(function() {
    "use strict";

    var WebWorld = 
        MACHINE.modules['whalesong/web-world/impl.rkt'].privateExports;
    var EventSource = WebWorld.EventSource;
    var EventHandler = WebWorld.EventHandler;
    var wrapFunction = WebWorld.wrapFunction;

    var makeClosure = plt.baselib.functions.makeClosure;
    var makePrimitiveProcedure = plt.baselib.functions.makePrimitiveProcedure;
    var finalizeClosureCall = plt.runtime.finalizeClosureCall;

    var checkProcedure = plt.baselib.check.checkProcedure;



    /**
     * Creates an event source coupled to a JavaScript function.  Calling the function
     * should cause the event source to fire.
     */
    var makeJsEventSource = function() {
        var enabled = false;
        var fireEvent;

        var JsEventSource = function() {};
        JsEventSource.prototype = plt.baselib.heir(EventSource.prototype);
        JsEventSource.prototype.onStart = function(_fireEvent) {
            enabled = true;
            fireEvent = _fireEvent;
        };
        JsEventSource.prototype.onStop = function() {
            enabled = false;
            fireEvent = void(0);
        };

        var sender = function(v) {
            if (enabled) {
                fireEvent(void(0), v);
            }
        };
        return { eventSource: new JsEventSource(),
                 sender: sender };
    };


    var makeJsWorldEvent = makeClosure(
        'make-js-world-event',
        0,
        function(M) {
            var eventSourceRecord = makeJsEventSource();
            eventSourceRecord.eventSource
            var makeHandler = makePrimitiveProcedure(
                'make-js-world-event',
                1,
                function(M) {
                    var onEvent = wrapFunction(checkProcedure(M, 'js-world-event-handler', 0));
                    return new EventHandler('js-world-event',
                                            eventSourceRecord.eventSource,
                                            onEvent);
                });
            finalizeClosureCall(M,
                                makeHandler, 
                                eventSourceRecord.sender);
        });


    EXPORTS['make-js-world-event'] = makeJsWorldEvent;

}());