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

import '../../../nutrition/domain/entities/meal_type.dart';
import '../controllers/meal_plan_calendar_controller.dart';
import '../controllers/recipe_import_controller.dart';
import '../widgets/assign_recipe_sheet.dart';
import '../widgets/weekly_calendar_view.dart';

/// GLP-1 meal planner: the responsive 7-day weekly calendar (Monday–Sunday)
/// with per-day protein rollups. Recipe import and browsing live in the
/// Recipe Vault; slots are filled via the searchable "+ Assign Recipe"
/// sheet.
class MealPlannerScreen extends ConsumerStatefulWidget {
  const MealPlannerScreen({super.key});

  @override
  ConsumerState<MealPlannerScreen> createState() => _MealPlannerScreenState();
}

class _MealPlannerScreenState extends ConsumerState<MealPlannerScreen> {
  /// Body height below which the page collapses into a single scrollable
  /// column: the week header plus a minimal usable calendar area. Below
  /// this, a plain `Column` would overflow and paint the yellow/black
  /// hatched stripes.
  static const double _kFullScrollThreshold = 360;

  /// Calendar height used in the fully-scrollable fallback layout; tall
  /// enough for the day header plus four meal slots.
  static const double _kCalendarScrollHeight = 560;

  @override
  Widget build(BuildContext context) {
    final calendarState = ref.watch(mealPlanCalendarControllerProvider);

    ref.listen(mealPlanCalendarControllerProvider, (previous, next) {
      if (next.errorMessage != null &&
          next.errorMessage != previous?.errorMessage) {
        _showErrorSnack(next.errorMessage!);
      }
    });

    return Scaffold(
      appBar: AppBar(title: const Text('Meal Planner')),
      body: LayoutBuilder(
        builder: (context, constraints) {
          // Short windows (e.g. resized desktop windows) can no longer fit
          // a useful calendar area; collapse the whole page into a single
          // scroll view instead of overflowing.
          if (constraints.maxHeight < _kFullScrollThreshold) {
            return SingleChildScrollView(
              padding: const EdgeInsets.only(bottom: 16),
              child: Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  _WeekNavigationHeader(state: calendarState),
                  SizedBox(
                    height: _kCalendarScrollHeight,
                    child: _buildCalendar(calendarState),
                  ),
                ],
              ),
            );
          }

          return Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              _WeekNavigationHeader(state: calendarState),
              const Divider(height: 1),
              Expanded(child: _buildCalendar(calendarState)),
            ],
          );
        },
      ),
    );
  }

  /// Weekly calendar grid (or the initial loading spinner).
  Widget _buildCalendar(MealPlanCalendarState calendarState) =>
      !calendarState.hasLoaded
          ? const Center(child: CircularProgressIndicator())
          : WeeklyCalendarView(
              state: calendarState,
              onSlotTapped: _onSlotTapped,
              onTogglePrepared: (slot) => ref
                  .read(mealPlanCalendarControllerProvider.notifier)
                  .togglePrepared(slot),
              onClearSlot: (slot) => ref
                  .read(mealPlanCalendarControllerProvider.notifier)
                  .clearSlot(slot),
            );

  void _showErrorSnack(String message) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(
        content: Text(message),
        backgroundColor: Theme.of(context).colorScheme.error,
      ),
    );
  }

  /// Opens the searchable assign sheet, populated from the Recipe Vault.
  Future<void> _onSlotTapped(DateTime day, MealType mealType) async {
    final calendarState = ref.read(mealPlanCalendarControllerProvider);
    final importState = ref.read(recipeImportControllerProvider);
    await showAssignRecipeSheet(
      context,
      day: day,
      mealType: mealType,
      savedRecipes: importState.savedRecipes,
      existingSlot: calendarState.slotFor(day, mealType),
    );
  }
}

/// Week navigation row: prev/next arrows, the visible week label, and a
/// "Today" shortcut.
class _WeekNavigationHeader extends StatelessWidget {
  const _WeekNavigationHeader({required this.state});

  final MealPlanCalendarState state;

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

    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
      child: Row(
        children: [
          IconButton(
            tooltip: 'Previous week',
            icon: const Icon(Icons.chevron_left),
            onPressed: state.isLoading
                ? null
                : () => _readController(context).previousWeek(),
          ),
          Expanded(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text(
                  state.weekLabel,
                  style: theme.textTheme.titleSmall
                      ?.copyWith(fontWeight: FontWeight.bold),
                ),
                Text(
                  'Monday – Sunday',
                  style: theme.textTheme.labelSmall
                      ?.copyWith(color: theme.colorScheme.outline),
                ),
              ],
            ),
          ),
          TextButton(
            onPressed: state.isLoading
                ? null
                : () => _readController(context).goToToday(),
            child: const Text('Today'),
          ),
          IconButton(
            tooltip: 'Next week',
            icon: const Icon(Icons.chevron_right),
            onPressed: state.isLoading
                ? null
                : () => _readController(context).nextWeek(),
          ),
          if (state.isLoading) ...[
            const SizedBox(width: 4),
            const SizedBox(
              width: 16,
              height: 16,
              child: CircularProgressIndicator(strokeWidth: 2),
            ),
            const SizedBox(width: 8),
          ],
        ],
      ),
    );
  }

  MealPlanCalendarController _readController(BuildContext context) =>
      ProviderScope.containerOf(context, listen: false)
          .read(mealPlanCalendarControllerProvider.notifier);
}