text: "use strict";
  /**
   * Copyright (c) 2015, Yaacov Zamir <kobi.zamir@gmail.com>
   *
   * Permission to use, copy, modify, and/or distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF  THIS SOFTWARE.
   */
  
  /**
   * Take a modbus serial function and convert it to use promises.
   *
   * @param {Function} f the function to convert
   * @return a function that calls function "f" and return a promise.
   * @private
   */
  const _convert = function(f) {
      const converted = function(address, arg, next) {
          const client = this;
          const id = this._unitID;
  
          /* the function check for a callback
           * if we have a callback, use it
           * o/w build a promise.
           */
          if (next) {
              // if we have a callback, use the callback
              f.bind(client)(id, address, arg, next);
          } else {
              // o/w use  a promise
              const promise = new Promise(function(resolve, reject) {
                  function cb(err, data) {
                      if (err) {
                          reject(err);
                      } else {
                          resolve(data);
                      }
                  }
  
                  f.bind(client)(id, address, arg, cb);
              });
  
              return promise;
          }
      };
  
      return converted;
  };
  
  /**
   * Adds promise API to a Modbus object.
   *
   * @param {ModbusRTU} Modbus the ModbusRTU object.
   */
  const addPromiseAPI = function(Modbus) {
  
      const cl = Modbus.prototype;
  
      // set/get unitID
      cl.setID = function(id) {this._unitID = Number(id);};
      cl.getID = function() {return this._unitID;};
  
      // set/get timeout
      cl.setTimeout = function(timeout) {this._timeout = timeout;};
      cl.getTimeout = function() {return this._timeout;};
  
      // convert functions to return promises
      cl.readCoils = _convert(cl.writeFC1);
      cl.readDiscreteInputs = _convert(cl.writeFC2);
      cl.readHoldingRegisters = _convert(cl.writeFC3);
      cl.readInputRegisters = _convert(cl.writeFC4);
      cl.writeCoil = _convert(cl.writeFC5);
      cl.writeRegister = _convert(cl.writeFC6);
      cl.writeCoils = _convert(cl.writeFC15);
      cl.writeRegisters = _convert(cl.writeFC16);
      cl.readFileRecords = _convert(cl.writeFC20);
      cl.readDeviceIdentification = _convert(cl.writeFC43);
  };
  
  /**
   * Promise API Modbus library.
   *
   * @type {addPromiseAPI}
   */
  module.exports = addPromiseAPI;
  