pub/petitparser/lib/src/debug/profile.dart

part of petitparser.debug;

/// Returns a transformed [parser] that when being used measures
/// the activation count and total time of each parser.
///
/// For example, the snippet
///
///     var parser = letter() & word().star();
///     profile(parser).parse('f1234567890');
///
/// produces the following output:
///
///      1  2006  Instance of 'SequenceParser'
///      1   697  Instance of 'PossessiveRepeatingParser'[0..*]
///     11   406  Instance of 'CharacterParser'[letter or digit expected]
///      1   947  Instance of 'CharacterParser'[letter expected]
///
/// The first number refers to the number of activations of each parser, and
/// the second number is the microseconds spent in this parser and all its
/// children.
Parser profile(Parser root, [OutputHandler output = print]) {
  Map<Parser, int> count = new Map();
  Map<Parser, Stopwatch> watch = new Map();
  List<Parser> parsers = new List();
  return new ContinuationParser(transformParser(root, (parser) {
    parsers.add(parser);
    return new ContinuationParser(parser, (continuation, context) {
      count[parser]++;
      watch[parser].start();
      var result = continuation(context);
      watch[parser].stop();
      return result;
    });
  }), (continuation, context) {
    parsers.forEach((parser) {
      count[parser] = 0;
      watch[parser] = new Stopwatch();
    });
    var result = continuation(context);
    parsers.forEach((parser) {
      output('${count[parser]}\t'
          '${watch[parser].elapsedMicroseconds}\t'
          '$parser');
    });
    return result;
  });
}