/* Based on mozplayer.js by Daniel Svensson, dsvensson@gmail.com */
function parseMetadata(ref) {
    var offset = 0;
    var read_int32 = function() {
        var value = Module.getValue(ref + offset, 'i32');
        offset += 4;
        return value;
    };
    var read_string = function() {
        var value = Module.Pointer_stringify(Module.getValue(ref + offset, 'i8*'));
        offset += 4;
        return value;
    };
    var res = {};
    res.length = read_int32();
    res.intro_length = read_int32();
    res.loop_length = read_int32();
    res.play_length = read_int32();
    offset += 4 * 12; // skip reserved fields
    res.system = read_string();
    res.game = read_string();
    res.song = read_string();
    res.author = read_string();
    res.copyright = read_string();
    res.comment = read_string();
    res.dumper = read_string();
    return res;
}
function loadArrayBuffer(url, done, fail) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);
    xhr.responseType = 'arraybuffer';
    xhr.onload = function() {
        if (this.status !== 200) {
            fail(this);
        } else {
            done(this);
        }
    };
    xhr.send();
}
var Player = Backbone.Model.extend({
    // libgme output is in stereo only
    channels: 2,
    // largest signed short integer value (16 bits), for scaling signal
    i16Max: Math.pow(2, 16 - 1) - 1,
    tracks: new Tracks(),
    defaults: {
        autoplay: false,
        repeat: false,
        random: false,
        track: new Track()
    },
    initialize: function() {
        window.AudioContext = (window.AudioContext || window.webkitAudioContext);
        if (window.AudioContext) {
            this.ctx = new window.AudioContext();
            this.ctxSize = 1024 * 4;
            this.bufferSize = this.ctxSize * this.channels;
            this.ref = Module._malloc(4);
            this.buffer = Module._malloc(this.bufferSize * 2);
            console.debug('Using Web Audio API');
        } else {
            console.error('Web Audio API is not supported, try another browser');
        }
    },
    load: function(data) {
        this.unload();
        var payload = new Uint8Array(data);
        var error = Module.ccall('gme_open_data', 'string', ['array', 'number', 'number', 'number'], [payload, payload.length, this.ref, this.ctx.sampleRate]);
        if (error !== '') {
            console.error('gme_open_data failed: ' + error);
            return;
        }
        this.emu = Module.getValue(this.ref, 'i32');
        var trackCount = Module.ccall('gme_track_count', 'number', ['number'], [this.emu]);
        var tis = [];
        for (var i = 0; i < trackCount; i++) {
            var trackInfo = this.getTrackInfo(i);
            trackInfo.id = i;
            tis.push(trackInfo);
        }
        this.tracks.reset(tis);
    },
    unload: function() {
        if (this.emu !== null) {
            Module.ccall('gme_delete', 'number', ['number'], [this.emu]);
            delete this.emu;
        }
        this.get('track').clear();
    },
    getTrackInfo: function(track) {
        var error = Module.ccall('gme_track_info', 'string', ['number', 'number', 'number'], [this.emu, this.ref, track]);
        if (error !== '') {
            console.error('gme_track_info failed: ' + error);
            return;
        }
        var memory = Module.getValue(this.ref, '*');
        var result = parseMetadata(memory);
        Module.ccall('gme_free_info', 'number', ['number'], [memory]);
        return result;
    },
    startTrack: function(track) {
        this.stop();
        var error = Module.ccall('gme_start_track', 'string', ['number', 'number'], [this.emu, track]);
        if (error !== '') {
            console.error('gme_start_track failed: ' + error);
            return;
        }
        this.set('track', this.tracks.get(track));
        this.get('track').set('status', 'stopped');
    },
    isTrackEnded: function() {
        return Module.ccall('gme_track_ended', 'number', ['number'], [this.emu]) === 1;
    },
    seek: function(msec) {
        var error = Module.ccall('gme_seek', 'string', ['number', 'number'], [this.emu, msec]);
        if (error !== '') {
            console.error('gme_seek failed: ' + error);
        }
    },
    tell: function() {
        return Module.ccall('gme_tell', 'number', ['number'], [this.emu]);
    },
    voiceCount: function() {
        return Module.ccall('gme_voice_count', 'number', ['number'], [this.emu]);
    },
    stop: function() {
        if (this.node) {
            this.node.disconnect();
            delete this.node;
        }
        this.get('track').set({'status': 'stopped', 'position': this.tell()});
    },
    play: function() {
        if (this.node) {
            return;
        }
        var limit = this.i16Max;
        var player = this;
        this.node = this.ctx.createScriptProcessor(this.ctxSize, 0, this.channels);
        this.node.onaudioprocess = function(e) {
            if (player.isTrackEnded()) {
                player.stop();
                player.trigger('ended');
                return;
            }
            var channels = [e.outputBuffer.getChannelData(0), e.outputBuffer.getChannelData(1)];
            var error = Module.ccall('gme_play', 'string', ['number', 'number', 'number'], [player.emu, player.bufferSize, player.buffer]);
            if (error !== '') {
                console.error('gme_play failed: ' + error);
                return;
            }
            for (var i = 0; i < player.bufferSize; i++) {
                for (var n = 0; n < e.outputBuffer.numberOfChannels; n++) {
                    channels[n][i] = Module.getValue(player.buffer + i * e.outputBuffer.numberOfChannels * 2 + n * 2, 'i16') / limit;
                }
            }
            player.get('track').set('position', player.tell());
        };
        this.node.connect(this.ctx.destination);
        this.ctx.resume();
        this.get('track').set('status', 'playing');
    }
});