import 'package:flutter/material.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 = {};
  final DeckStorage _deckStorage = DeckStorage();
  late PageController _pageController;
  Timer? _timer;
  int _remainingSeconds = 0;
  int _startTime = 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);
        
        // 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,
        );
      }
      
      // 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 {
          _startTime = DateTime.now().millisecondsSinceEpoch;
          _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;

  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 _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.saveDeck(updatedDeck);

    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(
        content: Text('Attempt saved. You can continue later.'),
        backgroundColor: Colors.blue,
        duration: 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,
      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.saveDeck(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: [
            // Only show "Continue Later" button if there's progress
            if (_hasAnyProgress)
              TextButton.icon(
                onPressed: _saveForLater,
                icon: const Icon(Icons.pause),
                label: const Text('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
                      ...List.generate(
                        question.answers.length,
                        (answerIndex) => Padding(
                          padding: const EdgeInsets.only(bottom: 8),
                          child: AnswerOption(
                            text: question.answers[answerIndex],
                            isSelected: isMultipleCorrect 
                                ? selectedIndices.contains(answerIndex)
                                : selectedIndex == answerIndex,
                            onTap: () {
                              // Update selection for this question
                              setState(() {
                                if (isMultipleCorrect) {
                                  if (selectedIndices.contains(answerIndex)) {
                                    selectedIndices.remove(answerIndex);
                                  } else {
                                    selectedIndices.add(answerIndex);
                                  }
                                  _answers[question.id] = selectedIndices.toList()..sort();
                                } else {
                                  selectedIndex = answerIndex;
                                  _answers[question.id] = selectedIndex;
                                }
                                // Update current question state if viewing it
                                if (index == _currentQuestionIndex) {
                                  if (isMultipleCorrect) {
                                    _selectedAnswerIndices = selectedIndices;
                                    _selectedAnswerIndex = null;
                                  } else {
                                    _selectedAnswerIndex = selectedIndex;
                                    _selectedAnswerIndices.clear();
                                  }
                                }
                              });
                            },
                            isCorrect: _deck != null && _deck!.config.immediateFeedbackEnabled &&
                                    (isMultipleCorrect 
                                        ? selectedIndices.contains(answerIndex)
                                        : selectedIndex == answerIndex)
                                ? question.isCorrectAnswer(answerIndex)
                                : 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,
                                          );
                                        });
                                        ScaffoldMessenger.of(context).showSnackBar(
                                          const SnackBar(
                                            content: Text('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,
                                          );
                                        });
                                        ScaffoldMessenger.of(context).showSnackBar(
                                          const SnackBar(
                                            content: Text('Question marked as Needs Practice'),
                                          ),
                                        );
                                      },
                                      icon: const Icon(Icons.school),
                                      label: const Text('Needs Practice'),
                                    ),
                                  ),
                                ],
                              ),
                            ],
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
              },
                    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: FilledButton.icon(
                      onPressed: _isLastQuestion 
                          ? (_hasAnswer ? _submitAnswer : null)
                          : _goToNextQuestion,
                      style: FilledButton.styleFrom(
                        padding: const EdgeInsets.symmetric(vertical: 18, horizontal: 24),
                        minimumSize: const Size(0, 56),
                        shape: RoundedRectangleBorder(
                          borderRadius: BorderRadius.circular(12),
                        ),
                      ),
                      icon: Icon(
                        _isLastQuestion ? Icons.check_circle : Icons.arrow_forward,
                        size: 24,
                        color: _isLastQuestion ? Colors.green : null,
                      ),
                      label: Text(
                        _isLastQuestion ? 'Complete' : 'Next',
                        style: const TextStyle(
                          fontSize: 16,
                          fontWeight: FontWeight.w600,
                          letterSpacing: 0.5,
                        ),
                      ),
                    ),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
      ),
    );
  }
}