PiliPlus/lib/utils/subtitle_utils.dart

import 'package:PiliPlus/models/common/enum_with_label.dart';
import 'package:collection/collection.dart' show IterableExtension;

enum SubtitleFormat implements EnumWithLabel {
  json('JSON'),
  vtt('WEBVTT'),
  srt('SRT');

  @override
  final String label;
  const SubtitleFormat(this.label);
}

abstract final class SubtitleUtils {
  static String _vttTimecode(num seconds) {
    final int h = seconds ~/ 3600;
    seconds %= 3600;
    final int m = seconds ~/ 60;
    seconds %= 60;
    final String sms = seconds.toStringAsFixed(3).padLeft(6, '0');
    return "${h.toString().padLeft(2, '0')}:${m.toString().padLeft(2, '0')}:$sms";
  }

  static String json2Vtt(List list) {
    final sb = StringBuffer('WEBVTT\n\n')
      ..writeAll(
        list.map(
          (item) =>
              '${_vttTimecode(item['from'])} --> ${_vttTimecode(item['to'])}\n${item['content'].trim()}',
        ),
        '\n\n',
      );
    return sb.toString();
  }

  static String _srtTimecode(num seconds) {
    final int h = seconds ~/ 3600;
    seconds %= 3600;
    final int m = seconds ~/ 60;
    seconds %= 60;
    final int s = seconds.toInt();
    final int ms = ((seconds - s) * 1000).round();
    return '${h.toString().padLeft(2, '0')}:${m.toString().padLeft(2, '0')}:${s.toString().padLeft(2, '0')},${ms.toString().padLeft(3, '0')}';
  }

  static String json2Srt(List list) {
    final sb = StringBuffer()
      ..writeAll(
        list.mapIndexed(
          (i, e) =>
              '${i + 1}\n${_srtTimecode(e['from'])} --> ${_srtTimecode(e['to'])}\n${e['content'].trim()}',
        ),
        '\n\n',
      );
    return sb.toString();
  }
}