/**
 * @class Ext.dd.Registry
 * Provides easy access to all drag drop components that are registered on a page.  Items can be retrieved either
 * directly by DOM node id, or by passing in the drag drop event that occurred and looking up the event target.
 * @singleton
 */
Ext.dd.Registry = function(){
    var elements = {}; 
    var handles = {}; 
    var autoIdSeed = 0;

    var getId = function(el, autogen){
        if(typeof el == "string"){
            return el;
        }
        var id = el.id;
        if(!id && autogen !== false){
            id = "extdd-" + (++autoIdSeed);
            el.id = id;
        }
        return id;
    };
    
    return {
    
/**
     * Resgister a drag drop element
     * @param {String/HTMLElement) element The id or DOM node to register
     * @param {Object} data (optional) An custom data object that will be passed between the elements that are involved
     * in drag drop operations.  You can populate this object with any arbitrary properties that your own code
     * knows how to interpret, plus there are some specific properties known to the Registry that should be
     * populated in the data object (if applicable):
     * 
Value      Description

---------  ------------------------------------------

handles    Array of DOM nodes that trigger dragging

           for the element being registered

isHandle   True if the element passed in triggers

           dragging itself, else false

     */
        register : function(el, data){
            data = data || {};
            if(typeof el == "string"){
                el = document.getElementById(el);
            }
            data.ddel = el;
            elements[getId(el)] = data;
            if(data.isHandle !== false){
                handles[data.ddel.id] = data;
            }
            if(data.handles){
                var hs = data.handles;
                for(var i = 0, len = hs.length; i < len; i++){
                	handles[getId(hs[i])] = data;
                }
            }
        },

    
/**
     * Unregister a drag drop element
     * @param {String/HTMLElement) element The id or DOM node to unregister
     */
        unregister : function(el){
            var id = getId(el, false);
            var data = elements[id];
            if(data){
                delete elements[id];
                if(data.handles){
                    var hs = data.handles;
                    for(var i = 0, len = hs.length; i < len; i++){
                    	delete handles[getId(hs[i], false)];
                    }
                }
            }
        },

    
/**
     * Returns the handle registered for a DOM Node by id
     * @param {String/HTMLElement} id The DOM node or id to look up
     * @return {Object} handle The custom handle data
     */
        getHandle : function(id){
            if(typeof id != "string"){ // must be element?
                id = id.id;
            }
            return handles[id];
        },

    
/**
     * Returns the handle that is registered for the DOM node that is the target of the event
     * @param {Event} e The event
     * @return {Object} handle The custom handle data
     */
        getHandleFromEvent : function(e){
            var t = Ext.lib.Event.getTarget(e);
            return t ? handles[t.id] : null;
        },

    
/**
     * Returns a custom data object that is registered for a DOM node by id
     * @param {String/HTMLElement} id The DOM node or id to look up
     * @return {Object} data The custom data
     */
        getTarget : function(id){
            if(typeof id != "string"){ // must be element?
                id = id.id;
            }
            return elements[id];
        },

    
/**
     * Returns a custom data object that is registered for the DOM node that is the target of the event
     * @param {Event} e The event
     * @return {Object} data The custom data
     */
        getTargetFromEvent : function(e){
            var t = Ext.lib.Event.getTarget(e);
            return t ? elements[t.id] || handles[t.id] : null;
        }
    };
}();