import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:practice_engine/practice_engine.dart';
import '../routes.dart';

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

  @override
  State<DeckImportScreen> createState() => _DeckImportScreenState();
}

class _DeckImportScreenState extends State<DeckImportScreen> {
  final TextEditingController _jsonController = TextEditingController();
  String? _errorMessage;
  bool _isLoading = false;

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

  Deck? _parseDeckFromJson(String jsonString) {
    try {
      final Map<String, dynamic> json = jsonDecode(jsonString);
      
      // Parse config
      final configJson = json['config'] as Map<String, dynamic>? ?? {};
      final config = DeckConfig(
        requiredConsecutiveCorrect: configJson['requiredConsecutiveCorrect'] as int? ?? 3,
        defaultAttemptSize: configJson['defaultAttemptSize'] as int? ?? 10,
        priorityIncreaseOnIncorrect: configJson['priorityIncreaseOnIncorrect'] as int? ?? 5,
        priorityDecreaseOnCorrect: configJson['priorityDecreaseOnCorrect'] as int? ?? 2,
        immediateFeedbackEnabled: configJson['immediateFeedbackEnabled'] as bool? ?? true,
      );

      // Parse questions
      final questionsJson = json['questions'] as List<dynamic>? ?? [];
      final questions = questionsJson.map((qJson) {
        final questionMap = qJson as Map<String, dynamic>;
        return Question(
          id: questionMap['id'] as String? ?? '',
          prompt: questionMap['prompt'] as String? ?? '',
          answers: (questionMap['answers'] as List<dynamic>?)
                  ?.map((e) => e.toString())
                  .toList() ??
              [],
          correctAnswerIndex: questionMap['correctAnswerIndex'] as int? ?? 0,
          consecutiveCorrect: questionMap['consecutiveCorrect'] as int? ?? 0,
          isKnown: questionMap['isKnown'] as bool? ?? false,
          priorityPoints: questionMap['priorityPoints'] as int? ?? 0,
          lastAttemptIndex: questionMap['lastAttemptIndex'] as int? ?? -1,
          totalCorrectAttempts: questionMap['totalCorrectAttempts'] as int? ?? 0,
          totalAttempts: questionMap['totalAttempts'] as int? ?? 0,
        );
      }).toList();

      // Create deck
      return Deck(
        id: json['id'] as String? ?? DateTime.now().millisecondsSinceEpoch.toString(),
        title: json['title'] as String? ?? 'Imported Deck',
        description: json['description'] as String? ?? '',
        questions: questions,
        config: config,
        currentAttemptIndex: json['currentAttemptIndex'] as int? ?? 0,
      );
    } catch (e) {
      throw FormatException('Invalid JSON format: $e');
    }
  }

  void _importDeck() {
    setState(() {
      _errorMessage = null;
      _isLoading = true;
    });

    try {
      if (_jsonController.text.trim().isEmpty) {
        throw FormatException('Please enter JSON data');
      }

      final deck = _parseDeckFromJson(_jsonController.text.trim());

      if (deck == null) {
        throw FormatException('Failed to parse deck');
      }

      if (deck.questions.isEmpty) {
        throw FormatException('Deck must contain at least one question');
      }

      // Navigate to deck overview with the imported deck
      Navigator.pushReplacementNamed(
        context,
        Routes.deckOverview,
        arguments: deck,
      );
    } catch (e) {
      setState(() {
        _errorMessage = e.toString();
        _isLoading = false;
      });
    }
  }

  void _loadSampleDeck() {
    final sampleJson = {
      'id': 'sample-deck',
      'title': 'Sample Practice Deck',
      'description': 'This is a sample deck for practicing. It contains various questions to help you learn.',
      'config': {
        'requiredConsecutiveCorrect': 3,
        'defaultAttemptSize': 10,
        'priorityIncreaseOnIncorrect': 5,
        'priorityDecreaseOnCorrect': 2,
        'immediateFeedbackEnabled': true,
      },
      'questions': List.generate(20, (i) {
        return {
          'id': 'q$i',
          'prompt': 'Sample Question $i?',
          'answers': ['Answer A', 'Answer B', 'Answer C', 'Answer D'],
          'correctAnswerIndex': i % 4,
          'isKnown': i < 5,
        };
      }),
    };

    _jsonController.text = const JsonEncoder.withIndent('  ').convert(sampleJson);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Import Deck'),
      ),
      body: SingleChildScrollView(
        padding: const EdgeInsets.all(16),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Card(
              child: Padding(
                padding: const EdgeInsets.all(16),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Text(
                      'Import Deck from JSON',
                      style: Theme.of(context).textTheme.titleLarge,
                    ),
                    const SizedBox(height: 8),
                    Text(
                      'Paste your deck JSON below. The format should include id, title, description, config, and questions.',
                      style: Theme.of(context).textTheme.bodyMedium,
                    ),
                  ],
                ),
              ),
            ),
            const SizedBox(height: 16),

            // JSON Input
            Card(
              child: Padding(
                padding: const EdgeInsets.all(16),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: [
                    Row(
                      mainAxisAlignment: MainAxisAlignment.spaceBetween,
                      children: [
                        Text(
                          'Deck JSON',
                          style: Theme.of(context).textTheme.titleMedium,
                        ),
                        TextButton.icon(
                          onPressed: _loadSampleDeck,
                          icon: const Icon(Icons.description),
                          label: const Text('Load Sample'),
                        ),
                      ],
                    ),
                    const SizedBox(height: 8),
                    TextField(
                      controller: _jsonController,
                      maxLines: 15,
                      decoration: InputDecoration(
                        hintText: 'Paste JSON here...',
                        border: const OutlineInputBorder(),
                        errorText: _errorMessage,
                      ),
                      style: const TextStyle(
                        fontFamily: 'monospace',
                        fontSize: 12,
                      ),
                    ),
                  ],
                ),
              ),
            ),
            const SizedBox(height: 24),

            // Error Message
            if (_errorMessage != null)
              Card(
                color: Colors.red.shade50,
                child: Padding(
                  padding: const EdgeInsets.all(16),
                  child: Row(
                    children: [
                      Icon(Icons.error, color: Colors.red.shade700),
                      const SizedBox(width: 12),
                      Expanded(
                        child: Text(
                          _errorMessage!,
                          style: TextStyle(color: Colors.red.shade700),
                        ),
                      ),
                    ],
                  ),
                ),
              ),

            if (_errorMessage != null) const SizedBox(height: 16),

            // Import Button
            FilledButton.icon(
              onPressed: _isLoading ? null : _importDeck,
              icon: _isLoading
                  ? const SizedBox(
                      width: 20,
                      height: 20,
                      child: CircularProgressIndicator(strokeWidth: 2),
                    )
                  : const Icon(Icons.upload),
              label: Text(_isLoading ? 'Importing...' : 'Import Deck'),
              style: FilledButton.styleFrom(
                padding: const EdgeInsets.symmetric(vertical: 16),
              ),
            ),

            const SizedBox(height: 16),

            // JSON Format Help
            ExpansionTile(
              title: const Text('JSON Format Help'),
              children: [
                Padding(
                  padding: const EdgeInsets.all(16),
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      const Text(
                        'Required fields:',
                        style: TextStyle(fontWeight: FontWeight.bold),
                      ),
                      const SizedBox(height: 8),
                      const Text('• id: string'),
                      const Text('• title: string'),
                      const Text('• description: string'),
                      const Text('• questions: array of question objects'),
                      const SizedBox(height: 16),
                      const Text(
                        'Question object format:',
                        style: TextStyle(fontWeight: FontWeight.bold),
                      ),
                      const SizedBox(height: 8),
                      const Text('• id: string (required)'),
                      const Text('• prompt: string (required)'),
                      const Text('• answers: array of strings (required)'),
                      const Text('• correctAnswerIndex: number (required)'),
                      const Text('• isKnown: boolean (optional)'),
                      const Text('• consecutiveCorrect: number (optional)'),
                      const Text('• priorityPoints: number (optional)'),
                      const SizedBox(height: 16),
                      const Text(
                        'Config object (optional):',
                        style: TextStyle(fontWeight: FontWeight.bold),
                      ),
                      const SizedBox(height: 8),
                      const Text('• requiredConsecutiveCorrect: number'),
                      const Text('• defaultAttemptSize: number'),
                      const Text('• priorityIncreaseOnIncorrect: number'),
                      const Text('• priorityDecreaseOnCorrect: number'),
                      const Text('• immediateFeedbackEnabled: boolean'),
                    ],
                  ),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }
}