import '../contracts/danmaku.dart';

const defaultDuplicateDanmakuMergeWindowSeconds = 1.0;

final _whitespacePattern = RegExp(r'\s+');

List<DanmakuComment> mergeDuplicateDanmakuComments(
  Iterable<DanmakuComment> comments, {
  double windowSeconds = defaultDuplicateDanmakuMergeWindowSeconds,
}) {
  if (windowSeconds < 0) {
    throw ArgumentError.value(
      windowSeconds,
      'windowSeconds',
      'must be non-negative',
    );
  }

  final sorted = comments.toList()..sort(_compareDanmakuComments);
  if (sorted.length < 2) return sorted;


  final keptByText = <String, List<DanmakuComment>>{};
  final passthrough = <DanmakuComment>[];

  for (final comment in sorted) {
    final key = _mergeKey(comment);
    if (key.isEmpty) {
      passthrough.add(comment);
      continue;
    }

    final kept = keptByText.putIfAbsent(key, () => []);
    final windowStart = kept.isEmpty ? null : kept.last.time;
    if (windowStart == null || comment.time - windowStart > windowSeconds) {
      kept.add(comment);
    }
  }

  return <DanmakuComment>[
    ...passthrough,
    for (final kept in keptByText.values) ...kept,
  ]..sort(_compareDanmakuComments);
}

int _compareDanmakuComments(DanmakuComment a, DanmakuComment b) {
  final timeOrder = a.time.compareTo(b.time);
  if (timeOrder != 0) return timeOrder;
  return a.cid.compareTo(b.cid);
}

String _mergeKey(DanmakuComment comment) {
  return comment.text.trim().replaceAll(_whitespacePattern, ' ');
}