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

	"use strict";

	/**
	 *  @class  A Timeline State. Provides the methods: <code>setStateAtTime("state", time)</code>
	 *          and <code>getValueAtTime(time)</code>.
	 *
	 *  @extends {Tone.Timeline}
	 *  @param {String} initial The initial state of the TimelineState. 
	 *                          Defaults to <code>undefined</code>
	 */
	Tone.TimelineState = function(initial){

		Tone.Timeline.call(this);

		/**
		 *  The initial state
		 *  @private
		 *  @type {String}
		 */
		this._initial = initial;
	};

	Tone.extend(Tone.TimelineState, Tone.Timeline);

	/**
	 *  Returns the scheduled state scheduled before or at
	 *  the given time.
	 *  @param  {Number}  time  The time to query.
	 *  @return  {String}  The name of the state input in setStateAtTime.
	 */
	Tone.TimelineState.prototype.getValueAtTime = function(time){
		var event = this.get(time);
		if (event !== null){
			return event.state;
		} else {
			return this._initial;
		}
	};

	/**
	 *  Add a state to the timeline.
	 *  @param  {String}  state The name of the state to set.
	 *  @param  {Number}  time  The time to query.
	 *  @returns {Tone.TimelineState} this
	 */
	Tone.TimelineState.prototype.setStateAtTime = function(state, time){
		//all state changes need to be >= the previous state time
		//TODO throw error if time < the previous event time
		this.add({
			"state" : state,
			"time" : time
		});
		return this;
	};

	/**
	 *  Return the event before the time with the given state
	 *  @param {Tone.State} state The state to look for
	 *  @param  {Time}  time  When to check before			
	 *  @return  {Object}  The event with the given state before the time
	 */
	Tone.TimelineState.prototype.getLastState = function(state, time){
		time = this.toSeconds(time);
		var index = this._search(time);
		for (var i = index; i >= 0; i--){
			var event = this._timeline[i];
			if (event.state === state){
				return event;
			}
		}
	};

	/**
	 *  Return the event after the time with the given state
	 *  @param {Tone.State} state The state to look for
	 *  @param  {Time}  time  When to check from
	 *  @return  {Object}  The event with the given state after the time
	 */
	Tone.TimelineState.prototype.getNextState = function(state, time){
		time = this.toSeconds(time);
		var index = this._search(time);
		if (index !== -1){
			for (var i = index; i < this._timeline.length; i++){
				var event = this._timeline[i];
				if (event.state === state){
					return event;
				}
			}
		}
	};

	return Tone.TimelineState;
});