code: function getRequiredFilename (name, callback) {
    var filepath = path.join(LOG_DIR, name);
  
    function getStats () {
  
      fs.stat(filepath, function (err, stats) {
        if (err) {
          callback(err, null);
        } else if (stats && stats.size >= MAX_FILE_SIZE) {
          createFile();
        } else {
          callback(null, name);
        }
      });
    }
  
    function createFile () {
      fs.writeFile(filepath, '[]', function (err) {
        if (err) {
          callback(err, null);
        } else {
          callback(null, name);
        }
      });
    }
  
    fs.exists(filepath, function (exists) {
      if (exists) {
        getStats();
      } else {
        createFile();
      }
    });
  }
docs: Determine the file to write the current log file to
  @param  {String}   name
  @param  {Function} callback