import 'package:flutter/material.dart';
import '../utils/top_snackbar.dart';
import 'package:practice_engine/practice_engine.dart';
import '../services/deck_storage.dart';

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

  @override
  State<DeckEditScreen> createState() => _DeckEditScreenState();
}

class _DeckEditScreenState extends State<DeckEditScreen> {
  Deck? _deck;
  late TextEditingController _titleController;
  late TextEditingController _descriptionController;
  final List<QuestionEditor> _questionEditors = [];
  final DeckStorage _deckStorage = DeckStorage();
  final ScrollController _scrollController = ScrollController();
  int? _focusNewQuestionIndex;

  @override
  void initState() {
    super.initState();
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (_deck == null) {
      final args = ModalRoute.of(context)?.settings.arguments;
      if (args is Deck) {
        _initializeFromDeck(args);
      }
    }
  }

  void _initializeFromDeck(Deck deck) {
    setState(() {
      _deck = deck;
      _titleController = TextEditingController(text: deck.title);
      _descriptionController = TextEditingController(text: deck.description);
      
      _questionEditors.clear();
      for (final question in deck.questions) {
        _questionEditors.add(QuestionEditor.fromQuestion(question));
      }
    });
  }

  @override
  void dispose() {
    _scrollController.dispose();
    _titleController.dispose();
    _descriptionController.dispose();
    for (final editor in _questionEditors) {
      editor.dispose();
    }
    super.dispose();
  }

  void _addQuestion() {
    setState(() {
      _questionEditors.add(QuestionEditor.empty());
      _focusNewQuestionIndex = _questionEditors.length - 1;
    });
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      final pos = _scrollController.position;
      if (pos.maxScrollExtent > pos.pixels) {
        _scrollController.animateTo(
          pos.maxScrollExtent,
          duration: const Duration(milliseconds: 300),
          curve: Curves.easeOut,
        );
      }
      Future.microtask(() {
        if (mounted) setState(() => _focusNewQuestionIndex = null);
      });
    });
  }

  void _removeQuestion(int index) {
    setState(() {
      _questionEditors.removeAt(index);
    });
  }

  void _save() {
    if (_deck == null) return;

    final title = _titleController.text.trim();
    if (title.isEmpty) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(
          content: Text('Deck title cannot be empty'),
          backgroundColor: Colors.red,
        ),
      );
      return;
    }

    // Validate all questions
    final questions = <Question>[];
    for (int i = 0; i < _questionEditors.length; i++) {
      final editor = _questionEditors[i];
      if (!editor.isValid) {
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text('Question ${i + 1} is invalid. Please fill in all fields.'),
            backgroundColor: Colors.red,
          ),
        );
        return;
      }
      questions.add(editor.toQuestion());
    }

    if (questions.isEmpty) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(
          content: Text('Deck must have at least one question'),
          backgroundColor: Colors.red,
        ),
      );
      return;
    }

    // Preserve attempt history and other deck data when editing
    final updatedDeck = _deck!.copyWith(
      title: title,
      description: _descriptionController.text.trim(),
      questions: questions,
      // Preserve attempt history, config, and current attempt index
      attemptHistory: _deck!.attemptHistory,
      config: _deck!.config,
      currentAttemptIndex: _deck!.currentAttemptIndex,
    );

    _deckStorage.saveDeckSync(updatedDeck);

    showTopSnackBar(
      context,
      message: 'Deck saved successfully',
      backgroundColor: Colors.green,
      duration: const Duration(seconds: 1),
    );

    Navigator.pop(context, updatedDeck);
  }

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

    return Scaffold(
      appBar: AppBar(
        title: const Text('Edit Deck'),
        actions: [
          IconButton(
            icon: const Icon(Icons.add),
            onPressed: _addQuestion,
            tooltip: 'Add Question',
          ),
          IconButton(
            icon: const Icon(Icons.save),
            onPressed: _save,
            tooltip: 'Save Deck',
          ),
        ],
      ),
      body: SingleChildScrollView(
        controller: _scrollController,
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            // Deck Title
            TextField(
              controller: _titleController,
              decoration: const InputDecoration(
                labelText: 'Deck Title',
                border: OutlineInputBorder(),
              ),
            ),
            const SizedBox(height: 16),

            // Deck Description
            TextField(
              controller: _descriptionController,
              decoration: const InputDecoration(
                labelText: 'Description (optional)',
                border: OutlineInputBorder(),
              ),
              maxLines: 3,
            ),
            const SizedBox(height: 24),

            // Questions Section
            Text(
              'Questions',
              style: Theme.of(context).textTheme.titleLarge,
            ),
            const SizedBox(height: 16),

            // Questions List
            ...List.generate(_questionEditors.length, (index) {
              return QuestionEditorCard(
                key: ValueKey('question_$index'),
                editor: _questionEditors[index],
                questionNumber: index + 1,
                onDelete: () => _removeQuestion(index),
                onUnflag: null,
                onChanged: () => setState(() {}),
                requestFocusOnPrompt: _focusNewQuestionIndex == index,
              );
            }),

            if (_questionEditors.isEmpty)
              Card(
                child: Padding(
                  padding: const EdgeInsets.all(32),
                  child: Center(
                    child: Column(
                      children: [
                        Icon(
                          Icons.quiz_outlined,
                          size: 48,
                          color: Theme.of(context).colorScheme.onSurface.withValues(alpha: 0.3),
                        ),
                        const SizedBox(height: 16),
                        Text(
                          'No questions yet',
                          style: Theme.of(context).textTheme.bodyLarge,
                        ),
                        const SizedBox(height: 8),
                        Text(
                          'Tap + in the app bar to add a question',
                          style: Theme.of(context).textTheme.bodySmall?.copyWith(
                                color: Theme.of(context).colorScheme.onSurface.withValues(alpha: 0.6),
                              ),
                        ),
                      ],
                    ),
                  ),
                ),
              ),

          ],
        ),
      ),
    );
  }
}

class QuestionEditorCard extends StatefulWidget {
  final QuestionEditor editor;
  final int questionNumber;
  final VoidCallback? onDelete;
  final VoidCallback? onUnflag;
  final VoidCallback onChanged;
  final bool requestFocusOnPrompt;

  const QuestionEditorCard({
    super.key,
    required this.editor,
    required this.questionNumber,
    this.onDelete,
    this.onUnflag,
    required this.onChanged,
    this.requestFocusOnPrompt = false,
  });

  @override
  State<QuestionEditorCard> createState() => _QuestionEditorCardState();
}

class _QuestionEditorCardState extends State<QuestionEditorCard> {
  final FocusNode _promptFocusNode = FocusNode();

  @override
  void dispose() {
    _promptFocusNode.dispose();
    super.dispose();
  }

  @override
  void didUpdateWidget(QuestionEditorCard oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.requestFocusOnPrompt && !oldWidget.requestFocusOnPrompt) {
      WidgetsBinding.instance.addPostFrameCallback((_) {
        if (mounted) _promptFocusNode.requestFocus();
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    if (widget.requestFocusOnPrompt) {
      WidgetsBinding.instance.addPostFrameCallback((_) {
        if (mounted) _promptFocusNode.requestFocus();
      });
    }
    return Card(
      margin: const EdgeInsets.only(bottom: 16),
      child: Padding(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: [
                Text(
                  'Question ${widget.questionNumber}',
                  style: Theme.of(context).textTheme.titleMedium,
                ),
                Row(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    if (widget.onUnflag != null)
                      IconButton(
                        icon: Icon(Icons.flag, color: Colors.orange.shade700),
                        onPressed: widget.onUnflag,
                        tooltip: 'Unflag',
                      ),
                    if (widget.onDelete != null)
                      IconButton(
                        icon: const Icon(Icons.delete, color: Colors.red),
                        onPressed: widget.onDelete,
                        tooltip: 'Delete Question',
                      ),
                  ],
                ),
              ],
            ),
            const SizedBox(height: 12),
            // Question Prompt
            TextField(
              controller: widget.editor.promptController,
              focusNode: _promptFocusNode,
              decoration: const InputDecoration(
                labelText: 'Question',
                border: OutlineInputBorder(),
              ),
              maxLines: 2,
            ),
            const SizedBox(height: 16),

            // Answers
            Text(
              'Answers',
              style: Theme.of(context).textTheme.titleSmall,
            ),
            const SizedBox(height: 8),
            ...List.generate(widget.editor.answerControllers.length, (index) {
              final isCorrect = widget.editor.correctAnswerIndices.contains(index);
              return Padding(
                padding: const EdgeInsets.only(bottom: 8),
                child: Row(
                  children: [
                    Checkbox(
                      value: isCorrect,
                      onChanged: (value) {
                        setState(() {
                          if (value == true) {
                            widget.editor.correctAnswerIndices.add(index);
                          } else {
                            widget.editor.correctAnswerIndices.remove(index);
                            // Ensure at least one answer is marked as correct
                            if (widget.editor.correctAnswerIndices.isEmpty && 
                                widget.editor.answerControllers.length > 0) {
                              widget.editor.correctAnswerIndices.add(0);
                            }
                          }
                        });
                        widget.onChanged();
                      },
                    ),
                    Expanded(
                      child: TextField(
                        controller: widget.editor.answerControllers[index],
                        decoration: InputDecoration(
                          labelText: 'Answer ${index + 1}',
                          border: const OutlineInputBorder(),
                          suffixIcon: isCorrect
                              ? const Icon(Icons.check_circle, color: Colors.green)
                              : null,
                        ),
                      ),
                    ),
                  ],
                ),
              );
            }),

            // Add/Remove Answer buttons
            Row(
              children: [
                TextButton.icon(
                  onPressed: () {
                    setState(() {
                      widget.editor.answerControllers.add(TextEditingController());
                    });
                    widget.onChanged();
                  },
                  icon: const Icon(Icons.add),
                  label: const Text('Add Answer'),
                ),
                if (widget.editor.answerControllers.length > 2)
                  TextButton.icon(
                    onPressed: () {
                      setState(() {
                        final lastIndex = widget.editor.answerControllers.length - 1;
                        // Remove the index from correct answers if it was marked
                        widget.editor.correctAnswerIndices.remove(lastIndex);
                        // Adjust indices if needed
                        widget.editor.correctAnswerIndices = widget.editor.correctAnswerIndices
                            .where((idx) => idx < lastIndex)
                            .toSet();
                        // Ensure at least one answer is marked as correct
                        if (widget.editor.correctAnswerIndices.isEmpty && 
                            widget.editor.answerControllers.length > 1) {
                          widget.editor.correctAnswerIndices.add(0);
                        }
                        widget.editor.answerControllers.removeLast().dispose();
                      });
                      widget.onChanged();
                    },
                    icon: const Icon(Icons.remove),
                    label: const Text('Remove Answer'),
                  ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

class QuestionEditor {
  final TextEditingController promptController;
  final List<TextEditingController> answerControllers;
  Set<int> correctAnswerIndices;
  final String? originalId;

  QuestionEditor({
    required this.promptController,
    required this.answerControllers,
    Set<int>? correctAnswerIndices,
    this.originalId,
  }) : correctAnswerIndices = correctAnswerIndices ?? {0};

  factory QuestionEditor.fromQuestion(Question question) {
    return QuestionEditor(
      promptController: TextEditingController(text: question.prompt),
      answerControllers: question.answers
          .map((answer) => TextEditingController(text: answer))
          .toList(),
      correctAnswerIndices: question.correctIndices.toSet(),
      originalId: question.id,
    );
  }

  factory QuestionEditor.empty() {
    return QuestionEditor(
      promptController: TextEditingController(),
      answerControllers: [
        TextEditingController(),
        TextEditingController(),
      ],
      correctAnswerIndices: {0},
    );
  }

  bool get isValid {
    if (promptController.text.trim().isEmpty) return false;
    if (answerControllers.length < 2) return false;
    for (final controller in answerControllers) {
      if (controller.text.trim().isEmpty) return false;
    }
    if (correctAnswerIndices.isEmpty) return false;
    if (correctAnswerIndices.any((idx) => idx < 0 || idx >= answerControllers.length)) {
      return false;
    }
    return true;
  }

  Question toQuestion() {
    return Question(
      id: originalId ?? DateTime.now().millisecondsSinceEpoch.toString(),
      prompt: promptController.text.trim(),
      answers: answerControllers.map((c) => c.text.trim()).toList(),
      correctAnswerIndices: correctAnswerIndices.toList()..sort(),
    );
  }

  void dispose() {
    promptController.dispose();
    for (final controller in answerControllers) {
      controller.dispose();
    }
  }

}