refactor(mpv): unify property decoding

lib/mpv/player/mpv_node_decoder.dart

@@ -0,0 +1,25 @@
+import 'dart:convert';
+
+/// Decodes an mpv node delivered either as a platform-channel value or JSON.
+abstract final class MpvNodeDecoder {
+  static List<Object?>? decodeList(Object? value) {
+    final decoded = _decode(value);
+    return decoded is List<Object?> ? decoded : null;
+  }
+
+  static Map<Object?, Object?>? decodeMap(Object? value) {
+    final decoded = _decode(value);
+    return decoded is Map<Object?, Object?> ? decoded : null;
+  }
+
+  static Object? _decode(Object? value) {
+    if (value is List || value is Map) return value;
+    if (value is! String || value.isEmpty) return null;
+
+    try {
+      return jsonDecode(value);
+    } on FormatException {
+      return null;
+    }
+  }
+}

lib/mpv/player/player_base.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:convert';
 import 'dart:math' as math;
 
 import 'package:collection/collection.dart';
@@ -11,6 +10,7 @@ import '../../utils/app_logger.dart';
 import '../../utils/track_label_builder.dart';
 import '../font_loader.dart';
 import '../models.dart';
+import 'mpv_node_decoder.dart';
 import 'player.dart';
 import 'player_state.dart';
 import 'player_stream_controllers.dart';
@@ -258,17 +258,7 @@ abstract class PlayerBase with PlayerStreamControllersMixin implements Player {
         break;
 
       case 'track-list':
-        List? trackList;
-        if (value is List) {
-          trackList = value;
-        } else if (value is String && value.isNotEmpty) {
-          try {
-            final parsed = jsonDecode(value);
-            if (parsed is List) trackList = parsed;
-          } catch (e) {
-            appLogger.d('Player: track-list parse failed', error: e);
-          }
-        }
+        final trackList = MpvNodeDecoder.decodeList(value);
         if (trackList != null) {
           final result = parseTrackList(trackList);
           _state = _state.copyWith(tracks: result.tracks);
@@ -298,17 +288,7 @@ abstract class PlayerBase with PlayerStreamControllersMixin implements Player {
         break;
 
       case 'audio-device-list':
-        List? deviceList;
-        if (value is List) {
-          deviceList = value;
-        } else if (value is String && value.isNotEmpty) {
-          try {
-            final parsed = jsonDecode(value);
-            if (parsed is List) deviceList = parsed;
-          } catch (e) {
-            appLogger.d('Player: device-list parse failed', error: e);
-          }
-        }
+        final deviceList = MpvNodeDecoder.decodeList(value);
         if (deviceList != null) {
           final devices = deviceList
               .whereType<Map>()
@@ -331,19 +311,13 @@ abstract class PlayerBase with PlayerStreamControllersMixin implements Player {
 
   /// Parse demuxer-cache-state property to extract seekable ranges and buffer end.
   void _handleDemuxerCacheState(dynamic value) {
-    Map? cacheState;
-    if (value is Map) {
-      cacheState = value;
-    } else if (value is String && value.isNotEmpty) {
+    if (value is String && value.isNotEmpty) {
       // Throttle JSON parsing to avoid ANR on low-end devices
       final nowMs = _throttleSw.elapsedMilliseconds;
       if (nowMs - _lastCacheStateMs < 250) return;
       _lastCacheStateMs = nowMs;
-      try {
-        final parsed = jsonDecode(value);
-        if (parsed is Map) cacheState = parsed;
-      } catch (_) {}
     }
+    final cacheState = MpvNodeDecoder.decodeMap(value);
     if (cacheState == null) return;
 
     // Extract cache-end for the single buffer duration (replaces demuxer-cache-time)

test/mpv/mpv_node_decoder_test.dart

@@ -0,0 +1,53 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/mpv/player/mpv_node_decoder.dart';
+
+void main() {
+  const nestedList = [
+    {
+      'type': 'audio',
+      'metadata': {
+        'values': [true, 2, 3.5, null],
+      },
+    },
+  ];
+  const nestedMap = {
+    'cache-end': 12.5,
+    'seekable-ranges': [
+      {'start': 1, 'end': 9.25},
+    ],
+  };
+
+  final cases = <({String name, Object? input, Object? list, Object? map})>[
+    (name: 'nested structured list', input: nestedList, list: nestedList, map: null),
+    (name: 'nested structured map', input: nestedMap, list: null, map: nestedMap),
+    (
+      name: 'valid list JSON',
+      input: '[{"type":"audio","metadata":{"values":[true,2,3.5,null]}}]',
+      list: nestedList,
+      map: null,
+    ),
+    (
+      name: 'valid map JSON',
+      input: '{"cache-end":12.5,"seekable-ranges":[{"start":1,"end":9.25}]}',
+      list: null,
+      map: nestedMap,
+    ),
+    (name: 'malformed JSON', input: '{not-json', list: null, map: null),
+    (name: 'JSON scalar', input: '42', list: null, map: null),
+    (name: 'structured scalar', input: 42, list: null, map: null),
+    (name: 'empty string', input: '', list: null, map: null),
+    (name: 'null', input: null, list: null, map: null),
+    (name: 'JSON null', input: 'null', list: null, map: null),
+    (name: 'empty structured list', input: const [], list: const [], map: null),
+    (name: 'empty structured map', input: const {}, list: null, map: const {}),
+    (name: 'empty JSON list', input: '[]', list: const [], map: null),
+    (name: 'empty JSON map', input: '{}', list: null, map: const {}),
+  ];
+
+  for (final testCase in cases) {
+    test(testCase.name, () {
+      expect(MpvNodeDecoder.decodeList(testCase.input), testCase.list);
+      expect(MpvNodeDecoder.decodeMap(testCase.input), testCase.map);
+    });
+  }
+}

test/mpv/player_native_bridge_test.dart

@@ -101,17 +101,29 @@ void main() {
               {'start': 1, 'end': 9.25},
             ],
           });
+          await sendObservation('audio-device-list', const [
+            {'name': 'speakers', 'description': 'Main speakers'},
+          ]);
 
           expect(player.state.tracks.audio.single.id, '7');
           expect(player.state.tracks.audio.single.title, 'Main');
           expect(player.state.buffer, const Duration(milliseconds: 12500));
           expect(player.state.bufferRanges.single.start, const Duration(seconds: 1));
           expect(player.state.bufferRanges.single.end, const Duration(milliseconds: 9250));
+          expect(player.state.audioDevices.single.name, 'speakers');
 
           // Unsupported mpv_node formats cross the native bridge as null and
           // must not erase the last valid structured observation.
-          await sendObservation('track-list', null);
-          expect(player.state.tracks.audio.single.id, '7');
+          for (final invalid in [null, '{not-json', 42]) {
+            await sendObservation('track-list', invalid);
+            await sendObservation('demuxer-cache-state', invalid);
+            await sendObservation('audio-device-list', invalid);
+
+            expect(player.state.tracks.audio.single.id, '7');
+            expect(player.state.buffer, const Duration(milliseconds: 12500));
+            expect(player.state.bufferRanges.single.end, const Duration(milliseconds: 9250));
+            expect(player.state.audioDevices.single.name, 'speakers');
+          }
         } finally {
           await player.dispose();
         }