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

import '../../../nutrition/domain/entities/meal_type.dart';
import '../../domain/entities/recipe.dart';
import '../controllers/meal_plan_calendar_controller.dart';
import '../controllers/recipe_import_controller.dart';
import '../widgets/assign_slot_dialog.dart';
import '../widgets/recipe_preview_dialog.dart';
import '../widgets/saved_recipes_tray.dart';
import '../widgets/weekly_calendar_view.dart';

/// GLP-1 meal planner: recipe URL import bar, saved-recipes tray, and the
/// responsive weekly calendar with drag-and-drop assignment and per-day
/// protein rollups.
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: fixed top sections (~340 dp) plus a minimal usable calendar
  /// area. Below this, a plain `Column` would overflow and paint the
  /// yellow/black hatched stripes.
  static const double _kFullScrollThreshold = 520;

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

  final TextEditingController _urlController = TextEditingController();
  bool _previewDialogVisible = false;

  @override
  void dispose() {
    _urlController.dispose();
    super.dispose();
  }

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

    // Open the preview modal when a scrape completes; surface messages as
    // snackbars.
    ref.listen(recipeImportControllerProvider, (previous, next) {
      if (next.previewRecipe != null &&
          previous?.previewRecipe == null &&
          !_previewDialogVisible) {
        _showPreview(next.previewRecipe!);
      }
      if (next.statusMessage != null &&
          next.statusMessage != previous?.statusMessage) {
        ScaffoldMessenger.of(context)
            .showSnackBar(SnackBar(content: Text(next.statusMessage!)));
      }
      if (next.errorMessage != null &&
          next.errorMessage != previous?.errorMessage &&
          next.previewRecipe == null) {
        _showErrorSnack(next.errorMessage!);
      }
    });

    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 & Import')),
      body: LayoutBuilder(
        builder: (context, constraints) {
          // Short windows (e.g. resized desktop windows) can no longer fit
          // the fixed top sections plus 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: [
                  _buildTopSections(importState, calendarState),
                  SizedBox(
                    height: _kCalendarScrollHeight,
                    child: _buildCalendar(calendarState),
                  ),
                ],
              ),
            );
          }

          return Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              _buildTopSections(importState, calendarState),
              Expanded(child: _buildCalendar(calendarState)),
            ],
          );
        },
      ),
    );
  }

  /// Import bar + saved recipes tray + week navigation header.
  Widget _buildTopSections(
    RecipeImportState importState,
    MealPlanCalendarState calendarState,
  ) =>
      Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          _RecipeImportBar(
            controller: _urlController,
            isLoading: importState.isImporting,
            onSubmit: _submitUrl,
          ),
          const SizedBox(height: 12),
          SavedRecipesTray(
            recipes: importState.savedRecipes,
            onAssignPressed: _openTrayAssign,
          ),
          const SizedBox(height: 12),
          _WeekNavigationHeader(state: calendarState),
          const Divider(height: 1),
        ],
      );

  /// Weekly calendar grid (or the initial loading spinner).
  Widget _buildCalendar(MealPlanCalendarState calendarState) =>
      !calendarState.hasLoaded
          ? const Center(child: CircularProgressIndicator())
          : WeeklyCalendarView(
              state: calendarState,
              onRecipeDropped: _onRecipeDropped,
              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,
      ),
    );
  }

  Future<void> _submitUrl() async {
    final url = _urlController.text;
    final notifier = ref.read(recipeImportControllerProvider.notifier);
    await notifier.submitUrl(url);
    if (mounted) _urlController.clear();
  }

  Future<void> _showPreview(Recipe recipe) async {
    _previewDialogVisible = true;
    final notifier = ref.read(recipeImportControllerProvider.notifier);
    final saved = await showRecipePreviewDialog(context, recipe: recipe);
    _previewDialogVisible = false;
    // Cancelling (or abandoning a failed save) clears the parked preview so
    // the modal never re-opens on the next rebuild.
    if (saved != true) notifier.dismissPreview();
  }

  void _onRecipeDropped(Recipe recipe, DateTime day, MealType mealType) {
    ref.read(mealPlanCalendarControllerProvider.notifier).assignRecipe(
          day: day,
          mealType: mealType,
          recipeId: recipe.id,
        );
  }

  void _onSlotTapped(DateTime day, MealType mealType) {
    final calendarState = ref.read(mealPlanCalendarControllerProvider);
    final importState = ref.read(recipeImportControllerProvider);
    showAssignSlotDialog(
      context,
      day: day,
      mealType: mealType,
      savedRecipes: importState.savedRecipes,
      existingSlot: calendarState.slotFor(day, mealType),
    );
  }

  void _openTrayAssign(Recipe recipe) {
    final calendarState = ref.read(mealPlanCalendarControllerProvider);
    final importState = ref.read(recipeImportControllerProvider);
    // Default target: today when inside the window, else the first day.
    final now = DateTime.now();
    final day = calendarState.days.firstWhere(
      (day) =>
          day.year == now.year &&
          day.month == now.month &&
          day.day == now.day,
      orElse: () => calendarState.days.first,
    );
    showAssignSlotDialog(
      context,
      day: day,
      mealType: MealType.breakfast,
      savedRecipes: importState.savedRecipes,
      existingSlot: calendarState.slotFor(day, MealType.breakfast),
    );
  }
}

/// URL import bar: text field + Import button with an inline loading
/// spinner.
class _RecipeImportBar extends StatelessWidget {
  const _RecipeImportBar({
    required this.controller,
    required this.isLoading,
    required this.onSubmit,
  });

  final TextEditingController controller;
  final bool isLoading;
  final VoidCallback onSubmit;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 16, 16, 0),
      child: Row(
        children: [
          Expanded(
            child: TextField(
              controller: controller,
              enabled: !isLoading,
              keyboardType: TextInputType.url,
              decoration: const InputDecoration(
                labelText: 'Recipe URL',
                hintText: 'https://example.com/best-lasagna',
                border: OutlineInputBorder(),
                isDense: true,
                prefixIcon: Icon(Icons.link),
              ),
              onSubmitted: (_) => onSubmit(),
            ),
          ),
          const SizedBox(width: 8),
          FilledButton.icon(
            onPressed: isLoading ? null : onSubmit,
            icon: isLoading
                ? const SizedBox(
                    width: 16,
                    height: 16,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  )
                : const Icon(Icons.download_outlined),
            label: const Text('Import'),
          ),
        ],
      ),
    );
  }
}

/// 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);
}