feat(player): swipe track headers and remove individual queue entries

test/player_track_swipe_test.dart

@@ -0,0 +1,144 @@
+import 'package:audio_service/audio_service.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/widgets/player_queue_dismissible.dart';
+import 'package:spotiflac_android/widgets/player_track_swipe.dart';
+
+void main() {
+  final queue = [
+    for (var i = 0; i < 3; i++)
+      MediaItem(id: '$i', title: 'Song $i', artist: 'Artist $i'),
+  ];
+
+  for (final reducedMotion in [false, true]) {
+    testWidgets(
+      'cover drag moves only titles and selects once ($reducedMotion)',
+      (tester) async {
+        var index = 0;
+        final selected = <int>[];
+        await tester.pumpWidget(
+          MaterialApp(
+            home: MediaQuery(
+              data: MediaQueryData(disableAnimations: reducedMotion),
+              child: StatefulBuilder(
+                builder: (context, setState) {
+                  return PlayerTrackSwipe(
+                    queue: queue,
+                    currentIndex: index,
+                    onSelected: (item) async {
+                      selected.add(queue.indexOf(item));
+                      setState(() => index = queue.indexOf(item));
+                    },
+                    child: Scaffold(
+                      body: Center(
+                        child: SizedBox(
+                          width: 300,
+                          child: Column(
+                            mainAxisSize: MainAxisSize.min,
+                            children: [
+                              const PlayerTrackSwipeRegion(
+                                child: SizedBox(
+                                  key: ValueKey('cover'),
+                                  width: 200,
+                                  height: 200,
+                                ),
+                              ),
+                              PlayerTrackSwipeTitles(
+                                current: queue[index],
+                                builder: (item) => Column(
+                                  crossAxisAlignment: CrossAxisAlignment.start,
+                                  children: [
+                                    Text(item.title),
+                                    Text(item.artist!),
+                                  ],
+                                ),
+                              ),
+                            ],
+                          ),
+                        ),
+                      ),
+                    ),
+                  );
+                },
+              ),
+            ),
+          ),
+        );
+        final cover = find.byKey(const ValueKey('cover'));
+        final coverRect = tester.getRect(cover);
+        final titleX = tester.getTopLeft(find.text('Song 0')).dx;
+        final gesture = await tester.startGesture(coverRect.center);
+        await gesture.moveBy(const Offset(110, 0));
+        await tester.pump();
+        expect(tester.getRect(cover), coverRect);
+        expect(tester.getTopLeft(find.text('Song 0')).dx, greaterThan(titleX));
+        expect(find.text('Song 1'), findsOneWidget);
+        await gesture.up();
+        await tester.pumpAndSettle();
+        expect(selected, [1]);
+        expect(tester.getTopLeft(find.text('Song 1')).dx, closeTo(titleX, 0.1));
+
+        await tester.drag(find.text('Song 1'), const Offset(-180, 0));
+        await tester.pumpAndSettle();
+        expect(selected, [1, 0]);
+        // At the first song the previous direction resists, then returns.
+        await tester.drag(cover, const Offset(-200, 0));
+        await tester.pumpAndSettle();
+        expect(selected, [1, 0]);
+        expect(tester.getTopLeft(find.text('Song 0')).dx, closeTo(titleX, 0.1));
+        await tester.drag(cover, const Offset(20, 0));
+        await tester.pumpAndSettle();
+        expect(selected, [1, 0]);
+        expect(tester.takeException(), isNull);
+      },
+    );
+  }
+
+  testWidgets('queue left swipe removes just that occurrence', (tester) async {
+    final entries = [queue[0], queue[0].copyWith(), queue[1]];
+    await tester.pumpWidget(
+      MaterialApp(
+        home: StatefulBuilder(
+          builder: (context, setState) => Scaffold(
+            body: Column(
+              children: [
+                for (final item in entries)
+                  PlayerQueueDismissible(
+                    key: ObjectKey(item),
+                    enabled: !identical(item, entries.first),
+                    onRemove: () => setState(() {
+                      entries.removeWhere((entry) => identical(entry, item));
+                    }),
+                    child: SizedBox(
+                      width: 320,
+                      height: 64,
+                      child: Text(item.title),
+                    ),
+                  ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.drag(
+      find.byType(PlayerQueueDismissible).at(1),
+      const Offset(280, 0),
+    );
+    await tester.pumpAndSettle();
+    expect(entries, hasLength(3));
+    await tester.drag(
+      find.byType(PlayerQueueDismissible).at(1),
+      const Offset(-280, 0),
+    );
+    await tester.pumpAndSettle();
+    expect(entries.map((item) => item.id), ['0', '1']);
+    await tester.drag(
+      find.byType(PlayerQueueDismissible).first,
+      const Offset(-280, 0),
+    );
+    await tester.pumpAndSettle();
+    expect(entries, hasLength(2));
+    expect(tester.takeException(), isNull);
+  });
+}