opt export subtitle

Signed-off-by: dom <githubaccount56556@proton.me>

lib/utils/subtitle_utils.dart

@@ -0,0 +1,57 @@
+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();
+  }
+}