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

import '../../../../core/database/app_database.dart';
import '../../../../core/utils/uuid.dart';
import '../../data/repositories/drift_pantry_repository.dart';
import '../../domain/entities/pantry_category.dart';
import '../../domain/entities/pantry_item.dart';
import '../../domain/repositories/pantry_repository.dart';
import '../../domain/value_objects/ingredient_name.dart';

/// Application-wide pantry repository (drift-backed).
///
/// Overridable in widget/unit tests with an in-memory fake.
final pantryRepositoryProvider = Provider<IPantryRepository>(
  (ref) => DriftPantryRepository(ref.watch(appDatabaseProvider)),
);

/// How the inventory list is organized on screen.
enum PantrySortMode { category, expiration }

/// Immutable snapshot of the pantry inventory state.
class PantryInventoryState {
  const PantryInventoryState({
    this.items = const [],
    this.sortMode = PantrySortMode.category,
    this.hasLoaded = false,
    this.errorMessage,
  });

  /// Sentinel allowing `copyWith` to explicitly reset a field to `null`.
  static const Object _keep = Object();

  /// Pantry rows (alphabetical, kept live by the repository watch stream).
  final List<PantryItem> items;

  /// Active list organization mode (aisles vs. expiration).
  final PantrySortMode sortMode;

  /// `true` once the first watch emission arrived (drives the spinner).
  final bool hasLoaded;

  /// Last load/persist failure message.
  final String? errorMessage;

  /// Non-empty aisles in category order for sectioned rendering.
  Map<PantryCategory, List<PantryItem>> get groupedByCategory {
    final grouped = <PantryCategory, List<PantryItem>>{};
    for (final category in PantryCategory.values) {
      final bucket = items
          .where((item) => item.category == category)
          .toList(growable: false);
      if (bucket.isNotEmpty) grouped[category] = bucket;
    }
    return grouped;
  }

  /// Items sorted soonest-expiration first; undated items sink to the bottom.
  List<PantryItem> get byExpiration {
    final sorted = List<PantryItem>.of(items);
    sorted.sort((a, b) {
      final aDate = a.expirationDate;
      final bDate = b.expirationDate;
      if (aDate == null && bDate == null) return a.name.compareTo(b.name);
      if (aDate == null) return 1;
      if (bDate == null) return -1;
      final byDate = aDate.compareTo(bDate);
      return byDate != 0 ? byDate : a.name.compareTo(b.name);
    });
    return sorted;
  }

  /// Items already expired or inside the warning window (drives badges).
  List<PantryItem> get expiringSoonItems {
    final flagged = <PantryItem>[];
    for (final item in items) {
      final status = item.expirationStatus();
      if (status == ExpirationStatus.expired ||
          status == ExpirationStatus.expiringSoon) {
        flagged.add(item);
      }
    }
    return flagged;
  }

  PantryInventoryState copyWith({
    List<PantryItem>? items,
    PantrySortMode? sortMode,
    bool? hasLoaded,
    Object? errorMessage = _keep,
  }) =>
      PantryInventoryState(
        items: items ?? this.items,
        sortMode: sortMode ?? this.sortMode,
        hasLoaded: hasLoaded ?? this.hasLoaded,
        errorMessage: identical(errorMessage, _keep)
            ? this.errorMessage
            : errorMessage as String?,
      );
}

/// Orchestrates the pantry inventory: streams stock from the repository,
/// supports quick increment/decrement adjustments, and owns the
/// aisle/expiration presentation modes.
class PantryInventoryController extends Notifier<PantryInventoryState> {
  @override
  PantryInventoryState build() {
    final subscription = ref
        .read(pantryRepositoryProvider)
        .watchItems()
        .listen(
          (items) => state = state.copyWith(items: items, hasLoaded: true),
          onError: (Object error, StackTrace stackTrace) {
            debugPrintStack(
              stackTrace: stackTrace,
              label: 'pantry inventory watch failed',
            );
            state = state.copyWith(errorMessage: 'Could not load the pantry.');
          },
        );
    ref.onDispose(subscription.cancel);
    return const PantryInventoryState();
  }

  /// Adds a new stock row; [name] is canonicalized for fuzzy recipe matching.
  Future<bool> addItem({
    required String name,
    required double quantityOnHand,
    required String unit,
    required PantryCategory category,
    DateTime? expirationDate,
  }) async {
    final key = canonicalIngredientName(name);
    if (key.isEmpty || quantityOnHand < 0) {
      state = state.copyWith(errorMessage: 'Enter a name and a valid quantity.');
      return false;
    }
    try {
      await ref.read(pantryRepositoryProvider).saveItem(
            PantryItem(
              id: generateUuid(),
              name: key,
              quantityOnHand: quantityOnHand,
              unit: unit,
              category: category,
              expirationDate: expirationDate,
              lastUpdated: DateTime.now(),
            ),
          );
      state = state.copyWith(errorMessage: null);
      return true;
    } catch (error, stackTrace) {
      debugPrintStack(stackTrace: stackTrace, label: 'pantry item save failed');
      state = state.copyWith(errorMessage: 'Could not save the item.');
      return false;
    }
  }

  /// Quick +/- stock adjustment for [item]; the level is clamped at zero.
  Future<void> adjustQuantity(PantryItem item, double delta) async {
    final next = item.quantityOnHand + delta;
    try {
      await ref.read(pantryRepositoryProvider).saveItem(
            item.copyWith(
              quantityOnHand: next < 0 ? 0 : next,
              lastUpdated: DateTime.now(),
            ),
          );
    } catch (error, stackTrace) {
      debugPrintStack(
        stackTrace: stackTrace,
        label: 'pantry quantity adjust failed',
      );
      state = state.copyWith(errorMessage: 'Could not update the stock level.');
    }
  }

  /// Removes the inventory row with [id].
  Future<void> deleteItem(String id) async {
    try {
      await ref.read(pantryRepositoryProvider).deleteItem(id);
    } catch (error, stackTrace) {
      debugPrintStack(
        stackTrace: stackTrace,
        label: 'pantry item delete failed',
      );
      state = state.copyWith(errorMessage: 'Could not delete the item.');
    }
  }

  /// Switches the list organization mode (aisles vs. expiration).
  void setSortMode(PantrySortMode mode) =>
      state = state.copyWith(sortMode: mode);

  /// Clears the last error (e.g. once the user has seen it).
  void clearError() => state = state.copyWith(errorMessage: null);
}

/// Exposes the [PantryInventoryController] to the widget tree.
final pantryInventoryControllerProvider =
    NotifierProvider<PantryInventoryController, PantryInventoryState>(
  PantryInventoryController.new,
);