import 'package:flutter/foundation.dart';

import '../models/bar_tab.dart';
import '../models/product.dart';
import '../models/tab_item.dart';
import '../services/bar_tab_service.dart';
import 'inventory_view_model.dart';

class BarScreenViewModel extends ChangeNotifier {
  final BarTabService barTabService;
  final InventoryViewModel inventory;

  BarScreenViewModel({required this.barTabService, required this.inventory});

  List<BarTab> _tabs = [];
  String? _selectedTabId;
  bool _isLoading = false;
  bool _hasLoaded = false;
  String? _errorMessage;

  List<BarTab> get tabs => _tabs;

  String? get selectedTabId => _selectedTabId;

  bool get isLoading => _isLoading;

  bool get hasLoaded => _hasLoaded;

  String? get errorMessage => _errorMessage;

  BarTab? get selectedTab {
    if (_selectedTabId == null) return null;

    try {
      return _tabs.firstWhere((tab) => tab.id == _selectedTabId);
    } catch (_) {
      return null;
    }
  }

  Future<void> ensureLoaded() async {
    if (_hasLoaded || _isLoading) return;

    await load();
  }

  Future<void> load() async {
    if (_isLoading) return;

    _isLoading = true;
    _errorMessage = null;
    notifyListeners();

    try {
      _tabs = await barTabService.getOpenTabs();

      if (_selectedTabId == null ||
          !_tabs.any((tab) => tab.id == _selectedTabId)) {
        _selectedTabId = _tabs.isEmpty ? null : _tabs.first.id;
      }
    } catch (_) {
      _errorMessage = 'Could not load bar screen.';
    } finally {
      _hasLoaded = true;
      _isLoading = false;
      notifyListeners();
    }
  }

  void selectTab(String tabId) {
    _selectedTabId = tabId;
    notifyListeners();
  }

  Future<void> createTab(String customerName) async {
    final tab = await barTabService.createTab(customerName: customerName);

    _selectedTabId = tab.id;
    await _reloadTabs();
  }

  Future<void> addProductToSelectedTab(Product product) async {
    final tab = selectedTab;

    if (tab == null) return;

    if (product.stockQuantity <= 0) {
      throw Exception('Product is out of stock.');
    }

    await barTabService.addProductToTab(
      tabId: tab.id,
      product: product,
      stockAdjustment: () => inventory.decreaseStock(product.id, 1),
    );

    await _reloadTabs();
  }

  Future<void> changeItemQuantity(TabItem item, int quantity) async {
    final difference = quantity - item.quantity;

    await barTabService.updateTabItemQuantity(
      tabItemId: item.id,
      quantity: quantity,
      stockAdjustment: () async {
        if (difference > 0) {
          await inventory.decreaseStock(item.productId, difference);
        } else if (difference < 0) {
          await inventory.increaseStock(item.productId, -difference);
        }
      },
    );

    await _reloadTabs();
  }

  Future<void> closeSelectedTab({String paymentMethod = 'cash'}) async {
    final tab = selectedTab;

    if (tab == null) return;

    await barTabService.closeTab(tab.id, paymentMethod: paymentMethod);

    await _reloadTabs();
  }

  Future<void> closeTab(String tabId, {String paymentMethod = 'cash'}) async {
    await barTabService.closeTab(tabId, paymentMethod: paymentMethod);

    await _reloadTabs();
  }

  Future<void> _reloadTabs() async {
    _tabs = await barTabService.getOpenTabs();

    if (_selectedTabId == null ||
        !_tabs.any((tab) => tab.id == _selectedTabId)) {
      _selectedTabId = _tabs.isEmpty ? null : _tabs.first.id;
    }

    notifyListeners();
  }
}