/**
 * @class Ext.util.ComponentDragger
 * 
A subclass of Ext.dd.DragTracker which handles dragging any Component.
 * 
This is configured with a Component to be made draggable, and a config object for the
 * {@link Ext.dd.DragTracker} class.
 * 
A {@link #} delegate may be provided which may be either the element to use as the mousedown target
 * or a {@link Ext.DomQuery} selector to activate multiple mousedown targets.
 * 

 */
Ext.define('Ext.util.ComponentDragger', {

    extend: 'Ext.dd.DragTracker',

    autoStart: 500,

    constructor: function(comp, config) {
        this.comp = comp;
        this.initialConstrainTo = config.constrainTo;
        this.callParent([ config ]);
    },

    onStart: function(e) {
        var me = this,
            comp = me.comp;

        // Cache the start [X, Y] array
        this.startPosition = comp.getPosition();

        // If client Component has a ghost method to show a lightweight version of itself
        // then use that as a drag proxy unless configured to liveDrag.
        if (comp.ghost && !comp.liveDrag) {
             me.proxy = comp.ghost();
             me.dragTarget = me.proxy.header.el;
        }

        // Set the constrainTo Region before we start dragging.
        if (me.constrain || me.constrainDelegate) {
            me.constrainTo = me.calculateConstrainRegion();
        }
    },

    calculateConstrainRegion: function() {
        var me = this,
            comp = me.comp,
            c = me.initialConstrainTo,
            delegateRegion,
            elRegion,
            shadowSize = comp.el.shadow && comp.el.shadow.offset;

        // The configured constrainTo might be a Region or an element
        if (!(c instanceof Ext.util.Region)) {
            c =  Ext.fly(c).getViewRegion();
        }

        // Reduce the constrain region to allow for shadow
        // TODO: Rewrite the Shadow class. When that's done, get the extra for each side from the Shadow.
        if (shadowSize) {
            c.adjust(0, -shadowSize, -shadowSize, shadowSize);
        }

        // If they only want to constrain the *delegate* to within the constrain region,
        // adjust the region to be larger based on the insets of the delegate from the outer
        // edges of the Component.
        if (!me.constrainDelegate) {
            delegateRegion = Ext.fly(me.dragTarget).getRegion();
            elRegion = me.proxy ? me.proxy.el.getRegion() : comp.el.getRegion();

            c.adjust(
                delegateRegion.top - elRegion.top,
                delegateRegion.right - elRegion.right,
                delegateRegion.bottom - elRegion.bottom,
                delegateRegion.left - elRegion.left
            );
        }
        return c;
    },

    // Move either the ghost or the Component to its new position on drag
    onDrag: function(e) {
        var me = this,
            comp = me.comp,
            offset = me.getOffset(me.constrain || me.constrainDelegate ? 'dragTarget' : null),
            newPos = [me.startPosition[0] + offset[0], me.startPosition[1] + offset[1]];

        if (this.proxy && !this.comp.liveDrag) {
            me.proxy.setPosition(newPos);
        } else {
            comp.setPosition(newPos);
        }
    },

    onEnd: function(e) {
        if (this.proxy && !this.comp.liveDrag) {
            this.comp.unghost();
        }

        // Windows save their state on drag
        (this.comp.isXType('window')) && this.comp.saveState();
    }
});