blocktrail / blocktrail-sdk-nodejs

var q = require('q');

var webworkify = require('webworkify');

/**

 * wrapper around creating / using webworker that reuses webworker instance

 *

 * @param self

 * @param workerModuleFactory

 * @param message

 * @returns {*}

 */

module.exports = exports = {

    workify: function(self, workerModuleFactory, onLoad, message) {

        if (typeof message === "undefined") {

            if (typeof onLoad !== "undefined") {

                message = onLoad;

        }

        // create promise for result

        var deferred = q.defer();

        try {

            // init worker if necessary

            if (typeof self.worker === "undefined") {

                self.worker = webworkify(workerModuleFactory());

                self.first = true;

                self.id = 0;

            }

            var worker = self.worker;

            // keep a unique id to distinguish between responses

            var id = self.id++;

            var onMessage = function(e) {

                if (self.first) {

                    self.first = false;

                    URL.revokeObjectURL(worker.objectURL);

                }

                // don't process messages that aren't for us

                if (e.data.id !== id) {

                    return;

                }

                deferred.resolve(e.data);

            };

            var onError = function(e) {

                deferred.reject(new Error(e.message.replace("Uncaught Error: ", '')));

            };

            var unsub = function() {

                worker.removeEventListener("message", onMessage);

                worker.removeEventListener("error", onError);

            };

            // register event listeners

            worker.addEventListener('message', onMessage, false);

            worker.addEventListener('error', onError, false);

            // submit message to worker to init work

            message.id = id;

            worker.postMessage(message);

            // return promise

            return deferred.promise.then(function(r) {

                unsub();

                return r;

            }, function(e) {

                unsub();

                throw e;

            });

        } catch (e) {

            deferred.reject(e);

            return deferred.promise;

        }

    }

};