Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 1803 insertions, 0 deletions

diff --git a/toolkit/components/places/PlacesTransactions.sys.mjs b/toolkit/components/places/PlacesTransactions.sys.mjs
new file mode 100644
index 0000000000..0c9accd3ba
--- /dev/null
+++ b/toolkit/components/places/PlacesTransactions.sys.mjs
@@ -0,0 +1,1803 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Overview
+ * --------
+ * This modules serves as the transactions manager for Places (hereinafter PTM).
+ * It implements all the elementary transactions for its UI commands: creating
+ * items, editing their various properties, and so forth.
+ *
+ * Note that since the effect of invoking a Places command is not limited to the
+ * window in which it was performed (e.g. a folder created in the Library may be
+ * the parent of a bookmark created in some browser window), PTM is a singleton.
+ * It's therefore unnecessary to initialize PTM in any way apart importing this
+ * module.
+ *
+ * PTM shares most of its semantics with common command pattern implementations.
+ * However, the asynchronous design of contemporary and future APIs, combined
+ * with the commitment to serialize all UI operations, does make things a little
+ * bit different.  For example, when |undo| is called in order to undo the top
+ * undo entry, the caller cannot tell for sure what entry would it be, because
+ * the execution of some transactions is either in process, or enqueued to be.
+ *
+ * Also note that unlike the nsITransactionManager, for example, this API is by
+ * no means generic.  That is, it cannot be used to execute anything but the
+ * elementary transactions implemented here (Please file a bug if you find
+ * anything uncovered).  More-complex transactions (e.g. creating a folder and
+ * moving a bookmark into it) may be implemented as a batch (see below).
+ *
+ * A note about GUIDs and item-ids
+ * -------------------------------
+ * There's an ongoing effort (see bug 1071511) to deprecate item-ids in Places
+ * in favor of GUIDs.  Both because new APIs (e.g. Bookmark.jsm) expose them to
+ * the minimum necessary, and because GUIDs play much better with implementing
+ * |redo|, this API doesn't support item-ids at all, and only accepts bookmark
+ * GUIDs, both for input (e.g. for setting the parent folder for a new bookmark)
+ * and for output (when the GUID for such a bookmark is propagated).
+ *
+ * Constructing transactions
+ * -------------------------
+ * At the bottom of this module you will find transactions for all Places UI
+ * commands.  They are exposed as constructors set on the PlacesTransactions
+ * object (e.g. PlacesTransactions.NewFolder).  The input for this constructors
+ * is taken in the form of a single argument, a plain object consisting of the
+ * properties for the transaction.  Input properties may be either required or
+ * optional (for example, |keyword| is required for the EditKeyword transaction,
+ * but optional for the NewBookmark transaction).
+ *
+ * To make things simple, a given input property has the same basic meaning and
+ * valid values across all transactions which accept it in the input object.
+ * Here is a list of all supported input properties along with their expected
+ * values:
+ *  - url: a URL object, an nsIURI object, or a href.
+ *  - urls: an array of urls, as above.
+ *  - tag - a string.
+ *  - tags: an array of strings.
+ *  - guid, parentGuid, newParentGuid: a valid Places GUID string.
+ *  - guids: an array of valid Places GUID strings.
+ *  - title: a string
+ *  - index, newIndex: the position of an item in its containing folder,
+ *    starting from 0.
+ *    integer and PlacesUtils.bookmarks.DEFAULT_INDEX
+ *
+ * If a required property is missing in the input object (e.g. not specifying
+ * parentGuid for NewBookmark), or if the value for any of the input properties
+ * is invalid "on the surface" (e.g. a numeric value for GUID, or a string that
+ * isn't 12-characters long), the transaction constructor throws right way.
+ * More complex errors (e.g. passing a non-existent GUID for parentGuid) only
+ * reveal once the transaction is executed.
+ *
+ * Executing Transactions (the |transact| method of transactions)
+ * --------------------------------------------------------------
+ * Once a transaction is created, you must call its |transact| method for it to
+ * be executed and take effect.  |transact| is an asynchronous method that takes
+ * no arguments, and returns a promise that resolves once the transaction is
+ * executed.  Executing one of the transactions for creating items (NewBookmark,
+ * NewFolder, NewSeparator) resolve to the new item's GUID.
+ * There's no resolution value for other transactions.
+ * If a transaction fails to execute, |transact| rejects and the transactions
+ * history is not affected.
+ *
+ * |transact| throws if it's called more than once (successfully or not) on the
+ * same transaction object.
+ *
+ * Batches
+ * -------
+ * Sometimes it is useful to "batch" or "merge" transactions.  For example,
+ * something like "Bookmark All Tabs" may be implemented as one NewFolder
+ * transaction followed by numerous NewBookmark transactions - all to be undone
+ * or redone in a single undo or redo command.  Use `PlacesTransactions.batch()`
+ * in such cases.
+ * It takes an array of transactions which will be executed in the given order
+ * and later be treated as a single entry in the transactions history.
+ * If a transaction depends on the results from a previous one, it can be
+ * replaced by a function that will be invoked with an array of results
+ * accumulated from the previous transactions, indexed in the same positions.
+ * The function should return the transaction to execute. For example:
+ *
+ *  let transactions = [
+ *    // Returns the GUID of the new bookmark.
+ *    PlacesTransactions.NewBookmark({
+ *      parentGuid: "someGUID",
+ *      title: "someTitle",
+ *      url: "https://www.mozilla.org/""
+ *    }),
+ *    previousResults => PlacesTransactions.EditKeyword({
+ *      // Get the GUID from the result of transactions[0].
+ *      guid: previousResults[0],
+ *      keyword: "someKeyword",
+ *    },
+ *  ];
+ *
+ * `PlacesTransactions.batch()` returns a promise resolved when the batch ends.
+ * The resolution value is an array with all the transaction return values
+ * indexed like the original transactions. So, for example, if a transaction
+ * returns an array of GUIDs, to get a list of all the created GUIDs for all the
+ * transactions one could use .flat() to flatten the array.
+ *
+ * If any transactions fails to execute, the batch continues (exceptions are
+ * logged) and the result of that transactions will be set to undefined.
+ * Only transactions that were executed successfully are added to the
+ * transactions history as part of the batch.
+ *
+ * Serialization
+ * -------------
+ * All |PlacesTransaction| operations are serialized.  That is, even though the
+ * implementation is asynchronous, the order in which PlacesTransactions methods
+ * is called does guarantee the order in which they are to be invoked.
+ *
+ * The only exception to this rule is |transact| calls done during a batch (see
+ * above).  |transact| calls are serialized with each other (and with undo, redo
+ * and clearTransactionsHistory), but they  are, of course, not serialized with
+ * batches.
+ *
+ * The transactions-history structure
+ * ----------------------------------
+ * The transactions-history is a two-dimensional stack of transactions: the
+ * transactions are ordered in reverse to the order they were committed.
+ * It's two-dimensional because PTM allows batching transactions together for
+ * the purpose of undo or redo (see Batches above).
+ *
+ * The undoPosition property is set to the index of the top entry. If there is
+ * no entry at that index, there is nothing to undo.
+ * Entries prior to undoPosition, if any, are redo entries, the first one being
+ * the top redo entry.
+ *
+ * [ [2nd redo txn, 1st redo txn],  <= 2nd redo entry
+ *   [2nd redo txn, 1st redo txn],  <= 1st redo entry
+ *   [1st undo txn, 2nd undo txn],  <= 1st undo entry
+ *   [1st undo txn, 2nd undo txn]   <= 2nd undo entry ]
+ * undoPostion: 2.
+ *
+ * Note that when a new entry is created, all redo entries are removed.
+ */
+
+const TRANSACTIONS_QUEUE_TIMEOUT_MS = 240000; // 4 Mins.
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+// Use a single queue bookmarks transaction manager. This pref exists as an
+// emergency switch-off, it will go away in the future.
+const prefs = {};
+XPCOMUtils.defineLazyPreferenceGetter(
+  prefs,
+  "USE_SINGLE_QUEUE",
+  "places.bookmarks.useSingleQueueTransactionManager",
+  true
+);
+
+import { PlacesUtils } from "resource://gre/modules/PlacesUtils.sys.mjs";
+
+function setTimeout(callback, ms) {
+  let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  timer.initWithCallback(callback, ms, timer.TYPE_ONE_SHOT);
+}
+
+const lazy = {};
+ChromeUtils.defineLazyGetter(lazy, "logger", function () {
+  return console.createInstance({
+    prefix: "PlacesTransactions",
+    maxLogLevel: Services.prefs.getCharPref(
+      "places.transactions.logLevel",
+      "Error"
+    ),
+  });
+});
+
+class TransactionsHistoryArray extends Array {
+  constructor() {
+    super();
+
+    // The index of the first undo entry (if any) - See the documentation
+    // at the top of this file.
+    this._undoPosition = 0;
+    // Outside of this module, the API of transactions is inaccessible, and so
+    // are any internal properties.  To achieve that, transactions are proxified
+    // in their constructors.  This maps the proxies to their respective raw
+    // objects.
+    this.proxifiedToRaw = new WeakMap();
+  }
+
+  get undoPosition() {
+    return this._undoPosition;
+  }
+
+  // Handy shortcuts
+  get topUndoEntry() {
+    return this.undoPosition < this.length ? this[this.undoPosition] : null;
+  }
+  get topRedoEntry() {
+    return this.undoPosition > 0 ? this[this.undoPosition - 1] : null;
+  }
+
+  /**
+   * Proxify a transaction object for consumers.
+   * @param rawTransaction
+   *        the raw transaction object.
+   * @return the proxified transaction object.
+   * @see getRawTransaction for retrieving the raw transaction.
+   */
+  proxifyTransaction(rawTransaction) {
+    let proxy = Object.freeze({
+      transact(inBatch, batchIndex) {
+        return TransactionsManager.transact(this, inBatch, batchIndex);
+      },
+      toString() {
+        return rawTransaction.toString();
+      },
+    });
+    this.proxifiedToRaw.set(proxy, rawTransaction);
+    return proxy;
+  }
+
+  /**
+   * Check if the given object is a the proxy object for some transaction.
+   * @param aValue
+   *        any JS value.
+   * @return true if aValue is the proxy object for some transaction, false
+   * otherwise.
+   */
+  isProxifiedTransactionObject(value) {
+    return this.proxifiedToRaw.has(value);
+  }
+
+  /**
+   * Get the raw transaction for the given proxy.
+   * @param aProxy
+   *        the proxy object
+   * @return the transaction proxified by aProxy; |undefined| is returned if
+   * aProxy is not a proxified transaction.
+   */
+  getRawTransaction(proxy) {
+    return this.proxifiedToRaw.get(proxy);
+  }
+
+  /**
+   * Add a transaction either as a new entry, if forced or if there are no undo
+   * entries, or to the top undo entry.
+   *
+   * @param aProxifiedTransaction
+   *        the proxified transaction object to be added to the transaction
+   *        history.
+   * @param [optional] aForceNewEntry
+   *        Force a new entry for the transaction. Default: false.
+   *        If false, an entry will we created only if there's no undo entry
+   *        to extend.
+   */
+  add(proxifiedTransaction, forceNewEntry = false) {
+    if (!this.isProxifiedTransactionObject(proxifiedTransaction)) {
+      throw new Error("aProxifiedTransaction is not a proxified transaction");
+    }
+
+    if (!this.length || forceNewEntry) {
+      this.clearRedoEntries();
+      lazy.logger.debug(`Adding transaction: ${proxifiedTransaction}`);
+      this.unshift([proxifiedTransaction]);
+    } else {
+      lazy.logger.debug(`Adding transaction: ${proxifiedTransaction}`);
+      this[this.undoPosition].unshift(proxifiedTransaction);
+    }
+  }
+
+  /**
+   * Clear all undo entries.
+   */
+  clearUndoEntries() {
+    lazy.logger.debug("Clearing undo entries");
+    if (this.undoPosition < this.length) {
+      this.splice(this.undoPosition);
+    }
+  }
+
+  /**
+   * Clear all redo entries.
+   */
+  clearRedoEntries() {
+    lazy.logger.debug("Clearing redo entries");
+    if (this.undoPosition > 0) {
+      this.splice(0, this.undoPosition);
+      this._undoPosition = 0;
+    }
+  }
+
+  /**
+   * Clear all entries.
+   */
+  clearAllEntries() {
+    lazy.logger.debug("Clearing all entries");
+    if (this.length) {
+      this.splice(0);
+      this._undoPosition = 0;
+    }
+  }
+}
+
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "TransactionsHistory",
+  () => new TransactionsHistoryArray()
+);
+
+export var PlacesTransactions = {
+  /**
+   * @see Batches in the module documentation.
+   */
+  batch(transactionsToBatch, batchName) {
+    if (!Array.isArray(transactionsToBatch) || !transactionsToBatch.length) {
+      throw new Error("Must pass a non-empty array");
+    }
+    if (
+      transactionsToBatch.some(
+        o =>
+          !lazy.TransactionsHistory.isProxifiedTransactionObject(o) &&
+          typeof o != "function"
+      )
+    ) {
+      throw new Error("Must pass only transactions or functions");
+    }
+    lazy.logger.debug(
+      `Batch ${batchName}: ${transactionsToBatch.length} transactions`
+    );
+    return TransactionsManager.batch(async function () {
+      lazy.logger.debug(`Batch ${batchName}: executing transactions`);
+      let accumulatedResults = [];
+      for (let txn of transactionsToBatch) {
+        try {
+          if (typeof txn == "function") {
+            txn = txn(accumulatedResults);
+          }
+          accumulatedResults.push(
+            await txn.transact(true, accumulatedResults.length)
+          );
+        } catch (ex) {
+          // TODO Bug 1865631: handle these errors better, currently we just
+          // continue, that works for non-dependent transactions, but will
+          // skip most of the work for functions depending on previous results.
+          // Moreover in both cases we should notify the user about the problem.
+          accumulatedResults.push(undefined);
+          // Using console.error() here sometimes fails, due to unknown XPC
+          // wrappers reasons, so just use our logger.
+          lazy.logger.error(`Failed to execute batched transaction: ${ex}`);
+        }
+      }
+      return accumulatedResults;
+    });
+  },
+
+  /**
+   * Asynchronously undo the transaction immediately after the current undo
+   * position in the transactions history in the reverse order, if any, and
+   * adjusts the undo position.
+   *
+   * @return {Promises).  The promise always resolves.
+   * @note All undo manager operations are queued. This means that transactions
+   * history may change by the time your request is fulfilled.
+   */
+  undo() {
+    lazy.logger.debug("undo() was invoked");
+    return TransactionsManager.undo();
+  },
+
+  /**
+   * Asynchronously redo the transaction immediately before the current undo
+   * position in the transactions history, if any, and adjusts the undo
+   * position.
+   *
+   * @return {Promises).  The promise always resolves.
+   * @note All undo manager operations are queued. This means that transactions
+   * history may change by the time your request is fulfilled.
+   */
+  redo() {
+    lazy.logger.debug("redo() was invoked");
+    return TransactionsManager.redo();
+  },
+
+  /**
+   * Asynchronously clear the undo, redo, or all entries from the transactions
+   * history.
+   *
+   * @param [optional] undoEntries
+   *        Whether or not to clear undo entries.  Default: true.
+   * @param [optional] redoEntries
+   *        Whether or not to clear undo entries.  Default: true.
+   *
+   * @return {Promises).  The promise always resolves.
+   * @throws if both aUndoEntries and aRedoEntries are false.
+   * @note All undo manager operations are queued. This means that transactions
+   * history may change by the time your request is fulfilled.
+   */
+  clearTransactionsHistory(undoEntries = true, redoEntries = true) {
+    lazy.logger.debug("clearTransactionsHistory() was invoked");
+    return TransactionsManager.clearTransactionsHistory(
+      undoEntries,
+      redoEntries
+    );
+  },
+
+  /**
+   * The numbers of entries in the transactions history.
+   */
+  get length() {
+    return lazy.TransactionsHistory.length;
+  },
+
+  /**
+   * Get the transaction history entry at a given index.  Each entry consists
+   * of one or more transaction objects.
+   *
+   * @param index
+   *        the index of the entry to retrieve.
+   * @return an array of transaction objects in their undo order (that is,
+   * reversely to the order they were executed).
+   * @throw if aIndex is invalid (< 0 or >= length).
+   * @note the returned array is a clone of the history entry and is not
+   * kept in sync with the original entry if it changes.
+   */
+  entry(index) {
+    if (!Number.isInteger(index) || index < 0 || index >= this.length) {
+      throw new Error("Invalid index");
+    }
+
+    return lazy.TransactionsHistory[index];
+  },
+
+  /**
+   * The index of the top undo entry in the transactions history.
+   * If there are no undo entries, it equals to |length|.
+   * Entries past this point
+   * Entries at and past this point are redo entries.
+   */
+  get undoPosition() {
+    return lazy.TransactionsHistory.undoPosition;
+  },
+
+  /**
+   * Shortcut for accessing the top undo entry in the transaction history.
+   */
+  get topUndoEntry() {
+    return lazy.TransactionsHistory.topUndoEntry;
+  },
+
+  /**
+   * Shortcut for accessing the top redo entry in the transaction history.
+   */
+  get topRedoEntry() {
+    return lazy.TransactionsHistory.topRedoEntry;
+  },
+};
+
+/**
+ * Helper for serializing the calls to TransactionsManager methods. It allows
+ * us to guarantee that the order in which TransactionsManager asynchronous
+ * methods are called also enforces the order in which they're executed, and
+ * that they are never executed in parallel.
+ *
+ * In other words: Enqueuer.enqueue(aFunc1); Enqueuer.enqueue(aFunc2) is roughly
+ * the same as Task.spawn(aFunc1).then(Task.spawn(aFunc2)).
+ */
+function Enqueuer(name) {
+  this._promise = Promise.resolve();
+  this._name = name;
+}
+Enqueuer.prototype = {
+  /**
+   * Spawn a functions once all previous functions enqueued are done running,
+   * and all promises passed to alsoWaitFor are no longer pending.
+   *
+   * @param   func
+   *          a function returning a promise.
+   * @return  a promise that resolves once aFunc is done running. The promise
+   *          "mirrors" the promise returned by aFunc.
+   */
+  enqueue(func) {
+    lazy.logger.debug(`${this._name} enqueing`);
+    // If a transaction awaits on a never resolved promise, or is mistakenly
+    // nested, it could hang the transactions queue forever.  Thus we timeout
+    // the execution after a meaningful amount of time, to ensure in any case
+    // we'll proceed after a while.
+    let timeoutPromise = new Promise((resolve, reject) => {
+      setTimeout(
+        () =>
+          reject(
+            new Error(
+              "PlacesTransaction timeout, most likely caused by unresolved pending work."
+            )
+          ),
+        TRANSACTIONS_QUEUE_TIMEOUT_MS
+      );
+    });
+    let promise = this._promise.then(() =>
+      Promise.race([func(), timeoutPromise])
+    );
+
+    // Propagate exceptions to the caller, but dismiss them internally.
+    this._promise = promise.catch(lazy.logger.error);
+    return promise;
+  },
+
+  /**
+   * Same as above, but for a promise returned by a function that already run.
+   * This is useful, for example, for serializing transact calls with undo calls,
+   * even though transact has its own Enqueuer.
+   *
+   * @param {Promise} otherPromise
+   *        any promise.
+   * @param {string} source
+   *        source for logging purposes
+   */
+  alsoWaitFor(otherPromise, source) {
+    lazy.logger.debug(`${this._name} alsoWaitFor: ${source}`);
+    // We don't care if aPromise resolves or rejects, but just that is not
+    // pending anymore.
+    // If a transaction awaits on a never resolved promise, or is mistakenly
+    // nested, it could hang the transactions queue forever.  Thus we timeout
+    // the execution after a meaningful amount of time, to ensure in any case
+    // we'll proceed after a while.
+    let timeoutPromise = new Promise((resolve, reject) => {
+      setTimeout(
+        () =>
+          reject(
+            new Error(
+              "PlacesTransaction timeout, most likely caused by unresolved pending work."
+            )
+          ),
+        TRANSACTIONS_QUEUE_TIMEOUT_MS
+      );
+    });
+    let promise = Promise.race([otherPromise, timeoutPromise]).catch(
+      console.error
+    );
+    this._promise = Promise.all([this._promise, promise]);
+  },
+
+  /**
+   * The promise for this queue.
+   */
+  get promise() {
+    return this._promise;
+  },
+};
+
+var TransactionsManager = {
+  // See the documentation at the top of this file. |transact| calls are not
+  // serialized with |batch| calls.
+  _mainEnqueuer: new Enqueuer("MainEnqueuer"),
+  _transactEnqueuer: new Enqueuer("TransactEnqueuer"),
+
+  // Transactions object should never be recycled (that is, |execute| should
+  // only be called once (or not at all) after they're constructed.
+  // This keeps track of all transactions which were executed.
+  _executedTransactions: new WeakSet(),
+
+  /**
+   * Execute a proxified transaction.
+   *
+   * @param {object} txnProxy The proxified transaction to execute.
+   * @param {boolean} [inBatch] Whether the transaction is part of a batch.
+   * @param {integer} [batchIndex] The index of the transaction in the batch array.
+   * @returns {Promise} resolved to the transaction return value once complete.
+   */
+  transact(txnProxy, inBatch = false, batchIndex = undefined) {
+    let rawTxn = lazy.TransactionsHistory.getRawTransaction(txnProxy);
+    if (!rawTxn) {
+      throw new Error("|transact| was called with an unexpected object");
+    }
+
+    if (this._executedTransactions.has(rawTxn)) {
+      throw new Error("Transactions objects may not be recycled.");
+    }
+
+    lazy.logger.debug(`transact() enqueue: ${txnProxy}`);
+
+    // Add it in advance so one doesn't accidentally do
+    // sameTxn.transact(); sameTxn.transact();
+    this._executedTransactions.add(rawTxn);
+
+    let task = async () => {
+      lazy.logger.debug(`transact execute(): ${txnProxy}`);
+      // Don't try to catch exceptions. If execute fails, we better not add the
+      // transaction to the undo stack.
+      let retval = await rawTxn.execute();
+
+      let forceNewEntry = !inBatch || batchIndex === 0;
+      lazy.TransactionsHistory.add(txnProxy, forceNewEntry);
+
+      this._updateCommandsOnActiveWindow();
+      return retval;
+    };
+
+    if (prefs.USE_SINGLE_QUEUE) {
+      return task();
+    }
+
+    let promise = this._transactEnqueuer.enqueue(task);
+    this._mainEnqueuer.alsoWaitFor(promise, "transact");
+    return promise;
+  },
+
+  batch(task) {
+    return this._mainEnqueuer.enqueue(task);
+  },
+
+  /**
+   * Undo the top undo entry, if any, and update the undo position accordingly.
+   */
+  undo() {
+    let promise = this._mainEnqueuer.enqueue(async () => {
+      lazy.logger.debug("Undo execute");
+      let entry = lazy.TransactionsHistory.topUndoEntry;
+      if (!entry) {
+        return;
+      }
+
+      for (let txnProxy of entry) {
+        try {
+          await lazy.TransactionsHistory.getRawTransaction(txnProxy).undo();
+        } catch (ex) {
+          // If one transaction is broken, it's not safe to work with any other
+          // undo entry.  Report the error and clear the undo history.
+          console.error(ex, "Can't undo a transaction, clearing undo entries.");
+          lazy.TransactionsHistory.clearUndoEntries();
+          return;
+        }
+      }
+      lazy.TransactionsHistory._undoPosition++;
+      this._updateCommandsOnActiveWindow();
+    });
+    if (!prefs.USE_SINGLE_QUEUE) {
+      this._transactEnqueuer.alsoWaitFor(promise, "undo");
+    }
+    return promise;
+  },
+
+  /**
+   * Redo the top redo entry, if any, and update the undo position accordingly.
+   */
+  redo() {
+    let promise = this._mainEnqueuer.enqueue(async () => {
+      lazy.logger.debug("Redo execute");
+      let entry = lazy.TransactionsHistory.topRedoEntry;
+      if (!entry) {
+        return;
+      }
+
+      for (let i = entry.length - 1; i >= 0; i--) {
+        let transaction = lazy.TransactionsHistory.getRawTransaction(entry[i]);
+        try {
+          if (transaction.redo) {
+            await transaction.redo();
+          } else {
+            await transaction.execute();
+          }
+        } catch (ex) {
+          // If one transaction is broken, it's not safe to work with any other
+          // redo entry. Report the error and clear the undo history.
+          console.error(ex, "Can't redo a transaction, clearing redo entries.");
+          lazy.TransactionsHistory.clearRedoEntries();
+          return;
+        }
+      }
+      lazy.TransactionsHistory._undoPosition--;
+      this._updateCommandsOnActiveWindow();
+    });
+    if (!prefs.USE_SINGLE_QUEUE) {
+      this._transactEnqueuer.alsoWaitFor(promise, "redo");
+    }
+    return promise;
+  },
+
+  clearTransactionsHistory(undoEntries, redoEntries) {
+    let promise = this._mainEnqueuer.enqueue(function () {
+      lazy.logger.debug(`ClearTransactionsHistory execute`);
+      if (undoEntries && redoEntries) {
+        lazy.TransactionsHistory.clearAllEntries();
+      } else if (undoEntries) {
+        lazy.TransactionsHistory.clearUndoEntries();
+      } else if (redoEntries) {
+        lazy.TransactionsHistory.clearRedoEntries();
+      } else {
+        throw new Error("either aUndoEntries or aRedoEntries should be true");
+      }
+    });
+
+    if (!prefs.USE_SINGLE_QUEUE) {
+      this._transactEnqueuer.alsoWaitFor(promise, "clearTransactionsHistory");
+    }
+    return promise;
+  },
+
+  // Updates commands in the undo group of the active window commands.
+  // Inactive windows commands will be updated on focus.
+  _updateCommandsOnActiveWindow() {
+    // Updating "undo" will cause a group update including "redo".
+    try {
+      let win = Services.focus.activeWindow;
+      if (win) {
+        win.updateCommands("undo");
+      }
+    } catch (ex) {
+      console.error(ex, "Couldn't update undo commands.");
+    }
+  },
+};
+
+/**
+ * Internal helper for defining the standard transactions and their input.
+ * It takes the required and optional properties, and generates the public
+ * constructor (which takes the input in the form of a plain object) which,
+ * when called, creates the argument-less "public" |execute| method by binding
+ * the input properties to the function arguments (required properties first,
+ * then the optional properties).
+ *
+ * If this seems confusing, look at the consumers.
+ *
+ * This magic serves two purposes:
+ * (1) It completely hides the transactions' internals from the module
+ *     consumers.
+ * (2) It keeps each transaction implementation to what is about, bypassing
+ *     all this bureaucracy while still validating input appropriately.
+ */
+function DefineTransaction(requiredProps = [], optionalProps = []) {
+  for (let prop of [...requiredProps, ...optionalProps]) {
+    if (!DefineTransaction.inputProps.has(prop)) {
+      throw new Error("Property '" + prop + "' is not defined");
+    }
+  }
+
+  let ctor = function (input) {
+    // We want to support both syntaxes:
+    // let t = new PlacesTransactions.NewBookmark(),
+    // let t = PlacesTransactions.NewBookmark()
+    if (this == PlacesTransactions) {
+      return new ctor(input);
+    }
+
+    if (requiredProps.length || optionalProps.length) {
+      // Bind the input properties to the arguments of execute.
+      input = DefineTransaction.verifyInput(
+        input,
+        requiredProps,
+        optionalProps
+      );
+      this.execute = this.execute.bind(this, input);
+    }
+    return lazy.TransactionsHistory.proxifyTransaction(this);
+  };
+  return ctor;
+}
+
+function simpleValidateFunc(checkFn) {
+  return v => {
+    if (!checkFn(v)) {
+      throw new Error("Invalid value");
+    }
+    return v;
+  };
+}
+
+DefineTransaction.strValidate = simpleValidateFunc(v => typeof v == "string");
+DefineTransaction.strOrNullValidate = simpleValidateFunc(
+  v => typeof v == "string" || v === null
+);
+DefineTransaction.indexValidate = simpleValidateFunc(
+  v => Number.isInteger(v) && v >= PlacesUtils.bookmarks.DEFAULT_INDEX
+);
+DefineTransaction.guidValidate = simpleValidateFunc(v =>
+  /^[a-zA-Z0-9\-_]{12}$/.test(v)
+);
+
+function isPrimitive(v) {
+  return v === null || (typeof v != "object" && typeof v != "function");
+}
+
+function checkProperty(obj, prop, required, checkFn) {
+  if (prop in obj) {
+    return checkFn(obj[prop]);
+  }
+
+  return !required;
+}
+
+DefineTransaction.childObjectValidate = function (obj) {
+  if (
+    obj &&
+    checkProperty(obj, "title", false, v => typeof v == "string") &&
+    !("type" in obj && obj.type != PlacesUtils.bookmarks.TYPE_BOOKMARK)
+  ) {
+    obj.url = DefineTransaction.urlValidate(obj.url);
+    let validKeys = ["title", "url"];
+    if (Object.keys(obj).every(k => validKeys.includes(k))) {
+      return obj;
+    }
+  }
+  throw new Error("Invalid child object");
+};
+
+DefineTransaction.urlValidate = function (url) {
+  if (url instanceof Ci.nsIURI) {
+    return URL.fromURI(url);
+  }
+  return new URL(url);
+};
+
+DefineTransaction.inputProps = new Map();
+DefineTransaction.defineInputProps = function (
+  names,
+  validateFn,
+  defaultValue
+) {
+  for (let name of names) {
+    this.inputProps.set(name, {
+      validateValue(value) {
+        if (value === undefined) {
+          return defaultValue;
+        }
+        try {
+          return validateFn(value);
+        } catch (ex) {
+          throw new Error(`Invalid value for input property ${name}: ${ex}`);
+        }
+      },
+
+      validateInput(input, required) {
+        if (required && !(name in input)) {
+          throw new Error(`Required input property is missing: ${name}`);
+        }
+        return this.validateValue(input[name]);
+      },
+
+      isArrayProperty: false,
+    });
+  }
+};
+
+DefineTransaction.defineArrayInputProp = function (name, basePropertyName) {
+  let baseProp = this.inputProps.get(basePropertyName);
+  if (!baseProp) {
+    throw new Error(`Unknown input property: ${basePropertyName}`);
+  }
+
+  this.inputProps.set(name, {
+    validateValue(aValue) {
+      if (aValue == undefined) {
+        return [];
+      }
+
+      if (!Array.isArray(aValue)) {
+        throw new Error(`${name} input property value must be an array`);
+      }
+
+      // We must create a new array in the local scope to avoid a memory leak due
+      // to the array global object. We can't use Cu.cloneInto as that doesn't
+      // handle the URIs. Slice & map also aren't good enough, so we start off
+      // with a clean array and insert what we need into it.
+      let newArray = [];
+      for (let item of aValue) {
+        newArray.push(baseProp.validateValue(item));
+      }
+      return newArray;
+    },
+
+    // We allow setting either the array property itself (e.g. urls), or a
+    // single element of it (url, in that example), that is then transformed
+    // into a single-element array.
+    validateInput(input, required) {
+      if (name in input) {
+        // It's not allowed to set both though.
+        if (basePropertyName in input) {
+          throw new Error(`It is not allowed to set both ${name} and
+                          ${basePropertyName} as  input properties`);
+        }
+        let array = this.validateValue(input[name]);
+        if (required && !array.length) {
+          throw new Error(`Empty array passed for required input property:
+                           ${name}`);
+        }
+        return array;
+      }
+      // If the property is required and it's not set as is, check if the base
+      // property is set.
+      if (required && !(basePropertyName in input)) {
+        throw new Error(`Required input property is missing: ${name}`);
+      }
+
+      if (basePropertyName in input) {
+        return [baseProp.validateValue(input[basePropertyName])];
+      }
+
+      return [];
+    },
+
+    isArrayProperty: true,
+  });
+};
+
+DefineTransaction.validatePropertyValue = function (prop, input, required) {
+  return this.inputProps.get(prop).validateInput(input, required);
+};
+
+DefineTransaction.getInputObjectForSingleValue = function (
+  input,
+  requiredProps,
+  optionalProps
+) {
+  // The following input forms may be deduced from a single value:
+  // * a single required property with or without optional properties (the given
+  //   value is set to the required property).
+  // * a single optional property with no required properties.
+  if (
+    requiredProps.length > 1 ||
+    (!requiredProps.length && optionalProps.length > 1)
+  ) {
+    throw new Error("Transaction input isn't an object");
+  }
+
+  let propName =
+    requiredProps.length == 1 ? requiredProps[0] : optionalProps[0];
+  let propValue =
+    this.inputProps.get(propName).isArrayProperty && !Array.isArray(input)
+      ? [input]
+      : input;
+  return { [propName]: propValue };
+};
+
+DefineTransaction.verifyInput = function (
+  input,
+  requiredProps = [],
+  optionalProps = []
+) {
+  if (!requiredProps.length && !optionalProps.length) {
+    return {};
+  }
+
+  // If there's just a single required/optional property, we allow passing it
+  // as is, so, for example, one could do PlacesTransactions.Remove(myGuid)
+  // rather than PlacesTransactions.Remove({ guid: myGuid}).
+  // This shortcut isn't supported for "complex" properties, like objects (note
+  // there is no use case for this at the moment anyway).
+  let isSinglePropertyInput =
+    isPrimitive(input) ||
+    Array.isArray(input) ||
+    input instanceof Ci.nsISupports;
+  if (isSinglePropertyInput) {
+    input = this.getInputObjectForSingleValue(
+      input,
+      requiredProps,
+      optionalProps
+    );
+  }
+
+  let fixedInput = {};
+  for (let prop of requiredProps) {
+    fixedInput[prop] = this.validatePropertyValue(prop, input, true);
+  }
+  for (let prop of optionalProps) {
+    fixedInput[prop] = this.validatePropertyValue(prop, input, false);
+  }
+
+  return fixedInput;
+};
+
+// Update the documentation at the top of this module if you add or
+// remove properties.
+DefineTransaction.defineInputProps(
+  ["url"],
+  DefineTransaction.urlValidate,
+  null
+);
+DefineTransaction.defineInputProps(
+  ["guid", "parentGuid", "newParentGuid"],
+  DefineTransaction.guidValidate
+);
+DefineTransaction.defineInputProps(
+  ["title", "postData"],
+  DefineTransaction.strOrNullValidate,
+  null
+);
+DefineTransaction.defineInputProps(
+  ["keyword", "oldKeyword", "oldTag", "tag"],
+  DefineTransaction.strValidate,
+  ""
+);
+DefineTransaction.defineInputProps(
+  ["index", "newIndex"],
+  DefineTransaction.indexValidate,
+  PlacesUtils.bookmarks.DEFAULT_INDEX
+);
+DefineTransaction.defineInputProps(
+  ["child"],
+  DefineTransaction.childObjectValidate
+);
+DefineTransaction.defineArrayInputProp("guids", "guid");
+DefineTransaction.defineArrayInputProp("urls", "url");
+DefineTransaction.defineArrayInputProp("tags", "tag");
+DefineTransaction.defineArrayInputProp("children", "child");
+
+/**
+ * Creates items (all types) from a bookmarks tree representation, as defined
+ * in PlacesUtils.promiseBookmarksTree.
+ *
+ * @param tree
+ *        the bookmarks tree object.  You may pass either a bookmarks tree
+ *        returned by promiseBookmarksTree, or a manually defined one.
+ * @param [optional] restoring (default: false)
+ *        Whether or not the items are restored.  Only in restore mode, are
+ *        the guid, dateAdded and lastModified properties honored.
+ * @note the id, root and charset properties of items in aBookmarksTree are
+ *       always ignored.  The index property is ignored for all items but the
+ *       root one.
+ * @return {Promise}
+ * @resolves to the guid of the new item.
+ */
+// TODO: Replace most of this with insertTree.
+function createItemsFromBookmarksTree(tree, restoring = false) {
+  async function createItem(
+    item,
+    parentGuid,
+    index = PlacesUtils.bookmarks.DEFAULT_INDEX
+  ) {
+    let guid;
+    let info = { parentGuid, index };
+    if (restoring) {
+      info.guid = item.guid;
+      info.dateAdded = PlacesUtils.toDate(item.dateAdded);
+      info.lastModified = PlacesUtils.toDate(item.lastModified);
+    }
+    let shouldResetLastModified = false;
+    switch (item.type) {
+      case PlacesUtils.TYPE_X_MOZ_PLACE: {
+        info.url = item.uri;
+        if (typeof item.title == "string") {
+          info.title = item.title;
+        }
+
+        guid = (await PlacesUtils.bookmarks.insert(info)).guid;
+
+        if ("keyword" in item) {
+          let { uri: url, keyword, postData } = item;
+          await PlacesUtils.keywords.insert({ url, keyword, postData });
+        }
+        if ("tags" in item) {
+          PlacesUtils.tagging.tagURI(
+            Services.io.newURI(item.uri),
+            item.tags.split(",")
+          );
+        }
+        break;
+      }
+      case PlacesUtils.TYPE_X_MOZ_PLACE_CONTAINER: {
+        info.type = PlacesUtils.bookmarks.TYPE_FOLDER;
+        if (typeof item.title == "string") {
+          info.title = item.title;
+        }
+        guid = (await PlacesUtils.bookmarks.insert(info)).guid;
+        if ("children" in item) {
+          for (let child of item.children) {
+            await createItem(child, guid);
+          }
+        }
+        if (restoring) {
+          shouldResetLastModified = true;
+        }
+        break;
+      }
+      case PlacesUtils.TYPE_X_MOZ_PLACE_SEPARATOR: {
+        info.type = PlacesUtils.bookmarks.TYPE_SEPARATOR;
+        guid = (await PlacesUtils.bookmarks.insert(info)).guid;
+        break;
+      }
+    }
+
+    if (shouldResetLastModified) {
+      let lastModified = PlacesUtils.toDate(item.lastModified);
+      await PlacesUtils.bookmarks.update({ guid, lastModified });
+    }
+
+    return guid;
+  }
+  return createItem(tree, tree.parentGuid, tree.index);
+}
+
+/** ***************************************************************************
+ * The Standard Places Transactions.
+ *
+ * See the documentation at the top of this file. The valid values for input
+ * are also documented there.
+ *****************************************************************************/
+
+var PT = PlacesTransactions;
+
+/**
+ * Transaction for creating a bookmark.
+ *
+ * Required Input Properties: url, parentGuid.
+ * Optional Input Properties: index, title, keyword, tags.
+ *
+ * When this transaction is executed, it's resolved to the new bookmark's GUID.
+ */
+PT.NewBookmark = DefineTransaction(
+  ["parentGuid", "url"],
+  ["index", "title", "tags"]
+);
+PT.NewBookmark.prototype = Object.seal({
+  async execute({ parentGuid, url, index, title, tags }) {
+    let info = { parentGuid, index, url, title };
+    // Filter tags to exclude already existing ones.
+    if (tags.length) {
+      let currentTags = PlacesUtils.tagging.getTagsForURI(url.URI);
+      tags = tags.filter(t => !currentTags.includes(t));
+    }
+
+    async function createItem() {
+      info = await PlacesUtils.bookmarks.insert(info);
+      if (tags.length) {
+        PlacesUtils.tagging.tagURI(url.URI, tags);
+      }
+    }
+
+    await createItem();
+
+    this.undo = async function () {
+      // Pick up the removed info so we have the accurate last-modified value.
+      await PlacesUtils.bookmarks.remove(info);
+      if (tags.length) {
+        PlacesUtils.tagging.untagURI(url.URI, tags);
+      }
+    };
+    this.redo = async function () {
+      await createItem();
+    };
+    return info.guid;
+  },
+  toString() {
+    return "NewBookmark";
+  },
+});
+
+/**
+ * Transaction for creating a folder.
+ *
+ * Required Input Properties: title, parentGuid.
+ * Optional Input Properties: index, children
+ *
+ * When this transaction is executed, it's resolved to the new folder's GUID.
+ */
+PT.NewFolder = DefineTransaction(
+  ["parentGuid", "title"],
+  ["index", "children"]
+);
+PT.NewFolder.prototype = Object.seal({
+  async execute({ parentGuid, title, index, children }) {
+    let folderGuid;
+    let info = {
+      children: [
+        {
+          // Ensure to specify a guid to be restored on redo.
+          guid: PlacesUtils.history.makeGuid(),
+          title,
+          type: PlacesUtils.bookmarks.TYPE_FOLDER,
+        },
+      ],
+      // insertTree uses guid as the parent for where it is being inserted
+      // into.
+      guid: parentGuid,
+    };
+
+    if (children && children.length) {
+      // Ensure to specify a guid for each child to be restored on redo.
+      info.children[0].children = children.map(c => {
+        c.guid = PlacesUtils.history.makeGuid();
+        return c;
+      });
+    }
+
+    async function createItem() {
+      // Note, insertTree returns an array, rather than the folder/child structure.
+      // For simplicity, we only get the new folder id here. This means that
+      // an undo then redo won't retain exactly the same information for all
+      // the child bookmarks, but we believe that isn't important at the moment.
+      let bmInfo = await PlacesUtils.bookmarks.insertTree(info);
+      // insertTree returns an array, but we only need to deal with the folder guid.
+      folderGuid = bmInfo[0].guid;
+
+      // Bug 1388097: insertTree doesn't handle inserting at a specific index for the folder,
+      // therefore we update the bookmark manually afterwards.
+      if (index != PlacesUtils.bookmarks.DEFAULT_INDEX) {
+        bmInfo[0].index = index;
+        bmInfo = await PlacesUtils.bookmarks.update(bmInfo[0]);
+      }
+    }
+    await createItem();
+
+    this.undo = async function () {
+      await PlacesUtils.bookmarks.remove(folderGuid);
+    };
+    this.redo = async function () {
+      await createItem();
+    };
+    return folderGuid;
+  },
+  toString() {
+    return "NewFolder";
+  },
+});
+
+/**
+ * Transaction for creating a separator.
+ *
+ * Required Input Properties: parentGuid.
+ * Optional Input Properties: index.
+ *
+ * When this transaction is executed, it's resolved to the new separator's
+ * GUID.
+ */
+PT.NewSeparator = DefineTransaction(["parentGuid"], ["index"]);
+PT.NewSeparator.prototype = Object.seal({
+  async execute(info) {
+    info.type = PlacesUtils.bookmarks.TYPE_SEPARATOR;
+    info = await PlacesUtils.bookmarks.insert(info);
+    this.undo = PlacesUtils.bookmarks.remove.bind(PlacesUtils.bookmarks, info);
+    this.redo = PlacesUtils.bookmarks.insert.bind(PlacesUtils.bookmarks, info);
+    return info.guid;
+  },
+  toString() {
+    return "NewSeparator";
+  },
+});
+
+/**
+ * Transaction for moving an item.
+ *
+ * Required Input Properties: guid, newParentGuid.
+ * Optional Input Properties  newIndex.
+ */
+PT.Move = DefineTransaction(["guids", "newParentGuid"], ["newIndex"]);
+PT.Move.prototype = Object.seal({
+  async execute({ guids, newParentGuid, newIndex }) {
+    let originalInfos = [];
+    let index = newIndex;
+
+    for (let guid of guids) {
+      // We need to save the original data for undo.
+      let originalInfo = await PlacesUtils.bookmarks.fetch(guid);
+      if (!originalInfo) {
+        throw new Error("Cannot move a non-existent item");
+      }
+
+      originalInfos.push(originalInfo);
+    }
+
+    await PlacesUtils.bookmarks.moveToFolder(guids, newParentGuid, index);
+
+    this.undo = async function () {
+      // Undo has the potential for moving multiple bookmarks to multiple different
+      // folders and positions, which is very complicated to manage. Therefore we do
+      // individual moves one at a time and hopefully everything is put back approximately
+      // where it should be.
+      for (let info of originalInfos) {
+        await PlacesUtils.bookmarks.update(info);
+      }
+    };
+    this.redo = PlacesUtils.bookmarks.moveToFolder.bind(
+      PlacesUtils.bookmarks,
+      guids,
+      newParentGuid,
+      index
+    );
+    return guids;
+  },
+  toString() {
+    return "Move";
+  },
+});
+
+/**
+ * Transaction for setting the title for an item.
+ *
+ * Required Input Properties: guid, title.
+ */
+PT.EditTitle = DefineTransaction(["guid", "title"]);
+PT.EditTitle.prototype = Object.seal({
+  async execute({ guid, title }) {
+    let originalInfo = await PlacesUtils.bookmarks.fetch(guid);
+    if (!originalInfo) {
+      throw new Error("cannot update a non-existent item");
+    }
+
+    let updateInfo = { guid, title };
+    updateInfo = await PlacesUtils.bookmarks.update(updateInfo);
+
+    this.undo = PlacesUtils.bookmarks.update.bind(
+      PlacesUtils.bookmarks,
+      originalInfo
+    );
+    this.redo = PlacesUtils.bookmarks.update.bind(
+      PlacesUtils.bookmarks,
+      updateInfo
+    );
+  },
+  toString() {
+    return "EditTitle";
+  },
+});
+
+/**
+ * Transaction for setting the URI for an item.
+ *
+ * Required Input Properties: guid, url.
+ */
+PT.EditUrl = DefineTransaction(["guid", "url"]);
+PT.EditUrl.prototype = Object.seal({
+  async execute({ guid, url }) {
+    let originalInfo = await PlacesUtils.bookmarks.fetch(guid);
+    if (!originalInfo) {
+      throw new Error("cannot update a non-existent item");
+    }
+    if (originalInfo.type != PlacesUtils.bookmarks.TYPE_BOOKMARK) {
+      throw new Error("Cannot edit url for non-bookmark items");
+    }
+
+    let uri = url.URI;
+    let originalURI = originalInfo.url.URI;
+    let originalTags = PlacesUtils.tagging.getTagsForURI(originalURI);
+    let updatedInfo = { guid, url };
+    let newURIAdditionalTags = null;
+
+    async function updateItem() {
+      updatedInfo = await PlacesUtils.bookmarks.update(updatedInfo);
+      // Move tags from the original URI to the new URI.
+      if (originalTags.length) {
+        // Untag the original URI only if this was the only bookmark.
+        if (!(await PlacesUtils.bookmarks.fetch({ url: originalInfo.url }))) {
+          PlacesUtils.tagging.untagURI(originalURI, originalTags);
+        }
+        let currentNewURITags = PlacesUtils.tagging.getTagsForURI(uri);
+        newURIAdditionalTags = originalTags.filter(
+          t => !currentNewURITags.includes(t)
+        );
+        if (newURIAdditionalTags && newURIAdditionalTags.length) {
+          PlacesUtils.tagging.tagURI(uri, newURIAdditionalTags);
+        }
+      }
+    }
+    await updateItem();
+
+    this.undo = async function () {
+      await PlacesUtils.bookmarks.update(originalInfo);
+      // Move tags from new URI to original URI.
+      if (originalTags.length) {
+        // Only untag the new URI if this is the only bookmark.
+        if (
+          newURIAdditionalTags &&
+          !!newURIAdditionalTags.length &&
+          !(await PlacesUtils.bookmarks.fetch({ url }))
+        ) {
+          PlacesUtils.tagging.untagURI(uri, newURIAdditionalTags);
+        }
+        PlacesUtils.tagging.tagURI(originalURI, originalTags);
+      }
+    };
+
+    this.redo = async function () {
+      updatedInfo = await updateItem();
+    };
+  },
+  toString() {
+    return "EditUrl";
+  },
+});
+
+/**
+ * Transaction for setting the keyword for a bookmark.
+ *
+ * Required Input Properties: guid, keyword.
+ * Optional Input Properties: postData, oldKeyword.
+ */
+PT.EditKeyword = DefineTransaction(
+  ["guid", "keyword"],
+  ["postData", "oldKeyword"]
+);
+PT.EditKeyword.prototype = Object.seal({
+  async execute({ guid, keyword, postData, oldKeyword }) {
+    let url;
+    let oldKeywordEntry;
+    if (oldKeyword) {
+      oldKeywordEntry = await PlacesUtils.keywords.fetch(oldKeyword);
+      url = oldKeywordEntry.url;
+      await PlacesUtils.keywords.remove(oldKeyword);
+    }
+
+    if (keyword) {
+      if (!url) {
+        url = (await PlacesUtils.bookmarks.fetch(guid)).url;
+      }
+      await PlacesUtils.keywords.insert({
+        url,
+        keyword,
+        postData: postData || (oldKeywordEntry ? oldKeywordEntry.postData : ""),
+      });
+    }
+
+    this.undo = async function () {
+      if (keyword) {
+        await PlacesUtils.keywords.remove(keyword);
+      }
+      if (oldKeywordEntry) {
+        await PlacesUtils.keywords.insert(oldKeywordEntry);
+      }
+    };
+  },
+  toString() {
+    return "EditKeyword";
+  },
+});
+
+/**
+ * Transaction for sorting a folder by name.
+ *
+ * Required Input Properties: guid.
+ */
+PT.SortByName = DefineTransaction(["guid"]);
+PT.SortByName.prototype = {
+  async execute({ guid }) {
+    let sortingMethod = (node_a, node_b) => {
+      if (
+        PlacesUtils.nodeIsContainer(node_a) &&
+        !PlacesUtils.nodeIsContainer(node_b)
+      ) {
+        return -1;
+      }
+      if (
+        !PlacesUtils.nodeIsContainer(node_a) &&
+        PlacesUtils.nodeIsContainer(node_b)
+      ) {
+        return 1;
+      }
+      return node_a.title.localeCompare(node_b.title);
+    };
+    let oldOrderGuids = [];
+    let newOrderGuids = [];
+    let preSepNodes = [];
+
+    // This is not great, since it does main-thread IO.
+    // PromiseBookmarksTree can't be used, since it' won't stop at the first level'.
+    let root = PlacesUtils.getFolderContents(guid, false, false).root;
+    for (let i = 0; i < root.childCount; ++i) {
+      let node = root.getChild(i);
+      oldOrderGuids.push(node.bookmarkGuid);
+      if (PlacesUtils.nodeIsSeparator(node)) {
+        if (preSepNodes.length) {
+          preSepNodes.sort(sortingMethod);
+          newOrderGuids.push(...preSepNodes.map(n => n.bookmarkGuid));
+          preSepNodes = [];
+        }
+        newOrderGuids.push(node.bookmarkGuid);
+      } else {
+        preSepNodes.push(node);
+      }
+    }
+    root.containerOpen = false;
+    if (preSepNodes.length) {
+      preSepNodes.sort(sortingMethod);
+      newOrderGuids.push(...preSepNodes.map(n => n.bookmarkGuid));
+    }
+    await PlacesUtils.bookmarks.reorder(guid, newOrderGuids);
+
+    this.undo = async function () {
+      await PlacesUtils.bookmarks.reorder(guid, oldOrderGuids);
+    };
+    this.redo = async function () {
+      await PlacesUtils.bookmarks.reorder(guid, newOrderGuids);
+    };
+  },
+  toString() {
+    return "SortByName";
+  },
+};
+
+/**
+ * Transaction for removing an item (any type).
+ *
+ * Required Input Properties: guids.
+ */
+PT.Remove = DefineTransaction(["guids"]);
+PT.Remove.prototype = {
+  async execute({ guids }) {
+    let removedItems = [];
+
+    for (let guid of guids) {
+      try {
+        // Although we don't strictly need to get this information for the remove,
+        // we do need it for the possibility of undo().
+        removedItems.push(await PlacesUtils.promiseBookmarksTree(guid));
+      } catch (ex) {
+        if (!ex.becauseInvalidURL) {
+          throw new Error(`Failed to get info for the guid: ${guid}: ${ex}`);
+        }
+        removedItems.push({ guid });
+      }
+    }
+
+    let removeThem = async function () {
+      if (removedItems.length) {
+        // We have to pass just the guids as although remove() accepts full
+        // info items, promiseBookmarksTree returns dateAdded and lastModified
+        // as PRTime rather than date types.
+        await PlacesUtils.bookmarks.remove(
+          removedItems.map(info => ({ guid: info.guid }))
+        );
+      }
+    };
+    await removeThem();
+
+    this.undo = async function () {
+      for (let info of removedItems) {
+        try {
+          await createItemsFromBookmarksTree(info, true);
+        } catch (ex) {
+          console.error(`Unable to undo removal of ${info.guid}`);
+        }
+      }
+    };
+    this.redo = removeThem;
+  },
+  toString() {
+    return "Remove";
+  },
+};
+
+/**
+ * Transaction for tagging urls.
+ *
+ * Required Input Properties: urls, tags.
+ */
+PT.Tag = DefineTransaction(["urls", "tags"]);
+PT.Tag.prototype = {
+  async execute({ urls, tags }) {
+    let onUndo = [],
+      onRedo = [];
+    for (let url of urls) {
+      if (!(await PlacesUtils.bookmarks.fetch({ url }))) {
+        // Tagging is only allowed for bookmarked URIs (but see 424160).
+        let createTxn = lazy.TransactionsHistory.getRawTransaction(
+          PT.NewBookmark({
+            url,
+            tags,
+            parentGuid: PlacesUtils.bookmarks.unfiledGuid,
+          })
+        );
+        await createTxn.execute();
+        onUndo.unshift(createTxn.undo.bind(createTxn));
+        onRedo.push(createTxn.redo.bind(createTxn));
+      } else {
+        let uri = url.URI;
+        let currentTags = PlacesUtils.tagging.getTagsForURI(uri);
+        let newTags = tags.filter(t => !currentTags.includes(t));
+        if (newTags.length) {
+          PlacesUtils.tagging.tagURI(uri, newTags);
+          onUndo.unshift(() => {
+            PlacesUtils.tagging.untagURI(uri, newTags);
+          });
+          onRedo.push(() => {
+            PlacesUtils.tagging.tagURI(uri, newTags);
+          });
+        }
+      }
+    }
+    this.undo = async function () {
+      for (let f of onUndo) {
+        await f();
+      }
+    };
+    this.redo = async function () {
+      for (let f of onRedo) {
+        await f();
+      }
+    };
+  },
+  toString() {
+    return "Tag";
+  },
+};
+
+/**
+ * Transaction for removing tags from a URI.
+ *
+ * Required Input Properties: urls.
+ * Optional Input Properties: tags.
+ *
+ * If |tags| is not set, all tags set for |url| are removed.
+ */
+PT.Untag = DefineTransaction(["urls"], ["tags"]);
+PT.Untag.prototype = {
+  execute({ urls, tags }) {
+    let onUndo = [],
+      onRedo = [];
+    for (let url of urls) {
+      let uri = url.URI;
+      let tagsToRemove;
+      let tagsSet = PlacesUtils.tagging.getTagsForURI(uri);
+      if (tags.length) {
+        tagsToRemove = tags.filter(t => tagsSet.includes(t));
+      } else {
+        tagsToRemove = tagsSet;
+      }
+      if (tagsToRemove.length) {
+        PlacesUtils.tagging.untagURI(uri, tagsToRemove);
+      }
+      onUndo.unshift(() => {
+        if (tagsToRemove.length) {
+          PlacesUtils.tagging.tagURI(uri, tagsToRemove);
+        }
+      });
+      onRedo.push(() => {
+        if (tagsToRemove.length) {
+          PlacesUtils.tagging.untagURI(uri, tagsToRemove);
+        }
+      });
+    }
+    this.undo = async function () {
+      for (let f of onUndo) {
+        await f();
+      }
+    };
+    this.redo = async function () {
+      for (let f of onRedo) {
+        await f();
+      }
+    };
+  },
+  toString() {
+    return "Untag";
+  },
+};
+
+/**
+ * Transaction for renaming a tag.
+ *
+ * Required Input Properties: oldTag, tag.
+ */
+PT.RenameTag = DefineTransaction(["oldTag", "tag"]);
+PT.RenameTag.prototype = {
+  async execute({ oldTag, tag }) {
+    // For now this is implemented by untagging and tagging all the bookmarks.
+    // We should create a specialized bookmarking API to just rename the tag.
+    let onUndo = [],
+      onRedo = [];
+    let urls = new Set();
+    await PlacesUtils.bookmarks.fetch({ tags: [oldTag] }, b => urls.add(b.url));
+    if (urls.size > 0) {
+      urls = Array.from(urls);
+      let tagTxn = lazy.TransactionsHistory.getRawTransaction(
+        PT.Tag({ urls, tags: [tag] })
+      );
+      await tagTxn.execute();
+      onUndo.unshift(tagTxn.undo.bind(tagTxn));
+      onRedo.push(tagTxn.redo.bind(tagTxn));
+      let untagTxn = lazy.TransactionsHistory.getRawTransaction(
+        PT.Untag({ urls, tags: [oldTag] })
+      );
+      await untagTxn.execute();
+      onUndo.unshift(untagTxn.undo.bind(untagTxn));
+      onRedo.push(untagTxn.redo.bind(untagTxn));
+
+      // Update all the place: queries that refer to this tag.
+      let db = await PlacesUtils.promiseDBConnection();
+      let rows = await db.executeCached(
+        `
+        SELECT h.url, b.guid, b.title
+        FROM moz_places h
+        JOIN moz_bookmarks b ON b.fk = h.id
+        WHERE url_hash BETWEEN hash("place", "prefix_lo")
+                           AND hash("place", "prefix_hi")
+          AND url LIKE :tagQuery
+      `,
+        { tagQuery: "%tag=%" }
+      );
+      for (let row of rows) {
+        let url = row.getResultByName("url");
+        try {
+          url = new URL(url);
+          let urlParams = new URLSearchParams(url.pathname);
+          let tags = urlParams.getAll("tag");
+          if (!tags.includes(oldTag)) {
+            continue;
+          }
+          if (tags.length > 1) {
+            // URLSearchParams cannot set more than 1 same-named param.
+            urlParams.delete("tag");
+            urlParams.set("tag", tag);
+            url = new URL(
+              url.protocol +
+                urlParams +
+                "&tag=" +
+                tags.filter(t => t != oldTag).join("&tag=")
+            );
+          } else {
+            urlParams.set("tag", tag);
+            url = new URL(url.protocol + urlParams);
+          }
+        } catch (ex) {
+          console.error(
+            "Invalid bookmark url: " + row.getResultByName("url") + ": " + ex
+          );
+          continue;
+        }
+        let guid = row.getResultByName("guid");
+        let title = row.getResultByName("title");
+
+        let editUrlTxn = lazy.TransactionsHistory.getRawTransaction(
+          PT.EditUrl({ guid, url })
+        );
+        await editUrlTxn.execute();
+        onUndo.unshift(editUrlTxn.undo.bind(editUrlTxn));
+        onRedo.push(editUrlTxn.redo.bind(editUrlTxn));
+        if (title == oldTag) {
+          let editTitleTxn = lazy.TransactionsHistory.getRawTransaction(
+            PT.EditTitle({ guid, title: tag })
+          );
+          await editTitleTxn.execute();
+          onUndo.unshift(editTitleTxn.undo.bind(editTitleTxn));
+          onRedo.push(editTitleTxn.redo.bind(editTitleTxn));
+        }
+      }
+    }
+    this.undo = async function () {
+      for (let f of onUndo) {
+        await f();
+      }
+    };
+    this.redo = async function () {
+      for (let f of onRedo) {
+        await f();
+      }
+    };
+  },
+  toString() {
+    return "RenameTag";
+  },
+};
+
+/**
+ * Transaction for copying an item.
+ *
+ * Required Input Properties: guid, newParentGuid
+ * Optional Input Properties: newIndex.
+ */
+PT.Copy = DefineTransaction(["guid", "newParentGuid"], ["newIndex"]);
+PT.Copy.prototype = {
+  async execute({ guid, newParentGuid, newIndex }) {
+    let creationInfo = null;
+    try {
+      creationInfo = await PlacesUtils.promiseBookmarksTree(guid);
+    } catch (ex) {
+      throw new Error(
+        "Failed to get info for the specified item (guid: " +
+          guid +
+          "). Ex: " +
+          ex
+      );
+    }
+    creationInfo.parentGuid = newParentGuid;
+    creationInfo.index = newIndex;
+
+    let newItemGuid = await createItemsFromBookmarksTree(creationInfo, false);
+    let newItemInfo = null;
+    this.undo = async function () {
+      if (!newItemInfo) {
+        newItemInfo = await PlacesUtils.promiseBookmarksTree(newItemGuid);
+      }
+      await PlacesUtils.bookmarks.remove(newItemGuid);
+    };
+    this.redo = async function () {
+      await createItemsFromBookmarksTree(newItemInfo, true);
+    };
+
+    return newItemGuid;
+  },
+  toString() {
+    return "Copy";
+  },
+};