/*
Script: Fx.Scroll.js
	Effect to smoothly scroll any element, including the window.

	License:
		MIT-style license.

	Authors:
		Valerio Proietti
*/

Fx.Scroll = new Class({

	Extends: Fx,

	options: {
		offset: {x: 0, y: 0},
		wheelStops: true
	},

	initialize: function(element, options){
		this.element = this.subject = document.id(element);
		this.parent(options);
		var cancel = this.cancel.bind(this, false);

		if ($type(this.element) != 'element') this.element = document.id(this.element.getDocument().body);

		var stopper = this.element;

		if (this.options.wheelStops){
			this.addEvent('start', function(){
				stopper.addEvent('mousewheel', cancel);
			}, true);
			this.addEvent('complete', function(){
				stopper.removeEvent('mousewheel', cancel);
			}, true);
		}
	},

	set: function(){
		var now = Array.flatten(arguments);
		this.element.scrollTo(now[0], now[1]);
	},

	compute: function(from, to, delta){
		return [0, 1].map(function(i){
			return Fx.compute(from[i], to[i], delta);
		});
	},

	start: function(x, y){
		if (!this.check(x, y)) return this;
		var offsetSize = this.element.getSize(), scrollSize = this.element.getScrollSize();
		var scroll = this.element.getScroll(), values = {x: x, y: y};
		for (var z in values){
			var max = scrollSize[z] - offsetSize[z];
			if ($chk(values[z])) values[z] = ($type(values[z]) == 'number') ? values[z].limit(0, max) : max;
			else values[z] = scroll[z];
			values[z] += this.options.offset[z];
		}
		return this.parent([scroll.x, scroll.y], [values.x, values.y]);
	},

	toTop: function(){
		return this.start(false, 0);
	},

	toLeft: function(){
		return this.start(0, false);
	},

	toRight: function(){
		return this.start('right', false);
	},

	toBottom: function(){
		return this.start(false, 'bottom');
	},

	toElement: function(el){
		var position = document.id(el).getPosition(this.element);
		return this.start(position.x, position.y);
	},

	scrollIntoView: function(el, axes, offset){
		axes = axes ? $splat(axes) : ['x','y'];
		var to = {};
		el = document.id(el);
		var pos = el.getPosition(this.element);
		var size = el.getSize();
		var scroll = this.element.getScroll();
		var containerSize = this.element.getSize();
		var edge = {
			x: pos.x + size.x,
			y: pos.y + size.y
		};
		['x','y'].each(function(axis) {
			if (axes.contains(axis)) {
				if (edge[axis] > scroll[axis] + containerSize[axis]) to[axis] = edge[axis] - containerSize[axis];
				if (pos[axis] < scroll[axis]) to[axis] = pos[axis];
			}
			if (to[axis] == null) to[axis] = scroll[axis];
			if (offset && offset[axis]) to[axis] = to[axis] + offset[axis];
		}, this);
		if (to.x != scroll.x || to.y != scroll.y) this.start(to.x, to.y);
		return this;
	}

});