/*
Script: Fx.Base.js
	Contains <Fx.Base>, the foundamentals of the MooTools Effects.

License:
	MIT-style license.
*/

var Fx = {};

/*
Class: Fx.Base
	Base class for the Effects.

Options:
	transition - the equation to use for the effect see <Fx.Transitions>; default is <Fx.Transitions.Sine.easeInOut>
	duration - the duration of the effect in ms; 500 is the default.
	unit - the unit is 'px' by default (other values include things like 'em' for fonts or '%').
	wait - boolean: to wait or not to wait for a current transition to end before running another of the same instance. defaults to true.
	fps - the frames per second for the transition; default is 50
	
Events:
	onStart - the function to execute as the effect begins; nothing (<Class.empty>) by default.
	onComplete - the function to execute after the effect has processed; nothing (<Class.empty>) by default.
	onCancel - the function to execute when you manually stop the effect.
*/

Fx.Base = new Class({

	options: {
		onStart: Class.empty,
		onComplete: Class.empty,
		onCancel: Class.empty,
		transition: function(p){
			return -(Math.cos(Math.PI * p) - 1) / 2;
		},
		duration: 500,
		unit: 'px',
		wait: true,
		fps: 50
	},

	init: function(options){
		this.element = this.element || null;
		this.setOptions(options);
		if (this.options.init) this.options.init.call(this);
	},

	step: function(){
		var time = $time();
		if (time < this.time + this.options.duration){
			this.delta = this.options.transition((time - this.time) / this.options.duration);
			this.setNow();
			this.increase();
		} else {
			this.stop(true);
			this.set(this.to);
			this.fireEvent('onComplete', this.element, 10);
			this.callChain();
		}
	},

	/*
	Property: set
		Immediately sets the value with no transition.

	Arguments:
		to - the point to jump to

	Example:
		>var myFx = new Fx.Style('myElement', 'opacity').set(0); //will make it immediately transparent
	*/

	set: function(to){
		this.now = to;
		this.increase();
		return this;
	},

	setNow: function(){
		this.now = this.compute(this.from, this.to);
	},

	compute: function(from, to){
		return (to - from) * this.delta + from;
	},

	/*
	Property: start
		Executes an effect from one position to the other.

	Arguments:
		from - integer: staring value
		to - integer: the ending value

	Examples:
		>var myFx = new Fx.Style('myElement', 'opacity').start(0,1); //display a transition from transparent to opaque.
	*/

	start: function(from, to){
		if (!this.options.wait) this.stop();
		else if (this.timer) return this;
		this.from = from;
		this.to = to;
		this.change = this.to - this.from;
		this.time = $time();
		this.timer = this.step.periodical(Math.round(1000 / this.options.fps), this);
		this.fireEvent('onStart', this.element);
		return this;
	},

	/*
	Property: stop
		Stops the transition.
	*/

	stop: function(end){
		if (!this.timer) return this;
		this.timer = $clear(this.timer);
		if (!end) this.fireEvent('onCancel', this.element);
		return this;
	}/*compatibility*/,
	
	custom: function(from, to){
		return this.start(from, to);
	},

	clearTimer: function(end){
		return this.stop(end);
	}

	/*end compatibility*/

});

Fx.Base.implement(new Chain, new Events, new Options);