Stage 2: Library search, filters and Exercise detail with Flip Animation

- LibraryFilter: word search on names; muscle (primary), equipment and
  level choices that widen within a filter and narrow across filters
- ExerciseBrowser (reusable for the Plan picker) with search field,
  filter sheets showing live result counts, a clear button and an
  empty state
- Exercise detail: start/end Flip Animation at each Mode's pace (still
  with reduced motion), facts, main/secondary muscles, numbered steps

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/exercises/library_filter_test.dart

@@ -0,0 +1,78 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:zenxercise/src/exercises/exercise.dart';
+import 'package:zenxercise/src/exercises/library_filter.dart';
+import 'package:zenxercise/src/modes/mode.dart';
+
+Exercise _exercise(
+  String name, {
+  List<String> primary = const ['hamstrings'],
+  List<String> secondary = const [],
+  String? equipment = 'body only',
+  String level = 'beginner',
+}) => Exercise(
+  id: name.replaceAll(' ', '_'),
+  name: name,
+  mode: Mode.workout,
+  category: 'strength',
+  level: level,
+  equipment: equipment,
+  primaryMuscles: primary,
+  secondaryMuscles: secondary,
+  instructions: const [],
+  imageCount: 0,
+);
+
+void main() {
+  final squat = _exercise('Barbell Full Squat', primary: ['quadriceps'], secondary: ['glutes'], equipment: 'barbell');
+  final curl = _exercise('Dumbbell Bicep Curl', primary: ['biceps'], equipment: 'dumbbell', level: 'intermediate');
+  final deadlift = _exercise('Romanian Deadlift', primary: ['hamstrings'], equipment: 'barbell', level: 'expert');
+  final mystery = _exercise('Mystery Move', primary: ['glutes'], equipment: null);
+  final all = [squat, curl, deadlift, mystery];
+
+  List<Exercise> apply(LibraryFilter f) => f.apply(all);
+
+  test('an empty filter keeps everything', () {
+    const filter = LibraryFilter();
+
+    expect(filter.isActive, isFalse);
+    expect(apply(filter), all);
+  });
+
+  test('search matches every word of the query anywhere in the name, ignoring case', () {
+    expect(apply(const LibraryFilter(query: 'squat')), [squat]);
+    expect(apply(const LibraryFilter(query: 'barbell SQU')), [squat]);
+    expect(apply(const LibraryFilter(query: '  dead  romanian ')), [deadlift]);
+    expect(apply(const LibraryFilter(query: 'curl squat')), isEmpty);
+  });
+
+  test('choices within one filter widen, filters together narrow', () {
+    expect(apply(const LibraryFilter(muscles: {'biceps', 'hamstrings'})), [curl, deadlift]);
+    expect(apply(const LibraryFilter(muscles: {'biceps', 'hamstrings'}, equipment: {'barbell'})), [deadlift]);
+    expect(apply(const LibraryFilter(levels: {'expert', 'intermediate'})), [curl, deadlift]);
+  });
+
+  test('the muscle filter looks at the primary muscles only', () {
+    expect(apply(const LibraryFilter(muscles: {'glutes'})), [mystery]);
+  });
+
+  test('an Exercise without equipment drops out once equipment is filtered', () {
+    expect(apply(const LibraryFilter(equipment: {'barbell', 'dumbbell', 'body only'})), [squat, curl, deadlift]);
+  });
+
+  test('toggling a choice adds and removes it, and clearing keeps the query', () {
+    final filter = const LibraryFilter(query: 'curl').toggleMuscle('biceps').toggleLevel('beginner');
+
+    expect(filter.muscles, {'biceps'});
+    expect(filter.toggleMuscle('biceps').muscles, isEmpty);
+    expect(filter.activeChoices, 2);
+    expect(filter.clearChoices(), const LibraryFilter(query: 'curl'));
+  });
+
+  test('the options are the values present, levels in their natural order', () {
+    final options = FilterOptions.of(all);
+
+    expect(options.muscles, ['biceps', 'glutes', 'hamstrings', 'quadriceps']);
+    expect(options.equipment, ['barbell', 'dumbbell']);
+    expect(options.levels, ['beginner', 'intermediate', 'expert']);
+  });
+}

test/support/test_app.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
@@ -7,25 +8,51 @@ import 'package:zenxercise/src/exercises/exercise_library.dart';
 import 'package:zenxercise/src/modes/mode.dart';
 import 'package:zenxercise/src/settings/settings_controller.dart';
 
-Exercise exercise(String id, Mode mode, {String? name, int imageCount = 0}) => Exercise(
+Exercise exercise(
+  String id,
+  Mode mode, {
+  String? name,
+  List<String> primary = const ['hamstrings'],
+  List<String> secondary = const [],
+  String? equipment = 'body only',
+  String level = 'beginner',
+  List<String> instructions = const ['Breathe.'],
+  int imageCount = 0,
+}) => Exercise(
   id: id,
   name: name ?? id.replaceAll('_', ' '),
   mode: mode,
   category: mode == Mode.stretching ? 'stretching' : 'strength',
-  level: 'beginner',
-  equipment: 'body only',
-  primaryMuscles: const ['hamstrings'],
-  secondaryMuscles: const [],
-  instructions: const ['Breathe.'],
+  level: level,
+  equipment: equipment,
+  primaryMuscles: primary,
+  secondaryMuscles: secondary,
+  instructions: instructions,
   imageCount: imageCount,
 );
 
+/// Two stretches and a squat. The 90/90 Hamstring's images exist in the real assets.
 final sampleLibrary = ExerciseLibrary([
-  exercise('Hamstring_Stretch', Mode.stretching),
-  exercise('Calf_Stretch', Mode.stretching),
-  exercise('Barbell_Squat', Mode.workout),
+  exercise(
+    '90_90_Hamstring',
+    Mode.stretching,
+    name: '90/90 Hamstring',
+    secondary: const ['calves'],
+    instructions: const ['Lie on your back.', 'Straighten one leg.'],
+    imageCount: 2,
+  ),
+  exercise('Calf_Stretch', Mode.stretching, primary: const ['calves'], equipment: 'other', level: 'intermediate'),
+  exercise('Barbell_Squat', Mode.workout, primary: const ['quadriceps'], equipment: 'barbell'),
 ]);
 
+/// A Pixel-sized screen instead of the default 800×600, so the floating
+/// navigation bar does not cover what a test taps.
+void usePhoneScreen(WidgetTester tester) {
+  tester.view.physicalSize = const Size(1080, 2400);
+  tester.view.devicePixelRatio = 2.75;
+  addTearDown(tester.view.reset);
+}
+
 /// The whole app over [library], with preferences starting from [prefs].
 Future<SettingsController> pumpApp(
   WidgetTester tester, {

test/views/home_view_test.dart

@@ -16,7 +16,7 @@ void main() {
 
     expect(styleOf(tester).mode, Mode.stretching);
     expect(find.text('2 stretches'), findsOneWidget);
-    expect(find.text('Hamstring Stretch'), findsOneWidget);
+    expect(find.text('90/90 Hamstring'), findsOneWidget);
 
     await tester.tap(find.text('Workout'));
     await tester.pumpAndSettle();
@@ -26,7 +26,7 @@ void main() {
     expect(styleOf(tester).brightness, Brightness.dark);
     expect(find.text('1 exercise'), findsOneWidget);
     expect(find.text('Barbell Squat'), findsOneWidget);
-    expect(find.text('Hamstring Stretch'), findsNothing);
+    expect(find.text('90/90 Hamstring'), findsNothing);
   });
 
   testWidgets('opens in the last-used Mode', (tester) async {

test/views/library_view_test.dart

@@ -0,0 +1,83 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:zenxercise/src/exercises/views/exercise_detail_view.dart';
+import 'package:zenxercise/src/exercises/views/flip_animation.dart';
+
+import '../support/test_app.dart';
+
+void main() {
+  Future<void> openLibrary(WidgetTester tester) async {
+    usePhoneScreen(tester);
+    await pumpApp(tester);
+    await tester.tap(find.byTooltip('Library'));
+    await tester.pumpAndSettle();
+  }
+
+  testWidgets('search narrows the list and the count follows', (tester) async {
+    await openLibrary(tester);
+
+    await tester.enterText(find.byType(TextField), 'calf');
+    await tester.pumpAndSettle();
+
+    expect(find.text('Calf Stretch'), findsOneWidget);
+    expect(find.text('90/90 Hamstring'), findsNothing);
+    expect(find.text('1 of 2 stretches'), findsOneWidget);
+  });
+
+  testWidgets('a muscle filter narrows the list and clearing brings everything back', (tester) async {
+    await openLibrary(tester);
+
+    await tester.tap(find.text('Muscle'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.widgetWithText(FilterChip, 'Calves'));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('Show 1 result'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Calf Stretch'), findsOneWidget);
+    expect(find.text('90/90 Hamstring'), findsNothing);
+
+    await tester.tap(find.byTooltip('Clear filters'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('90/90 Hamstring'), findsOneWidget);
+  });
+
+  testWidgets('no matches says so and offers to clear', (tester) async {
+    await openLibrary(tester);
+
+    await tester.enterText(find.byType(TextField), 'zzz');
+    await tester.pumpAndSettle();
+
+    expect(find.text('No matches'), findsOneWidget);
+
+    await tester.tap(find.text('Clear filters'));
+    await tester.pumpAndSettle();
+
+    expect(find.text('90/90 Hamstring'), findsOneWidget);
+    expect(find.text('zzz'), findsNothing);
+  });
+
+  testWidgets('an Exercise opens its detail page, whose images flip', (tester) async {
+    await openLibrary(tester);
+
+    await tester.tap(find.text('90/90 Hamstring'));
+    await tester.pumpAndSettle();
+
+    expect(find.byType(ExerciseDetailView), findsOneWidget);
+    int frame() => tester.state<FlipAnimationState>(find.byType(FlipAnimation)).frame;
+    expect(frame(), 0);
+    await tester.pump(const Duration(milliseconds: 1500));
+    expect(frame(), 1);
+
+    final page = find.descendant(of: find.byType(ExerciseDetailView), matching: find.byType(Scrollable)).first;
+    for (final text in ['Hamstrings', 'Calves', 'Lie on your back.']) {
+      await tester.scrollUntilVisible(find.text(text), 100, scrollable: page);
+      expect(find.text(text), findsOneWidget);
+    }
+
+    // Leave the page so its flip timer stops.
+    await tester.pageBack();
+    await tester.pumpAndSettle();
+  });
+}