toNfa method

@override Nfa toNfa()

Compiles this AST node into a nondeterministic finite automaton (Nfa).

Implementation

@override
Nfa toNfa() {
  final max = this.max;
  if (min == 0 && max == null) {
    final start = NfaState(isEnd: false);
    final end = NfaState(isEnd: true);
    final childNfa = child.toNfa();
    start.epsilons.add(end);
    start.epsilons.add(childNfa.start);
    childNfa.end.epsilons.add(end);
    childNfa.end.epsilons.add(childNfa.start);
    childNfa.end.isEnd = false;
    return Nfa(start: start, end: end);
  } else if (min == 0 && max == 1) {
    final start = NfaState(isEnd: false);
    final end = NfaState(isEnd: true);
    final childNfa = child.toNfa();
    start.epsilons.add(end);
    start.epsilons.add(childNfa.start);
    childNfa.end.epsilons.add(end);
    childNfa.end.isEnd = false;
    return Nfa(start: start, end: end);
  }
  final nfas = <Nfa>[];
  for (var i = 0; i < min; i++) {
    nfas.add(child.toNfa());
  }
  if (max == null) {
    nfas.add(QuantificationNode(child, 0, null).toNfa());
  } else {
    for (var i = 0; i < max - min; i++) {
      nfas.add(QuantificationNode(child, 0, 1).toNfa());
    }
  }
  if (nfas.isEmpty) {
    final start = NfaState(isEnd: false);
    final end = NfaState(isEnd: true);
    start.epsilons.add(end);
    return Nfa(start: start, end: end);
  }
  for (var i = 0; i < nfas.length - 1; i++) {
    final current = nfas[i];
    final next = nfas[i + 1];
    current.end.epsilons.add(next.start);
    current.end.isEnd = false;
  }
  return Nfa(start: nfas.first.start, end: nfas.last.end);
}