path: root/toolkit/components/jsdownloads/src/DownloadIntegration.jsm

/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
/* 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/. */

/**
 * Provides functions to integrate with the host application, handling for
 * example the global prompts on shutdown.
 */

"use strict";

this.EXPORTED_SYMBOLS = [
  "DownloadIntegration",
];

////////////////////////////////////////////////////////////////////////////////
//// Globals

const Cc = Components.classes;
const Ci = Components.interfaces;
const Cu = Components.utils;
const Cr = Components.results;

Cu.import("resource://gre/modules/Integration.jsm");
Cu.import("resource://gre/modules/XPCOMUtils.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "AsyncShutdown",
                                  "resource://gre/modules/AsyncShutdown.jsm");

XPCOMUtils.defineLazyModuleGetter(this, "DeferredTask",
                                  "resource://gre/modules/DeferredTask.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Downloads",
                                  "resource://gre/modules/Downloads.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "DownloadStore",
                                  "resource://gre/modules/DownloadStore.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "DownloadImport",
                                  "resource://gre/modules/DownloadImport.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "DownloadUIHelper",
                                  "resource://gre/modules/DownloadUIHelper.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
                                  "resource://gre/modules/FileUtils.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
                                  "resource://gre/modules/NetUtil.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "OS",
                                  "resource://gre/modules/osfile.jsm");
#ifdef MOZ_PLACES
XPCOMUtils.defineLazyModuleGetter(this, "PlacesUtils",
                                  "resource://gre/modules/PlacesUtils.jsm");
#endif
XPCOMUtils.defineLazyModuleGetter(this, "Promise",
                                  "resource://gre/modules/Promise.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Services",
                                  "resource://gre/modules/Services.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "Task",
                                  "resource://gre/modules/Task.jsm");
XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
                                  "resource://gre/modules/NetUtil.jsm");

XPCOMUtils.defineLazyServiceGetter(this, "gDownloadPlatform",
                                   "@mozilla.org/toolkit/download-platform;1",
                                   "mozIDownloadPlatform");
XPCOMUtils.defineLazyServiceGetter(this, "gEnvironment",
                                   "@mozilla.org/process/environment;1",
                                   "nsIEnvironment");
XPCOMUtils.defineLazyServiceGetter(this, "gMIMEService",
                                   "@mozilla.org/mime;1",
                                   "nsIMIMEService");
XPCOMUtils.defineLazyServiceGetter(this, "gExternalProtocolService",
                                   "@mozilla.org/uriloader/external-protocol-service;1",
                                   "nsIExternalProtocolService");

XPCOMUtils.defineLazyGetter(this, "gParentalControlsService", function() {
  if ("@mozilla.org/parental-controls-service;1" in Cc) {
    return Cc["@mozilla.org/parental-controls-service;1"]
      .createInstance(Ci.nsIParentalControlsService);
  }
  return null;
});

XPCOMUtils.defineLazyServiceGetter(this, "volumeService",
                                   "@mozilla.org/telephony/volume-service;1",
                                   "nsIVolumeService");

// We have to use the gCombinedDownloadIntegration identifier because, in this
// module only, the DownloadIntegration identifier refers to the base version.
Integration.downloads.defineModuleGetter(this, "gCombinedDownloadIntegration",
            "resource://gre/modules/DownloadIntegration.jsm",
            "DownloadIntegration");

const Timer = Components.Constructor("@mozilla.org/timer;1", "nsITimer",
                                     "initWithCallback");

/**
 * Indicates the delay between a change to the downloads data and the related
 * save operation.
 *
 * For best efficiency, this value should be high enough that the input/output
 * for opening or closing the target file does not overlap with the one for
 * saving the list of downloads.
 */
const kSaveDelayMs = 1500;

/**
 * This pref indicates if we have already imported (or attempted to import)
 * the downloads database from the previous SQLite storage.
 */
const kPrefImportedFromSqlite = "browser.download.importedFromSqlite";

/**
 * List of observers to listen against
 */
const kObserverTopics = [
  "quit-application-requested",
  "offline-requested",
  "last-pb-context-exiting",
  "last-pb-context-exited",
  "sleep_notification",
  "suspend_process_notification",
  "wake_notification",
  "resume_process_notification",
  "network:offline-about-to-go-offline",
  "network:offline-status-changed",
  "xpcom-will-shutdown",
];

////////////////////////////////////////////////////////////////////////////////
//// DownloadIntegration

/**
 * Provides functions to integrate with the host application, handling for
 * example the global prompts on shutdown.
 */
this.DownloadIntegration = {
  /**
   * Main DownloadStore object for loading and saving the list of persistent
   * downloads, or null if the download list was never requested and thus it
   * doesn't need to be persisted.
   */
  _store: null,

  /**
   * Returns whether data for blocked downloads should be kept on disk.
   * Implementations which support unblocking downloads may return true to
   * keep the blocked download on disk until its fate is decided.
   *
   * If a download is blocked and the partial data is kept the Download's
   * 'hasBlockedData' property will be true. In this state Download.unblock()
   * or Download.confirmBlock() may be used to either unblock the download or
   * remove the downloaded data respectively.
   *
   * Even if shouldKeepBlockedData returns true, if the download did not use a
   * partFile the blocked data will be removed - preventing the complete
   * download from existing on disk with its final filename.
   *
   * @return boolean True if data should be kept.
   */
  shouldKeepBlockedData() {
    const FIREFOX_ID = "{ec8030f7-c20a-464f-9b0e-13a3a9e97384}";
    return Services.appinfo.ID == FIREFOX_ID;
  },

  /**
   * Performs initialization of the list of persistent downloads, before its
   * first use by the host application.  This function may be called only once
   * during the entire lifetime of the application.
   *
   * @param list
   *        DownloadList object to be initialized.
   *
   * @return {Promise}
   * @resolves When the list has been initialized.
   * @rejects JavaScript exception.
   */
  initializePublicDownloadList: Task.async(function* (list) {
    try {
      yield this.loadPublicDownloadListFromStore(list);
    } catch (ex) {
      Cu.reportError(ex);
    }

    // After the list of persistent downloads has been loaded, we can add the
    // history observers, even if the load operation failed. This object is kept
    // alive by the history service.
    new DownloadHistoryObserver(list);
  }),

  /**
   * Called by initializePublicDownloadList to load the list of persistent
   * downloads, before its first use by the host application.  This function may
   * be called only once during the entire lifetime of the application.
   *
   * @param list
   *        DownloadList object to be populated with the download objects
   *        serialized from the previous session.  This list will be persisted
   *        to disk during the session lifetime.
   *
   * @return {Promise}
   * @resolves When the list has been populated.
   * @rejects JavaScript exception.
   */
  loadPublicDownloadListFromStore: Task.async(function* (list) {
    if (this._store) {
      throw new Error("Initialization may be performed only once.");
    }

    this._store = new DownloadStore(list, OS.Path.join(
                                             OS.Constants.Path.profileDir,
                                             "downloads.json"));
    this._store.onsaveitem = this.shouldPersistDownload.bind(this);

    try {
      if (this._importedFromSqlite) {
        yield this._store.load();
      } else {
        let sqliteDBpath = OS.Path.join(OS.Constants.Path.profileDir,
                                        "downloads.sqlite");

        if (yield OS.File.exists(sqliteDBpath)) {
          let sqliteImport = new DownloadImport(list, sqliteDBpath);
          yield sqliteImport.import();

          let importCount = (yield list.getAll()).length;
          if (importCount > 0) {
            try {
              yield this._store.save();
            } catch (ex) { }
          }

          // No need to wait for the file removal.
          OS.File.remove(sqliteDBpath).then(null, Cu.reportError);
        }

        Services.prefs.setBoolPref(kPrefImportedFromSqlite, true);

        // Don't even report error here because this file is pre Firefox 3
        // and most likely doesn't exist.
        OS.File.remove(OS.Path.join(OS.Constants.Path.profileDir,
                                    "downloads.rdf")).catch(() => {});

      }
    } catch (ex) {
      Cu.reportError(ex);
    }

    // Add the view used for detecting changes to downloads to be persisted.
    // We must do this after the list of persistent downloads has been loaded,
    // even if the load operation failed. We wait for a complete initialization
    // so other callers cannot modify the list without being detected. The
    // DownloadAutoSaveView is kept alive by the underlying DownloadList.
    yield new DownloadAutoSaveView(list, this._store).initialize();
  }),

  /**
   * Determines if a Download object from the list of persistent downloads
   * should be saved into a file, so that it can be restored across sessions.
   *
   * This function allows filtering out downloads that the host application is
   * not interested in persisting across sessions, for example downloads that
   * finished successfully.
   *
   * @param aDownload
   *        The Download object to be inspected.  This is originally taken from
   *        the global DownloadList object for downloads that were not started
   *        from a private browsing window.  The item may have been removed
   *        from the list since the save operation started, though in this case
   *        the save operation will be repeated later.
   *
   * @return True to save the download, false otherwise.
   */
  shouldPersistDownload(aDownload) {
    // On all platforms, we save all the downloads currently in progress, as
    // well as stopped downloads for which we retained partially downloaded
    // data or we have blocked data.
    if (!aDownload.stopped || aDownload.hasPartialData ||
        aDownload.hasBlockedData) {
      return true;
    }

    // On Desktop, stopped downloads for which we don't need to track the
    // presence of a ".part" file are only retained in the browser history.
    return false;
  },

  /**
   * Returns the system downloads directory asynchronously.
   *
   * @return {Promise}
   * @resolves The downloads directory string path.
   */
  getSystemDownloadsDirectory: Task.async(function* () {
    if (this._downloadsDirectory) {
      return this._downloadsDirectory;
    }

    let directoryPath = null;
#ifdef XP_WIN
    // For XP/2K, use My Documents/Downloads. Other version uses
    // the default Downloads directory.
    let version = parseFloat(Services.sysinfo.getProperty("version"));
    if (version < 6) {
      directoryPath = yield this._createDownloadsDirectory("Pers");
    } else {
      directoryPath = this._getDirectory("DfltDwnld");
    }

#elifdef XP_UNIX
    // For Linux, use XDG download dir, with a fallback to Home/Downloads
    // if the XDG user dirs are disabled.
    try {
      directoryPath = this._getDirectory("DfltDwnld");
    } catch(e) {
      directoryPath = yield this._createDownloadsDirectory("Home");
    }
#else
    directoryPath = yield this._createDownloadsDirectory("Home");
#endif

    this._downloadsDirectory = directoryPath;
    return this._downloadsDirectory;
  }),
  _downloadsDirectory: null,

  /**
   * Returns the user downloads directory asynchronously.
   *
   * @return {Promise}
   * @resolves The downloads directory string path.
   */
  getPreferredDownloadsDirectory: Task.async(function* () {
    let directoryPath = null;
    let prefValue = Services.prefs.getIntPref("browser.download.folderList", 1);

    switch(prefValue) {
      case 0: // Desktop
        directoryPath = this._getDirectory("Desk");
        break;
      case 1: // Downloads
        directoryPath = yield this.getSystemDownloadsDirectory();
        break;
      case 2: // Custom
        try {
          let directory = Services.prefs.getComplexValue("browser.download.dir",
                                                         Ci.nsIFile);
          directoryPath = directory.path;
          yield OS.File.makeDir(directoryPath, { ignoreExisting: true });
        } catch(ex) {
          // Either the preference isn't set or the directory cannot be created.
          directoryPath = yield this.getSystemDownloadsDirectory();
        }
        break;
      default:
        directoryPath = yield this.getSystemDownloadsDirectory();
    }
    return directoryPath;
  }),

  /**
   * Returns the temporary downloads directory asynchronously.
   *
   * @return {Promise}
   * @resolves The downloads directory string path.
   */
  getTemporaryDownloadsDirectory: Task.async(function* () {
    let directoryPath = null;
    directoryPath = this._getDirectory("TmpD");
    return directoryPath;
  }),

  /**
   * Checks to determine whether to block downloads for parental controls.
   *
   * aParam aDownload
   *        The download object.
   *
   * @return {Promise}
   * @resolves The boolean indicates to block downloads or not.
   */
  shouldBlockForParentalControls(aDownload) {
    let isEnabled = gParentalControlsService &&
                    gParentalControlsService.parentalControlsEnabled;
    let shouldBlock = isEnabled &&
                      gParentalControlsService.blockFileDownloadsEnabled;

    // Log the event if required by parental controls settings.
    if (isEnabled && gParentalControlsService.loggingEnabled) {
      gParentalControlsService.log(gParentalControlsService.ePCLog_FileDownload,
                                   shouldBlock,
                                   NetUtil.newURI(aDownload.source.url), null);
    }

    return Promise.resolve(shouldBlock);
  },

  /**
   * Checks to determine whether to block downloads for not granted runtime permissions.
   *
   * @return {Promise}
   * @resolves The boolean indicates to block downloads or not.
   */
  shouldBlockForRuntimePermissions() {
    return Promise.resolve(false);
  },

#ifdef XP_WIN
  /**
   * Checks whether downloaded files should be marked as coming from
   * Internet Zone.
   *
   * @return true if files should be marked
   */
  _shouldSaveZoneInformation() {
    let zonePref = 2;
    try {
      zonePref = Services.prefs.getIntPref("browser.download.saveZoneInformation");
    } catch (ex) {}
    
    switch (zonePref) {
      case 0: // Never
              return false;
      case 1: // Always
              return true;
      case 2: // System-defined
              let key = Cc["@mozilla.org/windows-registry-key;1"]
                       .createInstance(Ci.nsIWindowsRegKey);
              try {
                key.open(Ci.nsIWindowsRegKey.ROOT_KEY_CURRENT_USER,
                         "Software\\Microsoft\\Windows\\CurrentVersion\\Policies\\Attachments",
                         Ci.nsIWindowsRegKey.ACCESS_QUERY_VALUE);
                try {
                  return key.readIntValue("SaveZoneInformation") != 1;
                } finally {
                  key.close();
                }
              } catch (ex) {
                // If the key is not present, files should be marked by default.
                return true;
              }
      default: // Invalid pref value defaults marking files.
               return true;
    }
  },
#endif

  /**
   * Performs platform-specific operations when a download is done.
   *
   * aParam aDownload
   *        The Download object.
   *
   * @return {Promise}
   * @resolves When all the operations completed successfully.
   * @rejects JavaScript exception if any of the operations failed.
   */
  downloadDone: Task.async(function* (aDownload) {
#ifdef XP_WIN
    // On Windows, we mark any file saved to the NTFS file system as coming
    // from the Internet security zone unless Group Policy disables the
    // feature.  We do this by writing to the "Zone.Identifier" Alternate
    // Data Stream directly, because the Save method of the
    // IAttachmentExecute interface would trigger operations that may cause
    // the application to hang, or other performance issues.
    // The stream created in this way is forward-compatible with all the
    // current and future versions of Windows.
    if (this._shouldSaveZoneInformation()) {
      let zone;
      try {
        zone = gDownloadPlatform.mapUrlToZone(aDownload.source.url);
      } catch (e) {
        // Default to Internet Zone if mapUrlToZone failed for
        // whatever reason.
        zone = Ci.mozIDownloadPlatform.ZONE_INTERNET;
      }
      try {
        // Don't write zone IDs for Local, Intranet, or Trusted sites
        // to match Windows behavior.
        if (zone >= Ci.mozIDownloadPlatform.ZONE_INTERNET) {
          let streamPath = aDownload.target.path + ":Zone.Identifier";
          let stream = yield OS.File.open(
            streamPath,
            { create: true },
            { winAllowLengthBeyondMaxPathWithCaveats: true }
          );
          try {
            yield stream.write(new TextEncoder().encode("[ZoneTransfer]\r\nZoneId=" + zone + "\r\n"));
          } finally {
            yield stream.close();
          }
        }
      } catch (ex) {
        // If writing to the stream fails, we ignore the error and continue.
        // The Windows API error 123 (ERROR_INVALID_NAME) is expected to
        // occur when working on a file system that does not support
        // Alternate Data Streams, like FAT32, thus we don't report this
        // specific error.
        if (!(ex instanceof OS.File.Error) || ex.winLastError != 123) {
          Cu.reportError(ex);
        }
      }
    }
#endif

    // The file with the partially downloaded data has restrictive permissions
    // that don't allow other users on the system to access it.  Now that the
    // download is completed, we need to adjust permissions based on whether
    // this is a permanently downloaded file or a temporary download to be
    // opened read-only with an external application.
    try {
      // The following logic to determine whether this is a temporary download
      // is due to the fact that "deleteTempFileOnExit" is false on Mac, where
      // downloads to be opened with external applications are preserved in
      // the "Downloads" folder like normal downloads.
      let isTemporaryDownload =
        aDownload.launchWhenSucceeded && (aDownload.source.isPrivate ||
        Services.prefs.getBoolPref("browser.helperApps.deleteTempFileOnExit"));
      // Permanently downloaded files are made accessible by other users on
      // this system, while temporary downloads are marked as read-only.
      let options = {};
      if (isTemporaryDownload) {
        options.unixMode = 0o400;
        options.winAttributes = {readOnly: true};
      } else {
        options.unixMode = 0o666;
      }
      // On Unix, the umask of the process is respected.
      yield OS.File.setPermissions(aDownload.target.path, options);
    } catch (ex) {
      // We should report errors with making the permissions less restrictive
      // or marking the file as read-only on Unix and Mac, but this should not
      // prevent the download from completing.
      // The setPermissions API error EPERM is expected to occur when working
      // on a file system that does not support file permissions, like FAT32,
      // thus we don't report this error.
      if (!(ex instanceof OS.File.Error) || ex.unixErrno != OS.Constants.libc.EPERM) {
        Cu.reportError(ex);
      }
    }

    let aReferrer = null;
    if (aDownload.source.referrer) {
      aReferrer = NetUtil.newURI(aDownload.source.referrer);
    }

    gDownloadPlatform.downloadDone(NetUtil.newURI(aDownload.source.url),
                                   aReferrer,
                                   new FileUtils.File(aDownload.target.path),
                                   aDownload.contentType,
                                   aDownload.source.isPrivate);
  }),

  /**
   * Launches a file represented by the target of a download. This can
   * open the file with the default application for the target MIME type
   * or file extension, or with a custom application if
   * aDownload.launcherPath is set.
   *
   * @param    aDownload
   *           A Download object that contains the necessary information
   *           to launch the file. The relevant properties are: the target
   *           file, the contentType and the custom application chosen
   *           to launch it.
   *
   * @return {Promise}
   * @resolves When the instruction to launch the file has been
   *           successfully given to the operating system. Note that
   *           the OS might still take a while until the file is actually
   *           launched.
   * @rejects  JavaScript exception if there was an error trying to launch
   *           the file.
   */
  launchDownload: Task.async(function* (aDownload) {
    let file = new FileUtils.File(aDownload.target.path);

    // In case of a double extension, like ".tar.gz", we only
    // consider the last one, because the MIME service cannot
    // handle multiple extensions.
    let fileExtension = null, mimeInfo = null;
    let match = file.leafName.match(/\.([^.]+)$/);
    if (match) {
      fileExtension = match[1];
    }

#ifdef XP_WIN
    let isWindowsExe = fileExtension.toLowerCase() == "exe";
#else
    let isWindowsExe = false;
#endif

    // Ask for confirmation if the file is executable, except for .exe on
    // Windows where the operating system will show the prompt based on the
    // security zone.  We do this here, instead of letting the caller handle
    // the prompt separately in the user interface layer, for two reasons.  The
    // first is because of its security nature, so that add-ons cannot forget
    // to do this check.  The second is that the system-level security prompt
    // would be displayed at launch time in any case.
    if (file.isExecutable() && !isWindowsExe &&
        !(yield this.confirmLaunchExecutable(file.path))) {
      return;
    }

    try {
      // The MIME service might throw if contentType == "" and it can't find
      // a MIME type for the given extension, so we'll treat this case as
      // an unknown mimetype.
      mimeInfo = gMIMEService.getFromTypeAndExtension(aDownload.contentType,
                                                      fileExtension);
    } catch (e) { }

    if (aDownload.launcherPath) {
      if (!mimeInfo) {
        // This should not happen on normal circumstances because launcherPath
        // is only set when we had an instance of nsIMIMEInfo to retrieve
        // the custom application chosen by the user.
        throw new Error(
          "Unable to create nsIMIMEInfo to launch a custom application");
      }

      // Custom application chosen
      let localHandlerApp = Cc["@mozilla.org/uriloader/local-handler-app;1"]
                              .createInstance(Ci.nsILocalHandlerApp);
      localHandlerApp.executable = new FileUtils.File(aDownload.launcherPath);

      mimeInfo.preferredApplicationHandler = localHandlerApp;
      mimeInfo.preferredAction = Ci.nsIMIMEInfo.useHelperApp;

      this.launchFile(file, mimeInfo);
      return;
    }

#ifdef XP_WIN
    // When a file has no extension, and there's an executable file with the
    // same name in the same folder, the Windows shell can get confused.
    // For this reason, we show the file in the containing folder instead of
    // trying to open it.
    // We also don't trust mimeinfo; it could be a type we can forward to a
    // system handler, but it could also be an executable type, and we
    // don't have an exhaustive list with all of them.
    if (!fileExtension) {
      // We can't check for the existence of a same-name file with every
      // possible executable extension, so this is a catch-all.
      this.showContainingDirectory(aDownload.target.path);
      return;
    }
#endif

    // No custom application chosen, let's launch the file with the default
    // handler. First, let's try to launch it through the MIME service.
    if (mimeInfo) {
      mimeInfo.preferredAction = Ci.nsIMIMEInfo.useSystemDefault;

      try {
        this.launchFile(file, mimeInfo);
        return;
      } catch (ex) { }
    }

    // If it didn't work or if there was no MIME info available,
    // let's try to directly launch the file.
    try {
      this.launchFile(file);
      return;
    } catch (ex) { }

    // If our previous attempts failed, try sending it through
    // the system's external "file:" URL handler.
    gExternalProtocolService.loadUrl(NetUtil.newURI(file));
  }),

  /**
   * Asks for confirmation for launching the specified executable file. This
   * can be overridden by regression tests to avoid the interactive prompt.
   */
  confirmLaunchExecutable: Task.async(function* (path) {
    // We don't anchor the prompt to a specific window intentionally, not
    // only because this is the same behavior as the system-level prompt,
    // but also because the most recently active window is the right choice
    // in basically all cases.
    return yield DownloadUIHelper.getPrompter().confirmLaunchExecutable(path);
  }),

  /**
   * Launches the specified file, unless overridden by regression tests.
   */
  launchFile(file, mimeInfo) {
    if (mimeInfo) {
      mimeInfo.launchWithFile(file);
    } else {
      file.launch();
    }
  },

  /**
   * Shows the containing folder of a file.
   *
   * @param aFilePath
   *        The path to the file.
   *
   * @return {Promise}
   * @resolves When the instruction to open the containing folder has been
   *           successfully given to the operating system. Note that
   *           the OS might still take a while until the folder is actually
   *           opened.
   * @rejects  JavaScript exception if there was an error trying to open
   *           the containing folder.
   */
  showContainingDirectory: Task.async(function* (aFilePath) {
    let file = new FileUtils.File(aFilePath);

    try {
      // Show the directory containing the file and select the file.
      file.reveal();
      return;
    } catch (ex) { }

    // If reveal fails for some reason (e.g., it's not implemented on unix
    // or the file doesn't exist), try using the parent if we have it.
    let parent = file.parent;
    if (!parent) {
      throw new Error(
        "Unexpected reference to a top-level directory instead of a file");
    }

    try {
      // Open the parent directory to show where the file should be.
      parent.launch();
      return;
    } catch (ex) { }

    // If launch also fails (probably because it's not implemented), let
    // the OS handler try to open the parent.
    gExternalProtocolService.loadUrl(NetUtil.newURI(parent));
  }),

  /**
   * Calls the directory service, create a downloads directory and returns an
   * nsIFile for the downloads directory.
   *
   * @return {Promise}
   * @resolves The directory string path.
   */
  _createDownloadsDirectory(aName) {
    // We read the name of the directory from the list of translated strings
    // that is kept by the UI helper module, even if this string is not strictly
    // displayed in the user interface.
    let directoryPath = OS.Path.join(this._getDirectory(aName),
                                     DownloadUIHelper.strings.downloadsFolder);

    // Create the Downloads folder and ignore if it already exists.
    return OS.File.makeDir(directoryPath, { ignoreExisting: true })
                  .then(() => directoryPath);
  },

  /**
   * Returns the string path for the given directory service location name. This
   * can be overridden by regression tests to return the path of the system
   * temporary directory in all cases.
   */
  _getDirectory(name) {
    return Services.dirsvc.get(name, Ci.nsIFile).path;
  },

  /**
   * Register the downloads interruption observers.
   *
   * @param aList
   *        The public or private downloads list.
   * @param aIsPrivate
   *        True if the list is private, false otherwise.
   *
   * @return {Promise}
   * @resolves When the views and observers are added.
   */
  addListObservers(aList, aIsPrivate) {
    DownloadObserver.registerView(aList, aIsPrivate);
    if (!DownloadObserver.observersAdded) {
      DownloadObserver.observersAdded = true;
      for (let topic of kObserverTopics) {
        Services.obs.addObserver(DownloadObserver, topic, false);
      }
    }
    return Promise.resolve();
  },

  /**
   * Force a save on _store if it exists. Used to ensure downloads do not
   * persist after being sanitized.
   *
   * @return {Promise}
   * @resolves When _store.save() completes.
   */
  forceSave() {
    if (this._store) {
      return this._store.save();
    }
    return Promise.resolve();
  },

  /**
   * Checks if we have already imported (or attempted to import)
   * the downloads database from the previous SQLite storage.
   *
   * @return boolean True if we the previous DB was imported.
   */
  get _importedFromSqlite() {
    try {
      return Services.prefs.getBoolPref(kPrefImportedFromSqlite);
    } catch (ex) {
      return false;
    }
  },
};

////////////////////////////////////////////////////////////////////////////////
//// DownloadObserver

this.DownloadObserver = {
  /**
   * Flag to determine if the observers have been added previously.
   */
  observersAdded: false,

  /**
   * Timer used to delay restarting canceled downloads upon waking and returning
   * online.
   */
  _wakeTimer: null,

  /**
   * Set that contains the in progress publics downloads.
   * It's kept updated when a public download is added, removed or changes its
   * properties.
   */
  _publicInProgressDownloads: new Set(),

  /**
   * Set that contains the in progress private downloads.
   * It's kept updated when a private download is added, removed or changes its
   * properties.
   */
  _privateInProgressDownloads: new Set(),

  /**
   * Set that contains the downloads that have been canceled when going offline
   * or to sleep. These are started again when returning online or waking. This
   * list is not persisted so when exiting and restarting, the downloads will not
   * be started again.
   */
  _canceledOfflineDownloads: new Set(),

  /**
   * Registers a view that updates the corresponding downloads state set, based
   * on the aIsPrivate argument. The set is updated when a download is added,
   * removed or changes its properties.
   *
   * @param aList
   *        The public or private downloads list.
   * @param aIsPrivate
   *        True if the list is private, false otherwise.
   */
  registerView: function DO_registerView(aList, aIsPrivate) {
    let downloadsSet = aIsPrivate ? this._privateInProgressDownloads
                                  : this._publicInProgressDownloads;
    let downloadsView = {
      onDownloadAdded: aDownload => {
        if (!aDownload.stopped) {
          downloadsSet.add(aDownload);
        }
      },
      onDownloadChanged: aDownload => {
        if (aDownload.stopped) {
          downloadsSet.delete(aDownload);
        } else {
          downloadsSet.add(aDownload);
        }
      },
      onDownloadRemoved: aDownload => {
        downloadsSet.delete(aDownload);
        // The download must also be removed from the canceled when offline set.
        this._canceledOfflineDownloads.delete(aDownload);
      }
    };

    // We register the view asynchronously.
    aList.addView(downloadsView).then(null, Cu.reportError);
  },

  /**
   * Wrapper that handles the test mode before calling the prompt that display
   * a warning message box that informs that there are active downloads,
   * and asks whether the user wants to cancel them or not.
   *
   * @param aCancel
   *        The observer notification subject.
   * @param aDownloadsCount
   *        The current downloads count.
   * @param aPrompter
   *        The prompter object that shows the confirm dialog.
   * @param aPromptType
   *        The type of prompt notification depending on the observer.
   */
  _confirmCancelDownloads: function DO_confirmCancelDownload(
    aCancel, aDownloadsCount, aPrompter, aPromptType) {
    // If user has already dismissed the request, then do nothing.
    if ((aCancel instanceof Ci.nsISupportsPRBool) && aCancel.data) {
      return;
    }
    // Handle test mode
    if (gCombinedDownloadIntegration._testPromptDownloads) {
      gCombinedDownloadIntegration._testPromptDownloads = aDownloadsCount;
      return;
    }

    aCancel.data = aPrompter.confirmCancelDownloads(aDownloadsCount, aPromptType);
  },

  /**
   * Resume all downloads that were paused when going offline, used when waking
   * from sleep or returning from being offline.
   */
  _resumeOfflineDownloads: function DO_resumeOfflineDownloads() {
    this._wakeTimer = null;

    for (let download of this._canceledOfflineDownloads) {
      download.start().catch(() => {});
    }
  },

  ////////////////////////////////////////////////////////////////////////////
  //// nsIObserver

  observe: function DO_observe(aSubject, aTopic, aData) {
    let downloadsCount;
    let p = DownloadUIHelper.getPrompter();
    switch (aTopic) {
      case "quit-application-requested":
        downloadsCount = this._publicInProgressDownloads.size +
                         this._privateInProgressDownloads.size;
        this._confirmCancelDownloads(aSubject, downloadsCount, p, p.ON_QUIT);
        break;
      case "offline-requested":
        downloadsCount = this._publicInProgressDownloads.size +
                         this._privateInProgressDownloads.size;
        this._confirmCancelDownloads(aSubject, downloadsCount, p, p.ON_OFFLINE);
        break;
      case "last-pb-context-exiting":
        downloadsCount = this._privateInProgressDownloads.size;
        this._confirmCancelDownloads(aSubject, downloadsCount, p,
                                     p.ON_LEAVE_PRIVATE_BROWSING);
        break;
      case "last-pb-context-exited":
        let promise = Task.spawn(function() {
          let list = yield Downloads.getList(Downloads.PRIVATE);
          let downloads = yield list.getAll();

          // We can remove the downloads and finalize them in parallel.
          for (let download of downloads) {
            list.remove(download).then(null, Cu.reportError);
            download.finalize(true).then(null, Cu.reportError);
          }
        });
        // Handle test mode
        if (gCombinedDownloadIntegration._testResolveClearPrivateList) {
          gCombinedDownloadIntegration._testResolveClearPrivateList(promise);
        } else {
          promise.catch(ex => Cu.reportError(ex));
        }
        break;
      case "sleep_notification":
      case "suspend_process_notification":
      case "network:offline-about-to-go-offline":
        for (let download of this._publicInProgressDownloads) {
          download.cancel();
          this._canceledOfflineDownloads.add(download);
        }
        for (let download of this._privateInProgressDownloads) {
          download.cancel();
          this._canceledOfflineDownloads.add(download);
        }
        break;
      case "wake_notification":
      case "resume_process_notification":
        let wakeDelay = 10000;
        try {
          wakeDelay = Services.prefs.getIntPref("browser.download.manager.resumeOnWakeDelay");
        } catch(e) {}

        if (wakeDelay >= 0) {
          this._wakeTimer = new Timer(this._resumeOfflineDownloads.bind(this), wakeDelay,
                                      Ci.nsITimer.TYPE_ONE_SHOT);
        }
        break;
      case "network:offline-status-changed":
        if (aData == "online") {
          this._resumeOfflineDownloads();
        }
        break;
      // We need to unregister observers explicitly before we reach the
      // "xpcom-shutdown" phase, otherwise observers may be notified when some
      // required services are not available anymore. We can't unregister
      // observers on "quit-application", because this module is also loaded
      // during "make package" automation, and the quit notification is not sent
      // in that execution environment (bug 973637).
      case "xpcom-will-shutdown":
        for (let topic of kObserverTopics) {
          Services.obs.removeObserver(this, topic);
        }
        break;
    }
  },

  ////////////////////////////////////////////////////////////////////////////
  //// nsISupports

  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver])
};

////////////////////////////////////////////////////////////////////////////////
//// DownloadHistoryObserver

#ifdef MOZ_PLACES
/**
 * Registers a Places observer so that operations on download history are
 * reflected on the provided list of downloads.
 *
 * You do not need to keep a reference to this object in order to keep it alive,
 * because the history service already keeps a strong reference to it.
 *
 * @param aList
 *        DownloadList object linked to this observer.
 */
this.DownloadHistoryObserver = function (aList)
{
  this._list = aList;
  PlacesUtils.history.addObserver(this, false);
}

this.DownloadHistoryObserver.prototype = {
  /**
   * DownloadList object linked to this observer.
   */
  _list: null,

  ////////////////////////////////////////////////////////////////////////////
  //// nsISupports

  QueryInterface: XPCOMUtils.generateQI([Ci.nsINavHistoryObserver]),

  ////////////////////////////////////////////////////////////////////////////
  //// nsINavHistoryObserver

  onDeleteURI: function DL_onDeleteURI(aURI, aGUID) {
    this._list.removeFinished(download => aURI.equals(NetUtil.newURI(
                                                      download.source.url)));
  },

  onClearHistory: function DL_onClearHistory() {
    this._list.removeFinished();
  },

  onTitleChanged: function () {},
  onBeginUpdateBatch: function () {},
  onEndUpdateBatch: function () {},
  onVisit: function () {},
  onPageChanged: function () {},
  onDeleteVisits: function () {},
};
#else
/**
 * Empty implementation when we have no Places support, for example on B2G.
 */
this.DownloadHistoryObserver = function (aList) {}
#endif

////////////////////////////////////////////////////////////////////////////////
//// DownloadAutoSaveView

/**
 * This view can be added to a DownloadList object to trigger a save operation
 * in the given DownloadStore object when a relevant change occurs.  You should
 * call the "initialize" method in order to register the view and load the
 * current state from disk.
 *
 * You do not need to keep a reference to this object in order to keep it alive,
 * because the DownloadList object already keeps a strong reference to it.
 *
 * @param aList
 *        The DownloadList object on which the view should be registered.
 * @param aStore
 *        The DownloadStore object used for saving.
 */
this.DownloadAutoSaveView = function (aList, aStore)
{
  this._list = aList;
  this._store = aStore;
  this._downloadsMap = new Map();
  this._writer = new DeferredTask(() => this._store.save(), kSaveDelayMs);
  AsyncShutdown.profileBeforeChange.addBlocker("DownloadAutoSaveView: writing data",
                                               () => this._writer.finalize());
}

this.DownloadAutoSaveView.prototype = {
  /**
   * DownloadList object linked to this view.
   */
  _list: null,

  /**
   * The DownloadStore object used for saving.
   */
  _store: null,

  /**
   * True when the initial state of the downloads has been loaded.
   */
  _initialized: false,

  /**
   * Registers the view and loads the current state from disk.
   *
   * @return {Promise}
   * @resolves When the view has been registered.
   * @rejects JavaScript exception.
   */
  initialize: function ()
  {
    // We set _initialized to true after adding the view, so that
    // onDownloadAdded doesn't cause a save to occur.
    return this._list.addView(this).then(() => this._initialized = true);
  },

  /**
   * This map contains only Download objects that should be saved to disk, and
   * associates them with the result of their getSerializationHash function, for
   * the purpose of detecting changes to the relevant properties.
   */
  _downloadsMap: null,

  /**
   * DeferredTask for the save operation.
   */
  _writer: null,

  /**
   * Called when the list of downloads changed, this triggers the asynchronous
   * serialization of the list of downloads.
   */
  saveSoon: function ()
  {
    this._writer.arm();
  },

  //////////////////////////////////////////////////////////////////////////////
  //// DownloadList view

  onDownloadAdded: function (aDownload)
  {
    if (gCombinedDownloadIntegration.shouldPersistDownload(aDownload)) {
      this._downloadsMap.set(aDownload, aDownload.getSerializationHash());
      if (this._initialized) {
        this.saveSoon();
      }
    }
  },

  onDownloadChanged: function (aDownload)
  {
    if (!gCombinedDownloadIntegration.shouldPersistDownload(aDownload)) {
      if (this._downloadsMap.has(aDownload)) {
        this._downloadsMap.delete(aDownload);
        this.saveSoon();
      }
      return;
    }

    let hash = aDownload.getSerializationHash();
    if (this._downloadsMap.get(aDownload) != hash) {
      this._downloadsMap.set(aDownload, hash);
      this.saveSoon();
    }
  },

  onDownloadRemoved: function (aDownload)
  {
    if (this._downloadsMap.has(aDownload)) {
      this._downloadsMap.delete(aDownload);
      this.saveSoon();
    }
  },
};