/* Events
 *
 * A _very_ simple event manager, here only to keep this project framework agnostic, replace with something more robust.
 *
 */

(function (exports) {
    "use strict";

    /**
     * Events provides a VERY simple event manager, with just the minimum needed to support this app, if you're
     * doing anything interesting, replace this with the event system from a framework.
     *
     * @param eventSet : optional, pass an array of event types and the class will throw if an unknown event is
     * mentioned, useful for catching typos in event names
     * @constructor
     */
    var Events = function (eventSet) {

        this.eventSet = eventSet;
        this.eventHandlers = {};

        /**
         * register for an event
         * @param event : the event (string) to listen for
         * @param callback : function to call when event is triggered, args will be whatever is passed to trigger
         * @param context : optional, context for callback function
         */
        this.on = function (event, callback, context) {
            if (this.eventSet && this.eventSet.indexOf(event) === -1) {
                throw "Unknown event: " + event;
            }
            var handlers = this.eventHandlers[event] || (this.eventHandlers[event] = []);
            handlers.push({ callback: callback, context: context });
        };

        /**
         * unregister for (an) event(s)
         * @param event : event (string) to stop listening, or undefined to match all events
         * @param callback : function to remove, or undefined to match all functions
         * @param context : context to remove, optional
         * Note: implication is that calling off() with no args removes all handlers for all events
         */
        this.off = function (event, callback, context) {
            for (var evt in this.eventHandlers) {
                if (!event || event == evt) {
                    this.eventHandlers[evt] = this.eventHandlers[evt].filter(function (element) {
                        return (callback && callback != element.callback) || (context && context != element.context)
                    });
                }
            }

        };

        /**
         * triggers an event, calling all the handlers
         * @param event : the event (string) to trigger
         * @param args : any/all remaining arguments to trigger will be passed to the handlers
         */
        this.trigger = function (event, args) {
            if (this.eventSet && this.eventSet.indexOf(event) === -1) {
                throw "Unknown event: " + event;
            }
            var handlers = this.eventHandlers[event];
            if (handlers) {
                for (var i = 0; i < handlers.length; i++) {
                    handlers[i].callback.apply(handlers[i].context, Array.prototype.slice.call(arguments, 1));
                }
            }
        };
    };

    exports.Events = Events;
}(window));