Implement chrome.downloads.onDeterminingFilename()

chrome/renderer/resources/extensions/downloads_custom_bindings.js

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Custom bindings for the downloads API.
+
+var downloadsNatives = requireNative('downloads');
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
+var sendRequest = require('sendRequest').sendRequest;
+
+function DownloadsEvent(eventName,
+                        opt_argSchemas,
+                        ignored_extraArgSchemas,
+                        opt_eventOptions) {
+  if (typeof eventName != 'string')
+    throw new Error('chrome.DownloadsEvent requires an event name.');
+  // onDeterminingFilename is the only special event in chrome.downloads.
+  if (eventName != 'downloads.onDeterminingFilename') {
+    return new chrome.Event(eventName, opt_argSchemas, opt_eventOptions);
+  }
+
+  this.eventName_ = eventName;
+  // ExtensionDownloadsEventRouter can't send a SuggestFilenameCallback, so
+  // slice it out of the event schema, leaving only the DownloadItem.
+  this.argSchemas_ = opt_argSchemas.slice(0, 1);
+  this.eventOptions_ = chromeHidden.parseEventOptions(opt_eventOptions);
+  this.subEvents_ = [];
+}
+
+// Test if the given callback is registered for this event.
+DownloadsEvent.prototype.hasListener = function(cb) {
+  if (!this.eventOptions_.supportsListeners)
+    throw new Error('This event does not support listeners.');
+  return this.findListener_(cb) > -1;
+};
+
+// Test if any callbacks are registered for this event.
+DownloadsEvent.prototype.hasListeners = function() {
+  if (!this.eventOptions_.supportsListeners)
+    throw new Error('This event does not support listeners.');
+  return (this.subEvents_.length > 0);
+};
+
+DownloadsEvent.prototype.addListener = function(cb) {
+  if (!this.eventOptions_.supportsListeners)
+    throw new Error('This event does not support listeners.');
+  var entry = {callback: cb};
+  entry.determiner_id = downloadsNatives.GetFilenameDeterminerId();
+  entry.subEvent = new chrome.Event(
+      this.eventName_ + '/' + entry.determiner_id, this.argSchemas_);
+  entry.subEventCallback = function() {
+    var downloadItem = arguments[0];
+    // Copy the id so that extensions can't change downloadItem.id.
+    var downloadId = downloadItem.id;
+    var suggestable = true;
+    function suggest(result) {
+      if (!suggestable)
+        return;

[Matt Perry, 2013/02/22 22:53:06]

Also print an error (console.error) explaining how suggest can only be called
once.

+      suggestable = false;
+      if ((typeof(result) == 'object') &&
+          result.filename &&
+          (typeof(result.filename) == 'string') &&
+          ((result.overwrite === undefined) ||
+           (typeof(result.overwrite) == 'boolean'))) {
+        chromeHidden.internalAPIs.downloadsInternal.determineFilename(
+            entry.determiner_id,
+            downloadId,
+            result.filename,
+            result.overwrite || false);
+      } else {
+        chromeHidden.internalAPIs.downloadsInternal.determineFilename(
+            entry.determiner_id,
+            downloadId);
+      }
+    }
+    try {
+      if (cb.apply(null, [downloadItem, suggest]) !== true)
+        suggest();
+    } catch (e) {
+      suggest();
+      throw e;
+    }
+  };
+  this.subEvents_.push(entry);
+  entry.subEvent.addListener(entry.subEventCallback);
+};
+
+DownloadsEvent.prototype.removeListener = function(cb) {
+  if (!this.eventOptions_.supportsListeners)
+    throw new Error('This event does not support listeners.');
+  var idx;
+  while ((idx = this.findListener_(cb)) >= 0) {
+    var e = this.subEvents_[idx];
+    e.subEvent.removeListener(e.subEventCallback);
+    if (e.subEvent.hasListeners()) {
+      console.error('Internal error: subEvent has orphaned listeners.');
+    }
+    this.subEvents_.splice(idx, 1);
+  }
+};
+
+DownloadsEvent.prototype.findListener_ = function(cb) {
+  for (var i in this.subEvents_) {
+    var e = this.subEvents_[i];
+    if (e.callback === cb) {
+      if (e.subEvent.findListener_(e.subEventCallback) > -1)
+        return i;
+      console.error('Internal error: subEvent has no callback.');
+    }
+  }
+
+  return -1;
+};
+
+DownloadsEvent.prototype.addRules = function(rules, opt_cb) {
+  if (!this.eventOptions_.supportsRules)
+    throw new Error('This event does not support rules.');
+  this.eventForRules_.addRules(rules, opt_cb);
+}
+
+DownloadsEvent.prototype.removeRules = function(ruleIdentifiers, opt_cb) {
+  if (!this.eventOptions_.supportsRules)
+    throw new Error('This event does not support rules.');
+  this.eventForRules_.removeRules(ruleIdentifiers, opt_cb);
+}
+
+DownloadsEvent.prototype.getRules = function(ruleIdentifiers, cb) {
+  if (!this.eventOptions_.supportsRules)
+    throw new Error('This event does not support rules.');
+  this.eventForRules_.getRules(ruleIdentifiers, cb);
+}
+
+chromeHidden.registerCustomEvent('downloads', DownloadsEvent);