michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /**
michael@0:  * Handles serialization of Download objects and persistence into a file, so
michael@0:  * that the state of downloads can be restored across sessions.
michael@0:  *
michael@0:  * The file is stored in JSON format, without indentation.  With indentation
michael@0:  * applied, the file would look like this:
michael@0:  *
michael@0:  * {
michael@0:  *   "list": [
michael@0:  *     {
michael@0:  *       "source": "http://www.example.com/download.txt",
michael@0:  *       "target": "/home/user/Downloads/download.txt"
michael@0:  *     },
michael@0:  *     {
michael@0:  *       "source": {
michael@0:  *         "url": "http://www.example.com/download.txt",
michael@0:  *         "referrer": "http://www.example.com/referrer.html"
michael@0:  *       },
michael@0:  *       "target": "/home/user/Downloads/download-2.txt"
michael@0:  *     }
michael@0:  *   ]
michael@0:  * }
michael@0:  */
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: this.EXPORTED_SYMBOLS = [
michael@0:   "DownloadStore",
michael@0: ];
michael@0: 
michael@0: ////////////////////////////////////////////////////////////////////////////////
michael@0: //// Globals
michael@0: 
michael@0: const Cc = Components.classes;
michael@0: const Ci = Components.interfaces;
michael@0: const Cu = Components.utils;
michael@0: const Cr = Components.results;
michael@0: 
michael@0: Cu.import("resource://gre/modules/XPCOMUtils.jsm");
michael@0: 
michael@0: XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
michael@0:                                   "resource://gre/modules/Downloads.jsm");
michael@0: XPCOMUtils.defineLazyModuleGetter(this, "OS",
michael@0:                                   "resource://gre/modules/osfile.jsm")
michael@0: XPCOMUtils.defineLazyModuleGetter(this, "Task",
michael@0:                                   "resource://gre/modules/Task.jsm");
michael@0: 
michael@0: XPCOMUtils.defineLazyGetter(this, "gTextDecoder", function () {
michael@0:   return new TextDecoder();
michael@0: });
michael@0: 
michael@0: XPCOMUtils.defineLazyGetter(this, "gTextEncoder", function () {
michael@0:   return new TextEncoder();
michael@0: });
michael@0: 
michael@0: ////////////////////////////////////////////////////////////////////////////////
michael@0: //// DownloadStore
michael@0: 
michael@0: /**
michael@0:  * Handles serialization of Download objects and persistence into a file, so
michael@0:  * that the state of downloads can be restored across sessions.
michael@0:  *
michael@0:  * @param aList
michael@0:  *        DownloadList object to be populated or serialized.
michael@0:  * @param aPath
michael@0:  *        String containing the file path where data should be saved.
michael@0:  */
michael@0: this.DownloadStore = function (aList, aPath)
michael@0: {
michael@0:   this.list = aList;
michael@0:   this.path = aPath;
michael@0: }
michael@0: 
michael@0: this.DownloadStore.prototype = {
michael@0:   /**
michael@0:    * DownloadList object to be populated or serialized.
michael@0:    */
michael@0:   list: null,
michael@0: 
michael@0:   /**
michael@0:    * String containing the file path where data should be saved.
michael@0:    */
michael@0:   path: "",
michael@0: 
michael@0:   /**
michael@0:    * This function is called with a Download object as its first argument, and
michael@0:    * should return true if the item should be saved.
michael@0:    */
michael@0:   onsaveitem: () => true,
michael@0: 
michael@0:   /**
michael@0:    * Loads persistent downloads from the file to the list.
michael@0:    *
michael@0:    * @return {Promise}
michael@0:    * @resolves When the operation finished successfully.
michael@0:    * @rejects JavaScript exception.
michael@0:    */
michael@0:   load: function DS_load()
michael@0:   {
michael@0:     return Task.spawn(function task_DS_load() {
michael@0:       let bytes;
michael@0:       try {
michael@0:         bytes = yield OS.File.read(this.path);
michael@0:       } catch (ex if ex instanceof OS.File.Error && ex.becauseNoSuchFile) {
michael@0:         // If the file does not exist, there are no downloads to load.
michael@0:         return;
michael@0:       }
michael@0: 
michael@0:       let storeData = JSON.parse(gTextDecoder.decode(bytes));
michael@0: 
michael@0:       // Create live downloads based on the static snapshot.
michael@0:       for (let downloadData of storeData.list) {
michael@0:         try {
michael@0:           let download = yield Downloads.createDownload(downloadData);
michael@0:           try {
michael@0:             if (!download.succeeded && !download.canceled && !download.error) {
michael@0:               // Try to restart the download if it was in progress during the
michael@0:               // previous session.
michael@0:               download.start();
michael@0:             } else {
michael@0:               // If the download was not in progress, try to update the current
michael@0:               // progress from disk.  This is relevant in case we retained
michael@0:               // partially downloaded data.
michael@0:               yield download.refresh();
michael@0:             }
michael@0:           } finally {
michael@0:             // Add the download to the list if we succeeded in creating it,
michael@0:             // after we have updated its initial state.
michael@0:             yield this.list.add(download);
michael@0:           }
michael@0:         } catch (ex) {
michael@0:           // If an item is unrecognized, don't prevent others from being loaded.
michael@0:           Cu.reportError(ex);
michael@0:         }
michael@0:       }
michael@0:     }.bind(this));
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Saves persistent downloads from the list to the file.
michael@0:    *
michael@0:    * If an error occurs, the previous file is not deleted.
michael@0:    *
michael@0:    * @return {Promise}
michael@0:    * @resolves When the operation finished successfully.
michael@0:    * @rejects JavaScript exception.
michael@0:    */
michael@0:   save: function DS_save()
michael@0:   {
michael@0:     return Task.spawn(function task_DS_save() {
michael@0:       let downloads = yield this.list.getAll();
michael@0: 
michael@0:       // Take a static snapshot of the current state of all the downloads.
michael@0:       let storeData = { list: [] };
michael@0:       let atLeastOneDownload = false;
michael@0:       for (let download of downloads) {
michael@0:         try {
michael@0:           if (!this.onsaveitem(download)) {
michael@0:             continue;
michael@0:           }
michael@0:           storeData.list.push(download.toSerializable());
michael@0:           atLeastOneDownload = true;
michael@0:         } catch (ex) {
michael@0:           // If an item cannot be converted to a serializable form, don't
michael@0:           // prevent others from being saved.
michael@0:           Cu.reportError(ex);
michael@0:         }
michael@0:       }
michael@0: 
michael@0:       if (atLeastOneDownload) {
michael@0:         // Create or overwrite the file if there are downloads to save.
michael@0:         let bytes = gTextEncoder.encode(JSON.stringify(storeData));
michael@0:         yield OS.File.writeAtomic(this.path, bytes,
michael@0:                                   { tmpPath: this.path + ".tmp" });
michael@0:       } else {
michael@0:         // Remove the file if there are no downloads to save at all.
michael@0:         try {
michael@0:           yield OS.File.remove(this.path);
michael@0:         } catch (ex if ex instanceof OS.File.Error &&
michael@0:                  (ex.becauseNoSuchFile || ex.becauseAccessDenied)) {
michael@0:           // On Windows, we may get an access denied error instead of a no such
michael@0:           // file error if the file existed before, and was recently deleted.
michael@0:         }
michael@0:       }
michael@0:     }.bind(this));
michael@0:   },
michael@0: };