1  var iterate    = require('./lib/iterate.js')
 2    , initState  = require('./lib/state.js')
 3    , terminator = require('./lib/terminator.js')
 4    ;
 5  
 6  // Public API
 7  module.exports = serialOrdered;
 8  // sorting helpers
 9  module.exports.ascending  = ascending;
10  module.exports.descending = descending;
11  
12  /**
13   * Runs iterator over provided sorted array elements in series
14   *
15   * @param   {array|object} list - array or object (named list) to iterate over
16   * @param   {function} iterator - iterator to run
17   * @param   {function} sortMethod - custom sort function
18   * @param   {function} callback - invoked when all elements processed
19   * @returns {function} - jobs terminator
20   */
21  function serialOrdered(list, iterator, sortMethod, callback)
22  {
23    var state = initState(list, sortMethod);
24  
25    iterate(list, iterator, state, function iteratorHandler(error, result)
26    {
27      if (error)
28      {
29        callback(error, result);
30        return;
31      }
32  
33      state.index++;
34  
35      // are we there yet?
36      if (state.index < (state['keyedList'] || list).length)
37      {
38        iterate(list, iterator, state, iteratorHandler);
39        return;
40      }
41  
42      // done here
43      callback(null, state.results);
44    });
45  
46    return terminator.bind(state, callback);
47  }
48  
49  /*
50   * -- Sort methods
51   */
52  
53  /**
54   * sort helper to sort array elements in ascending order
55   *
56   * @param   {mixed} a - an item to compare
57   * @param   {mixed} b - an item to compare
58   * @returns {number} - comparison result
59   */
60  function ascending(a, b)
61  {
62    return a < b ? -1 : a > b ? 1 : 0;
63  }
64  
65  /**
66   * sort helper to sort array elements in descending order
67   *
68   * @param   {mixed} a - an item to compare
69   * @param   {mixed} b - an item to compare
70   * @returns {number} - comparison result
71   */
72  function descending(a, b)
73  {
74    return -1 * ascending(a, b);
75  }