import 'package:flutter/material.dart';
import '../utils/top_snackbar.dart';
import 'dart:math' as math;
import 'dart:async';
import 'dart:ui';
import 'package:practice_engine/practice_engine.dart';
import '../routes.dart';
import '../widgets/question_card.dart';
import '../widgets/answer_option.dart';
import '../services/deck_storage.dart';

/// Custom 3D cube page transformer
class CubePageTransitionsBuilder extends PageTransitionsBuilder {
  const CubePageTransitionsBuilder();

  @override
  Widget buildTransitions<T extends Object?>(
    PageRoute<T> route,
    BuildContext context,
    Animation<double> animation,
    Animation<double> secondaryAnimation,
    Widget child,
  ) {
    return _CubeTransition(
      animation: animation,
      child: child,
    );
  }
}

class _CubeTransition extends StatelessWidget {
  final Animation<double> animation;
  final Widget child;

  const _CubeTransition({
    required this.animation,
    required this.child,
  });

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: animation,
      builder: (context, child) {
        final value = animation.value;
        final angle = (1.0 - value) * math.pi / 2;
        final opacity = value < 0.5 ? 0.0 : (value - 0.5) * 2;
        
        return Transform(
          alignment: Alignment.centerLeft,
          transform: Matrix4.identity()
            ..setEntry(3, 2, 0.001)
            ..rotateY(angle),
          child: Opacity(
            opacity: opacity.clamp(0.0, 1.0),
            child: child,
          ),
        );
      },
      child: child,
    );
  }
}

class AttemptScreen extends StatefulWidget {
  const AttemptScreen({super.key});

  @override
  State<AttemptScreen> createState() => _AttemptScreenState();
}

class _AttemptScreenState extends State<AttemptScreen> {
  Deck? _deck;
  Attempt? _attempt;
  AttemptService? _attemptService;
  int _currentQuestionIndex = 0;
  int? _selectedAnswerIndex; // For single answer questions (backward compatibility)
  Set<int> _selectedAnswerIndices = {}; // For multiple answer questions
  Map<String, dynamic> _answers = {}; // Can store int or List<int>
  Map<String, bool> _manualOverrides = {};
  /// Display order of answer indices per question (shuffled for new attempts).
  Map<String, List<int>> _answerOrderPerQuestion = {};
  final DeckStorage _deckStorage = DeckStorage();
  late PageController _pageController;
  Timer? _timer;
  int _remainingSeconds = 0;

  @override
  void initState() {
    super.initState();
    _attemptService = AttemptService();
    _pageController = PageController();
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (_deck == null) {
      // Get deck from route arguments
      final args = ModalRoute.of(context)?.settings.arguments;
      bool? includeKnown;
      bool? resumeAttempt;
      
      if (args is Map<String, dynamic>) {
        _deck = args['deck'] as Deck? ?? _createSampleDeck();
        includeKnown = args['includeKnown'] as bool?;
        resumeAttempt = args['resumeAttempt'] as bool? ?? false;
      } else if (args is Deck) {
        _deck = args;
        resumeAttempt = false;
      } else {
        _deck = _createSampleDeck();
        resumeAttempt = false;
      }
      
      // Check if we should resume an incomplete attempt
      if (resumeAttempt == true && _deck!.incompleteAttempt != null) {
        final incomplete = _deck!.incompleteAttempt!;
        _attempt = incomplete.toAttempt(_deck!.questions);
        _currentQuestionIndex = incomplete.currentQuestionIndex;
        _answers = Map<String, dynamic>.from(incomplete.answers);
        _manualOverrides = Map<String, bool>.from(incomplete.manualOverrides);
        // Resumed attempt: use identity order so saved answers (original indices) match
        _answerOrderPerQuestion = {
          for (final q in _attempt!.questions)
            q.id: List.generate(q.answers.length, (i) => i),
        };
        // Restore selected answer for current question
        _loadQuestionState();
        // Initialize PageController to the current question index
        WidgetsBinding.instance.addPostFrameCallback((_) {
          if (_pageController.hasClients) {
            _pageController.jumpToPage(_currentQuestionIndex);
          }
        });
      } else {
        _attempt = _attemptService!.createAttempt(
          deck: _deck!,
          includeKnown: includeKnown,
        );
        // New attempt: randomize answer order per question when deck config enables it
        _answerOrderPerQuestion = {};
        final shuffleAnswers = _deck!.config.shuffleAnswerOrder;
        for (final q in _attempt!.questions) {
          final order = List.generate(q.answers.length, (i) => i);
          if (shuffleAnswers) {
            order.shuffle(math.Random());
          }
          _answerOrderPerQuestion[q.id] = order;
        }
      }
      
      // Initialize timer if time limit is set
      if (_deck!.config.timeLimitSeconds != null) {
        if (resumeAttempt == true && _deck!.incompleteAttempt != null) {
          // Use remaining time from incomplete attempt
          if (_deck!.incompleteAttempt!.remainingSeconds != null) {
            _remainingSeconds = _deck!.incompleteAttempt!.remainingSeconds!;
          } else {
            // Fallback: calculate remaining time when resuming (for backward compatibility)
            final pausedAt = _deck!.incompleteAttempt!.pausedAt;
            final elapsedSeconds = (DateTime.now().millisecondsSinceEpoch - pausedAt) ~/ 1000;
            _remainingSeconds = (_deck!.config.timeLimitSeconds! - elapsedSeconds).clamp(0, _deck!.config.timeLimitSeconds!);
          }
        } else {
          _remainingSeconds = _deck!.config.timeLimitSeconds!;
        }
        _startTimer();
      }
    }
  }

  void _startTimer() {
    _timer?.cancel();
    _timer = Timer.periodic(const Duration(seconds: 1), (timer) {
      if (!mounted) {
        timer.cancel();
        return;
      }
      
      setState(() {
        if (_remainingSeconds > 0) {
          _remainingSeconds--;
        } else {
          // Time expired
          timer.cancel();
          _handleTimeExpired();
        }
      });
    });
  }

  void _handleTimeExpired() {
    // Auto-submit the attempt when time expires
    if (_attempt != null && _deck != null) {
      _completeAttempt();
    }
  }

  @override
  void dispose() {
    _timer?.cancel();
    _pageController.dispose();
    super.dispose();
  }

  Deck _createSampleDeck() {
    const config = DeckConfig();
    final questions = List.generate(10, (i) {
      return Question(
        id: 'q$i',
        prompt: 'Sample Question $i?',
        answers: ['A', 'B', 'C', 'D'],
        correctAnswerIndices: [i % 4],
      );
    });
    return Deck(
      id: 'sample',
      title: 'Sample',
      description: 'Sample',
      questions: questions,
      config: config,
    );
  }

  Question get _currentQuestion => _attempt!.questions[_currentQuestionIndex];
  bool get _isLastQuestion => _currentQuestionIndex == _attempt!.questions.length - 1;
  bool get _hasMultipleCorrect => _currentQuestion.hasMultipleCorrectAnswers;
  bool get _hasAnswer {
    if (_hasMultipleCorrect) {
      return _selectedAnswerIndices.isNotEmpty;
    } else {
      return _selectedAnswerIndex != null;
    }
  }
  
  /// Returns true if at least one question has been answered (progress has been made)
  bool get _hasAnyProgress => _answers.isNotEmpty || _manualOverrides.isNotEmpty;
  
  /// Returns true if there are unanswered questions
  bool get _hasUnansweredQuestions {
    if (_attempt == null) return false;
    for (final question in _attempt!.questions) {
      if (!_answers.containsKey(question.id)) {
        return true;
      }
    }
    return false;
  }
  
  /// Returns the index of the first unanswered question, or null if all are answered
  int? get _firstUnansweredQuestionIndex {
    if (_attempt == null) return null;
    for (int i = 0; i < _attempt!.questions.length; i++) {
      if (!_answers.containsKey(_attempt!.questions[i].id)) {
        return i;
      }
    }
    return null;
  }
  
  /// Returns the index of the next unanswered question after current, or null
  int? get _nextUnansweredQuestionIndex {
    if (_attempt == null) return null;
    for (int i = _currentQuestionIndex + 1; i < _attempt!.questions.length; i++) {
      if (!_answers.containsKey(_attempt!.questions[i].id)) {
        return i;
      }
    }
    return null;
  }

  void _goToPreviousQuestion() {
    if (_currentQuestionIndex > 0) {
      // Save current answer if any
      if (_hasAnswer) {
        if (_hasMultipleCorrect) {
          _answers[_currentQuestion.id] = _selectedAnswerIndices.toList()..sort();
        } else {
          _answers[_currentQuestion.id] = _selectedAnswerIndex!;
        }
      }
      
      _pageController.previousPage(
        duration: const Duration(milliseconds: 300),
        curve: Curves.easeInOut,
      );
    }
  }

  void _goToNextQuestion() {
    if (_currentQuestionIndex < _attempt!.questions.length - 1) {
      // Save current answer if any
      if (_hasAnswer) {
        if (_hasMultipleCorrect) {
          _answers[_currentQuestion.id] = _selectedAnswerIndices.toList()..sort();
        } else {
          _answers[_currentQuestion.id] = _selectedAnswerIndex!;
        }
      }
      
      _pageController.nextPage(
        duration: const Duration(milliseconds: 300),
        curve: Curves.easeInOut,
      );
    }
  }
  
  String _formatTime(int seconds) {
    final hours = seconds ~/ 3600;
    final minutes = (seconds % 3600) ~/ 60;
    final secs = seconds % 60;
    
    if (hours > 0) {
      return '${hours}h ${minutes}m ${secs}s';
    } else if (minutes > 0) {
      return '${minutes}m ${secs}s';
    } else {
      return '${secs}s';
    }
  }
  
  void _onPageChanged(int index) {
    setState(() {
      _currentQuestionIndex = index;
      _loadQuestionState();
    });
  }

  void _loadQuestionState() {
    // Load saved answer for current question
    final currentQuestionId = _currentQuestion.id;
    final savedAnswer = _answers[currentQuestionId];
    
    if (savedAnswer != null) {
      if (savedAnswer is int) {
        _selectedAnswerIndex = savedAnswer;
        _selectedAnswerIndices.clear();
      } else if (savedAnswer is List<int>) {
        _selectedAnswerIndices = savedAnswer.toSet();
        _selectedAnswerIndex = null;
      }
    } else {
      _selectedAnswerIndex = null;
      _selectedAnswerIndices.clear();
    }
  }

  void _submitAnswer() {
    if (!_hasAnswer) return;

    // Store answer(s) based on question type
    if (_hasMultipleCorrect) {
      _answers[_currentQuestion.id] = _selectedAnswerIndices.toList()..sort();
    } else {
      _answers[_currentQuestion.id] = _selectedAnswerIndex!;
    }

    if (_isLastQuestion) {
      _completeAttempt();
    } else {
      _goToNextQuestion();
    }
  }
  
  void _completeAttemptWithUnanswered() async {
    // Ask for confirmation
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('Complete Attempt?'),
        content: Column(
          mainAxisSize: MainAxisSize.min,
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            const Text('There are still unanswered questions.'),
            const SizedBox(height: 8),
            Text(
              'Are you sure you want to complete this attempt?',
              style: Theme.of(context).textTheme.bodyMedium,
            ),
          ],
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context, false),
            child: const Text('Cancel'),
          ),
          FilledButton(
            onPressed: () => Navigator.pop(context, true),
            child: const Text('Complete Anyway'),
          ),
        ],
      ),
    );
    
    if (confirmed == true && mounted) {
      _completeAttempt();
    }
  }
  
  void _jumpToFirstUnanswered() {
    // Save current answer if any
    if (_hasAnswer) {
      if (_hasMultipleCorrect) {
        _answers[_currentQuestion.id] = _selectedAnswerIndices.toList()..sort();
      } else {
        _answers[_currentQuestion.id] = _selectedAnswerIndex!;
      }
    }
    
    final firstUnanswered = _firstUnansweredQuestionIndex;
    if (firstUnanswered != null && _pageController.hasClients) {
      _pageController.animateToPage(
        firstUnanswered,
        duration: const Duration(milliseconds: 300),
        curve: Curves.easeInOut,
      );
    }
  }
  
  void _goToNextUnanswered() {
    // Save current answer if any
    if (_hasAnswer) {
      if (_hasMultipleCorrect) {
        _answers[_currentQuestion.id] = _selectedAnswerIndices.toList()..sort();
      } else {
        _answers[_currentQuestion.id] = _selectedAnswerIndex!;
      }
    }
    
    final nextUnanswered = _nextUnansweredQuestionIndex;
    if (nextUnanswered != null && _pageController.hasClients) {
      _pageController.animateToPage(
        nextUnanswered,
        duration: const Duration(milliseconds: 300),
        curve: Curves.easeInOut,
      );
    }
  }

  void _saveForLater() {
    if (_deck == null || _attempt == null) return;

    // Save current answer if selected
    if (_hasAnswer) {
      if (_hasMultipleCorrect) {
        _answers[_currentQuestion.id] = _selectedAnswerIndices.toList()..sort();
      } else {
        _answers[_currentQuestion.id] = _selectedAnswerIndex!;
      }
    }

    // Create incomplete attempt
    final incompleteAttempt = IncompleteAttempt(
      attemptId: _attempt!.id,
      questionIds: _attempt!.questions.map((q) => q.id).toList(),
      startTime: _attempt!.startTime,
      currentQuestionIndex: _currentQuestionIndex,
      answers: _answers,
      manualOverrides: _manualOverrides,
      pausedAt: DateTime.now().millisecondsSinceEpoch,
      remainingSeconds: _deck!.config.timeLimitSeconds != null ? _remainingSeconds : null,
    );

    // Update deck with incomplete attempt
    final updatedDeck = _deck!.copyWith(incompleteAttempt: incompleteAttempt);
    _deckStorage.saveDeckSync(updatedDeck);

    showTopSnackBar(
      context,
      message: 'Attempt saved. You can continue later.',
      backgroundColor: Colors.blue,
      duration: const Duration(seconds: 2),
    );

    Navigator.pop(context);
  }

  void _completeAttempt() {
    if (_deck == null || _attempt == null || _attemptService == null) return;
    
    final endTime = DateTime.now().millisecondsSinceEpoch;
    final result = _attemptService!.processAttempt(
      deck: _deck!,
      attempt: _attempt!,
      answers: _answers,
      manualOverrides: _manualOverrides,
      endTime: endTime,
    );

    // Add attempt to history
    final historyEntry = AttemptHistoryEntry.fromAttemptResult(
      result: result.result,
      totalQuestionsInDeck: result.updatedDeck.numberOfQuestions,
      knownCount: result.updatedDeck.knownCount,
      timestamp: endTime,
    );
    final updatedDeckWithHistory = result.updatedDeck.copyWith(
      attemptHistory: [...result.updatedDeck.attemptHistory, historyEntry],
      clearIncompleteAttempt: true, // Clear incomplete attempt when completed
    );

    // Save the updated deck to storage
    _deckStorage.saveDeckSync(updatedDeckWithHistory);

    Navigator.pushReplacementNamed(
      context,
      Routes.attemptResult,
      arguments: {
        'deck': updatedDeckWithHistory,
        'result': result.result,
        'attempt': _attempt,
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    if (_deck == null || _attempt == null) {
      return const Scaffold(
        body: Center(child: CircularProgressIndicator()),
      );
    }

    return PopScope(
      canPop: false,
      onPopInvoked: (bool didPop) async {
        if (didPop) return;
        // Only prompt to save if there's actual progress (at least one question answered)
        if (!_hasAnyProgress) {
          // No progress made, just allow exit without prompt
          if (mounted) {
            Navigator.of(context).pop();
          }
          return;
        }
        
        // Ask if user wants to save for later
        final shouldSave = await showDialog<bool>(
          context: context,
          builder: (context) => AlertDialog(
            title: const Text('Exit Attempt?'),
            content: const Text(
              'Your progress will be lost. Would you like to save this attempt to continue later?',
            ),
            actions: [
              TextButton(
                onPressed: () => Navigator.pop(context, false),
                child: const Text('Discard'),
              ),
              TextButton(
                onPressed: () => Navigator.pop(context, true),
                child: const Text('Save for Later'),
              ),
            ],
          ),
        );

        if (!mounted) return;
        
        if (shouldSave == true) {
          _saveForLater();
          // _saveForLater will handle navigation
        } else if (shouldSave == false) {
          // User chose to discard, allow pop
          Navigator.of(context).pop();
        }
        // If cancelled (shouldSave == null), don't pop
      },
      child: Scaffold(
        appBar: AppBar(
          title: Text('Attempt - ${_deck!.title}'),
          actions: [
            // Flag current question for review
            Builder(
              builder: (context) {
                if (_attempt!.questions.isEmpty) return const SizedBox.shrink();
                final currentQuestionId = _attempt!.questions[_currentQuestionIndex].id;
                final isFlagged = _deck!.questions
                    .where((q) => q.id == currentQuestionId)
                    .firstOrNull
                    ?.isFlagged ?? false;
                return IconButton(
                  onPressed: () {
                    setState(() {
                      _deck = DeckService.toggleQuestionFlag(
                        deck: _deck!,
                        questionId: currentQuestionId,
                      );
                      _deckStorage.saveDeckSync(_deck!);
                    });
                    showTopSnackBar(
                      context,
                      message: isFlagged ? 'Question unflagged' : 'Question flagged for review',
                      backgroundColor: isFlagged ? null : Colors.orange,
                    );
                  },
                  icon: Icon(
                    isFlagged ? Icons.flag : Icons.outlined_flag,
                    color: isFlagged ? Colors.red : null,
                  ),
                  tooltip: isFlagged ? 'Unflag question' : 'Flag for review',
                );
              },
            ),
            if (_hasUnansweredQuestions)
              IconButton(
                onPressed: _jumpToFirstUnanswered,
                icon: const Icon(Icons.skip_next),
                tooltip: 'Jump to first unanswered question',
              ),
            if (_hasAnyProgress)
              IconButton(
                onPressed: _saveForLater,
                icon: const Icon(Icons.pause),
                tooltip: 'Continue Later',
              ),
          ],
        ),
            body: Column(
              children: [
                // Time Limit Countdown Bar (if time limit is set)
                if (_deck!.config.timeLimitSeconds != null)
                  Container(
                    height: 6,
                    color: Theme.of(context).colorScheme.surfaceContainerHighest,
                    child: FractionallySizedBox(
                      alignment: Alignment.centerLeft,
                      widthFactor: _remainingSeconds / _deck!.config.timeLimitSeconds!,
                      child: Container(
                        decoration: BoxDecoration(
                          color: _remainingSeconds <= 60
                              ? Colors.red
                              : _remainingSeconds <= 300
                                  ? Colors.orange
                                  : Colors.green,
                        ),
                      ),
                    ),
                  ),
                // Progress Indicator
                LinearProgressIndicator(
                  value: (_currentQuestionIndex + 1) / _attempt!.questions.length,
                  minHeight: 4,
                ),
                const SizedBox(height: 8),
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 16),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Text(
                  'Question ${_currentQuestionIndex + 1} of ${_attempt!.questions.length}',
                  style: Theme.of(context).textTheme.bodyMedium,
                ),
                Row(
                  children: [
                    if (_deck!.config.timeLimitSeconds != null)
                      Container(
                        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
                        decoration: BoxDecoration(
                          color: _remainingSeconds <= 60
                              ? Colors.red.withValues(alpha: 0.2)
                              : _remainingSeconds <= 300
                                  ? Colors.orange.withValues(alpha: 0.2)
                                  : Colors.green.withValues(alpha: 0.2),
                          borderRadius: BorderRadius.circular(12),
                        ),
                        child: Text(
                          _formatTime(_remainingSeconds),
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            color: _remainingSeconds <= 60
                                ? Colors.red
                                : _remainingSeconds <= 300
                                    ? Colors.orange
                                    : Colors.green,
                          ),
                        ),
                      ),
                    if (_deck!.config.timeLimitSeconds != null && _currentQuestion.isKnown)
                      const SizedBox(width: 8),
                    if (_currentQuestion.isKnown)
                      const Chip(
                        label: Text('Known'),
                        avatar: Icon(Icons.check_circle, size: 18),
                      ),
                  ],
                ),
              ],
            ),
          ),

          // Question Card with PageView for 3D transitions
          Expanded(
            child: PageView.builder(
              controller: _pageController,
              onPageChanged: _onPageChanged,
              itemCount: _attempt!.questions.length,
              physics: const BouncingScrollPhysics(), // Always allow swiping, validation happens in onPageChanged
              itemBuilder: (context, index) {
                final question = _attempt!.questions[index];
                final isMultipleCorrect = question.hasMultipleCorrectAnswers;
                final savedAnswer = _answers[question.id];
                
                // Determine selected answers for this question
                int? selectedIndex;
                Set<int> selectedIndices = {};
                if (savedAnswer != null) {
                  if (savedAnswer is int) {
                    selectedIndex = savedAnswer;
                  } else if (savedAnswer is List<int>) {
                    selectedIndices = savedAnswer.toSet();
                  }
                }
                
                return AnimatedBuilder(
                  animation: _pageController,
                  builder: (context, child) {
                    double value = 1.0;
                    double angle = 0.0;
                    if (_pageController.position.haveDimensions) {
                      value = _pageController.page! - index;
                      value = (1 - (value.abs() * 0.5)).clamp(0.0, 1.0);
                      
                      // Calculate rotation angle for 3D cube effect
                      final pageOffset = _pageController.page! - index;
                      if (pageOffset.abs() < 1.0) {
                        angle = pageOffset * math.pi / 2;
                      } else if (pageOffset < 0) {
                        angle = -math.pi / 2;
                      } else {
                        angle = math.pi / 2;
                      }
                    }
                    
                    return Transform(
                      alignment: Alignment.centerLeft,
                      transform: Matrix4.identity()
                        ..setEntry(3, 2, 0.001)
                        ..rotateY(angle),
                      child: Opacity(
                        opacity: value.clamp(0.0, 1.0),
                        child: child,
                      ),
                    );
                  },
                  child: SingleChildScrollView(
                    padding: const EdgeInsets.all(16),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.stretch,
                      children: [
                        QuestionCard(question: question),
                        const SizedBox(height: 24),

                      // Answer Options (displayed in shuffled order; we store original indices)
                      ...() {
                        final order = _answerOrderPerQuestion[question.id] ??
                            List.generate(question.answers.length, (i) => i);
                        return List.generate(
                          question.answers.length,
                          (displayIndex) {
                            final originalIndex = order[displayIndex];
                            return Padding(
                              padding: const EdgeInsets.only(bottom: 8),
                              child: AnswerOption(
                                text: question.answers[originalIndex],
                                isSelected: isMultipleCorrect
                                    ? selectedIndices.contains(originalIndex)
                                    : selectedIndex == originalIndex,
                                onTap: () {
                                  setState(() {
                                    if (isMultipleCorrect) {
                                      if (selectedIndices.contains(originalIndex)) {
                                        selectedIndices.remove(originalIndex);
                                      } else {
                                        selectedIndices.add(originalIndex);
                                      }
                                      _answers[question.id] = selectedIndices.toList()..sort();
                                    } else {
                                      if (selectedIndex == originalIndex) {
                                        selectedIndex = null;
                                        _answers.remove(question.id);
                                      } else {
                                        selectedIndex = originalIndex;
                                        _answers[question.id] = selectedIndex;
                                      }
                                    }
                                    if (index == _currentQuestionIndex) {
                                      if (isMultipleCorrect) {
                                        _selectedAnswerIndices = selectedIndices;
                                        _selectedAnswerIndex = null;
                                      } else {
                                        _selectedAnswerIndex = selectedIndex;
                                        _selectedAnswerIndices.clear();
                                      }
                                    }
                                  });
                                },
                                isCorrect: _deck != null && _deck!.config.immediateFeedbackEnabled &&
                                        (isMultipleCorrect
                                            ? selectedIndices.contains(originalIndex)
                                            : selectedIndex == originalIndex)
                                    ? question.isCorrectAnswer(originalIndex)
                                    : null,
                                isMultipleChoice: isMultipleCorrect,
                              ),
                            );
                          },
                        );
                      }(),

                      const SizedBox(height: 24),

                      // Manual Override Buttons
                      Card(
                        child: Padding(
                          padding: const EdgeInsets.all(16),
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.stretch,
                            children: [
                              Text(
                                'Manual Override',
                                style: Theme.of(context).textTheme.titleSmall,
                              ),
                              const SizedBox(height: 12),
                              Row(
                                children: [
                                  Expanded(
                                    child: OutlinedButton.icon(
                                      onPressed: () {
                                        setState(() {
                                          _manualOverrides[question.id] = false;
                                          _deck = DeckService.markQuestionAsKnown(
                                            deck: _deck!,
                                            questionId: question.id,
                                          );
                                        });
                                        showTopSnackBar(
                                          context,
                                          message: 'Question marked as Known',
                                          backgroundColor: Colors.green,
                                        );
                                      },
                                      icon: const Icon(Icons.check_circle),
                                      label: const Text('Mark as Known'),
                                    ),
                                  ),
                                  const SizedBox(width: 8),
                                  Expanded(
                                    child: OutlinedButton.icon(
                                      onPressed: () {
                                        setState(() {
                                          _manualOverrides[question.id] = true;
                                          _deck = DeckService.markQuestionAsNeedsPractice(
                                            deck: _deck!,
                                            questionId: question.id,
                                          );
                                        });
                                        showTopSnackBar(
                                          context,
                                          message: 'Question marked as Needs Practice',
                                        );
                                      },
                                      icon: const Icon(Icons.school),
                                      label: const Text('Needs Practice'),
                                    ),
                                  ),
                                ],
                              ),
                            ],
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
                ); // Close AnimatedBuilder
              },
              pageSnapping: true,
            ),
          ),

          // Navigation Buttons
          Container(
            padding: const EdgeInsets.all(16),
            decoration: BoxDecoration(
              color: Theme.of(context).colorScheme.surface,
              boxShadow: [
                BoxShadow(
                  color: Colors.black.withValues(alpha: 0.05),
                  blurRadius: 4,
                  offset: const Offset(0, -2),
                ),
              ],
            ),
            child: SafeArea(
              child: Row(
                children: [
                  // Previous Button
                  Expanded(
                    child: OutlinedButton.icon(
                      onPressed: _currentQuestionIndex > 0 ? _goToPreviousQuestion : null,
                      style: OutlinedButton.styleFrom(
                        padding: const EdgeInsets.symmetric(vertical: 18, horizontal: 24),
                        minimumSize: const Size(0, 56),
                        shape: RoundedRectangleBorder(
                          borderRadius: BorderRadius.circular(12),
                        ),
                      ),
                      icon: const Icon(Icons.arrow_back, size: 20),
                      label: const Text(
                        'Previous',
                        style: TextStyle(
                          fontSize: 16,
                          fontWeight: FontWeight.w600,
                          letterSpacing: 0.5,
                        ),
                      ),
                    ),
                  ),
                  const SizedBox(width: 12),
                  // Next/Complete Button
                  Expanded(
                    child: _isLastQuestion
                        ? _buildCompleteButton()
                        : _buildNextButton(),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
      ),
    );
  }
  
  Widget _buildCompleteButton() {
    final hasUnanswered = _hasUnansweredQuestions;
    // Allow completing if current question is answered OR if there are unanswered questions (to show warning)
    final canComplete = _hasAnswer || hasUnanswered;
    
    return FilledButton.icon(
      onPressed: canComplete
          ? (hasUnanswered ? _completeAttemptWithUnanswered : _submitAnswer)
          : null,
      style: FilledButton.styleFrom(
        padding: const EdgeInsets.symmetric(vertical: 18, horizontal: 24),
        minimumSize: const Size(0, 56),
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(12),
        ),
      ),
      icon: Icon(
        hasUnanswered ? Icons.warning : Icons.check_circle,
        size: 24,
        color: hasUnanswered ? null : Colors.green,
      ),
      label: const Text(
        'Complete',
        style: TextStyle(
          fontSize: 16,
          fontWeight: FontWeight.w600,
          letterSpacing: 0.5,
        ),
      ),
    );
  }
  
  Widget _buildNextButton() {
    final nextUnanswered = _nextUnansweredQuestionIndex;
    final hasUnansweredAhead = nextUnanswered != null;
    
    return FilledButton.icon(
      onPressed: hasUnansweredAhead ? _goToNextUnanswered : _goToNextQuestion,
      style: FilledButton.styleFrom(
        padding: const EdgeInsets.symmetric(vertical: 18, horizontal: 24),
        minimumSize: const Size(0, 56),
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(12),
        ),
      ),
      icon: const Icon(
        Icons.arrow_forward,
        size: 24,
      ),
      label: const Text(
        'Next',
        style: TextStyle(
          fontSize: 16,
          fontWeight: FontWeight.w600,
          letterSpacing: 0.5,
        ),
      ),
    );
  }
}