import 'dart:math' as math;

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 '../../core/theme/app_colors.dart';
import '../../shared/models/home_summary.dart';
import '../profile/profile_provider.dart';
import 'home_provider.dart';

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

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final state = ref.watch(homeProvider);
    final userName = ref.watch(profileProvider).valueOrNull?.name;

    final goalType = ref.watch(
        profileProvider.select((asyncUser) => asyncUser.valueOrNull?.goal));

    return Scaffold(
      body: state.when(
        loading: () => const Center(child: CircularProgressIndicator()),
        error: (_, __) => Center(
          child: FilledButton(
            onPressed: () => ref.read(homeProvider.notifier).load(),
            child: const Text('Повторить'),
          ),
        ),
        data: (summary) => RefreshIndicator(
          onRefresh: () => ref.read(homeProvider.notifier).load(),
          child: CustomScrollView(
            slivers: [
              _AppBar(summary: summary, userName: userName),
              SliverPadding(
                padding: const EdgeInsets.fromLTRB(16, 0, 16, 100),
                sliver: SliverList(
                  delegate: SliverChildListDelegate([
                    const SizedBox(height: 16),
                    _CaloriesCard(today: summary.today, goalType: goalType),
                    const SizedBox(height: 16),
                    _TodayMealsCard(plan: summary.today.plan),
                    if (summary.expiringSoon.isNotEmpty) ...[
                      const SizedBox(height: 16),
                      _ExpiringBanner(items: summary.expiringSoon),
                    ],
                    const SizedBox(height: 16),
                    _QuickActionsRow(date: summary.today.date),
                    if (summary.recommendations.isNotEmpty) ...[
                      const SizedBox(height: 20),
                      _SectionTitle('Рекомендуем приготовить'),
                      const SizedBox(height: 12),
                      _RecommendationsRow(recipes: summary.recommendations),
                    ],
                  ]),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

// ── App bar ───────────────────────────────────────────────────

class _AppBar extends StatelessWidget {
  final HomeSummary summary;
  final String? userName;
  const _AppBar({required this.summary, this.userName});

  String get _greetingBase {
    final hour = DateTime.now().hour;
    if (hour < 12) return 'Доброе утро';
    if (hour < 18) return 'Добрый день';
    return 'Добрый вечер';
  }

  String get _greeting {
    final name = userName;
    if (name != null && name.isNotEmpty) return '$_greetingBase, $name!';
    return _greetingBase;
  }

  String get _dateLabel {
    final now = DateTime.now();
    const months = [
      'января', 'февраля', 'марта', 'апреля', 'мая', 'июня',
      'июля', 'августа', 'сентября', 'октября', 'ноября', 'декабря',
    ];
    return '${now.day} ${months[now.month - 1]}';
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return SliverAppBar(
      pinned: false,
      floating: true,
      title: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(_greeting, style: theme.textTheme.titleMedium),
          Text(
            _dateLabel,
            style: theme.textTheme.bodySmall
                ?.copyWith(color: theme.colorScheme.onSurfaceVariant),
          ),
        ],
      ),
    );
  }
}

// ── Calories card ─────────────────────────────────────────────

class _CaloriesCard extends StatelessWidget {
  final TodaySummary today;
  final String? goalType;

  const _CaloriesCard({required this.today, required this.goalType});

  @override
  Widget build(BuildContext context) {
    if (today.dailyGoal == 0) return const SizedBox.shrink();

    final theme = Theme.of(context);
    final logged = today.loggedCalories.toInt();
    final goal = today.dailyGoal;
    final rawProgress =
        goal > 0 ? today.loggedCalories / goal : 0.0;
    final isOverGoal = rawProgress > 1.0;
    final ringColor = _ringColorFor(rawProgress, goalType);

    final String secondaryLabel;
    final Color secondaryColor;
    if (isOverGoal) {
      final overBy = (today.loggedCalories - goal).toInt();
      secondaryLabel = '+$overBy перебор';
      secondaryColor = AppColors.error;
    } else {
      final remaining = today.remainingCalories.toInt();
      secondaryLabel = 'осталось $remaining';
      secondaryColor = AppColors.textSecondary;
    }

    return Card(
      child: Padding(
        padding: const EdgeInsets.all(20),
        child: Row(
          children: [
            SizedBox(
              width: 160,
              height: 160,
              child: Stack(
                alignment: Alignment.center,
                children: [
                  CustomPaint(
                    size: const Size(160, 160),
                    painter: _CalorieRingPainter(
                      rawProgress: rawProgress,
                      ringColor: ringColor,
                    ),
                  ),
                  Column(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      Text(
                        '$logged',
                        style: theme.textTheme.headlineMedium?.copyWith(
                          fontWeight: FontWeight.w700,
                          color: ringColor,
                        ),
                      ),
                      Text(
                        'ккал',
                        style: theme.textTheme.bodySmall?.copyWith(
                          color: AppColors.textSecondary,
                        ),
                      ),
                      const SizedBox(height: 4),
                      Text(
                        'цель: $goal',
                        style: theme.textTheme.labelSmall?.copyWith(
                          color: AppColors.textSecondary,
                        ),
                      ),
                    ],
                  ),
                ],
              ),
            ),
            const SizedBox(width: 20),
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  _CalorieStat(
                    label: 'Потреблено',
                    value: '$logged ккал',
                    valueColor: ringColor,
                  ),
                  const SizedBox(height: 12),
                  _CalorieStat(
                    label: isOverGoal ? 'Превышение' : 'Осталось',
                    value: secondaryLabel,
                    valueColor: secondaryColor,
                  ),
                  const SizedBox(height: 12),
                  _CalorieStat(
                    label: 'Цель',
                    value: '$goal ккал',
                    valueColor: AppColors.textPrimary,
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class _CalorieStat extends StatelessWidget {
  final String label;
  final String value;
  final Color valueColor;

  const _CalorieStat({
    required this.label,
    required this.value,
    required this.valueColor,
  });

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Text(
          label,
          style: theme.textTheme.labelSmall
              ?.copyWith(color: AppColors.textSecondary),
        ),
        const SizedBox(height: 2),
        Text(
          value,
          style: theme.textTheme.bodyMedium?.copyWith(
            color: valueColor,
            fontWeight: FontWeight.w600,
          ),
        ),
      ],
    );
  }
}

// ── Ring colour logic ──────────────────────────────────────────

// Returns the ring stroke colour based on rawProgress and goal type.
// See docs/calorie_ring_color_spec.md for full specification.
Color _ringColorFor(double rawProgress, String? goalType) {
  switch (goalType) {
    case 'lose':
      // Ceiling semantics: over goal is bad
      if (rawProgress >= 1.10) return AppColors.error;
      if (rawProgress >= 0.95) return AppColors.warning;
      if (rawProgress >= 0.75) return AppColors.success;
      return AppColors.primary;

    case 'maintain':
      // Bidirectional target: closeness in either direction is good
      if (rawProgress >= 1.25) return AppColors.error;
      if (rawProgress >= 1.11) return AppColors.warning;
      if (rawProgress >= 0.90) return AppColors.success;
      if (rawProgress >= 0.70) return AppColors.warning;
      return AppColors.primary;

    case 'gain':
      // Floor semantics: under goal is bad, over is neutral
      if (rawProgress < 0.60) return AppColors.error;
      if (rawProgress < 0.85) return AppColors.warning;
      if (rawProgress <= 1.15) return AppColors.success;
      return AppColors.primary;

    default:
      return AppColors.primary;
  }
}

// ── Ring painter ───────────────────────────────────────────────

class _CalorieRingPainter extends CustomPainter {
  final double rawProgress;
  final Color ringColor;

  const _CalorieRingPainter({
    required this.rawProgress,
    required this.ringColor,
  });

  @override
  void paint(Canvas canvas, Size size) {
    final center = Offset(size.width / 2, size.height / 2);
    final radius = (size.width - 20) / 2; // 10 px inset on each side
    const strokeWidth = 10.0;
    const overflowStrokeWidth = 6.0;
    // Arc starts at 12 o'clock (−π/2) and goes clockwise
    const startAngle = -math.pi / 2;

    // Background track — full circle
    final trackPaint = Paint()
      ..color = AppColors.separator.withValues(alpha: 0.5)
      ..style = PaintingStyle.stroke
      ..strokeWidth = strokeWidth
      ..strokeCap = StrokeCap.round;
    canvas.drawCircle(center, radius, trackPaint);

    // Primary arc — clamp sweep to max one full circle
    final clampedProgress = rawProgress.clamp(0.0, 1.0);
    if (clampedProgress > 0) {
      final arcPaint = Paint()
        ..color = ringColor
        ..style = PaintingStyle.stroke
        ..strokeWidth = strokeWidth
        ..strokeCap = StrokeCap.round;
      canvas.drawArc(
        Rect.fromCircle(center: center, radius: radius),
        startAngle,
        clampedProgress * 2 * math.pi,
        false,
        arcPaint,
      );
    }

    // Overflow arc — second lap when rawProgress > 1.0
    if (rawProgress > 1.0) {
      final overflowProgress = rawProgress - 1.0;
      final overflowPaint = Paint()
        ..color = ringColor.withValues(alpha: 0.70)
        ..style = PaintingStyle.stroke
        ..strokeWidth = overflowStrokeWidth
        ..strokeCap = StrokeCap.round;
      canvas.drawArc(
        Rect.fromCircle(center: center, radius: radius),
        startAngle,
        overflowProgress.clamp(0.0, 1.0) * 2 * math.pi,
        false,
        overflowPaint,
      );
    }
  }

  @override
  bool shouldRepaint(_CalorieRingPainter oldDelegate) =>
      oldDelegate.rawProgress != rawProgress ||
      oldDelegate.ringColor != ringColor;
}

// ── Today meals card ──────────────────────────────────────────

class _TodayMealsCard extends StatelessWidget {
  final List<TodayMealPlan> plan;
  const _TodayMealsCard({required this.plan});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Padding(
          padding: const EdgeInsets.only(bottom: 8),
          child: Text('Приёмы пищи сегодня',
              style: theme.textTheme.titleSmall),
        ),
        Card(
          child: Column(
            children: plan.asMap().entries.map((entry) {
              final i = entry.key;
              final meal = entry.value;
              return Column(
                children: [
                  _MealRow(meal: meal),
                  if (i < plan.length - 1)
                    const Divider(height: 1, indent: 16),
                ],
              );
            }).toList(),
          ),
        ),
      ],
    );
  }
}

class _MealRow extends StatelessWidget {
  final TodayMealPlan meal;
  const _MealRow({required this.meal});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return ListTile(
      leading: Text(meal.mealEmoji, style: const TextStyle(fontSize: 24)),
      title: Text(meal.mealLabel, style: theme.textTheme.labelMedium),
      subtitle: meal.hasRecipe
          ? Text(meal.recipeTitle!, style: theme.textTheme.bodyMedium)
          : Text(
              'Не запланировано',
              style: theme.textTheme.bodyMedium?.copyWith(
                color: theme.colorScheme.onSurfaceVariant,
                fontStyle: FontStyle.italic,
              ),
            ),
      trailing: meal.calories != null
          ? Text(
              '≈${meal.calories!.toInt()} ккал',
              style: theme.textTheme.bodySmall?.copyWith(
                  color: theme.colorScheme.onSurfaceVariant),
            )
          : const Icon(Icons.chevron_right),
      onTap: () => context.push('/menu'),
    );
  }
}

// ── Expiring banner ───────────────────────────────────────────

class _ExpiringBanner extends StatelessWidget {
  final List<ExpiringSoon> items;
  const _ExpiringBanner({required this.items});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final color = theme.colorScheme.errorContainer;
    final onColor = theme.colorScheme.onErrorContainer;

    return GestureDetector(
      onTap: () => context.push('/products'),
      child: Container(
        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
        decoration: BoxDecoration(
          color: color,
          borderRadius: BorderRadius.circular(12),
        ),
        child: Row(
          children: [
            Icon(Icons.warning_amber_rounded, color: onColor, size: 20),
            const SizedBox(width: 10),
            Expanded(
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text(
                    'Истекает срок годности',
                    style: theme.textTheme.labelMedium
                        ?.copyWith(color: onColor, fontWeight: FontWeight.w600),
                  ),
                  Text(
                    items
                        .take(3)
                        .map((e) => '${e.name} — ${e.expiryLabel}')
                        .join(', '),
                    style: theme.textTheme.bodySmall?.copyWith(color: onColor),
                  ),
                ],
              ),
            ),
            Icon(Icons.chevron_right, color: onColor),
          ],
        ),
      ),
    );
  }
}

// ── Quick actions ─────────────────────────────────────────────

class _QuickActionsRow extends StatelessWidget {
  final String date;
  const _QuickActionsRow({required this.date});

  @override
  Widget build(BuildContext context) {
    return Row(
      children: [
        Expanded(
          child: _ActionButton(
            icon: Icons.document_scanner_outlined,
            label: 'Сканировать',
            onTap: () => context.push('/scan'),
          ),
        ),
        const SizedBox(width: 8),
        Expanded(
          child: _ActionButton(
            icon: Icons.calendar_month_outlined,
            label: 'Меню',
            onTap: () => context.push('/menu'),
          ),
        ),
        const SizedBox(width: 8),
        Expanded(
          child: _ActionButton(
            icon: Icons.book_outlined,
            label: 'Дневник',
            onTap: () => context.push('/menu/diary', extra: date),
          ),
        ),
      ],
    );
  }
}

class _ActionButton extends StatelessWidget {
  final IconData icon;
  final String label;
  final VoidCallback onTap;
  const _ActionButton(
      {required this.icon, required this.label, required this.onTap});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Card(
      child: InkWell(
        onTap: onTap,
        borderRadius: BorderRadius.circular(12),
        child: Padding(
          padding: const EdgeInsets.symmetric(vertical: 14),
          child: Column(
            children: [
              Icon(icon, size: 24),
              const SizedBox(height: 6),
              Text(label,
                  style: theme.textTheme.labelSmall,
                  textAlign: TextAlign.center),
            ],
          ),
        ),
      ),
    );
  }
}

// ── Section title ─────────────────────────────────────────────

class _SectionTitle extends StatelessWidget {
  final String text;
  const _SectionTitle(this.text);

  @override
  Widget build(BuildContext context) =>
      Text(text, style: Theme.of(context).textTheme.titleSmall);
}

// ── Recommendations row ───────────────────────────────────────

class _RecommendationsRow extends StatelessWidget {
  final List<HomeRecipe> recipes;
  const _RecommendationsRow({required this.recipes});

  @override
  Widget build(BuildContext context) {
    return SizedBox(
      height: 168,
      child: ListView.separated(
        scrollDirection: Axis.horizontal,
        itemCount: recipes.length,
        separatorBuilder: (_, __) => const SizedBox(width: 12),
        itemBuilder: (context, index) =>
            _RecipeCard(recipe: recipes[index]),
      ),
    );
  }
}

class _RecipeCard extends StatelessWidget {
  final HomeRecipe recipe;
  const _RecipeCard({required this.recipe});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);

    return SizedBox(
      width: 140,
      child: Card(
        clipBehavior: Clip.antiAlias,
        child: InkWell(
          onTap: () {}, // recipes detail can be added later
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              recipe.imageUrl.isNotEmpty
                  ? CachedNetworkImage(
                      imageUrl: recipe.imageUrl,
                      height: 96,
                      width: double.infinity,
                      fit: BoxFit.cover,
                      errorWidget: (_, __, ___) => _imagePlaceholder(),
                    )
                  : _imagePlaceholder(),
              Padding(
                padding: const EdgeInsets.fromLTRB(8, 6, 8, 4),
                child: Text(
                  recipe.title,
                  style: theme.textTheme.bodySmall
                      ?.copyWith(fontWeight: FontWeight.w600),
                  maxLines: 2,
                  overflow: TextOverflow.ellipsis,
                ),
              ),
              if (recipe.calories != null)
                Padding(
                  padding: const EdgeInsets.fromLTRB(8, 0, 8, 6),
                  child: Text(
                    '≈${recipe.calories!.toInt()} ккал',
                    style: theme.textTheme.labelSmall?.copyWith(
                        color: theme.colorScheme.onSurfaceVariant),
                  ),
                ),
            ],
          ),
        ),
      ),
    );
  }

  Widget _imagePlaceholder() => Container(
        height: 96,
        color: Colors.grey.shade200,
        child: const Icon(Icons.restaurant, color: Colors.grey),
      );
}