/*
 * Ext JS Library 2.0 Copyright(c) 2006-2007, Ext JS, LLC. licensing@extjs.com
 * 
 * http://extjs.com/license
 */

Ext.dd.DragTracker = function(config) {
	Ext.apply(this, config);
	this.addEvents('mousedown', 'mouseup', 'mousemove', 'dragstart', 'dragend',
			'drag');

	this.dragRegion = new Ext.lib.Region(0, 0, 0, 0);

	if (this.el) {
		this.initEl(this.el);
	}
}

Ext.extend(Ext.dd.DragTracker, Ext.util.Observable, {
			active : false,
			tolerance : 5,
			autoStart : false,

			initEl : function(el) {
				this.el = Ext.get(el);
				el.on('mousedown', this.onMouseDown, this, this.delegate ? {
							delegate : this.delegate
						} : undefined);
			},

			destroy : function() {
				this.el.un('mousedown', this.onMouseDown, this);
			},

			onMouseDown : function(e, target) {
				if (this.fireEvent('mousedown', this, e) !== false
						&& this.onBeforeStart(e) !== false) {
					this.startXY = this.lastXY = e.getXY();
					this.dragTarget = this.delegate ? target : this.el.dom;
					e.preventDefault();
					var doc = Ext.getDoc();
					doc.on('mouseup', this.onMouseUp, this);
					doc.on('mousemove', this.onMouseMove, this);
					doc.on('selectstart', this.stopSelect, this);
					if (this.autoStart) {
						this.timer = this.triggerStart
								.defer(	this.autoStart === true
												? 1000
												: this.autoStart, this);
					}
				}
			},

			onMouseMove : function(e, target) {
				e.preventDefault();
				var xy = e.getXY(), s = this.startXY;
				this.lastXY = xy;
				if (!this.active) {
					if (Math.abs(s[0] - xy[0]) > this.tolerance
							|| Math.abs(s[1] - xy[1]) > this.tolerance) {
						this.triggerStart();
					} else {
						return;
					}
				}
				this.fireEvent('mousemove', this, e);
				this.onDrag(e);
				this.fireEvent('drag', this, e);
			},

			onMouseUp : function(e) {
				var doc = Ext.getDoc();
				doc.un('mousemove', this.onMouseMove, this);
				doc.un('mouseup', this.onMouseUp, this);
				doc.un('selectstart', this.stopSelect, this);
				e.preventDefault();
				this.clearStart();
				this.active = false;
				delete this.elRegion;
				this.fireEvent('mouseup', this, e);
				this.onEnd(e);
				this.fireEvent('dragend', this, e);
			},

			triggerStart : function(isTimer) {
				this.clearStart();
				this.active = true;
				this.onStart(this.startXY);
				this.fireEvent('dragstart', this, this.startXY);
			},

			clearStart : function() {
				if (this.timer) {
					clearTimeout(this.timer);
					delete this.timer;
				}
			},

			stopSelect : function(e) {
				e.stopEvent();
				return false;
			},

			onBeforeStart : function(e) {

			},

			onStart : function(xy) {

			},

			onDrag : function(e) {

			},

			onEnd : function(e) {

			},

			getDragTarget : function() {
				return this.dragTarget;
			},

			getDragCt : function() {
				return this.el;
			},

			getXY : function(constrain) {
				return constrain ? this.constrainModes[constrain].call(this,
						this.lastXY) : this.lastXY;
			},

			getOffset : function(constrain) {
				var xy = this.getXY(constrain);
				var s = this.startXY;
				return [s[0] - xy[0], s[1] - xy[1]];
			},

			constrainModes : {
				'point' : function(xy) {

					if (!this.elRegion) {
						this.elRegion = this.getDragCt().getRegion();
					}

					var dr = this.dragRegion;

					dr.left = xy[0];
					dr.top = xy[1];
					dr.right = xy[0];
					dr.bottom = xy[1];

					dr.constrainTo(this.elRegion);

					return [dr.left, dr.top];
				}
			}
		});