import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import 'package:image_picker/image_picker.dart';

import '../../core/auth/auth_provider.dart';
import 'recognition_service.dart';

// Provider wired to the shared ApiClient.
final _recognitionServiceProvider = Provider<RecognitionService>((ref) {
  return RecognitionService(ref.read(apiClientProvider));
});

/// Entry screen — lets the user choose how to add products.
/// If [GoRouterState.extra] is a non-null String, it is treated as a meal type ID
/// and the screen immediately opens the camera for dish recognition.
class ScanScreen extends ConsumerStatefulWidget {
  const ScanScreen({super.key});

  @override
  ConsumerState<ScanScreen> createState() => _ScanScreenState();
}

class _ScanScreenState extends ConsumerState<ScanScreen> {
  bool _autoStarted = false;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    if (_autoStarted) return;
    final mealType = GoRouterState.of(context).extra as String?;
    if (mealType != null && mealType.isNotEmpty) {
      _autoStarted = true;
      // Defer to avoid calling context navigation during build.
      WidgetsBinding.instance.addPostFrameCallback((_) {
        if (mounted) {
          _pickAndRecognize(context, _Mode.dish, mealType: mealType);
        }
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Добавить продукты')),
      body: ListView(
        padding: const EdgeInsets.all(20),
        children: [
          const SizedBox(height: 16),
          Text(
            'Выберите способ',
            style: Theme.of(context).textTheme.titleLarge,
            textAlign: TextAlign.center,
          ),
          const SizedBox(height: 32),
          _ModeCard(
            emoji: '🧾',
            title: 'Сфотографировать чек',
            subtitle: 'Распознаем все продукты из чека',
            onTap: () => _pickAndRecognize(context, _Mode.receipt),
          ),
          const SizedBox(height: 16),
          _ModeCard(
            emoji: '🥦',
            title: 'Сфотографировать продукты',
            subtitle: 'Холодильник, стол, полка — до 3 фото',
            onTap: () => _pickAndRecognize(context, _Mode.products),
          ),
          const SizedBox(height: 16),
          _ModeCard(
            emoji: '🍽️',
            title: 'Определить блюдо',
            subtitle: 'КБЖУ≈ по фото готового блюда',
            onTap: () => _pickAndRecognize(context, _Mode.dish),
          ),
          const SizedBox(height: 16),
          _ModeCard(
            emoji: '✏️',
            title: 'Добавить вручную',
            subtitle: 'Ввести название, количество и срок',
            onTap: () => context.push('/products/add'),
          ),
        ],
      ),
    );
  }

  Future<void> _pickAndRecognize(
    BuildContext context,
    _Mode mode, {
    String? mealType,
  }) async {
    final picker = ImagePicker();

    List<XFile> files = [];

    if (mode == _Mode.products) {
      // Allow up to 3 images.
      final picked = await picker.pickMultiImage(
        imageQuality: 70,
        maxWidth: 1024,
        maxHeight: 1024,
      );
      if (picked.isEmpty) return;
      files = picked.take(3).toList();
    } else {
      final source = await _chooseSource(context);
      if (source == null) return;
      final picked = await picker.pickImage(
        source: source,
        imageQuality: 70,
        maxWidth: 1024,
        maxHeight: 1024,
      );
      if (picked == null) return;
      files = [picked];
    }

    if (!context.mounted) return;
    final service = ref.read(_recognitionServiceProvider);

    // Show loading overlay while the AI processes.
    showDialog(
      context: context,
      barrierDismissible: false,
      builder: (_) => const _LoadingDialog(),
    );

    try {
      switch (mode) {
        case _Mode.receipt:
          final result = await service.recognizeReceipt(files.first);
          if (context.mounted) {
            Navigator.pop(context); // close loading
            context.push('/scan/confirm', extra: result.items);
          }
        case _Mode.products:
          final items = await service.recognizeProducts(files);
          if (context.mounted) {
            Navigator.pop(context);
            context.push('/scan/confirm', extra: items);
          }
        case _Mode.dish:
          final dish = await service.recognizeDish(files.first);
          if (context.mounted) {
            Navigator.pop(context);
            context.push('/scan/dish', extra: {'dish': dish, 'meal_type': mealType});
          }
      }
    } catch (recognitionError) {
      debugPrint('Recognition error: $recognitionError');
      if (context.mounted) {
        Navigator.pop(context); // close loading
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(
            content: Text('Не удалось распознать. Попробуйте ещё раз.'),
          ),
        );
      }
    }
  }

  Future<ImageSource?> _chooseSource(BuildContext context) async {
    return showModalBottomSheet<ImageSource>(
      context: context,
      builder: (_) => SafeArea(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            ListTile(
              leading: const Icon(Icons.camera_alt),
              title: const Text('Камера'),
              onTap: () => Navigator.pop(context, ImageSource.camera),
            ),
            ListTile(
              leading: const Icon(Icons.photo_library),
              title: const Text('Галерея'),
              onTap: () => Navigator.pop(context, ImageSource.gallery),
            ),
          ],
        ),
      ),
    );
  }
}

// ---------------------------------------------------------------------------
// Mode enum
// ---------------------------------------------------------------------------

enum _Mode { receipt, products, dish }

// ---------------------------------------------------------------------------
// Widgets
// ---------------------------------------------------------------------------

class _ModeCard extends StatelessWidget {
  const _ModeCard({
    required this.emoji,
    required this.title,
    required this.subtitle,
    required this.onTap,
  });

  final String emoji;
  final String title;
  final String subtitle;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Card(
      child: ListTile(
        contentPadding:
            const EdgeInsets.symmetric(horizontal: 20, vertical: 12),
        leading: Text(emoji, style: const TextStyle(fontSize: 32)),
        title: Text(title, style: theme.textTheme.titleMedium),
        subtitle: Text(subtitle, style: theme.textTheme.bodySmall),
        trailing: const Icon(Icons.chevron_right),
        onTap: onTap,
      ),
    );
  }
}

class _LoadingDialog extends StatelessWidget {
  const _LoadingDialog();

  @override
  Widget build(BuildContext context) {
    return const AlertDialog(
      content: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          CircularProgressIndicator(),
          SizedBox(height: 16),
          Text('Распознаём...'),
        ],
      ),
    );
  }
}