web-audio-scheduler/lib/WebAudioScheduler.js

Event Scheduler for Web Audio API

"use strict";

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }

var events = require("events");
var defaults = require("./utils/defaults");
var defaultContext = require("./defaultContext");

var WebAudioScheduler = function (_events$EventEmitter) {
  _inherits(WebAudioScheduler, _events$EventEmitter);

  function WebAudioScheduler(opts) {
    _classCallCheck(this, WebAudioScheduler);

    opts = opts || /* istanbul ignore next */{};

    var _this = _possibleConstructorReturn(this, (WebAudioScheduler.__proto__ || Object.getPrototypeOf(WebAudioScheduler)).call(this));

    _this.context = defaults(opts.context, defaultContext);
    _this.interval = defaults(opts.interval, 0.025);
    _this.aheadTime = defaults(opts.aheadTime, 0.1);
    _this.timerAPI = defaults(opts.timerAPI, global);
    _this.playbackTime = _this.currentTime;

    _this._timerId = 0;
    _this._schedId = 0;
    _this._scheds = [];
    return _this;
  }

  _createClass(WebAudioScheduler, [{
    key: "start",
    value: function start(callback, args) {
      var loop = this.process.bind(this);

      if (this._timerId === 0) {
        this._timerId = this.timerAPI.setInterval(loop, this.interval * 1000);

        this.emit("start");

        if (callback) {
          this.insert(this.context.currentTime, callback, args);
          loop();
        }
      } else if (callback) {
        this.insert(this.context.currentTime, callback, args);
      }

      return this;
    }
  }, {
    key: "stop",
    value: function stop() {
      var reset = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : true;

      if (this._timerId !== 0) {
        this.timerAPI.clearInterval(this._timerId);
        this._timerId = 0;

        this.emit("stop");
      }

      if (reset) {
        this._scheds.splice(0);
      }

      return this;
    }
  }, {
    key: "insert",
    value: function insert(time, callback, args) {
      var id = ++this._schedId;
      var event = { id: id, time: time, callback: callback, args: args };
      var scheds = this._scheds;

      if (scheds.length === 0 || scheds[scheds.length - 1].time <= time) {
        scheds.push(event);
      } else {
        for (var i = 0, imax = scheds.length; i < imax; i++) {
          if (time < scheds[i].time) {
            scheds.splice(i, 0, event);
            break;
          }
        }
      }

      return id;
    }
  }, {
    key: "nextTick",
    value: function nextTick(time, callback, args) {
      if (typeof time === "function") {
        args = callback;
        callback = time;
        time = this.playbackTime;
      }

      return this.insert(time + this.aheadTime, callback, args);
    }
  }, {
    key: "remove",
    value: function remove(schedId) {
      var scheds = this._scheds;

      if (typeof schedId === "number") {
        for (var i = 0, imax = scheds.length; i < imax; i++) {
          if (schedId === scheds[i].id) {
            scheds.splice(i, 1);
            break;
          }
        }
      }

      return schedId;
    }
  }, {
    key: "removeAll",
    value: function removeAll() {
      this._scheds.splice(0);
    }
  }, {
    key: "process",
    value: function process() {
      var t0 = this.context.currentTime;
      var t1 = t0 + this.aheadTime;

      this._process(t0, t1);
    }
  }, {
    key: "_process",
    value: function _process(t0, t1) {
      var scheds = this._scheds;
      var playbackTime = t0;

      this.playbackTime = playbackTime;
      this.emit("process", { playbackTime: playbackTime });

      while (scheds.length && scheds[0].time < t1) {
        var event = scheds.shift();
        var _playbackTime = event.time;
        var args = event.args;

        this.playbackTime = _playbackTime;

        event.callback({ playbackTime: _playbackTime, args: args });
      }

      this.playbackTime = playbackTime;
      this.emit("processed", { playbackTime: playbackTime });
    }
  }, {
    key: "state",
    get: function get() {
      return this._timerId !== 0 ? "running" : "suspended";
    }
  }, {
    key: "currentTime",
    get: function get() {
      return this.context.currentTime;
    }
  }, {
    key: "events",
    get: function get() {
      return this._scheds.slice();
    }
  }]);

  return WebAudioScheduler;
}(events.EventEmitter);

module.exports = WebAudioScheduler;