook => {
+              return record => {
+                  const result = hook(payload, this);
+                  const resultThenable = result && typeof result.then === "function";
+                  const resultChanges = result && Object.prototype.hasOwnProperty.call(result, "changes");
+                  if (!(resultThenable || resultChanges)) {
+                      throw new Error(`Invalid return value for hook: ${JSON.stringify(result)} has no 'then()' or 'changes' properties`);
+                  }
+                  return result;
+              };
+          }), payload);
+      }
+      /**
+       * Publish local changes to the remote server and updates the passed
+       * {@link SyncResultObject} with publication results.
+       *
+       * Options:
+       * - {String} strategy: The selected sync strategy.
+       * - {Object} headers: The HTTP headers to use in the request.
+       * - {int} retry: The number of retries to do if the HTTP request fails.
+       *
+       * @param  {KintoClient.Collection} client           Kinto client Collection instance.
+       * @param  {SyncResultObject}       syncResultObject The sync result object.
+       * @param  {Object}                 changes          The change object.
+       * @param  {Array}                  changes.toDelete The list of records to delete.
+       * @param  {Array}                  changes.toSync   The list of records to create/update.
+       * @param  {Object}                 options          The options object.
+       * @return {Promise}
+       */
+      async pushChanges(client, changes, syncResultObject, options = {}) {
+          if (!syncResultObject.ok) {
+              return syncResultObject;
+          }
+          const safe = !options.strategy || options.strategy !== Collection.CLIENT_WINS;
+          const toDelete = changes.filter(r => r._status == "deleted");
+          const toSync = changes.filter(r => r._status != "deleted");
+          // Perform a batch request with every changes.
+          const synced = await client.batch(batch => {
+              toDelete.forEach(r => {
+                  // never published locally deleted records should not be pusblished
+                  if (r.last_modified) {
+                      batch.deleteRecord(r);
+                  }
+              });
+              toSync.forEach(r => {
+                  // Clean local fields (like _status) before sending to server.
+                  const published = this.cleanLocalFields(r);
+                  if (r._status === "created") {
+                      batch.createRecord(published);
+                  }
+                  else {
+                      batch.updateRecord(published);
+                  }
+              });
+          }, {
+              headers: options.headers,
+              retry: options.retry,
+              safe,
+              aggregate: true,
+          });
+          // Store outgoing errors into sync result object
+          syncResultObject.add("errors", synced.errors.map(e => (Object.assign(Object.assign({}, e), { type: "outgoing" }))));
+          // Store outgoing conflicts into sync result object
+          const conflicts = [];
+          for (const { type, local, remote } of synced.conflicts) {
+              // Note: we ensure that local data are actually available, as they may
+              // be missing in the case of a published deletion.
+              const safeLocal = (local && local.data) || { id: remote.id };
+              const realLocal = await this._decodeRecord("remote", safeLocal);
+              // We can get "null" from the remote side if we got a conflict
+              // and there is no remote version available; see kinto-http.js
+              // batch.js:aggregate.
+              const realRemote = remote && (await this._decodeRecord("remote", remote));
+              const conflict = { type, local: realLocal, remote: realRemote };
+              conflicts.push(conflict);
+          }
+          syncResultObject.add("conflicts", conflicts);
+          // Records that must be deleted are either deletions that were pushed
+          // to server (published) or deleted records that were never pushed (skipped).
+          const missingRemotely = synced.skipped.map(r => (Object.assign(Object.assign({}, r), { deleted: true })));
+          // For created and updated records, the last_modified coming from server
+          // will be stored locally.
+          // Reflect publication results locally using the response from
+          // the batch request.
+          const published = synced.published.map(c => c.data);
+          const toApplyLocally = published.concat(missingRemotely);
+          // Apply the decode transformers, if any
+          const decoded = await Promise.all(toApplyLocally.map(record => {
+              return this._decodeRecord("remote", record);
+          }));
+          // We have to update the local records with the responses of the server
+          // (eg. last_modified values etc.).
+          if (decoded.length > 0 || conflicts.length > 0) {
+              await this._applyPushedResults(syncResultObject, decoded, conflicts, options.strategy);
+          }
+          return syncResultObject;
+      }
+      /**
+       * Return a copy of the specified record without the local fields.
+       *
+       * @param  {Object} record  A record with potential local fields.
+       * @return {Object}
+       */
+      cleanLocalFields(record) {
+          const localKeys = RECORD_FIELDS_TO_CLEAN.concat(this.localFields);
+          return omitKeys(record, localKeys);
+      }
+      /**
+       * Resolves a conflict, updating local record according to proposed
+       * resolution — keeping remote record `last_modified` value as a reference for
+       * further batch sending.
+       *
+       * @param  {Object} conflict   The conflict object.
+       * @param  {Object} resolution The proposed record.
+       * @return {Promise}
+       */
+      resolve(conflict, resolution) {
+          return this.db.execute(transaction => {
+              const updated = this._resolveRaw(conflict, resolution);
+              transaction.update(updated);
+              return { data: updated, permissions: {} };
+          });
+      }
+      /**
+       * @private
+       */
+      _resolveRaw(conflict, resolution) {
+          const resolved = Object.assign(Object.assign({}, resolution), {
+              // Ensure local record has the latest authoritative timestamp
+              last_modified: conflict.remote && conflict.remote.last_modified });
+          // If the resolution object is strictly equal to the
+          // remote record, then we can mark it as synced locally.
+          // Otherwise, mark it as updated (so that the resolution is pushed).
+          const synced = deepEqual(resolved, conflict.remote);
+          return markStatus(resolved, synced ? "synced" : "updated");
+      }
+      /**
+       * Synchronize remote and local data. The promise will resolve with a
+       * {@link SyncResultObject}, though will reject:
+       *
+       * - if the server is currently backed off;
+       * - if the server has been detected flushed.
+       *
+       * Options:
+       * - {Object} headers: HTTP headers to attach to outgoing requests.
+       * - {String} expectedTimestamp: A timestamp to use as a "cache busting" query parameter.
+       * - {Number} retry: Number of retries when server fails to process the request (default: 1).
+       * - {Collection.strategy} strategy: See {@link Collection.strategy}.
+       * - {Boolean} ignoreBackoff: Force synchronization even if server is currently
+       *   backed off.
+       * - {String} bucket: The remove bucket id to use (default: null)
+       * - {String} collection: The remove collection id to use (default: null)
+       * - {String} remote The remote Kinto server endpoint to use (default: null).
+       *
+       * @param  {Object} options Options.
+       * @return {Promise}
+       * @throws {Error} If an invalid remote option is passed.
+       */
+      async sync(options = {
+          strategy: Collection.strategy.MANUAL,
+          headers: {},
+          retry: 1,
+          ignoreBackoff: false,
+          bucket: null,
+          collection: null,
+          remote: null,
+          expectedTimestamp: null,
+      }) {
+          options = Object.assign(Object.assign({}, options), { bucket: options.bucket || this.bucket, collection: options.collection || this.name });
+          const previousRemote = this.api.remote;
+          if (options.remote) {
+              // Note: setting the remote ensures it's valid, throws when invalid.
+              this.api.remote = options.remote;
+          }
+          if (!options.ignoreBackoff && this.api.backoff > 0) {
+              const seconds = Math.ceil(this.api.backoff / 1000);
+              return Promise.reject(new Error(`Server is asking clients to back off; retry in ${seconds}s or use the ignoreBackoff option.`));
+          }
+          const client = this.api
+              .bucket(options.bucket)
+              .collection(options.collection);
+          const result = new SyncResultObject();
+          try {
+              // Fetch collection metadata.
+              await this.pullMetadata(client, options);
+              // Fetch last changes from the server.
+              await this.pullChanges(client, result, options);
+              const { lastModified } = result;
+              if (options.strategy != Collection.strategy.PULL_ONLY) {
+                  // Fetch local changes
+                  const toSync = await this.gatherLocalChanges();
+                  // Publish local changes and pull local resolutions
+                  await this.pushChanges(client, toSync, result, options);
+                  // Publish local resolution of push conflicts to server (on CLIENT_WINS)
+                  const resolvedUnsynced = result.resolved.filter(r => r._status !== "synced");
+                  if (resolvedUnsynced.length > 0) {
+                      const resolvedEncoded = await Promise.all(resolvedUnsynced.map(resolution => {
+                          let record = resolution.accepted;
+                          if (record === null) {
+                              record = { id: resolution.id, _status: resolution._status };
+                          }
+                          return this._encodeRecord("remote", record);
+                      }));
+                      await this.pushChanges(client, resolvedEncoded, result, options);
+                  }
+                  // Perform a last pull to catch changes that occured after the last pull,
+                  // while local changes were pushed. Do not do it nothing was pushed.
+                  if (result.published.length > 0) {
+                      // Avoid redownloading our own changes during the last pull.
+                      const pullOpts = Object.assign(Object.assign({}, options), { lastModified, exclude: result.published });
+                      await this.pullChanges(client, result, pullOpts);
+                  }
+              }
+              // Don't persist lastModified value if any conflict or error occured
+              if (result.ok) {
+                  // No conflict occured, persist collection's lastModified value
+                  this._lastModified = await this.db.saveLastModified(result.lastModified);
+              }
+          }
+          catch (e) {
+              this.events.emit("sync:error", Object.assign(Object.assign({}, options), { error: e }));
+              throw e;
+          }
+          finally {
+              // Ensure API default remote is reverted if a custom one's been used
+              this.api.remote = previousRemote;
+          }
+          this.events.emit("sync:success", Object.assign(Object.assign({}, options), { result }));
+          return result;
+      }
+      /**
+       * Load a list of records already synced with the remote server.
+       *
+       * The local records which are unsynced or whose timestamp is either missing
+       * or superior to those being loaded will be ignored.
+       *
+       * @deprecated Use {@link importBulk} instead.
+       * @param  {Array} records The previously exported list of records to load.
+       * @return {Promise} with the effectively imported records.
+       */
+      async loadDump(records) {
+          return this.importBulk(records);
+      }
+      /**
+       * Load a list of records already synced with the remote server.
+       *
+       * The local records which are unsynced or whose timestamp is either missing
+       * or superior to those being loaded will be ignored.
+       *
+       * @param  {Array} records The previously exported list of records to load.
+       * @return {Promise} with the effectively imported records.
+       */
+      async importBulk(records) {
+          if (!Array.isArray(records)) {
+              throw new Error("Records is not an array.");
+          }
+          for (const record of records) {
+              if (!Object.prototype.hasOwnProperty.call(record, "id") ||
+                  !this.idSchema.validate(record.id)) {
+                  throw new Error("Record has invalid ID: " + JSON.stringify(record));
+              }
+              if (!record.last_modified) {
+                  throw new Error("Record has no last_modified value: " + JSON.stringify(record));
+              }
+          }
+          // Fetch all existing records from local database,
+          // and skip those who are newer or not marked as synced.
+          // XXX filter by status / ids in records
+          const { data } = await this.list({}, { includeDeleted: true });
+          const existingById = data.reduce((acc, record) => {
+              acc[record.id] = record;
+              return acc;
+          }, {});
+          const newRecords = records.filter(record => {
+              const localRecord = existingById[record.id];
+              const shouldKeep =
+              // No local record with this id.
+              localRecord === undefined ||
+                  // Or local record is synced
+                  (localRecord._status === "synced" &&
+                      // And was synced from server
+                      localRecord.last_modified !== undefined &&
+                      // And is older than imported one.
+                      record.last_modified > localRecord.last_modified);
+              return shouldKeep;
+          });
+          return await this.db.importBulk(newRecords.map(markSynced));
+      }
+      async pullMetadata(client, options = {}) {
+          const { expectedTimestamp, headers } = options;
+          const query = expectedTimestamp
+              ? { query: { _expected: expectedTimestamp } }
+              : undefined;
+          const metadata = await client.getData(Object.assign(Object.assign({}, query), { headers }));
+          return this.db.saveMetadata(metadata);
+      }
+      async metadata() {
+          return this.db.getMetadata();
+      }
+  }
+  /**
+   * A Collection-oriented wrapper for an adapter's transaction.
+   *
+   * This defines the high-level functions available on a collection.
+   * The collection itself offers functions of the same name. These will
+   * perform just one operation in its own transaction.
+   */
+  class CollectionTransaction {
+      constructor(collection, adapterTransaction) {
+          this.collection = collection;
+          this.adapterTransaction = adapterTransaction;
+          this._events = [];
+      }
+      _queueEvent(action, payload) {
+          this._events.push({ action, payload });
+      }
+      /**
+       * Emit queued events, to be called once every transaction operations have
+       * been executed successfully.
+       */
+      emitEvents() {
+          for (const { action, payload } of this._events) {
+              this.collection.events.emit(action, payload);
+          }
+          if (this._events.length > 0) {
+              const targets = this._events.map(({ action, payload }) => (Object.assign({ action }, payload)));
+              this.collection.events.emit("change", { targets });
+          }
+          this._events = [];
+      }
+      /**
+       * Retrieve a record by its id from the local database, or
+       * undefined if none exists.
+       *
+       * This will also return virtually deleted records.
+       *
+       * @param  {String} id
+       * @return {Object}
+       */
+      getAny(id) {
+          const record = this.adapterTransaction.get(id);
+          return { data: record, permissions: {} };
+      }
+      /**
+       * Retrieve a record by its id from the local database.
+       *
+       * Options:
+       * - {Boolean} includeDeleted: Include virtually deleted records.
+       *
+       * @param  {String} id
+       * @param  {Object} options
+       * @return {Object}
+       */
+      get(id, options = { includeDeleted: false }) {
+          const res = this.getAny(id);
+          if (!res.data ||
+              (!options.includeDeleted && res.data._status === "deleted")) {
+              throw new Error(`Record with id=${id} not found.`);
+          }
+          return res;
+      }
+      /**
+       * Deletes a record from the local database.
+       *
+       * Options:
+       * - {Boolean} virtual: When set to `true`, doesn't actually delete the record,
+       *   update its `_status` attribute to `deleted` instead (default: true)
+       *
+       * @param  {String} id       The record's Id.
+       * @param  {Object} options  The options object.
+       * @return {Object}
+       */
+      delete(id, options = { virtual: true }) {
+          // Ensure the record actually exists.
+          const existing = this.adapterTransaction.get(id);
+          const alreadyDeleted = existing && existing._status == "deleted";
+          if (!existing || (alreadyDeleted && options.virtual)) {
+              throw new Error(`Record with id=${id} not found.`);
+          }
+          // Virtual updates status.
+          if (options.virtual) {
+              this.adapterTransaction.update(markDeleted(existing));
+          }
+          else {
+              // Delete for real.
+              this.adapterTransaction.delete(id);
+          }
+          this._queueEvent("delete", { data: existing });
+          return { data: existing, permissions: {} };
+      }
+      /**
+       * Soft delete all records from the local database.
+       *
+       * @param  {Array} ids        Array of non-deleted Record Ids.
+       * @return {Object}
+       */
+      deleteAll(ids) {
+          const existingRecords = [];
+          ids.forEach(id => {
+              existingRecords.push(this.adapterTransaction.get(id));
+              this.delete(id);
+          });
+          this._queueEvent("deleteAll", { data: existingRecords });
+          return { data: existingRecords, permissions: {} };
+      }
+      /**
+       * Deletes a record from the local database, if any exists.
+       * Otherwise, do nothing.
+       *
+       * @param  {String} id       The record's Id.
+       * @return {Object}
+       */
+      deleteAny(id) {
+          const existing = this.adapterTransaction.get(id);
+          if (existing) {
+              this.adapterTransaction.update(markDeleted(existing));
+              this._queueEvent("delete", { data: existing });
+          }
+          return { data: Object.assign({ id }, existing), deleted: !!existing, permissions: {} };
+      }
+      /**
+       * Adds a record to the local database, asserting that none
+       * already exist with this ID.
+       *
+       * @param  {Object} record, which must contain an ID
+       * @return {Object}
+       */
+      create(record) {
+          if (typeof record !== "object") {
+              throw new Error("Record is not an object.");
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              throw new Error("Cannot create a record missing id");
+          }
+          if (!this.collection.idSchema.validate(record.id)) {
+              throw new Error(`Invalid Id: ${record.id}`);
+          }
+          this.adapterTransaction.create(record);
+          this._queueEvent("create", { data: record });
+          return { data: record, permissions: {} };
+      }
+      /**
+       * Updates a record from the local database.
+       *
+       * Options:
+       * - {Boolean} synced: Sets record status to "synced" (default: false)
+       * - {Boolean} patch:  Extends the existing record instead of overwriting it
+       *   (default: false)
+       *
+       * @param  {Object} record
+       * @param  {Object} options
+       * @return {Object}
+       */
+      update(record, options = { synced: false, patch: false }) {
+          if (typeof record !== "object") {
+              throw new Error("Record is not an object.");
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              throw new Error("Cannot update a record missing id.");
+          }
+          if (!this.collection.idSchema.validate(record.id)) {
+              throw new Error(`Invalid Id: ${record.id}`);
+          }
+          const oldRecord = this.adapterTransaction.get(record.id);
+          if (!oldRecord) {
+              throw new Error(`Record with id=${record.id} not found.`);
+          }
+          const newRecord = options.patch ? Object.assign(Object.assign({}, oldRecord), record) : record;
+          const updated = this._updateRaw(oldRecord, newRecord, options);
+          this.adapterTransaction.update(updated);
+          this._queueEvent("update", { data: updated, oldRecord });
+          return { data: updated, oldRecord, permissions: {} };
+      }
+      /**
+       * Lower-level primitive for updating a record while respecting
+       * _status and last_modified.
+       *
+       * @param  {Object} oldRecord: the record retrieved from the DB
+       * @param  {Object} newRecord: the record to replace it with
+       * @return {Object}
+       */
+      _updateRaw(oldRecord, newRecord, { synced = false } = {}) {
+          const updated = Object.assign({}, newRecord);
+          // Make sure to never loose the existing timestamp.
+          if (oldRecord && oldRecord.last_modified && !updated.last_modified) {
+              updated.last_modified = oldRecord.last_modified;
+          }
+          // If only local fields have changed, then keep record as synced.
+          // If status is created, keep record as created.
+          // If status is deleted, mark as updated.
+          const isIdentical = oldRecord &&
+              recordsEqual(oldRecord, updated, this.collection.localFields);
+          const keepSynced = isIdentical && oldRecord._status == "synced";
+          const neverSynced = !oldRecord || (oldRecord && oldRecord._status == "created");
+          const newStatus = keepSynced || synced ? "synced" : neverSynced ? "created" : "updated";
+          return markStatus(updated, newStatus);
+      }
+      /**
+       * Upsert a record into the local database.
+       *
+       * This record must have an ID.
+       *
+       * If a record with this ID already exists, it will be replaced.
+       * Otherwise, this record will be inserted.
+       *
+       * @param  {Object} record
+       * @return {Object}
+       */
+      upsert(record) {
+          if (typeof record !== "object") {
+              throw new Error("Record is not an object.");
+          }
+          if (!Object.prototype.hasOwnProperty.call(record, "id")) {
+              throw new Error("Cannot update a record missing id.");
+          }
+          if (!this.collection.idSchema.validate(record.id)) {
+              throw new Error(`Invalid Id: ${record.id}`);
+          }
+          let oldRecord = this.adapterTransaction.get(record.id);
+          const updated = this._updateRaw(oldRecord, record);
+          this.adapterTransaction.update(updated);
+          // Don't return deleted records -- pretend they are gone
+          if (oldRecord && oldRecord._status == "deleted") {
+              oldRecord = undefined;
+          }
+          if (oldRecord) {
+              this._queueEvent("update", { data: updated, oldRecord });
+          }
+          else {
+              this._queueEvent("create", { data: updated });
+          }
+          return { data: updated, oldRecord, permissions: {} };
+      }
+  }
+
+  const DEFAULT_BUCKET_NAME = "default";
+  const DEFAULT_REMOTE = "http://localhost:8888/v1";
+  const DEFAULT_RETRY = 1;
+  /**
+   * KintoBase class.
+   */
+  class KintoBase {
+      /**
+       * Provides a public access to the base adapter class. Users can create a
+       * custom DB adapter by extending {@link BaseAdapter}.
+       *
+       * @type {Object}
+       */
+      static get adapters() {
+          return {
+              BaseAdapter: BaseAdapter,
+          };
+      }
+      /**
+       * Synchronization strategies. Available strategies are:
+       *
+       * - `MANUAL`: Conflicts will be reported in a dedicated array.
+       * - `SERVER_WINS`: Conflicts are resolved using remote data.
+       * - `CLIENT_WINS`: Conflicts are resolved using local data.
+       *
+       * @type {Object}
+       */
+      static get syncStrategy() {
+          return Collection.strategy;
+      }
+      /**
+       * Constructor.
+       *
+       * Options:
+       * - `{String}`       `remote`         The server URL to use.
+       * - `{String}`       `bucket`         The collection bucket name.
+       * - `{EventEmitter}` `events`         Events handler.
+       * - `{BaseAdapter}`  `adapter`        The base DB adapter class.
+       * - `{Object}`       `adapterOptions` Options given to the adapter.
+       * - `{Object}`       `headers`        The HTTP headers to use.
+       * - `{Object}`       `retry`          Number of retries when the server fails to process the request (default: `1`)
+       * - `{String}`       `requestMode`    The HTTP CORS mode to use.
+       * - `{Number}`       `timeout`        The requests timeout in ms (default: `5000`).
+       *
+       * @param  {Object} options The options object.
+       */
+      constructor(options = {}) {
+          const defaults = {
+              bucket: DEFAULT_BUCKET_NAME,
+              remote: DEFAULT_REMOTE,
+              retry: DEFAULT_RETRY,
+          };
+          this._options = Object.assign(Object.assign({}, defaults), options);
+          if (!this._options.adapter) {
+              throw new Error("No adapter provided");
+          }
+          this._api = null;
+          /**
+           * The event emitter instance.
+           * @type {EventEmitter}
+           */
+          this.events = this._options.events;
+      }
+      /**
+       * The kinto HTTP client instance.
+       * @type {KintoClient}
+       */
+      get api() {
+          const { events, headers, remote, requestMode, retry, timeout, } = this._options;
+          if (!this._api) {
+              this._api = new this.ApiClass(remote, {
+                  events,
+                  headers,
+                  requestMode,
+                  retry,
+                  timeout,
+              });
+          }
+          return this._api;
+      }
+      /**
+       * Creates a {@link Collection} instance. The second (optional) parameter
+       * will set collection-level options like e.g. `remoteTransformers`.
+       *
+       * @param  {String} collName The collection name.
+       * @param  {Object} [options={}]                 Extra options or override client's options.
+       * @param  {Object} [options.idSchema]           IdSchema instance (default: UUID)
+       * @param  {Object} [options.remoteTransformers] Array<RemoteTransformer> (default: `[]`])
+       * @param  {Object} [options.hooks]              Array<Hook> (default: `[]`])
+       * @param  {Object} [options.localFields]        Array<Field> (default: `[]`])
+       * @return {Collection}
+       */
+      collection(collName, options = {}) {
+          if (!collName) {
+              throw new Error("missing collection name");
+          }
+          const { bucket, events, adapter, adapterOptions } = Object.assign(Object.assign({}, this._options), options);
+          const { idSchema, remoteTransformers, hooks, localFields } = options;
+          return new Collection(bucket, collName, this, {
+              events,
+              adapter,
+              adapterOptions,
+              idSchema,
+              remoteTransformers,
+              hooks,
+              localFields,
+          });
+      }
+  }
+
+  /*
+   *
+   * Licensed under the Apache License, Version 2.0 (the "License");
+   * you may not use this file except in compliance with the License.
+   * You may obtain a copy of the License at
+   *
+   *     http://www.apache.org/licenses/LICENSE-2.0
+   *
+   * Unless required by applicable law or agreed to in writing, software
+   * distributed under the License is distributed on an "AS IS" BASIS,
+   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   * See the License for the specific language governing permissions and
+   * limitations under the License.
+   */
+  const { setTimeout, clearTimeout } = ChromeUtils.importESModule("resource://gre/modules/Timer.sys.mjs");
+  const { XPCOMUtils } = ChromeUtils.importESModule("resource://gre/modules/XPCOMUtils.sys.mjs");
+  XPCOMUtils.defineLazyGlobalGetters(global, ["fetch", "indexedDB"]);
+  ChromeUtils.defineESModuleGetters(global, {
+      EventEmitter: "resource://gre/modules/EventEmitter.sys.mjs"
+  });
+  // Use standalone kinto-http module landed in FFx.
+  ChromeUtils.defineModuleGetter(global, "KintoHttpClient", "resource://services-common/kinto-http-client.js");
+  XPCOMUtils.defineLazyGetter(global, "generateUUID", () => {
+      const { generateUUID } = Cc["@mozilla.org/uuid-generator;1"].getService(Ci.nsIUUIDGenerator);
+      return generateUUID;
+  });
+  class Kinto extends KintoBase {
+      static get adapters() {
+          return {
+              BaseAdapter,
+              IDB,
+          };
+      }
+      get ApiClass() {
+          return KintoHttpClient;
+      }
+      constructor(options = {}) {
+          const events = {};
+          EventEmitter.decorate(events);
+          const defaults = {
+              adapter: IDB,
+              events,
+          };
+          super(Object.assign(Object.assign({}, defaults), options));
+      }
+      collection(collName, options = {}) {
+          const idSchema = {
+              validate(id) {
+                  return typeof id == "string" && RE_RECORD_ID.test(id);
+              },
+              generate() {
+                  return generateUUID()
+                      .toString()
+                      .replace(/[{}]/g, "");
+              },
+          };
+          return super.collection(collName, Object.assign({ idSchema }, options));
+      }
+  }
+
+  return Kinto;
+
+})));