kaiwa/public/sound-effect-manager.js

/*
SoundEffectManager

Loads and plays sound effects useing
HTML5 Web Audio API (as only available in webkit, at the moment).

By @HenrikJoreteg from &yet
*/
/*global webkitAudioContext define*/
(function () {
    var root = this;

    function SoundEffectManager() {
        this.support = !!window.webkitAudioContext;
        if (this.support) {
            this.context = new webkitAudioContext();
        }
        this.sounds = {};
    }

    // async load a file at a given URL, store it as 'name'.
    SoundEffectManager.prototype.loadFile = function (url, name, delay) {
        if (this.support) {
            this._loadWebAudioFile(url, name, delay);
        } else {
            this._loadWaveFile(url.replace('.mp3', '.wav'), name, delay);
        }
    };

    // async load a file at a given URL, store it as 'name'.
    SoundEffectManager.prototype._loadWebAudioFile = function (url, name, delay) {
        if (!this.support) return;
        var self = this,
            request = new XMLHttpRequest();

        request.open("GET", url, true);
        request.responseType = "arraybuffer";
        request.onload = function () {
            self.sounds[name] = self.context.createBuffer(request.response, true);
        };

        setTimeout(function () {
            request.send();
        }, delay || 0);
    };

    SoundEffectManager.prototype._loadWaveFile = function (url, name, delay, multiplexLimit) {
        var self = this,
            limit = multiplexLimit || 3;
        setTimeout(function () {
            var a, i = 0;

            self.sounds[name] = [];
            while (i < limit) {
                a = new Audio();
                a.src = url;
                a.load();
                self.sounds[name][i++] = a;
            }
        }, delay || 0);
    };

    SoundEffectManager.prototype._playWebAudio = function (soundName) {
        var buffer = this.sounds[soundName],
            source;

        if (!buffer) return;

        // creates a sound source
        source = this.context.createBufferSource();
        // tell the source which sound to play
        source.buffer = buffer;
        // connect the source to the context's destination (the speakers)
        source.connect(this.context.destination);
        // play it
        source.noteOn(0);
    };

    SoundEffectManager.prototype._playWavAudio = function (soundName, loop) {
        var self = this,
            audio = this.sounds[soundName],
            howMany = audio && audio.length || 0,
            i = 0,
            currSound;

        if (!audio) return;

        while (i < howMany) {
            currSound = audio[i++];
            // this covers case where we loaded an unplayable file type
            if (currSound.error) return;
            if (currSound.currentTime === 0 || currSound.currentTime === currSound.duration) {
                currSound.currentTime = 0;
                currSound.loop = !!loop;
                i = howMany;
                return currSound.play();
            }
        }
    };

    SoundEffectManager.prototype.play = function (soundName, loop) {
        if (this.support) {
            this._playWebAudio(soundName, loop);
        } else {
            return this._playWavAudio(soundName, loop);
        }
    };

    SoundEffectManager.prototype.stop = function (soundName) {
        if (this.support) {
            // TODO: this
        } else {
            var soundArray = this.sounds[soundName],
                howMany = soundArray && soundArray.length || 0,
                i = 0,
                currSound;

            while (i < howMany) {
                currSound = soundArray[i++];
                currSound.pause();
                currSound.currentTime = 0;
            }
        }
    };

    // attach to window or export with commonJS
    if (typeof module !== "undefined") {
        module.exports = SoundEffectManager;
    } else if (typeof root.define === "function" && define.amd) {
        root.define(SoundEffectManager);
    } else {
        root.SoundEffectManager = SoundEffectManager;
    }

})();