/**
     * The State class maintains state for a collection of named items, with 
     * a varying number of properties defined.
     *
     * It avoids the need to create a separate class for the item, and separate instances 
     * of these classes for each item, by storing the state in a 2 level hash table, 
     * improving performance when the number of items is likely to be large.
     *
     * @constructor
     * @class State
     */
    Y.State = function() {
        /**
         * Hash of attributes
         * @property data
         */
        this.data = {};
    };

    Y.State.prototype = {

        /**
         * Adds a property to an item.
         *
         * @method add
         * @param name {String} The name of the item.
         * @param key {String} The name of the property.
         * @param val {Any} The value of the property.
         */
        add : function(name, key, val) {
            var d = this.data;
            d[name] = d[name] || {};
            d[name][key] = val;
        },

        /**
         * Adds multiple properties to an item.
         *
         * @method addAll
         * @param name {String} The name of the item.
         * @param o {Object} A hash of property/value pairs.
         */
        addAll: function(name, o) {
            var key;

            for (key in o) {
                if (o.hasOwnProperty(key)) {
                    this.add(name, key, o[key]);
                }
            }
        },

        /**
         * Removes a property from an item.
         *
         * @method remove
         * @param name {String} The name of the item.
         * @param key {String} The property to remove.
         */
        remove: function(name, key) {
            var d = this.data;
            if (d[name]) {
                delete d[name][key];
            }
        },

        /**
         * Removes multiple properties from an item, or remove the item completely.
         *
         * @method removeAll
         * @param name {String} The name of the item.
         * @param o {Object|Array} Collection of properties to delete. If not provided, the entire item is removed.
         */
        removeAll: function(name, o) {
            var d = this.data;

            if (!o) {
                if (d[name]) {
                    delete d[name];
                }
            } else {
                Y.each(o, function(v, k) {
                    if(Y.Lang.isString(k)) {
                        this.remove(name, k);
                    } else {
                        this.remove(name, v);
                    }
                }, this);
            }
        },

        /**
         * For a given item, returns the value of the property requested, or undefined if not found.
         *
         * @method get
         * @param name {String} The name of the item
         * @param key {String} Optional. The property value to retrieve.
         * @return {Any} The value of the supplied property.
         */
        get: function(name, key) {
            var d = this.data;
            return (d[name]) ? d[name][key] : undefined;
        },

        /**
         * For the given item, returns an object with all of the
         * item's property/value pairs. By default the object returned
         * is a shallow copy of the stored data, but passing in true
         * as the second parameter will return a reference to the stored
         * data.
         *
         * @method getAll
         * @param name {String} The name of the item
         * @param reference {boolean} true, if you want a reference to the stored
         * object 
         * @return {Object} An object with property/value pairs for the item.
         */
        getAll : function(name, reference) {
            var d = this.data, o;

            if (!reference) {
                Y.each(d[name], function(v, k) {
                        o = o || {};
                        o[k] = v;
                });
            } else {
                o = d[name];
            }

            return o;
        }
    };