tryMatch method

@override int tryMatch(String input, int start, int end)

Returns the end index (exclusive) of the longest prefix of input matched by this pattern, or -1 if no prefix of input matches.

Implementation

@override
int tryMatch(String input, int start, int end) {
  var result = -1;
  var currentStates = <NfaState>{};
  var nextStates = <NfaState>{};
  _addStates(this.start, currentStates, start, end);
  if (currentStates.any((state) => state.isEnd)) {
    result = start;
  }
  for (var i = start; i < end; i++) {
    final value = input.codeUnitAt(i);
    nextStates.clear();
    for (final state in currentStates) {
      final nextState = state.transitions[value];
      if (nextState != null) {
        _addStates(nextState, nextStates, i + 1, end);
      }
      for (final nextState in state.dots) {
        _addStates(nextState, nextStates, i + 1, end);
      }
    }
    if (nextStates.isEmpty) {
      break;
    }
    (currentStates, nextStates) = (nextStates, currentStates);
    if (currentStates.any((state) => state.isEnd)) {
      result = i + 1;
    }
  }
  return result;
}