/* 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/. */

"use strict";

var Cc = SpecialPowers.Cc;
var Ci = SpecialPowers.Ci;

// Specifies whether we are using fake streams to run this automation
var FAKE_ENABLED = true;
var TEST_AUDIO_FREQ = 1000;
try {
  var audioDevice = SpecialPowers.getCharPref('media.audio_loopback_dev');
  var videoDevice = SpecialPowers.getCharPref('media.video_loopback_dev');
  dump('TEST DEVICES: Using media devices:\n');
  dump('audio: ' + audioDevice + '\nvideo: ' + videoDevice + '\n');
  FAKE_ENABLED = false;
  TEST_AUDIO_FREQ = 440;
} catch (e) {
  dump('TEST DEVICES: No test devices found (in media.{audio,video}_loopback_dev, using fake streams.\n');
  FAKE_ENABLED = true;
}

/**
 * This class provides helpers around analysing the audio content in a stream
 * using WebAudio AnalyserNodes.
 *
 * @constructor
 * @param {object} stream
 *                 A MediaStream object whose audio track we shall analyse.
 */
function AudioStreamAnalyser(ac, stream) {
  this.audioContext = ac;
  this.stream = stream;
  this.sourceNodes = [];
  this.analyser = this.audioContext.createAnalyser();
  // Setting values lower than default for speedier testing on emulators
  this.analyser.smoothingTimeConstant = 0.2;
  this.analyser.fftSize = 1024;
  this.connectTrack = t => {
    let source = this.audioContext.createMediaStreamSource(new MediaStream([t]));
    this.sourceNodes.push(source);
    source.connect(this.analyser);
  };
  this.stream.getAudioTracks().forEach(t => this.connectTrack(t));
  this.onaddtrack = ev => this.connectTrack(ev.track);
  this.stream.addEventListener("addtrack", this.onaddtrack);
  this.data = new Uint8Array(this.analyser.frequencyBinCount);
}

AudioStreamAnalyser.prototype = {
  /**
   * Get an array of frequency domain data for our stream's audio track.
   *
   * @returns {array} A Uint8Array containing the frequency domain data.
   */
  getByteFrequencyData: function() {
    this.analyser.getByteFrequencyData(this.data);
    return this.data;
  },

  /**
   * Append a canvas to the DOM where the frequency data are drawn.
   * Useful to debug tests.
   */
  enableDebugCanvas: function() {
    var cvs = this.debugCanvas = document.createElement("canvas");
    const content = document.getElementById("content");
    content.insertBefore(cvs, content.children[0]);

    // Easy: 1px per bin
    cvs.width = this.analyser.frequencyBinCount;
    cvs.height = 128;
    cvs.style.border = "1px solid red";

    var c = cvs.getContext('2d');
    c.fillStyle = 'black';

    var self = this;
    function render() {
      c.clearRect(0, 0, cvs.width, cvs.height);
      var array = self.getByteFrequencyData();
      for (var i = 0; i < array.length; i++) {
        c.fillRect(i, (cvs.height - (array[i] / 2)), 1, cvs.height);
      }
      if (!cvs.stopDrawing) {
        requestAnimationFrame(render);
      }
    }
    requestAnimationFrame(render);
  },

  /**
   * Stop drawing of and remove the debug canvas from the DOM if it was
   * previously added.
   */
  disableDebugCanvas: function() {
    if (!this.debugCanvas || !this.debugCanvas.parentElement) {
      return;
    }

    this.debugCanvas.stopDrawing = true;
    this.debugCanvas.parentElement.removeChild(this.debugCanvas);
  },

  /**
   * Disconnects the input stream from our internal analyser node.
   * Call this to reduce main thread processing, mostly necessary on slow
   * devices.
   */
  disconnect: function() {
    this.disableDebugCanvas();
    this.sourceNodes.forEach(n => n.disconnect());
    this.sourceNodes = [];
    this.stream.removeEventListener("addtrack", this.onaddtrack);
  },

  /**
   * Return a Promise, that will be resolved when the function passed as
   * argument, when called, returns true (meaning the analysis was a
   * success).
   *
   * @param {function} analysisFunction
   *        A fonction that performs an analysis, and returns true if the
   *        analysis was a success (i.e. it found what it was looking for)
   */
  waitForAnalysisSuccess: function(analysisFunction) {
    var self = this;
    return new Promise((resolve, reject) => {
      function analysisLoop() {
        var success = analysisFunction(self.getByteFrequencyData());
        if (success) {
          resolve();
          return;
        }
        // else, we need more time
        requestAnimationFrame(analysisLoop);
      }
      // We need to give the Analyser some time to start gathering data.
      wait(200).then(analysisLoop);
    });
  },

  /**
   * Return the FFT bin index for a given frequency.
   *
   * @param {double} frequency
   *        The frequency for whicht to return the bin number.
   * @returns {integer} the index of the bin in the FFT array.
   */
  binIndexForFrequency: function(frequency) {
    return 1 + Math.round(frequency *
                          this.analyser.fftSize /
                          this.audioContext.sampleRate);
  },

  /**
   * Reverse operation, get the frequency for a bin index.
   *
   * @param {integer} index an index in an FFT array
   * @returns {double} the frequency for this bin
   */
  frequencyForBinIndex: function(index) {
    return (index - 1) *
           this.audioContext.sampleRate /
           this.analyser.fftSize;
  }
};

/**
 * Creates a MediaStream with an audio track containing a sine tone at the
 * given frequency.
 *
 * @param {AudioContext} ac
 *        AudioContext in which to create the OscillatorNode backing the stream
 * @param {double} frequency
 *        The frequency in Hz of the generated sine tone
 * @returns {MediaStream} the MediaStream containing sine tone audio track
 */
function createOscillatorStream(ac, frequency) {
  var osc = ac.createOscillator();
  osc.frequency.value = frequency;

  var oscDest = ac.createMediaStreamDestination();
  osc.connect(oscDest);
  osc.start();
  return oscDest.stream;
}

/**
 * Create the necessary HTML elements for head and body as used by Mochitests
 *
 * @param {object} meta
 *        Meta information of the test
 * @param {string} meta.title
 *        Description of the test
 * @param {string} [meta.bug]
 *        Bug the test was created for
 * @param {boolean} [meta.visible=false]
 *        Visibility of the media elements
 */
function realCreateHTML(meta) {
  var test = document.getElementById('test');

  // Create the head content
  var elem = document.createElement('meta');
  elem.setAttribute('charset', 'utf-8');
  document.head.appendChild(elem);

  var title = document.createElement('title');
  title.textContent = meta.title;
  document.head.appendChild(title);

  // Create the body content
  var anchor = document.createElement('a');
  anchor.textContent = meta.title;
  if (meta.bug) {
    anchor.setAttribute('href', 'https://bugzilla.mozilla.org/show_bug.cgi?id=' + meta.bug);
  } else {
    anchor.setAttribute('target', '_blank');
  }

  document.body.insertBefore(anchor, test);

  var display = document.createElement('p');
  display.setAttribute('id', 'display');
  document.body.insertBefore(display, test);

  var content = document.createElement('div');
  content.setAttribute('id', 'content');
  content.style.display = meta.visible ? 'block' : "none";
  document.body.appendChild(content);
}

/**
 * Creates an element of the given type, assigns the given id, sets the controls
 * and autoplay attributes and adds it to the content node.
 *
 * @param {string} type
 *        Defining if we should create an "audio" or "video" element
 * @param {string} id
 *        A string to use as the element id.
 */
function createMediaElement(type, id) {
  const element = document.createElement(type);
  element.setAttribute('id', id);
  element.setAttribute('height', 100);
  element.setAttribute('width', 150);
  element.setAttribute('controls', 'controls');
  element.setAttribute('autoplay', 'autoplay');
  document.getElementById('content').appendChild(element);

  return element;
}

/**
 * Returns an existing element for the given track with the given idPrefix,
 * as it was added by createMediaElementForTrack().
 *
 * @param {MediaStreamTrack} track
 *        Track used as the element's source.
 * @param {string} idPrefix
 *        A string to use as the element id. The track id will also be appended.
 */
function getMediaElementForTrack(track, idPrefix) {
  return document.getElementById(idPrefix + '_' + track.id);
}

/**
 * Create a media element with a track as source and attach it to the content
 * node.
 *
 * @param {MediaStreamTrack} track
 *        Track for use as source.
 * @param {string} idPrefix
 *        A string to use as the element id. The track id will also be appended.
 * @return {HTMLMediaElement} The created HTML media element
 */
function createMediaElementForTrack(track, idPrefix) {
  const id = idPrefix + '_' + track.id;
  const element = createMediaElement(track.kind, id);
  element.srcObject = new MediaStream([track]);

  return element;
}


/**
 * Wrapper function for mediaDevices.getUserMedia used by some tests. Whether
 * to use fake devices or not is now determined in pref further below instead.
 *
 * @param {Dictionary} constraints
 *        The constraints for this mozGetUserMedia callback
 */
function getUserMedia(constraints) {
  info("Call getUserMedia for " + JSON.stringify(constraints));
  return navigator.mediaDevices.getUserMedia(constraints)
    .then(stream => (checkMediaStreamTracks(constraints, stream), stream));
}

// These are the promises we use to track that the prerequisites for the test
// are in place before running it.
var setTestOptions;
var testConfigured = new Promise(r => setTestOptions = r);

function setupEnvironment() {
  if (!window.SimpleTest) {
    // Running under Steeplechase
    return;
  }

  var defaultMochitestPrefs = {
    'set': [
      ['media.peerconnection.enabled', true],
      ['media.peerconnection.identity.enabled', true],
      ['media.peerconnection.identity.timeout', 120000],
      ['media.peerconnection.ice.stun_client_maximum_transmits', 14],
      ['media.peerconnection.ice.trickle_grace_period', 30000],
      ['media.navigator.permission.disabled', true],
      ['media.navigator.streams.fake', FAKE_ENABLED],
      ['media.getusermedia.screensharing.enabled', true],
      ['media.getusermedia.screensharing.allowed_domains', "mochi.test"],
      ['media.getusermedia.audiocapture.enabled', true],
      ['media.recorder.audio_node.enabled', true]
    ]
  };

  const isAndroid = !!navigator.userAgent.includes("Android");

  if (isAndroid) {
    defaultMochitestPrefs.set.push(
      ["media.navigator.video.default_width", 320],
      ["media.navigator.video.default_height", 240],
      ["media.navigator.video.max_fr", 10],
      ["media.autoplay.enabled", true]
    );
  }

  // Running as a Mochitest.
  SimpleTest.requestFlakyTimeout("WebRTC inherently depends on timeouts");
  window.finish = () => SimpleTest.finish();
  SpecialPowers.pushPrefEnv(defaultMochitestPrefs, setTestOptions);

  // We don't care about waiting for this to complete, we just want to ensure
  // that we don't build up a huge backlog of GC work.
  SpecialPowers.exactGC();
}

// This is called by steeplechase; which provides the test configuration options
// directly to the test through this function.  If we're not on steeplechase,
// the test is configured directly and immediately.
function run_test(is_initiator,timeout) {
  var options = { is_local: is_initiator,
                  is_remote: !is_initiator };

  setTimeout(() => {
    unexpectedEventArrived(new Error("PeerConnectionTest timed out after "+timeout+"s"));
  }, timeout);

  // Also load the steeplechase test code.
  var s = document.createElement("script");
  s.src = "/test.js";
  s.onload = () => setTestOptions(options);
  document.head.appendChild(s);
}

function runTestWhenReady(testFunc) {
  setupEnvironment();
  return testConfigured.then(options => testFunc(options))
    .catch(e => {
      ok(false, 'Error executing test: ' + e +
        ((typeof e.stack === 'string') ?
        (' ' + e.stack.split('\n').join(' ... ')) : ''));
      SimpleTest.finish();
    });
}


/**
 * Checks that the media stream tracks have the expected amount of tracks
 * with the correct kind and id based on the type and constraints given.
 *
 * @param {Object} constraints specifies whether the stream should have
 *                             audio, video, or both
 * @param {String} type the type of media stream tracks being checked
 * @param {sequence<MediaStreamTrack>} mediaStreamTracks the media stream
 *                                     tracks being checked
 */
function checkMediaStreamTracksByType(constraints, type, mediaStreamTracks) {
  if (constraints[type]) {
    is(mediaStreamTracks.length, 1, 'One ' + type + ' track shall be present');

    if (mediaStreamTracks.length) {
      is(mediaStreamTracks[0].kind, type, 'Track kind should be ' + type);
      ok(mediaStreamTracks[0].id, 'Track id should be defined');
    }
  } else {
    is(mediaStreamTracks.length, 0, 'No ' + type + ' tracks shall be present');
  }
}

/**
 * Check that the given media stream contains the expected media stream
 * tracks given the associated audio & video constraints provided.
 *
 * @param {Object} constraints specifies whether the stream should have
 *                             audio, video, or both
 * @param {MediaStream} mediaStream the media stream being checked
 */
function checkMediaStreamTracks(constraints, mediaStream) {
  checkMediaStreamTracksByType(constraints, 'audio',
    mediaStream.getAudioTracks());
  checkMediaStreamTracksByType(constraints, 'video',
    mediaStream.getVideoTracks());
}

/**
 * Check that a media stream contains exactly a set of media stream tracks.
 *
 * @param {MediaStream} mediaStream the media stream being checked
 * @param {Array} tracks the tracks that should exist in mediaStream
 * @param {String} [message] an optional message to pass to asserts
 */
function checkMediaStreamContains(mediaStream, tracks, message) {
  message = message ? (message + ": ") : "";
  tracks.forEach(t => ok(mediaStream.getTrackById(t.id),
                         message + "MediaStream " + mediaStream.id +
                         " contains track " + t.id));
  is(mediaStream.getTracks().length, tracks.length,
     message + "MediaStream " + mediaStream.id + " contains no extra tracks");
}

function checkMediaStreamCloneAgainstOriginal(clone, original) {
  isnot(clone.id.length, 0, "Stream clone should have an id string");
  isnot(clone, original,
        "Stream clone should be different from the original");
  isnot(clone.id, original.id,
        "Stream clone's id should be different from the original's");
  is(clone.getAudioTracks().length, original.getAudioTracks().length,
     "All audio tracks should get cloned");
  is(clone.getVideoTracks().length, original.getVideoTracks().length,
     "All video tracks should get cloned");
  is(clone.active, original.active,
     "Active state should be preserved");
  original.getTracks()
          .forEach(t => ok(!clone.getTrackById(t.id),
                           "The clone's tracks should be originals"));
}

function checkMediaStreamTrackCloneAgainstOriginal(clone, original) {
  isnot(clone.id.length, 0,
        "Track clone should have an id string");
  isnot(clone, original,
        "Track clone should be different from the original");
  isnot(clone.id, original.id,
        "Track clone's id should be different from the original's");
  is(clone.kind, original.kind,
     "Track clone's kind should be same as the original's");
  is(clone.enabled, original.enabled,
     "Track clone's kind should be same as the original's");
  is(clone.readyState, original.readyState,
     "Track clone's readyState should be same as the original's");
}

/*** Utility methods */

/** The dreadful setTimeout, use sparingly */
function wait(time, message) {
  return new Promise(r => setTimeout(() => r(message), time));
}

/** The even more dreadful setInterval, use even more sparingly */
function waitUntil(func, time) {
  return new Promise(resolve => {
    var interval = setInterval(() => {
      if (func())  {
        clearInterval(interval);
        resolve();
      }
    }, time || 200);
  });
}

/** Time out while waiting for a promise to get resolved or rejected. */
var timeout = (promise, time, msg) =>
  Promise.race([promise, wait(time).then(() => Promise.reject(new Error(msg)))]);

/** Adds a |finally| function to a promise whose argument is invoked whether the
 * promise is resolved or rejected, and that does not interfere with chaining.*/
var addFinallyToPromise = promise => {
  promise.finally = func => {
    return promise.then(
      result => {
        func();
        return Promise.resolve(result);
      },
      error => {
        func();
        return Promise.reject(error);
      }
    );
  }
  return promise;
}

/** Use event listener to call passed-in function on fire until it returns true */
var listenUntil = (target, eventName, onFire) => {
  return new Promise(resolve => target.addEventListener(eventName,
                                                        function callback(event) {
    var result = onFire(event);
    if (result) {
      target.removeEventListener(eventName, callback, false);
      resolve(result);
    }
  }, false));
};

/* Test that a function throws the right error */
function mustThrowWith(msg, reason, f) {
  try {
    f();
    ok(false, msg + " must throw");
  } catch (e) {
    is(e.name, reason, msg + " must throw: " + e.message);
  }
};


/*** Test control flow methods */

/**
 * Generates a callback function fired only under unexpected circumstances
 * while running the tests. The generated function kills off the test as well
 * gracefully.
 *
 * @param {String} [message]
 *        An optional message to show if no object gets passed into the
 *        generated callback method.
 */
function generateErrorCallback(message) {
  var stack = new Error().stack.split("\n");
  stack.shift(); // Don't include this instantiation frame

  /**
   * @param {object} aObj
   *        The object fired back from the callback
   */
  return aObj => {
    if (aObj) {
      if (aObj.name && aObj.message) {
        ok(false, "Unexpected callback for '" + aObj.name +
           "' with message = '" + aObj.message + "' at " +
           JSON.stringify(stack));
      } else {
        ok(false, "Unexpected callback with = '" + aObj +
           "' at: " + JSON.stringify(stack));
      }
    } else {
      ok(false, "Unexpected callback with message = '" + message +
         "' at: " + JSON.stringify(stack));
    }
    throw new Error("Unexpected callback");
  }
}

var unexpectedEventArrived;
var rejectOnUnexpectedEvent = new Promise((x, reject) => {
  unexpectedEventArrived = reject;
});

/**
 * Generates a callback function fired only for unexpected events happening.
 *
 * @param {String} description
          Description of the object for which the event has been fired
 * @param {String} eventName
          Name of the unexpected event
 */
function unexpectedEvent(message, eventName) {
  var stack = new Error().stack.split("\n");
  stack.shift(); // Don't include this instantiation frame

  return e => {
    var details = "Unexpected event '" + eventName + "' fired with message = '" +
        message + "' at: " + JSON.stringify(stack);
    ok(false, details);
    unexpectedEventArrived(new Error(details));
  }
}

/**
 * Implements the one-shot event pattern used throughout.  Each of the 'onxxx'
 * attributes on the wrappers can be set with a custom handler.  Prior to the
 * handler being set, if the event fires, it causes the test execution to halt.
 * That handler is used exactly once, after which the original, error-generating
 * handler is re-installed.  Thus, each event handler is used at most once.
 *
 * @param {object} wrapper
 *        The wrapper on which the psuedo-handler is installed
 * @param {object} obj
 *        The real source of events
 * @param {string} event
 *        The name of the event
 */
function createOneShotEventWrapper(wrapper, obj, event) {
  var onx = 'on' + event;
  var unexpected = unexpectedEvent(wrapper, event);
  wrapper[onx] = unexpected;
  obj[onx] = e => {
    info(wrapper + ': "on' + event + '" event fired');
    e.wrapper = wrapper;
    wrapper[onx](e);
    wrapper[onx] = unexpected;
  };
}

/**
 * Returns a promise that resolves when `target` has raised an event with the
 * given name the given number of times. Cancel the returned promise by passing
 * in a `cancelPromise` and resolve it.
 *
 * @param {object} target
 *        The target on which the event should occur.
 * @param {string} name
 *        The name of the event that should occur.
 * @param {integer} count
 *        Optional number of times the event should be raised before resolving.
 * @param {promise} cancelPromise
 *        Optional promise that on resolving rejects the returned promise,
 *        so we can avoid logging results after a test has finished.
 * @returns {promise} A promise that resolves to the last of the seen events.
 */
function haveEvents(target, name, count, cancelPromise) {
  var listener;
  var counter = count || 1;
  return Promise.race([
    (cancelPromise || new Promise(() => {})).then(e => Promise.reject(e)),
    new Promise(resolve =>
        target.addEventListener(name, listener = e => (--counter < 1 && resolve(e))))
  ])
  .then(e => (target.removeEventListener(name, listener), e));
};

/**
 * Returns a promise that resolves when `target` has raised an event with the
 * given name. Cancel the returned promise by passing in a `cancelPromise` and
 * resolve it.
 *
 * @param {object} target
 *        The target on which the event should occur.
 * @param {string} name
 *        The name of the event that should occur.
 * @param {promise} cancelPromise
 *        Optional promise that on resolving rejects the returned promise,
 *        so we can avoid logging results after a test has finished.
 * @returns {promise} A promise that resolves to the seen event.
 */
function haveEvent(target, name, cancelPromise) {
  return haveEvents(target, name, 1, cancelPromise);
};

/**
 * Returns a promise that resolves if the target has not seen the given event
 * after one crank (or until the given timeoutPromise resolves) of the event
 * loop.
 *
 * @param {object} target
 *        The target on which the event should not occur.
 * @param {string} name
 *        The name of the event that should not occur.
 * @param {promise} timeoutPromise
 *        Optional promise defining how long we should wait before resolving.
 * @returns {promise} A promise that is rejected if we see the given event, or
 *                    resolves after a timeout otherwise.
 */
function haveNoEvent(target, name, timeoutPromise) {
  return haveEvent(target, name, timeoutPromise || wait(0))
    .then(() => Promise.reject(new Error("Too many " + name + " events")),
          () => {});
};

/**
 * Returns a promise that resolves after the target has seen the given number
 * of events but no such event in a following crank of the event loop.
 *
 * @param {object} target
 *        The target on which the events should occur.
 * @param {string} name
 *        The name of the event that should occur.
 * @param {integer} count
 *        Optional number of times the event should be raised before resolving.
 * @param {promise} cancelPromise
 *        Optional promise that on resolving rejects the returned promise,
 *        so we can avoid logging results after a test has finished.
 * @returns {promise} A promise that resolves to the last of the seen events.
 */
function haveEventsButNoMore(target, name, count, cancelPromise) {
  return haveEvents(target, name, count, cancelPromise)
    .then(e => haveNoEvent(target, name).then(() => e));
};

/**
 * This class executes a series of functions in a continuous sequence.
 * Promise-bearing functions are executed after the previous promise completes.
 *
 * @constructor
 * @param {object} framework
 *        A back reference to the framework which makes use of the class. It is
 *        passed to each command callback.
 * @param {function[]} commandList
 *        Commands to set during initialization
 */
function CommandChain(framework, commandList) {
  this._framework = framework;
  this.commands = commandList || [ ];
}

CommandChain.prototype = {
  /**
   * Start the command chain.  This returns a promise that always resolves
   * cleanly (this catches errors and fails the test case).
   */
  execute: function () {
    return this.commands.reduce((prev, next, i) => {
      if (typeof next !== 'function' || !next.name) {
        throw new Error('registered non-function' + next);
      }

      return prev.then(() => {
        info('Run step ' + (i + 1) + ': ' + next.name);
        return Promise.race([ next(this._framework), rejectOnUnexpectedEvent ]);
      });
    }, Promise.resolve())
      .catch(e =>
             ok(false, 'Error in test execution: ' + e +
                ((typeof e.stack === 'string') ?
                 (' ' + e.stack.split('\n').join(' ... ')) : '')));
  },

  /**
   * Add new commands to the end of the chain
   */
  append: function(commands) {
    this.commands = this.commands.concat(commands);
  },

  /**
   * Returns the index of the specified command in the chain.
   * @param {occurrence} Optional param specifying which occurrence to match,
   * with 0 representing the first occurrence.
   */
  indexOf: function(functionOrName, occurrence) {
    occurrence = occurrence || 0;
    return this.commands.findIndex(func => {
      if (typeof functionOrName === 'string') {
        if (func.name !== functionOrName) {
          return false;
        }
      } else if (func !== functionOrName) {
        return false;
      }
      if (occurrence) {
        --occurrence;
        return false;
      }
      return true;
    });
  },

  mustHaveIndexOf: function(functionOrName, occurrence) {
    var index = this.indexOf(functionOrName, occurrence);
    if (index == -1) {
      throw new Error("Unknown test: " + functionOrName);
    }
    return index;
  },

  /**
   * Inserts the new commands after the specified command.
   */
  insertAfter: function(functionOrName, commands, all, occurrence) {
    this._insertHelper(functionOrName, commands, 1, all, occurrence);
  },

  /**
   * Inserts the new commands after every occurrence of the specified command
   */
  insertAfterEach: function(functionOrName, commands) {
    this._insertHelper(functionOrName, commands, 1, true);
  },

  /**
   * Inserts the new commands before the specified command.
   */
  insertBefore: function(functionOrName, commands, all, occurrence) {
    this._insertHelper(functionOrName, commands, 0, all, occurrence);
  },

  _insertHelper: function(functionOrName, commands, delta, all, occurrence) {
    occurrence = occurrence || 0;
    for (var index = this.mustHaveIndexOf(functionOrName, occurrence);
         index !== -1;
         index = this.indexOf(functionOrName, ++occurrence)) {
      this.commands = [].concat(
        this.commands.slice(0, index + delta),
        commands,
        this.commands.slice(index + delta));
      if (!all) {
        break;
      }
    }
  },

  /**
   * Removes the specified command, returns what was removed.
   */
  remove: function(functionOrName, occurrence) {
    return this.commands.splice(this.mustHaveIndexOf(functionOrName, occurrence), 1);
  },

  /**
   * Removes all commands after the specified one, returns what was removed.
   */
  removeAfter: function(functionOrName, occurrence) {
    return this.commands.splice(this.mustHaveIndexOf(functionOrName, occurrence) + 1);
  },

  /**
   * Removes all commands before the specified one, returns what was removed.
   */
  removeBefore: function(functionOrName, occurrence) {
    return this.commands.splice(0, this.mustHaveIndexOf(functionOrName, occurrence));
  },

  /**
   * Replaces a single command, returns what was removed.
   */
  replace: function(functionOrName, commands) {
    this.insertBefore(functionOrName, commands);
    return this.remove(functionOrName);
  },

  /**
   * Replaces all commands after the specified one, returns what was removed.
   */
  replaceAfter: function(functionOrName, commands, occurrence) {
    var oldCommands = this.removeAfter(functionOrName, occurrence);
    this.append(commands);
    return oldCommands;
  },

  /**
   * Replaces all commands before the specified one, returns what was removed.
   */
  replaceBefore: function(functionOrName, commands) {
    var oldCommands = this.removeBefore(functionOrName);
    this.insertBefore(functionOrName, commands);
    return oldCommands;
  },

  /**
   * Remove all commands whose name match the specified regex.
   */
  filterOut: function (id_match) {
    this.commands = this.commands.filter(c => !id_match.test(c.name));
  },
};

function AudioStreamHelper() {
  this._context = new AudioContext();
}

AudioStreamHelper.prototype = {
  checkAudio: function(stream, analyser, fun) {
    /*
    analyser.enableDebugCanvas();
    return analyser.waitForAnalysisSuccess(fun)
      .then(() => analyser.disableDebugCanvas());
    */
    return analyser.waitForAnalysisSuccess(fun);
  },

  checkAudioFlowing: function(stream) {
    var analyser = new AudioStreamAnalyser(this._context, stream);
    var freq = analyser.binIndexForFrequency(TEST_AUDIO_FREQ);
    return this.checkAudio(stream, analyser, array => array[freq] > 200);
  },

  checkAudioNotFlowing: function(stream) {
    var analyser = new AudioStreamAnalyser(this._context, stream);
    var freq = analyser.binIndexForFrequency(TEST_AUDIO_FREQ);
    return this.checkAudio(stream, analyser, array => array[freq] < 50);
  }
}

function VideoStreamHelper() {
  this._helper = new CaptureStreamTestHelper2D(50,50);
  this._canvas = this._helper.createAndAppendElement('canvas', 'source_canvas');
  // Make sure this is initted
  this._helper.drawColor(this._canvas, this._helper.green);
  this._stream = this._canvas.captureStream(10);
}

VideoStreamHelper.prototype = {
  stream: function() {
    return this._stream;
  },

  startCapturingFrames: function() {
    var i = 0;
    var helper = this;
    return setInterval(function() {
      try {
        helper._helper.drawColor(helper._canvas,
                                 i ? helper._helper.green : helper._helper.red);
        i = 1 - i;
        helper._stream.requestFrame();
      } catch (e) {
        // ignore; stream might have shut down, and we don't bother clearing
        // the setInterval.
      }
    }, 500);
  },

  waitForFrames: function(canvas, timeout_value) {
    var intervalId = this.startCapturingFrames();
    timeout_value = timeout_value || 8000;

    return addFinallyToPromise(timeout(
      Promise.all([
        this._helper.waitForPixelColor(canvas, this._helper.green, 128,
                                       canvas.id + " should become green"),
        this._helper.waitForPixelColor(canvas, this._helper.red, 128,
                                       canvas.id + " should become red")
      ]),
      timeout_value,
      "Timed out waiting for frames")).finally(() => clearInterval(intervalId));
  },

  verifyNoFrames: function(canvas) {
    return this.waitForFrames(canvas).then(
      () => ok(false, "Color should not change"),
      () => ok(true, "Color should not change")
    );
  }
}


function IsMacOSX10_6orOlder() {
  if (navigator.platform.indexOf("Mac") !== 0) {
    return false;
  }

  var version = Cc["@mozilla.org/system-info;1"]
      .getService(Ci.nsIPropertyBag2)
      .getProperty("version");
  // the next line is correct: Mac OS 10.6 corresponds to Darwin version 10.x !
  // Mac OS 10.7 is Darwin version 11.x. the |version| string we've got here
  // is the Darwin version.
  return (parseFloat(version) < 11.0);
}

(function(){
  var el = document.createElement("link");
  el.rel = "stylesheet";
  el.type = "text/css";
  el.href= "/tests/SimpleTest/test.css";
  document.head.appendChild(el);
}());
