import 'dart:convert';

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

/// Screen that shows flagged questions in the same editable card layout as deck edit,
/// with Save, Unflag per question, and export/copy as JSON.
class FlaggedQuestionsScreen extends StatefulWidget {
  const FlaggedQuestionsScreen({super.key});

  @override
  State<FlaggedQuestionsScreen> createState() => _FlaggedQuestionsScreenState();
}

class _FlaggedQuestionsScreenState extends State<FlaggedQuestionsScreen> {
  Deck? _deck;
  final List<QuestionEditor> _editors = [];
  final DeckStorage _deckStorage = DeckStorage();
  String? _lastDeckId;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    final deck = ModalRoute.of(context)?.settings.arguments as Deck?;
    if (deck == null) return;
    if (_deck?.id != deck.id || _lastDeckId != deck.id) {
      _lastDeckId = deck.id;
      _loadDeck(deck);
    }
  }

  void _loadDeck(Deck deck) {
    final fresh = _deckStorage.getDeckSync(deck.id) ?? deck;
    setState(() {
      _deck = fresh;
      for (final e in _editors) {
        e.dispose();
      }
      _editors.clear();
      for (final q in fresh.flaggedQuestions) {
        _editors.add(QuestionEditor.fromQuestion(q));
      }
    });
  }

  @override
  void dispose() {
    for (final e in _editors) {
      e.dispose();
    }
    super.dispose();
  }

  void _unflag(int index) {
    if (_deck == null || index < 0 || index >= _editors.length) return;
    final questionId = _editors[index].originalId;
    if (questionId == null) return;
    final updatedQuestions = _deck!.questions.map((q) {
      if (q.id == questionId) return q.copyWith(isFlagged: false);
      return q;
    }).toList();
    final updatedDeck = _deck!.copyWith(questions: updatedQuestions);
    _deckStorage.saveDeckSync(updatedDeck);
    _editors[index].dispose();
    setState(() {
      _deck = updatedDeck;
      _editors.removeAt(index);
    });
    showTopSnackBar(context, message: 'Question unflagged');
  }

  void _save() {
    if (_deck == null) return;
    for (int i = 0; i < _editors.length; i++) {
      final editor = _editors[i];
      if (!editor.isValid) {
        showTopSnackBar(
          context,
          message: 'Question ${i + 1} is invalid. Fill in all fields.',
          backgroundColor: Colors.red,
        );
        return;
      }
    }
    final questionMap = Map<String, Question>.fromEntries(
      _deck!.questions.map((q) => MapEntry(q.id, q)),
    );
    for (final editor in _editors) {
      final id = editor.originalId;
      if (id == null) continue;
      final existing = questionMap[id];
      if (existing == null) continue;
      final updated = existing.copyWith(
        prompt: editor.promptController.text.trim(),
        answers: editor.answerControllers.map((c) => c.text.trim()).toList(),
        correctAnswerIndices: editor.correctAnswerIndices.toList()..sort(),
      );
      questionMap[id] = updated;
    }
    final updatedQuestions = _deck!.questions.map((q) => questionMap[q.id] ?? q).toList();
    final updatedDeck = _deck!.copyWith(questions: updatedQuestions);
    _deckStorage.saveDeckSync(updatedDeck);
    setState(() => _deck = updatedDeck);
    showTopSnackBar(
      context,
      message: 'Changes saved',
      backgroundColor: Colors.green,
    );
  }

  void _copyJson() {
    final questions = _editors.map((e) => e.toQuestion()).toList();
    if (questions.isEmpty) {
      showTopSnackBar(context, message: 'No questions to copy');
      return;
    }
    final json = _questionsToJson(questions);
    Clipboard.setData(ClipboardData(text: json));
    showTopSnackBar(context, message: '${questions.length} question(s) copied as JSON');
  }

  void _exportJson() {
    final questions = _editors.map((e) => e.toQuestion()).toList();
    if (questions.isEmpty) {
      showTopSnackBar(context, message: 'No questions to export');
      return;
    }
    final json = _questionsToJson(questions);
    Clipboard.setData(ClipboardData(text: json));
    showTopSnackBar(
      context,
      message: 'JSON copied to clipboard. Paste into a file to save.',
    );
  }

  String _questionsToJson(List<Question> questions) {
    final list = questions.map((q) => {
      'id': q.id,
      'prompt': q.prompt,
      'answers': q.answers,
      'correctAnswerIndices': q.correctAnswerIndices,
    }).toList();
    return const JsonEncoder.withIndent('  ').convert(list);
  }

  @override
  Widget build(BuildContext context) {
    if (_deck == null) {
      return Scaffold(
        appBar: AppBar(title: const Text('Flagged questions')),
        body: const Center(child: CircularProgressIndicator()),
      );
    }

    final hasEditors = _editors.isNotEmpty;
    return Scaffold(
      appBar: AppBar(
        title: Text('Flagged questions (${_editors.length})'),
        actions: [
          if (hasEditors) ...[
            IconButton(
              onPressed: _save,
              icon: const Icon(Icons.save),
              tooltip: 'Save',
            ),
            IconButton(
              onPressed: _copyJson,
              icon: const Icon(Icons.copy),
              tooltip: 'Copy as JSON',
            ),
            IconButton(
              onPressed: _exportJson,
              icon: const Icon(Icons.file_download),
              tooltip: 'Export as JSON',
            ),
          ],
        ],
      ),
      body: !hasEditors
          ? Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Icon(
                    Icons.flag_outlined,
                    size: 64,
                    color: Theme.of(context).colorScheme.onSurface.withValues(alpha: 0.3),
                  ),
                  const SizedBox(height: 16),
                  Text(
                    'No flagged questions',
                    style: Theme.of(context).textTheme.titleLarge,
                  ),
                  const SizedBox(height: 8),
                  Text(
                    'Flag questions during an attempt to see them here.',
                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                          color: Theme.of(context).colorScheme.onSurface.withValues(alpha: 0.6),
                        ),
                    textAlign: TextAlign.center,
                  ),
                ],
              ),
            )
          : SingleChildScrollView(
              padding: const EdgeInsets.all(16),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  ...List.generate(_editors.length, (index) {
                    return QuestionEditorCard(
                      key: ValueKey('flagged_${_editors[index].originalId}_$index'),
                      editor: _editors[index],
                      questionNumber: index + 1,
                      onDelete: null,
                      onUnflag: () => _unflag(index),
                      onChanged: () => setState(() {}),
                    );
                  }),
                ],
              ),
            ),
    );
  }
}