Function parser

tasks/docs/metadata.js:39–130

* Parses a file for metadata and stores result in data object. * @param {File} file - object provided by map-stream. * @param {function(?,File)} - callback provided by map-stream to * reply when done.

(file, callback)

 * reply when done.
 */
function parser(file, callback) {
  // file exit conditions
  if(file.isNull()) {
    return callback(null, file); // pass along
  }

  if(file.isStream()) {
    return callback(new Error('Streaming not supported'));
  }

  try {

    let
      /** @type {string} */
      text     = String(file.contents.toString('utf8')),
      lines    = text.split('\n'),
      filename = file.path.substring(0, file.path.length - 4),
      key      = 'server/documents',
      position = filename.indexOf(key)
    ;

    // exit conditions
    if(!lines) {
      return;
    }
    if(position < 0) {
      return callback(null, file);
    }

    filename = filename.substring(position + key.length + 1, filename.length);

    let
      lineCount = lines.length,
      active    = false,
      yaml      = [],
      categories = [
        'UI Element',
        'UI Global',
        'UI Collection',
        'UI View',
        'UI Module',
        'UI Behavior'
      ],
      index,
      meta,
      line
    ;

    for(index = 0; index < lineCount; index++) {

      line = lines[index];

      // Wait for metadata block to begin
      if(!active) {
        if(startsWith(line, '---')) {
          active = true;
        }
        continue;