Initial commit: watch-together phases 0-4 + presence hardening, internet-tested

apps/desktop/lib/src/playback/playback_controller.dart

@@ -0,0 +1,102 @@
+import 'dart:io';
+
+import 'package:flutter/widgets.dart';
+import 'package:media_kit/media_kit.dart';
+
+import '../sync/room_diff.dart';
+
+class PlaybackController {
+  late final Player player;
+  bool _ready = false;
+
+  Future<void> init() async {
+    player = Player(
+        configuration: PlayerConfiguration(
+      bufferSize: 64 * 1024 * 1024,
+      vo: Platform.environment['SYNC_RELAY_VO'],
+    ));
+    _ready = true;
+    await _pinBufferProps();
+  }
+
+  Future<void> _pin(String property, String value) async {
+    try {
+      final dynamic platform = player.platform;
+      await platform?.setProperty(property, value);
+    } catch (e, st) {
+      debugPrint('pin $property=$value failed: $e\n$st');
+    }
+  }
+
+  Future<void> _pinBufferProps() async {
+    await _pin('demuxer-readahead-secs', '10');
+    await _pin('cache-secs', '10');
+    final hwdec = Platform.environment['SYNC_RELAY_HWDEC'];
+    if (hwdec != null && hwdec.isNotEmpty) {
+      await _pin('hwdec', hwdec);
+    }
+    await _pin('stream-lavf-o',
+        'reconnect_streamed=1,reconnect_on_http_error=1,reconnect_delay_max=4');
+  }
+
+  Future<void> openUrl(String url) async {
+    if (!_ready) return;
+    try {
+      await player.open(Media(url), play: false);
+    } catch (e, st) {
+      debugPrint('open $url failed: $e\n$st');
+      rethrow;
+    }
+  }
+
+  double get positionSecs =>
+      player.state.position.inMilliseconds / 1000.0;
+
+  double get bufferedSecsAhead {
+    final ahead =
+        (player.state.buffer - player.state.position).inMilliseconds / 1000.0;
+    if (ahead.isNaN || ahead < 0) return 0;
+    return ahead;
+  }
+
+  double get durationSecs =>
+      player.state.duration.inMilliseconds / 1000.0;
+
+  Future<void> apply(List<PlayerAction> actions) async {
+    for (final action in actions) {
+      try {
+        switch (action) {
+          case SeekAction(:final position):
+            if ((positionSecs - position).abs() < 0.5) break;
+            await player.seek(Duration(milliseconds: (position * 1000).round()));
+          case TransportAction(:final playing):
+            if (playing) {
+              await player.play();
+            } else {
+              await player.pause();
+            }
+          case RateAction(:final rate):
+            await player.setRate(rate);
+        }
+      } catch (e, st) {
+        debugPrint('player action $action failed: $e\n$st');
+      }
+    }
+  }
+
+  Future<void> dispose() async {
+    _ready = false;
+    try {
+      await player.dispose();
+    } catch (_) {}
+  }
+
+  Future<void> stop() async {
+    if (!_ready) return;
+    try {
+      await player.stop();
+    } catch (e, st) {
+      debugPrint('player stop failed: $e\n$st');
+    }
+  }
+}