/**
* See [Demo.js](https://github.com/liabru/matter-js/blob/master/demo/js/Demo.js) 
* and [DemoMobile.js](https://github.com/liabru/matter-js/blob/master/demo/js/DemoMobile.js) for usage examples.
*
* @class Events
*/

var Events = {};

module.exports = Events;

var Common = require('./Common');

(function() {

    /**
     * Subscribes a callback function to the given object's `eventName`.
     * @method on
     * @param {} object
     * @param {string} eventNames
     * @param {function} callback
     */
    Events.on = function(object, eventNames, callback) {
        var names = eventNames.split(' '),
            name;

        for (var i = 0; i < names.length; i++) {
            name = names[i];
            object.events = object.events || {};
            object.events[name] = object.events[name] || [];
            object.events[name].push(callback);
        }

        return callback;
    };

    /**
     * Removes the given event callback. If no callback, clears all callbacks in `eventNames`. If no `eventNames`, clears all events.
     * @method off
     * @param {} object
     * @param {string} eventNames
     * @param {function} callback
     */
    Events.off = function(object, eventNames, callback) {
        if (!eventNames) {
            object.events = {};
            return;
        }

        // handle Events.off(object, callback)
        if (typeof eventNames === 'function') {
            callback = eventNames;
            eventNames = Common.keys(object.events).join(' ');
        }

        var names = eventNames.split(' ');

        for (var i = 0; i < names.length; i++) {
            var callbacks = object.events[names[i]],
                newCallbacks = [];

            if (callback) {
                for (var j = 0; j < callbacks.length; j++) {
                    if (callbacks[j] !== callback)
                        newCallbacks.push(callbacks[j]);
                }
            }

            object.events[names[i]] = newCallbacks;
        }
    };

    /**
     * Fires all the callbacks subscribed to the given object's `eventName`, in the order they subscribed, if any.
     * @method trigger
     * @param {} object
     * @param {string} eventNames
     * @param {} event
     */
    Events.trigger = function(object, eventNames, event) {
        var names,
            name,
            callbacks,
            eventClone;

        if (object.events) {
            if (!event)
                event = {};

            names = eventNames.split(' ');

            for (var i = 0; i < names.length; i++) {
                name = names[i];
                callbacks = object.events[name];

                if (callbacks) {
                    eventClone = Common.clone(event, false);
                    eventClone.name = name;
                    eventClone.source = object;

                    for (var j = 0; j < callbacks.length; j++) {
                        callbacks[j].apply(object, [eventClone]);
                    }
                }
            }
        }
    };

})();