/*
Class: Slider
        Creates a slider with two elements: a knob and a container. Returns the values.
Note:
        The Slider requires an XHTML doctype.
Arguments:
        element - the knob container
        knob - the handle
        options - see Options below
        maxknob - an optional maximum slider handle
Options:
	start - the minimum value for your slider.
	end - the maximum value for your slider.
        mode - either 'horizontal' or 'vertical'. defaults to horizontal.
        offset - relative offset for knob position. default to 0.
        knobheight - positions the max slider knob
Events:
        onChange - a function to fire when the value changes.
        onComplete - a function to fire when you're done dragging.
        onTick - optionally, you can alter the onTick behavior, for example displaying an effect of the knob moving to the desired position.
                Passes as parameter the new position.
*/
var Slider = new Class({

	options: {
		onChange: Class.empty,
		onComplete: Class.empty,
		onTick: function(pos){
			this.moveKnob.setStyle(this.p, pos);			
		},
		start: 0,
		end: 100,
		offset: 0,
		knobheight: 20,
		mode: 'horizontal'
	},

    initialize: function(el, knob, options, maxknob) {
		this.element = $(el);
		this.knob = $(knob);
		this.setOptions(options);
		this.previousChange = -1;
		this.previousEnd = -1;
		this.step = -1;
		this.options.steps = this.options.end - this.options.start;
		
		if(maxknob!=null)
			this.maxknob = $(maxknob);
		else
			this.element.addEvent('mousedown', this.clickedElement.bindWithEvent(this));
		var mod, offset;
		switch(this.options.mode){
			case 'horizontal':
				this.z = 'x';
				this.p = 'left';
				mod = {'x': 'left', 'y': false};
				offset = 'offsetWidth';
				break;
			case 'vertical':
				this.z = 'y';
				this.p = 'top';
				mod = {'x': false, 'y': 'top'};
				offset = 'offsetHeight';
		}
		this.max = this.element[offset] - this.knob[offset] + (this.options.offset * 2);
		this.half = this.knob[offset]/2;
		this.getPos = this.element['get' + this.p.capitalize()].bind(this.element);
		this.knob.setStyle('position', 'relative').setStyle(this.p, - this.options.offset);
		if(maxknob != null) {
			this.maxPreviousChange = -1;
			this.maxPreviousEnd = -1;
			this.maxstep = this.options.end;
			this.maxknob.setStyle('position', 'relative').setStyle(this.p, + this.max - this.options.offset).setStyle('bottom', this.options.knobheight);
		}
		var lim = {};
		lim[this.z] = [- this.options.offset, this.max - this.options.offset];
		this.drag = new Drag.Base(this.knob, {
			limit: lim,
			modifiers: mod,
			snap: 0,
			onStart: function(){
					this.draggedKnob();
			}.bind(this),
			onDrag: function(){
					this.draggedKnob();
			}.bind(this),
			onComplete: function(){
					this.draggedKnob();
					this.end();
			}.bind(this)
		});
		if(maxknob != null) {  
			this.maxdrag = new Drag.Base(this.maxknob, {
				limit: lim,
				modifiers: mod,
				snap: 0, 
				onStart: function(){
					this.draggedKnob(1);
				}.bind(this),
				onDrag: function(){
					this.draggedKnob(1);
				}.bind(this),
				onComplete: function(){
					this.draggedKnob(1);
					this.end();
				}.bind(this)
			});
		}
		
		if (this.options.initialize) this.options.initialize.call(this);
    },

	setMin: function(stepMin){
		this.step = stepMin.limit(this.options.start, this.options.end);
		this.checkStep();
		this.end();
		this.moveKnob = this.knob;
		this.fireEvent('onTick', this.toPosition(this.step));
		return this;
	},

	setMax: function(stepMax){
		this.maxstep = stepMax.limit(this.options.start, this.options.end);
		this.checkStep(1);
		this.end();
		this.moveKnob = this.maxknob;
		this.fireEvent('onTick', this.toPosition(this.maxstep));
		return this;
	},

	clickedElement: function(event){
		var position = event.page[this.z] - this.getPos() - this.half;
		position = position.limit(-this.options.offset, this.max -this.options.offset);
		this.step = this.toStep(position);
		this.checkStep();
		this.end();
		this.fireEvent('onTick', position);
	},

	draggedKnob: function(mx){
		if(mx==null) {
			this.step = this.toStep(this.drag.value.now[this.z]);
			this.checkStep();
		}
		else {  
			this.maxstep = this.toStep(this.maxdrag.value.now[this.z]);
			this.checkStep(1);
		}
	},

	checkStep: function(mx){
		if(mx==null) {
			if (this.previousChange != this.step){
				this.previousChange = this.step;
			}
		}
		else {  
			if (this.maxPreviousChange != this.maxstep){
				this.maxPreviousChange = this.maxstep;
			}
		}
		
		if(this.maxknob!=null) {
			if(this.step < this.maxstep)
				this.fireEvent('onChange', { minpos: this.step, maxpos: this.maxstep });
			else    
				this.fireEvent('onChange', { minpos: this.maxstep, maxpos: this.step });
		}
		else {  
			this.fireEvent('onChange', this.step);
		}
	},

	end: function(){
		if (this.previousEnd !== this.step || (this.maxknob != null && this.maxPreviousEnd != this.maxstep)) {
			
			this.previousEnd = this.step;

			if(this.maxknob != null) {
				this.maxPreviousEnd = this.maxstep;

				if(this.step < this.maxstep)
					this.fireEvent('onComplete', { minpos: this.step + '', maxpos: this.maxstep + '' });
				else    
					this.fireEvent('onComplete', { minpos: this.maxstep + '', maxpos: this.step + '' });
			}
			else {  
				this.fireEvent('onComplete', this.step + '');
			}
		}
	},
	
	toStep: function(position){
		return Math.round((position + this.options.offset) / this.max * this.options.steps) + this.options.start;
	},

	toPosition: function(step){
		return (this.max * step / this.options.steps) - (this.max * this.options.start / this.options.steps) - this.options.offset;
	}

});

Slider.implement(new Events);
Slider.implement(new Options);