@webgap/notifier/index.js

Webgap abstraction notification module.

/**
 * (C) Copyright 2015 WebGAP (http://www.webgap.eu/).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Created by: ManuelMartins
 * Created on: 05-03-2015
 *
 */

"use strict";

var underscore = require('underscore');
var async = require('async');
var util = require('util');
var systems = {};
var defaultSystem;

/**
 * Sends a notification to the specified systems
 *
 * @param {Object} options
 * @param {Object} options.notification
 * @param {Array}  options.notificationSystems
 * @param callback
 */
module.exports.notify = function notify(options, callback) {
  callback = callback || function noop(err) {
    console.warn('Something went wrong. Couldn\'t process the notification. %s', err);
    return;
  };
  if (options) {
    // handle notification systems
    if (!options.notificationSystems) {
      if (!defaultSystem) {
        return callback(new Error('No \'defaultSystem\' defined and no option \'notificationSystems\' provided.'));
      } else {
        options.notificationSystems = [defaultSystem];
      }
    } else {
      if (!Array.isArray(options.notificationSystems)) {
        options.notificationSystems = [options.notificationSystems];
      }
    }
    // ensure the message is not delivered through the same system multiple times
    options.notificationSystems = underscore.uniq(options.notificationSystems);
    // notify using the requested systems
    async.each(options.notificationSystems, function sendNotification(system, done) {
      var instance = systems[system] ? systems[system].instance : null;
      if (instance) {
        try {
          instance.notify(options.notification, function afterNotify(err) {
            return done(err);
          });
        } catch (err) {
          return done(err);
        }
      } else {
        console.warn('Trying to notify using a non registered system: %s', system);
        return done();
      }
    }, callback);
  } else {
    return callback(new Error('No \'options\' provided. Cannot do anything from nothing.'));
  }
};

/**
 * Register a new Notification System
 *
 * @param {Object}  system
 * @param {string}  system.name the name of the system - will be used later to identify this system
 * @param {Object}  system.instance an instance of a class which implements a method notify
 * @param {boolean} system.defaultSystem true if you want it tobe the default system to notify
 * @throws Error if class doesn't implements a \'notify\' function
 */
module.exports.register = function register(system) {
  system = system || {};
  // check if class implements a notify method
  if (system.instance && typeof system.instance.notify !== 'function') {
    throw new Error(util.format('The class provided must implement a \'notify\' function. Cannot register Notification System: %s', system.name));
  }
  if (systems[system.name]) {
    console.warn('Notification system with name %s is already registered. Please unregister if is the case, or change the name and try again.', system.name);
    return false;
  }
  systems[system.name] = {};
  systems[system.name].instance = system.instance;
  systems[system.name].name = system.name;
  systems[system.name].default = Boolean(system.defaultSystem) ? system.defaultSystem : false;
  console.info('%s notification system registered.', system.name);
  if (systems[system.name].default) {
    defaultSystem = system.name;
    console.info('%s is now the default notification system.', defaultSystem);
  }
  return true;
};

/**
 * Unregister a Notification System
 *
 * @param {string} systemName the name of the system to unregister
 */
module.exports.unregister = function unregister(systemName) {
  delete systems[systemName];
  console.info('%s notification system unregistered.', systemName);
};