Add a StateManager for managing hotwording state based on various factors

chrome/browser/resources/hotword/state_manager.js

Index: chrome/browser/resources/hotword/state_manager.js
diff --git a/chrome/browser/resources/hotword/state_manager.js b/chrome/browser/resources/hotword/state_manager.js
new file mode 100644
index 0000000000000000000000000000000000000000..25000e8c7cec198931b915321c4e59f871ae5cd5
--- /dev/null
+++ b/chrome/browser/resources/hotword/state_manager.js
@@ -0,0 +1,193 @@
+// Copyright (c) 2014 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.
+
+/**
+ * @fileoverview Class to manage hotwording state.

[Dan Beam, 2014/08/27 20:08:37]

nit: if it fits, one-liner -- /** ... */

[Dan Beam, 2014/08/27 20:08:37]

this isn't a particularly useful comment and should probably be close to
@constructor for StateManager if it's class-specific

[Anand Mistry (off Chromium), 2014/08/28 00:59:26]

Done.

+ */
+

[Dan Beam, 2014/08/27 20:08:37]

remove \n

[Anand Mistry (off Chromium), 2014/08/28 00:59:26]

Done.

+cr.define('hotword', function() {
+  'use strict';
+
+  /**
+   * @constructor
+   * @struct
+   */
+  function StateManager() {
+    /**
+     * Current state.
+     * @private {hotword.StateManager.State_}
+     */
+    this.state_ = State_.STOPPED;
+
+    /**
+     * Current hotwording status.
+     * @private {?chrome.hotwordPrivate.StatusDetails}
+     */
+    this.hotwordStatus_ = null;
+
+    /**
+     * NaCl plugin manager.
+     * @private {?hotword.NaClManager}
+     */
+    this.pluginManager_ = null;
+
+    // Get the initial status.
+    chrome.hotwordPrivate.getStatus(this.handleStatus_.bind(this));
+  }
+
+  /**
+   * @enum {number}
+   * @private
+   */
+  StateManager.State_ = {
+    STOPPED: 0,
+    STARTING: 1,
+    RUNNING: 2,
+    ERROR: 3,
+  };
+  var State_ = StateManager.State_;
+
+  /**
+   * Request status details update. Intended to be called from the
+   * hotwordPrivate.onEnabledChanged() event.
+   */
+  StateManager.prototype.updateStatus = function() {

[Dan Beam, 2014/08/27 20:08:37]

nit: just assign whole prototype

  StateManager.prototype = {
    ...
    updateState: function() {
      ...
    },
    ...
  };

[Anand Mistry (off Chromium), 2014/08/28 00:59:25]

Done.

+    chrome.hotwordPrivate.getStatus(this.handleStatus_.bind(this));
+  };
+
+  /**
+   * Callback for hotwordPrivate.getStatus() function.
+   * @param {chrome.hotwordPrivate.StatusDetails} status Current hotword status.
+   * @private
+   */
+  StateManager.prototype.handleStatus_ = function(status) {
+    this.hotwordStatus_ = status;
+    this.updateStateFromStatus_();
+  };
+
+  /**
+   * Updates state based on the current status.
+   * @private
+   */
+  StateManager.prototype.updateStateFromStatus_ = function() {
+    if (this.hotwordStatus_.enabled) {
+      // Hotwording is enabled.
+      // TODO(amistry): Have a separate alwaysOnEnabled flag. For now, treat
+      // "enabled" as "always on enabled".
+      this.startDetector_();
+    } else {
+      // Not enabled. Shut down if running.
+      this.shutdownDetector_();
+    }
+  };
+
+  /**
+   * Starts the hotword detector.
+   * @private
+   */
+  StateManager.prototype.startDetector_ = function() {
+    // Last attempt to start detector resulted in an error.
+    if (this.state_ == State_.ERROR) {
+      // TODO(amistry): Do some error rate tracking here and disable the
+      // extension if we error too often.
+    }
+
+    if (!this.pluginManager_) {
+      this.state_ = State_.STARTING;
+      this.pluginManager_ = new hotword.NaClManager();
+      this.pluginManager_.addEventListener(hotword.constants.Event.READY,
+                                           this.onReady_.bind(this));
+      this.pluginManager_.addEventListener(hotword.constants.Event.ERROR,
+                                           this.onError_.bind(this));
+      this.pluginManager_.addEventListener(hotword.constants.Event.TRIGGER,
+                                           this.onTrigger_.bind(this));
+      chrome.runtime.getPlatformInfo(function(platform) {
+        var naclArch = platform.nacl_arch;
+
+        // googDucking set to false so that audio output level from other tabs
+        // is not affected when hotword is enabled. https://crbug.com/357773
+        // content/common/media/media_stream_options.cc
+        var constraints = /** @type {googMediaStreamConstraints} */
+            ({audio: {optional: [{googDucking: false}]}});
+        navigator.webkitGetUserMedia(
+            /** @type {MediaStreamConstraints} */ (constraints),
+            function(stream) {
+              if (!this.pluginManager_.initialize(naclArch, stream)) {
+                this.state_ = State_.ERROR;
+                this.shutdownPluginManager_();
+              }
+            }.bind(this),
+            function(error) {
+              this.state_ = State_.ERROR;
+              this.pluginManager_ = null;
+            }.bind(this));
+      }.bind(this));
+    } else if (this.state_ != State_.STARTING) {
+      // Don't try to start a starting detector.
+      this.state_ = State_.RUNNING;
+      this.pluginManager_.startRecognizer();
+    }
+  };
+
+  /**
+   * Shuts down and removes the plugin manager, if it exists.
+   * @private
+   */
+  StateManager.prototype.shutdownPluginManager_ = function() {
+    if (this.pluginManager_) {
+      this.pluginManager_.shutdown();
+      this.pluginManager_ = null;
+    }
+  };
+
+  /**
+   * Shuts down the hotword detector.
+   * @private
+   */
+  StateManager.prototype.shutdownDetector_ = function() {
+    this.state_ = State_.STOPPED;
+    this.shutdownPluginManager_();
+  };
+
+  /**
+   * Handle the hotword plugin being ready to start.
+   * @private
+   */
+  StateManager.prototype.onReady_ = function() {
+    if (this.state_ != State_.STARTING) {
+      // Shouldn't be running while starting.

[Dan Beam, 2014/08/27 20:08:37]

this comment is confusing because you say the code is starting inside a state !=
STARTING block

[Anand Mistry (off Chromium), 2014/08/28 00:59:26]

Done.

+      assert(this.state_ != State_.RUNNING);
+      this.shutdownPluginManager_();
+      return;
+    }
+    this.state_ = State_.RUNNING;
+    this.pluginManager_.startRecognizer();
+  };
+
+  /**
+   * Handle an error from the hotword plugin.
+   * @private
+   */
+  StateManager.prototype.onError_ = function() {
+    this.state_ = State_.ERROR;
+    this.shutdownPluginManager_();
+  };
+
+  /**
+   * Handle hotword triggering.
+   * @private
+   */
+  StateManager.prototype.onTrigger_ = function() {
+    assert(this.pluginManager_);
+    // Detector implicitly stops when the hotword is detected.
+    this.state_ = State_.STOPPED;
+
+    chrome.hotwordPrivate.notifyHotwordRecognition('search', function() {});
+  };
+
+  return {
+    StateManager: StateManager
+  };
+

[Dan Beam, 2014/08/27 20:08:37]

nit: remove \n

[Anand Mistry (off Chromium), 2014/08/28 00:59:25]

Done.

+});