text: // Copyright (c) 2015 Uber Technologies, Inc.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  'use strict';
  
  module.exports = AbstractNetworkMessage;
  
  var EventEmitter = require('events').EventEmitter;
  var robb = require('robb/src/robb');
  var util = require('util');
  
  function AbstractNetworkMessage(options) {
      options = options || {};
  
      if (!robb.isUnsignedInt(options.index)) {
          throw new Error('Message requires to be reliably sent with an index');
      }
  
      this.index = options.index;
  
      if (typeof options.replyCallback === 'function') {
          this.replyCallback = options.replyCallback;
      } else {
          this.replyCallback = null;
      }
  }
  
  util.inherits(AbstractNetworkMessage, EventEmitter);
  
  AbstractNetworkMessage.type = 'Abstract';
  
  AbstractNetworkMessage.prototype.toJSON = function() {
      var type = Object.getPrototypeOf(this).constructor.type;
      if (type === AbstractNetworkMessage.type) {
          throw new Error('Cannot call toJSON on an AbstractNetworkMessage');
      }
      return {
          type: type,
          index: this.index
      };
  };
  