/*
This file is part of Ext JS 3.4

Copyright (c) 2011-2013 Sencha Inc

Contact:  http://www.sencha.com/contact

GNU General Public License Usage
This file may be used under the terms of the GNU General Public License version 3.0 as
published by the Free Software Foundation and appearing in the file LICENSE included in the
packaging of this file.

Please review the following information to ensure the GNU General Public License version 3.0
requirements will be met: http://www.gnu.org/copyleft/gpl.html.

If you are unsure which license is appropriate for your use, please contact the sales department
at http://www.sencha.com/contact.

Build date: 2013-04-03 15:07:25
*/
/**
 * @class Ext.dd.DragTracker
 * @extends Ext.util.Observable
 * A DragTracker listens for drag events on an Element and fires events at the start and end of the drag,
 * as well as during the drag. This is useful for components such as {@link Ext.slider.MultiSlider}, where there is
 * an element that can be dragged around to change the Slider's value.
 * DragTracker provides a series of template methods that should be overridden to provide functionality
 * in response to detected drag operations. These are onBeforeStart, onStart, onDrag and onEnd.
 * See {@link Ext.slider.MultiSlider}'s initEvents function for an example implementation.
 */
Ext.dd.DragTracker = Ext.extend(Ext.util.Observable,  {    
    /**
     * @cfg {Boolean} active
	 * Defaults to <tt>false</tt>.
	 */	
    active: false,
    /**
     * @cfg {Number} tolerance
	 * Number of pixels the drag target must be moved before dragging is considered to have started. Defaults to <tt>5</tt>.
	 */	
    tolerance: 5,
    /**
     * @cfg {Boolean/Number} autoStart
	 * Defaults to <tt>false</tt>. Specify <tt>true</tt> to defer trigger start by 1000 ms.
	 * Specify a Number for the number of milliseconds to defer trigger start.
	 */	
    autoStart: false,
    
    constructor : function(config){
        Ext.apply(this, config);
	    this.addEvents(
	        /**
	         * @event mousedown
	         * @param {Object} this
	         * @param {Object} e event object
	         */
	        'mousedown',
	        /**
	         * @event mouseup
	         * @param {Object} this
	         * @param {Object} e event object
	         */
	        'mouseup',
	        /**
	         * @event mousemove
	         * @param {Object} this
	         * @param {Object} e event object
	         */
	        'mousemove',
	        /**
	         * @event dragstart
	         * @param {Object} this
	         * @param {Object} e event object
	         */
	        'dragstart',
	        /**
	         * @event dragend
	         * @param {Object} this
	         * @param {Object} e event object
	         */
	        'dragend',
	        /**
	         * @event drag
	         * @param {Object} this
	         * @param {Object} e event object
	         */
	        'drag'
	    );
	
	    this.dragRegion = new Ext.lib.Region(0,0,0,0);
	
	    if(this.el){
	        this.initEl(this.el);
	    }
        Ext.dd.DragTracker.superclass.constructor.call(this, config);
    },

    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);
        delete this.el;
    },

    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;
            if(this.preventDefault !== false){
                e.preventDefault();
            }
            Ext.getDoc().on({
                scope: this,
                mouseup: this.onMouseUp,
                mousemove: this.onMouseMove,
                selectstart: this.stopSelect
            });
            if(this.autoStart){
                this.timer = this.triggerStart.defer(this.autoStart === true ? 1000 : this.autoStart, this, [e]);
            }
        }
    },

    onMouseMove: function(e, target){
        // HACK: IE hack to see if button was released outside of window. Resolved in IE9.
        var ieCheck = Ext.isIE6 || Ext.isIE7 || Ext.isIE8;
        if(this.active && ieCheck && !e.browserEvent.button){
            e.preventDefault();
            this.onMouseUp(e);
            return;
        }

        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(e);
            }else{
                return;
            }
        }
        this.fireEvent('mousemove', this, e);
        this.onDrag(e);
        this.fireEvent('drag', this, e);
    },

    onMouseUp: function(e) {
        var doc = Ext.getDoc(),
            wasActive = this.active;
            
        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);
        if(wasActive){
            this.onEnd(e);
            this.fireEvent('dragend', this, e);
        }
    },

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

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

    stopSelect : function(e) {
        e.stopEvent();
        return false;
    },
    
    /**
     * Template method which should be overridden by each DragTracker instance. Called when the user first clicks and
     * holds the mouse button down. Return false to disallow the drag
     * @param {Ext.EventObject} e The event object
     */
    onBeforeStart : function(e) {

    },

    /**
     * Template method which should be overridden by each DragTracker instance. Called when a drag operation starts
     * (e.g. the user has moved the tracked element beyond the specified tolerance)
     * @param {Ext.EventObject} e The event object
     */
    onStart : function(xy) {

    },

    /**
     * Template method which should be overridden by each DragTracker instance. Called whenever a drag has been detected.
     * @param {Ext.EventObject} e The event object
     */
    onDrag : function(e) {

    },

    /**
     * Template method which should be overridden by each DragTracker instance. Called when a drag operation has been completed
     * (e.g. the user clicked and held the mouse down, dragged the element and then released the mouse button)
     * @param {Ext.EventObject} e The event object
     */
    onEnd : function(e) {

    },

    /**
     * Returns the drag target
     * @return {Ext.Element} The element currently being tracked
     */
    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),
            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];
        }
    }
});