mergeNestedSelector function

List<SimpleSelectorSequence> mergeNestedSelector(List<SimpleSelectorSequence> parent, List<SimpleSelectorSequence> current)

Merge the nested selector sequences current to the parent sequences or substitue any & with the parent selector.

Implementation

List<SimpleSelectorSequence> mergeNestedSelector(
    List<SimpleSelectorSequence> parent, List<SimpleSelectorSequence> current) {
  // If any & operator then the parent selector will be substituted otherwise
  // the parent selector is pre-pended to the current selector.
  var hasThis = current.any((s) => s.simpleSelector.isThis);

  var newSequence = <SimpleSelectorSequence>[];

  if (!hasThis) {
    // If no & in the sector group then prefix with the parent selector.
    newSequence.addAll(parent);
    newSequence.addAll(_convertToDescendentSequence(current));
  } else {
    for (var sequence in current) {
      if (sequence.simpleSelector.isThis) {
        // Substitue the & with the parent selector and only use a combinator
        // descendant if & is prefix by a sequence with an empty name e.g.,
        // "... + &", "&", "... ~ &", etc.
        var hasPrefix = newSequence.isNotEmpty && newSequence.last.simpleSelector.name.isNotEmpty;
        newSequence.addAll(hasPrefix ? _convertToDescendentSequence(parent) : parent);
      } else {
        newSequence.add(sequence);
      }
    }
  }

  return newSequence;
}