import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:kouyu_english/core/app_state.dart';
import 'package:kouyu_english/core/generated_content.dart';
import 'package:kouyu_english/core/models.dart';
import 'package:kouyu_english/features/dialogue/dialogue_flow.dart';
import 'package:kouyu_english/features/review/review_page.dart';
import 'package:kouyu_english/features/shell/learning_shell.dart';
import 'package:shared_preferences/shared_preferences.dart';

import 'package:kouyu_english/core/courses/course_repository.dart';
import 'support/app_assets.dart';

void main() {
  setUp(() {
    SharedPreferences.setMockInitialValues({});
  });

  testWidgets('Onboarding PlacementPage back button returns to WelcomePage', (
    tester,
  ) async {
    await pumpLoadedApp(tester);
    await tester.pumpAndSettle();

    expect(find.text('每天 20 分钟，\n说出能用的英语。'), findsOneWidget);
    await tester.tap(find.text('继续'));
    await tester.pumpAndSettle();

    expect(find.text('从哪里开始？'), findsOneWidget);
    expect(find.byIcon(Icons.arrow_back), findsOneWidget);

    await tester.tap(find.byIcon(Icons.arrow_back));
    await tester.pumpAndSettle();

    expect(find.text('每天 20 分钟，\n说出能用的英语。'), findsOneWidget);
  });

  testWidgets('Profile sub-page back button returns to 我的', (tester) async {
    final state = AppState()..finishOnboarding();
    await tester.pumpWidget(MaterialApp(home: LearningShell(state: state)));
    await tester.pumpAndSettle();

    await tester.tap(find.text('我的'));
    await tester.pumpAndSettle();

    final preferences = find.text('学习偏好');
    await tester.ensureVisible(preferences);
    await tester.tap(preferences);
    await tester.pumpAndSettle();

    expect(find.text('每日学习时间'), findsOneWidget);
    await tester.tap(find.byType(BackButton));
    await tester.pumpAndSettle();

    expect(find.text('每日学习时间'), findsNothing);
    expect(find.text('学习偏好'), findsOneWidget);
  });

  testWidgets('LessonFlow back button returns to tab', (tester) async {
    final state = AppState()..finishOnboarding();
    await tester.pumpWidget(MaterialApp(home: LearningShell(state: state)));
    await tester.pumpAndSettle();

    expect(find.text('开始今天的学习'), findsOneWidget);
    await tester.tap(find.text('开始今天的学习'));
    await tester.pumpAndSettle();

    // In LessonFlow
    expect(find.byIcon(Icons.arrow_back), findsOneWidget);

    // Tap back button
    await tester.tap(find.byIcon(Icons.arrow_back));
    await tester.pumpAndSettle();

    expect(find.text('开始今天的学习'), findsOneWidget);
  });

  testWidgets('学习 tab shows today task and the lesson path', (tester) async {
    final state = AppState()..finishOnboarding();
    await tester.pumpWidget(MaterialApp(home: LearningShell(state: state)));
    await tester.pumpAndSettle();

    expect(find.byType(NavigationDestination), findsNWidgets(4));
    expect(find.text('今日新课'), findsOneWidget);
    expect(find.text('课程路径'), findsOneWidget);
    expect(find.textContaining('第 1 课 · '), findsWidgets);
  });

  testWidgets('DialogueSummaryPage has back button', (tester) async {
    var backCalled = false;
    await tester.pumpWidget(
      MaterialApp(
        home: DialogueSummaryPage(
          summary: const DialogueSummaryData(
            completedTasks: ['介绍姓名'],
            personalSentence: 'My name is Shen.',
            usedHelp: false,
          ),
          onHome: () {},
          onLesson: () {},
          onRetry: () {},
          onBack: () => backCalled = true,
        ),
      ),
    );
    await tester.pumpAndSettle();

    expect(find.text('对话完成'), findsNWidgets(2)); // AppBar title and Eyebrow
    expect(find.byIcon(Icons.arrow_back), findsOneWidget);

    await tester.tap(find.byIcon(Icons.arrow_back));
    await tester.pumpAndSettle();

    expect(backCalled, isTrue);
  });

  testWidgets('AdaptiveLessonPage has back button in all states', (
    tester,
  ) async {
    final state = AppState()..finishOnboarding();

    // 1. Empty state
    var finished = false;
    await tester.pumpWidget(
      MaterialApp(
        home: AdaptiveLessonPage(
          state: state,
          onFinished: () => finished = true,
        ),
      ),
    );
    await tester.pumpAndSettle();

    expect(find.text('AI 四技能补练'), findsNWidgets(2));
    expect(find.byIcon(Icons.arrow_back), findsOneWidget);
    await tester.tap(find.byIcon(Icons.arrow_back));
    expect(finished, isTrue);

    // 2. Active lesson state
    state.cacheApprovedAdaptiveLesson(
      const GeneratedLesson(
        lessonId: 'adapt-1',
        revision: 1,
        stageVersion: 'A0',
        abilityIds: ['greeting'],
        prerequisiteIds: [],
        targetItemIds: ['name'],
        receptiveChunks: ['My name is Mia.'],
        previewItemIds: ['name'],
        estimatedMinutes: 5,
        tasks: [
          GeneratedLessonTask(
            taskId: 't1',
            skill: 'listening',
            type: 'listen',
            prompt: '听并写出名字',
            stimulus: 'My name is Mia.',
            answer: 'Mia',
            targetItemIds: ['name'],
          ),
        ],
      ),
      auditor: 'test',
    );

    finished = false;
    await tester.pumpWidget(
      MaterialApp(
        home: AdaptiveLessonPage(
          state: state,
          onFinished: () => finished = true,
        ),
      ),
    );
    await tester.pumpAndSettle();

    expect(find.byIcon(Icons.arrow_back), findsOneWidget);
    await tester.tap(find.byIcon(Icons.arrow_back));
    expect(finished, isTrue);
  });

  testWidgets(
    'AssessmentPreparationPage and AssessmentPage have back buttons',
    (tester) async {
      final state = AppState()..finishOnboarding();
      await tester.pumpWidget(MaterialApp(home: LearningShell(state: state)));
      await tester.pumpAndSettle();

      // Navigate to "我的"
      await tester.tap(find.text('我的'));
      await tester.pumpAndSettle();

      final assessments = find.text('四技能评估');
      await tester.ensureVisible(assessments);
      await tester.tap(assessments);
      await tester.pumpAndSettle();

      // Open assessment pack A0-E1
      final packAButton = find.text('开始 A0-E1');
      await tester.ensureVisible(packAButton);
      await tester.pumpAndSettle();

      expect(packAButton, findsOneWidget);
      await tester.tap(packAButton);
      await tester.pumpAndSettle();

      // In AssessmentPreparationPage
      expect(find.text('评估准备'), findsOneWidget);
      expect(find.byIcon(Icons.arrow_back), findsOneWidget);

      // Start assessment
      await tester.tap(find.text('开始评估'));
      await tester.pumpAndSettle();

      // In AssessmentPage
      expect(find.byIcon(Icons.arrow_back), findsOneWidget);

      // Returns to 我的
      await tester.tap(find.byIcon(Icons.arrow_back));
      await tester.pumpAndSettle();
      expect(find.text('评估准备'), findsNothing);
      expect(find.text('四技能评估'), findsOneWidget);
    },
  );

  testWidgets(
    'LessonFlow on complete step: back button finalizes segment and advances lesson',
    (tester) async {
      await tester.runAsync(
        () => CourseRepository.instance.load(levels: {'A0'}),
      );
      final state = AppState()..finishOnboarding();
      expect(state.activeLessonId, 'a0-01');

      await tester.pumpWidget(MaterialApp(home: LearningShell(state: state)));
      await tester.pumpAndSettle();

      // Tap '开始今天的学习' to enter LessonFlow
      await tester.tap(find.text('开始今天的学习'));
      await tester.pumpAndSettle();

      // Complete all steps of a0-01
      state.completePreview();
      state.completeListening(recognized: true);
      state.completeSpeaking();
      state.completeReading();
      state.completeWriting(assisted: false, rawAnswer: 'hello');
      state.completeLessonDialogue();
      state.completeIndependentAttempt(assisted: false, rawAnswer: 'hello');
      expect(state.lessonStep, LessonStep.complete);
      await tester.pumpAndSettle();

      // We should be in lesson flow complete screen
      expect(find.text('本段已保存'), findsOneWidget);
      expect(find.text('回到首页'), findsOneWidget);
      expect(find.byIcon(Icons.arrow_back), findsOneWidget);

      // Tap the top-left AppBar back button instead of '回到首页'
      await tester.tap(find.byIcon(Icons.arrow_back));
      await tester.pumpAndSettle();

      // Should be back on the 学习 tab, and lesson must have advanced to a0-02
      expect(state.completedLessonIds, contains('a0-01'));
      expect(state.activeLessonId, 'a0-02');
      expect(find.textContaining('第 2 课 · '), findsWidgets);
    },
  );

  testWidgets(
    'TodayTaskCard reflects multi-segment progress and completed fallback',
    (tester) async {
      await tester.runAsync(
        () => CourseRepository.instance.load(levels: {'A0'}),
      );
      final state = AppState()..finishOnboarding();
      state.activeLessonId = 'a0-04'; // a0-04 has 3 segments

      await tester.pumpWidget(MaterialApp(home: LearningShell(state: state)));
      await tester.pumpAndSettle();

      // Segment 1 (initial)
      expect(find.text('今日新课'), findsOneWidget);
      expect(find.text('开始今天的学习'), findsOneWidget);

      // Now complete segment 1
      state.completeSegment('a0-04', 0);
      await tester.pumpAndSettle();

      // Segment 2 (resuming)
      expect(find.text('继续课程'), findsOneWidget);
      expect(find.text('继续学习第 2 段'), findsOneWidget);
      expect(find.textContaining('第 2/3 段'), findsWidgets);

      // If activeLessonId is marked as completed, card targets next incomplete
      state.completedLessonIds.add('a0-04');
      state.notifyListeners();
      await tester.pumpAndSettle();

      // Should target a0-01 or next incomplete, not show completed lesson
      expect(find.text('继续课程'), findsNothing);
      expect(find.textContaining('第 1 课 · '), findsWidgets);
    },
  );
}