/**
 * @class Ext.panel.Proxy
 * @extends Object
 * A custom drag proxy implementation specific to {@link Ext.panel.Panel}s. This class
 * is primarily used internally for the Panel's drag drop implementation, and
 * should never need to be created directly.
 * @constructor
 * @param panel The {@link Ext.panel.Panel} to proxy for
 * @param config Configuration options
 */
Ext.define('Ext.panel.Proxy', {
    
    alternateClassName: 'Ext.dd.PanelProxy',
    
    constructor: function(panel, config){
        /**
         * @property panel
         * @type Ext.panel.Panel
         */
        this.panel = panel;
        this.id = this.panel.id +'-ddproxy';
        Ext.apply(this, config);
    },

    /**
     * @cfg {Boolean} insertProxy True to insert a placeholder proxy element
     * while dragging the panel, false to drag with no proxy (defaults to true).
     * Most Panels are not absolute positioned and therefore we need to reserve
     * this space.
     */
    insertProxy: true,

    // private overrides
    setStatus: Ext.emptyFn,
    reset: Ext.emptyFn,
    update: Ext.emptyFn,
    stop: Ext.emptyFn,
    sync: Ext.emptyFn,

    /**
     * Gets the proxy's element
     * @return {Element} The proxy's element
     */
    getEl: function(){
        return this.ghost.el;
    },

    /**
     * Gets the proxy's ghost Panel
     * @return {Panel} The proxy's ghost Panel
     */
    getGhost: function(){
        return this.ghost;
    },

    /**
     * Gets the proxy element. This is the element that represents where the
     * Panel was before we started the drag operation.
     * @return {Element} The proxy's element
     */
    getProxy: function(){
        return this.proxy;
    },

    /**
     * Hides the proxy
     */
    hide : function(){
        if (this.ghost) {
            if (this.proxy) {
                this.proxy.remove();
                delete this.proxy;
            }

            // Unghost the Panel, do not move the Panel to where the ghost was
            this.panel.unghost(null, false);
            delete this.ghost;
        }
    },

    /**
     * Shows the proxy
     */
    show: function(){
        if (!this.ghost) {
            var panelSize = this.panel.getSize();
            this.panel.el.setVisibilityMode(Ext.core.Element.DISPLAY);
            this.ghost = this.panel.ghost();
            if (this.insertProxy) {
                // bc Panels aren't absolute positioned we need to take up the space
                // of where the panel previously was
                this.proxy = this.panel.el.insertSibling({cls: Ext.baseCSSPrefix + 'panel-dd-spacer'});
                this.proxy.setSize(panelSize);
            }
        }
    },

    // private
    repair: function(xy, callback, scope) {
        this.hide();
        if (typeof callback == "function") {
            callback.call(scope || this);
        }
    },

    /**
     * Moves the proxy to a different position in the DOM.  This is typically
     * called while dragging the Panel to keep the proxy sync'd to the Panel's
     * location.
     * @param {HTMLElement} parentNode The proxy's parent DOM node
     * @param {HTMLElement} before (optional) The sibling node before which the
     * proxy should be inserted (defaults to the parent's last child if not
     * specified)
     */
    moveProxy : function(parentNode, before){
        if (this.proxy) {
            parentNode.insertBefore(this.proxy.dom, before);
        }
    }
});