/**
 *  This is the only function called in a objects `onFrame` handler.
 *  If the objects has callbacks in it's `data._customHandlers` property,
 *  each of these is called.
 *
 *  @private
 *  @method frameManagerHandler
 *  @param {Object} ev The event object
 *  @for frameManager
 */
function frameManagerHandler(ev) {
        var item = this;
        if (typeof item.data === "undefined") {
            item.data = {};
        }
        if (typeof item.data._customHandlers !== "undefined" &&
            item.data._customHandlersCount > 0
        ) {
            // parcourir les handlers et les declencher
            for (var i in item.data._customHandlers) {
                if (item.data._customHandlers.hasOwnProperty(i)) {
                    if (typeof item.data._customHandlers[i] === "function") {
                        item.data._customHandlers[i].call(item, ev);
                    }
                }
            }
        }
    }
    /**
     *  The `frameManager` is used to bind and unbind multiple callbacks to an object's
     *  `onFrame`. If an object has at least one handler, it's `onFrame` handler will be
     *  {{#crossLink "frameManager/frameManagerHandler:method"}}{{/crossLink}}.
     *
     *  @class frameManager
     *  @static
     */
module.exports = {
    /**
     * Add a callback to a paper.js Item's `onFrame` event.
     * The Item itself will be the `thisValue` and the event object `ev` will be the first argument
     * 
     * @param {Object} item paper.js Item
     * @param {String} name An identifier for this callback
     * @param {Function} callback
     * @param {Object} parentItem If provided, the callback will be called on parentItem.onFrame event instead of item.onFrame
     * @example
     *      animatePaper.frameManager.add(circle,"goUp",function(ev) {
     *          // Animation logic
     *      });
     * @method add
     */
    add: function(item, name, callback, parentItem) {
        if (typeof item.data._customHandlers === "undefined") {
            item.data._customHandlers = {};
            item.data._customHandlersCount = 0;
        }
        item.data._customHandlers[name] = callback;
        item.data._customHandlersCount += 1;
        if (item.data._customHandlersCount > 0) {
            if (typeof parentItem !== "undefined") {
                parentItem.onFrame = frameManagerHandler;
            } else {
                item.onFrame = frameManagerHandler;
            }
        }

        return name;
    },
    /**
     * Remove a callback from an item's `onFrame` handler.
     * 
     * @param {Object} item paper.js Item object
     * @param {String} name The identifier of the callback you want to remove
     * @method remove
     */
    remove: function(item, name) {
        if (typeof item.data._customHandlers !== "undefined") {
            item.data._customHandlers[name] = null;
            item.data._customHandlersCount -= 1;
            if (item.data._customHandlersCount <= 0) {
                item.data._customHandlersCount = 0;

            }
        }
    }
};