// Copyright IBM Corp. 2014,2016. All Rights Reserved.
  // Node module: loopback-connector
  // This file is licensed under the MIT License.
  // License text available at https://opensource.org/licenses/MIT
  
  'use strict';
  
  var createPromiseCallback = require('./utils').createPromiseCallback;
  
  module.exports = JSONStringPacker;
  
  var ISO_DATE_REGEXP = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*))(?:Z|(\+|-)([\d|:]*))?$/;
  
  /**
   * Create a new Packer instance that can be used to convert between JavaScript
   * objects and a JsonString representation in a String.
   *
   * @param {String} encoding Buffer encoding refer to https://nodejs.org/api/buffer.html#buffer_buffers_and_character_encodings
   */
  function JSONStringPacker(encoding) {
    this.encoding = encoding || 'base64';
  }
  
  /**
   * Encode the provided value to a `JsonString`.
   *
   * @param {*} value Any value (string, number, object)
   * @callback {Function} cb The callback to receive the parsed result.
   * @param {Error} err
   * @param {Buffer} data The encoded value
   * @promise
   */
  JSONStringPacker.prototype.encode = function(value, cb) {
    var encoding = this.encoding;
  
    cb = cb || createPromiseCallback();
    try {
      var data = JSON.stringify(value, function(key, value) {
        if (Buffer.isBuffer(this[key])) {
          return {
            type: 'Buffer',
            data: this[key].toString(encoding),
          };
        } else {
          return value;
        }
      });
  
      setImmediate(function() {
        cb(null, data);
      });
    } catch (err) {
      setImmediate(function() {
        cb(err);
      });
    }
    return cb.promise;
  };
  
  /**
   * Decode the JsonString value back to a JavaScript value.
   * @param {String} jsonString The JsonString input.
   * @callback {Function} cb The callback to receive the composed value.
   * @param {Error} err
   * @param {*} value Decoded value.
   * @promise
   */
  JSONStringPacker.prototype.decode = function(jsonString, cb) {
    var encoding = this.encoding;
  
    cb = cb || createPromiseCallback();
    try {
      var value = JSON.parse(jsonString, function(k, v) {
        if (v && v.type && v.type === 'Buffer') {
          return new Buffer(v.data, encoding);
        }
  
        if (ISO_DATE_REGEXP.exec(v)) {
          return new Date(v);
        }
  
        return v;
      });
  
      setImmediate(function() {
        cb(null, value);
      });
    } catch (err) {
      setImmediate(function() {
        cb(err);
      });
    }
    return cb.promise;
  };