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

import '../../shared/models/menu.dart';
import 'menu_provider.dart';

class MenuScreen extends ConsumerWidget {
  const MenuScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final week = ref.watch(currentWeekProvider);
    final state = ref.watch(menuProvider(week));

    return Scaffold(
      appBar: AppBar(
        title: const Text('Меню'),
        actions: [
          IconButton(
            icon: const Icon(Icons.refresh),
            onPressed: () => ref.read(menuProvider(week).notifier).load(),
          ),
        ],
        bottom: _WeekNavBar(week: week, ref: ref),
      ),
      body: state.when(
        loading: () => const _MenuSkeleton(),
        error: (err, _) => _ErrorView(
          onRetry: () => ref.read(menuProvider(week).notifier).load(),
        ),
        data: (plan) => plan == null
            ? _EmptyState(
                onGenerate: () =>
                    ref.read(menuProvider(week).notifier).generate(),
              )
            : _MenuContent(plan: plan, week: week),
      ),
      floatingActionButton: state.maybeWhen(
        data: (_) => _GenerateFab(week: week),
        orElse: () => null,
      ),
    );
  }
}

// ── Week navigation app-bar bottom ────────────────────────────

class _WeekNavBar extends StatelessWidget implements PreferredSizeWidget {
  final String week;
  final WidgetRef ref;

  const _WeekNavBar({required this.week, required this.ref});

  @override
  Size get preferredSize => const Size.fromHeight(40);

  String _weekLabel(String week) {
    try {
      final parts = week.split('-W');
      if (parts.length != 2) return week;
      final year = int.parse(parts[0]);
      final w = int.parse(parts[1]);
      final monday = _mondayOfISOWeek(year, w);
      final sunday = monday.add(const Duration(days: 6));
      const months = [
        'янв', 'фев', 'мар', 'апр', 'май', 'июн',
        'июл', 'авг', 'сен', 'окт', 'ноя', 'дек',
      ];
      return '${monday.day}–${sunday.day} ${months[sunday.month - 1]}';
    } catch (_) {
      return week;
    }
  }

  DateTime _mondayOfISOWeek(int year, int w) {
    final jan4 = DateTime.utc(year, 1, 4);
    final monday1 = jan4.subtract(Duration(days: jan4.weekday - 1));
    return monday1.add(Duration(days: (w - 1) * 7));
  }

  String _offsetWeek(String week, int offsetWeeks) {
    try {
      final parts = week.split('-W');
      final year = int.parse(parts[0]);
      final w = int.parse(parts[1]);
      final monday = _mondayOfISOWeek(year, w);
      final newMonday = monday.add(Duration(days: offsetWeeks * 7));
      final (ny, nw) = _isoWeekOf(newMonday);
      return '$ny-W${nw.toString().padLeft(2, '0')}';
    } catch (_) {
      return week;
    }
  }

  (int, int) _isoWeekOf(DateTime dt) {
    final thu = dt.add(Duration(days: 4 - (dt.weekday == 7 ? 0 : dt.weekday)));
    final jan1 = DateTime.utc(thu.year, 1, 1);
    final w = ((thu.difference(jan1).inDays) / 7).ceil();
    return (thu.year, w);
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        IconButton(
          icon: const Icon(Icons.chevron_left),
          onPressed: () {
            ref.read(currentWeekProvider.notifier).state =
                _offsetWeek(week, -1);
          },
        ),
        Text(_weekLabel(week), style: Theme.of(context).textTheme.bodyMedium),
        IconButton(
          icon: const Icon(Icons.chevron_right),
          onPressed: () {
            ref.read(currentWeekProvider.notifier).state =
                _offsetWeek(week, 1);
          },
        ),
      ],
    );
  }
}

// ── Menu content ──────────────────────────────────────────────

class _MenuContent extends StatelessWidget {
  final MenuPlan plan;
  final String week;

  const _MenuContent({required this.plan, required this.week});

  @override
  Widget build(BuildContext context) {
    return ListView(
      padding: const EdgeInsets.only(bottom: 120),
      children: [
        ...plan.days.map((day) => _DayCard(day: day, week: week)),
        const SizedBox(height: 8),
        Padding(
          padding: const EdgeInsets.symmetric(horizontal: 16),
          child: OutlinedButton.icon(
            onPressed: () =>
                context.push('/menu/shopping-list', extra: week),
            icon: const Icon(Icons.shopping_cart_outlined),
            label: const Text('Список покупок'),
          ),
        ),
      ],
    );
  }
}

class _DayCard extends StatelessWidget {
  final MenuDay day;
  final String week;

  const _DayCard({required this.day, required this.week});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 12, 16, 0),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Row(
            children: [
              Text(
                '${day.dayName}, ${day.shortDate}',
                style: theme.textTheme.titleSmall
                    ?.copyWith(fontWeight: FontWeight.w600),
              ),
              const Spacer(),
              Text(
                '${day.totalCalories.toInt()} ккал',
                style: theme.textTheme.bodySmall?.copyWith(
                    color: theme.colorScheme.onSurfaceVariant),
              ),
            ],
          ),
          const SizedBox(height: 8),
          Card(
            child: Column(
              children: day.meals.asMap().entries.map((entry) {
                final index = entry.key;
                final slot = entry.value;
                return Column(
                  children: [
                    _MealRow(slot: slot, week: week),
                    if (index < day.meals.length - 1)
                      const Divider(height: 1),
                  ],
                );
              }).toList(),
            ),
          ),
        ],
      ),
    );
  }
}

class _MealRow extends ConsumerWidget {
  final MealSlot slot;
  final String week;

  const _MealRow({required this.slot, required this.week});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final theme = Theme.of(context);
    final recipe = slot.recipe;

    return ListTile(
      contentPadding:
          const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
      leading: ClipRRect(
        borderRadius: BorderRadius.circular(8),
        child: recipe?.imageUrl.isNotEmpty == true
            ? CachedNetworkImage(
                imageUrl: recipe!.imageUrl,
                width: 56,
                height: 56,
                fit: BoxFit.cover,
                errorWidget: (_, __, ___) => _placeholder(),
              )
            : _placeholder(),
      ),
      title: Row(
        children: [
          Text(slot.mealEmoji, style: const TextStyle(fontSize: 14)),
          const SizedBox(width: 4),
          Text(slot.mealLabel, style: theme.textTheme.labelMedium),
          if (recipe?.nutrition?.calories != null) ...[
            const Spacer(),
            Text(
              '≈${recipe!.nutrition!.calories.toInt()} ккал',
              style: theme.textTheme.labelSmall?.copyWith(
                  color: theme.colorScheme.onSurfaceVariant),
            ),
          ],
        ],
      ),
      subtitle: recipe != null
          ? Text(recipe.title, style: theme.textTheme.bodyMedium)
          : Text(
              'Не задано',
              style: theme.textTheme.bodyMedium?.copyWith(
                color: theme.colorScheme.onSurfaceVariant,
                fontStyle: FontStyle.italic,
              ),
            ),
      trailing: TextButton(
        onPressed: () => _showChangeDialog(context, ref),
        child: const Text('Изменить'),
      ),
    );
  }

  Widget _placeholder() => Container(
        width: 56,
        height: 56,
        color: Colors.grey.shade200,
        child: const Icon(Icons.restaurant, color: Colors.grey),
      );

  void _showChangeDialog(BuildContext context, WidgetRef ref) {
    showDialog(
      context: context,
      builder: (ctx) => AlertDialog(
        title: Text('Изменить ${slot.mealLabel.toLowerCase()}?'),
        content: const Text(
            'Удалите текущий рецепт из слота — новый появится после следующей генерации.'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx),
            child: const Text('Отмена'),
          ),
          if (slot.recipe != null)
            TextButton(
              onPressed: () async {
                Navigator.pop(ctx);
                await ref
                    .read(menuProvider(week).notifier)
                    .deleteItem(slot.id);
              },
              child: const Text('Убрать рецепт'),
            ),
        ],
      ),
    );
  }
}

// ── Generate FAB ──────────────────────────────────────────────

class _GenerateFab extends ConsumerWidget {
  final String week;

  const _GenerateFab({required this.week});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    return FloatingActionButton.extended(
      onPressed: () => _confirmGenerate(context, ref),
      icon: const Icon(Icons.auto_awesome),
      label: const Text('Сгенерировать меню'),
    );
  }

  void _confirmGenerate(BuildContext context, WidgetRef ref) {
    showDialog(
      context: context,
      builder: (ctx) => AlertDialog(
        title: const Text('Сгенерировать меню?'),
        content: const Text(
            'Gemini составит меню на неделю с учётом ваших продуктов и целей. Текущее меню будет заменено.'),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx),
            child: const Text('Отмена'),
          ),
          FilledButton(
            onPressed: () {
              Navigator.pop(ctx);
              ref.read(menuProvider(week).notifier).generate();
            },
            child: const Text('Сгенерировать'),
          ),
        ],
      ),
    );
  }
}

// ── Skeleton ──────────────────────────────────────────────────

class _MenuSkeleton extends StatelessWidget {
  const _MenuSkeleton();

  @override
  Widget build(BuildContext context) {
    final color = Theme.of(context).colorScheme.surfaceContainerHighest;
    return ListView(
      padding: const EdgeInsets.all(16),
      children: [
        const Padding(
          padding: EdgeInsets.symmetric(vertical: 20),
          child: Column(
            children: [
              CircularProgressIndicator(),
              SizedBox(height: 16),
              Text('Составляем меню на неделю...'),
              SizedBox(height: 4),
              Text(
                'Учитываем ваши продукты и цели',
                style: TextStyle(color: Colors.grey),
              ),
            ],
          ),
        ),
        for (int i = 0; i < 3; i++) ...[
          _shimmer(color, height: 16, width: 160),
          const SizedBox(height: 8),
          _shimmer(color, height: 90),
          const SizedBox(height: 16),
        ],
      ],
    );
  }

  Widget _shimmer(Color color, {double height = 60, double? width}) =>
      Container(
        height: height,
        width: width,
        margin: const EdgeInsets.only(bottom: 6),
        decoration: BoxDecoration(
          color: color,
          borderRadius: BorderRadius.circular(8),
        ),
      );
}

// ── Empty state ───────────────────────────────────────────────

class _EmptyState extends StatelessWidget {
  final VoidCallback onGenerate;

  const _EmptyState({required this.onGenerate});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Center(
      child: Padding(
        padding: const EdgeInsets.all(32),
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(Icons.calendar_today_outlined,
                size: 72, color: theme.colorScheme.onSurfaceVariant),
            const SizedBox(height: 16),
            Text('Меню не составлено',
                style: theme.textTheme.titleMedium),
            const SizedBox(height: 8),
            Text(
              'Нажмите кнопку ниже, чтобы Gemini составил меню на неделю с учётом ваших продуктов',
              textAlign: TextAlign.center,
              style: theme.textTheme.bodyMedium
                  ?.copyWith(color: theme.colorScheme.onSurfaceVariant),
            ),
            const SizedBox(height: 24),
            FilledButton.icon(
              onPressed: onGenerate,
              icon: const Icon(Icons.auto_awesome),
              label: const Text('Сгенерировать меню'),
            ),
          ],
        ),
      ),
    );
  }
}

// ── Error view ────────────────────────────────────────────────

class _ErrorView extends StatelessWidget {
  final VoidCallback onRetry;

  const _ErrorView({required this.onRetry});

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          const Icon(Icons.error_outline, size: 48, color: Colors.red),
          const SizedBox(height: 12),
          const Text('Не удалось загрузить меню'),
          const SizedBox(height: 12),
          FilledButton(
              onPressed: onRetry, child: const Text('Повторить')),
        ],
      ),
    );
  }
}