define(["Tone/core/Tone", "Tone/type/Ticks"], function(Tone){

	/**
	 *  @class Tone.TransportEvent is an internal class used by (Tone.Transport)[Transport]
	 *         to schedule events. Do no invoke this class directly, it is
	 *         handled from within Tone.Transport.
	 *  @extends {Tone}
	 *  @param {Object} options
	 */
	Tone.TransportEvent = function(Transport, options){

		options = Tone.defaultArg(options, Tone.TransportEvent.defaults);
		Tone.call(this);

		/**
		 * Reference to the Transport that created it
		 * @type {Tone.Transport}
		 */
		this.Transport = Transport;

		/**
		 * The unique id of the event
		 * @type {Number}
		 */
		this.id = Tone.TransportEvent._eventId++;

		/**
		 * The time the event starts
		 * @type {Ticks}
		 */
		this.time = Tone.Ticks(options.time);

		/**
		 * The callback to invoke
		 * @type {Function}
		 */
		this.callback = options.callback;

		/**
		 * If the event should be removed after being created.
		 * @type {Boolean}
		 * @private
		 */
		this._once = options.once;
	};

	Tone.extend(Tone.TransportEvent);

	/**
	 * The defaults
	 * @static
	 * @type {Object}
	 */
	Tone.TransportEvent.defaults = {
		"once" : false,
		"callback" : Tone.noOp,
	};

	/**
	 * Current ID counter
	 * @private
	 * @static
	 * @type {Number}
	 */
	Tone.TransportEvent._eventId = 0;

	/**
	 * Invoke the event callback.
	 * @param  {Time} time  The AudioContext time in seconds of the event
	 */
	Tone.TransportEvent.prototype.invoke = function(time){
		if (this.callback){
			this.callback(time);
			if (this._once && this.Transport){
				this.Transport.clear(this.id);
			}
		}
	};

	/**
	 * Clean up
	 * @return {Tone.TransportEvent} this
	 */
	Tone.TransportEvent.prototype.dispose = function(){
		Tone.prototype.dispose.call(this);
		this.Transport = null;
		this.callback = null;
		this.time = null;
		return this;
	};

	return Tone.TransportEvent;
});