piano/js/midi/io.js

/*jshint browser:true, bitwise:false */
/*globals App */

/**
 * io.js
 *
 * Handle communication with MIDI inputs and outputs
 * Request navigator access to MIDI devices
 */
(function () {
    'use strict';
    
    /**
     * Wrap around low-level MIDI output
     *
     * @param {native: MIDIOutput}  Native MIDIOutput to wrap around
     */
    function Output(native) {
        this.native = native || {
            send: function () {}
        };
    }
    
    /**
     * List of MIDI channel events
     */
    Output.messages = {
        noteOff: 0x80,
        noteOn: 0x90,
        noteAftertouch: 0xA0,
        controller: 0xB0,
        programChange: 0xC0,
        channelAftertouch: 0xD0,
        pitchBend: 0xE0
    };
    
    /**
     * List of controller types
     * (not complete)
     */
    Output.controllers = {
        modulationWheel: 1,
        volume: 7,
        pan: 10,
        expression: 11,
        sustainPedal: 64
    };
    
	Output.prototype.programChange = function (channel, program, delay) {
		this.native.send([
            Output.messages.programChange + channel,
            program
        ], (delay || 0) * 1000);
	};

	Output.prototype.noteOn = function (channel, note, velocity, delay) {
		this.native.send([
            Output.messages.noteOn + channel,
            note,
            velocity
        ], (delay || 0) * 1000);
	};

	Output.prototype.noteOff = function (channel, note, delay) {
		this.native.send([
            Output.messages.noteOff + channel,
            note,
            0
        ], (delay || 0) * 1000);
	};
    
    Output.prototype.noteAftertouch = function (channel, note, amount, delay) {
        this.native.send([
            Output.messages.noteAftertouch + channel,
            note,
            amount
        ], (delay || 0) * 1000);
    };
    
    Output.prototype.controller = function (channel, type, value, delay) {
        this.native.send([
            Output.messages.controller + channel,
            type,
            value
        ], (delay || 0) * 1000);
    };
    
    Output.prototype.programChange = function (channel, program, delay) {
        this.native.send([
            Output.messages.programChange + channel,
            program
        ], (delay || 0) * 1000);
    };
    
    Output.prototype.channelAftertouch = function (channel, amount, delay) {
        this.native.send([
            Output.messages.channelAftertouch + channel,
            amount
        ], (delay || 0) * 1000);
    };
    
    Output.prototype.pitchBend = function (channel, value, delay) {
        var lsb, msb;
        
        value += 8192;
        lsb = value & 127;
        msb = value >> 7;
        
        this.native.send([
            Output.messages.pitchBend + channel,
            lsb,
            msb
        ], (delay || 0) * 1000);
    };
    
    /**
     * Request MIDI access, select first available output
     *
     * @return Promise
     */
    function connect() {
        var promise;
        
        promise = new window.Promise(function (resolve, reject) {
            var ignoreAlert = "Si vous continuez, " +
                "<em>aucun son ne sera émis ou reçu,</em> mais vous " +
                "pourrez utiliser les autres fonctionnalités " +
                "du logiciel.";
            
            // by default, we use a no-op output
            App.MIDI.output = new Output();
            
            navigator.requestMIDIAccess().then(function (access) {
                var outputs = access.outputs(),
                    output;

                if (outputs && outputs.length) {
                    output = new Output(outputs[0]);
                    App.MIDI.output = output;

                    resolve(output);
                } else {
                    reject(new Error(
                        "Aucun synthétiseur MIDI n'est disponible. Sur " +
                            "systèmes d'exploitation, un synthétiseur " +
                            "est disponible par défaut. S'il ce n'est pas " +
                            "votre cas, il faudra utiliser un logiciel " +
                            "tiers pour synthétiser les sons.<br /><br />" +
                            ignoreAlert
                    ));
                }
            }).catch(function () {
                reject(new Error(
                    "Impossible d'obtenir un accès aux contrôleurs " +
                        "MIDI, il est possible que votre système ne " +
                        "supporte pas la norme MIDI ou bien que " +
                        "vous ayez refusé l'accès à ces périphériques. " +
                        "<br /><br />" + ignoreAlert
                ));
            });
        });
        
        return promise;
    }
    
    App.MIDI.connect = connect;
}());