Wain-PC/work-wrap

(function () {
    var functionToObjectURL = function (fn) {
            var blob, stringFunc = fn.toString();
            stringFunc = stringFunc.substring(stringFunc.indexOf('{') + 1, stringFunc.lastIndexOf('}'));
            try {
                blob = new Blob([stringFunc], {'type': 'text/javascript'});
            } catch (error) { // Backwards-compatibility
                var BlobBuilder = window.BlobBuilder || window.WebKitBlobBuilder || window.MozBlobBuilder;
                blob = new BlobBuilder();
                blob.append(stringFunc);
                blob = blob.getBlob();
            }
            return (window.URL || window.webkitURL).createObjectURL(blob);
        },
        fnUrl = functionToObjectURL(function () {
            self.onmessage = function (event) {
                var message = event.data,
                    args = message.args.map(function (arg) {
                        if (arg && arg.indexOf && !arg.indexOf('!FN!')) {
                            return eval('(' + arg.substr(4) + ')');
                        }
                        return arg;
                    });

                try {
                    self.postMessage({
                        id: message.id,
                        result: eval('(' + message.func + ')').apply(null, args)
                    });
                } catch (e) {
                    self.postMessage({id: message.id, error: e.message});
                }
            }
        }),
        createAndListen = function () {
            var worker = new Worker(fnUrl);
            worker.queue = {index: 0};
            worker.addEventListener('message', function (e) {
                if (e.data.hasOwnProperty('result')) {
                    this.queue[e.data.id].resolve(e.data.result);
                }
                else {
                    this.queue[e.data.id].reject(e.data.error);
                }
                delete this.queue[e.data.id];
            });
            return worker;
        };

    window.Worker.wrap = function (fn) {
        var worker = createAndListen(),
            retFunc = function () {
                var args = Array.prototype.slice.call(arguments).map(function (arg) {
                    if (typeof arg === 'function') {
                        return '!FN!' + arg.toString();
                    }
                    return arg;
                });

                if (!worker) {
                    return Promise.reject("Worker has been terminated. Call `.restart()` before trying again.");
                }

                worker.postMessage({
                    id: ++worker.queue.index,
                    func: fn.toString(),
                    args: args
                });
                return (function (index) {
                    return new Promise(function (resolve, reject) {
                        worker.queue[index] = {
                            resolve: resolve,
                            reject: reject
                        };
                    });
                })(worker.queue.index);


            };
        retFunc.terminate = function () {
            if (!worker) {
                return false;
            }
            worker.terminate();
            worker = null;
            return true;
        };

        retFunc.restart = function () {
            worker = createAndListen();
        };
        return retFunc;
    };
})();