audio.js

/* Usage:

	channel.emit('audio:play',message);
	channel.emit('audio:on');
	channel.emit('audio:off');

*/

// Sounds module, used for emitting those annoying bl-up sounds when receiving a message
define(['queue','mediator'], function (queue,mediator) {

	var 	ac = false,
		enabled = true,

		channel = mediator(),

		// Recursive function for playing tones, takes an array of [tone,start_ms,duration_ms] - entries
		// i is only used for recursion
		playTones = function (tones, i) {

			// Parameter defaults
			i = (i === undefined) ? 0 : i;

			// Stop if we've reached the end of iteration, and require ac
			if( !(i < Object.keys(tones).length) || !ac || !enabled ) return;

			// Add tones to execution queue
			var 	current_tones = tones[i],
					freqs = current_tones[0],
					start = current_tones[1],
					duration = current_tones[2];

			var o = ac.createOscillator();
			var g = ac.createGain();
			o.frequency.value = freqs;
			o.connect(g);
			g.gain.value = 0.25;
			g.connect(ac.destination);
			queue.add_function_delayed(start,function() { o.noteOn(0); });
			queue.add_function_delayed(start+duration,function() { o.noteOff(0); });

			// Iterate, or start playing
			i++;
			if( i < Object.keys(tones).length  ) {
				exports.playTones(tones,i);
			} else {
				queue.run();

			}

		},

		on = function() {
			enabled = true;
		},

		off = function() {
			enabled = false;
		};

	if( window.AudioContext || window.webkitAudioContext ) ac = new ( window.AudioContext || window.webkitAudioContext );

	channel.on('audio:play',function(message) { playTones(message) });
	channel.on('audio:on',function(message) { on(); });
	channel.on('audio:off',function(message) { off(); });

	return exports;

});