import 'package:drift/drift.dart';
import 'package:uuid/uuid.dart';

import '../database/app_database.dart';
import '../models/bar_tab.dart';
import '../models/product.dart';
import '../models/tab_item.dart';

abstract class BarTabService {
  Future<List<BarTab>> getOpenTabs();

  Future<BarTab?> getTabById(String id);

  Future<BarTab> createTab({
    required String customerName,
  });

  Future<void> addProductToTab({
    required String tabId,
    required Product product,
  });

  Future<void> updateTabItemQuantity({
    required String tabItemId,
    required int quantity,
  });

  Future<void> closeTab(String tabId);
}

class DriftBarTabService implements BarTabService {
  final AppDatabase database;
  final _uuid = const Uuid();

  DriftBarTabService({
    required this.database,
  });

  TabItem _mapItemRow(TabItemRow row) {
    return TabItem(
      id: row.id,
      tabId: row.tabId,
      productId: row.productId,
      productName: row.productName,
      quantity: row.quantity,
      unitPriceInCents: row.unitPriceInCents,
    );
  }

  BarTab _mapTabRow(
      BarTabRow row,
      List<TabItem> items,
      ) {
    return BarTab(
      id: row.id,
      customerName: row.customerName,
      status: row.status,
      openedAt: row.openedAt,
      closedAt: row.closedAt,
      items: items,
    );
  }

  Future<List<TabItem>> _getItemsForTab(String tabId) async {
    final query = database.select(database.tabItems)
      ..where((item) => item.tabId.equals(tabId))
      ..orderBy([
            (item) => OrderingTerm.asc(item.createdAt),
      ]);

    final rows = await query.get();

    return rows.map(_mapItemRow).toList();
  }

  @override
  Future<List<BarTab>> getOpenTabs() async {
    final query = database.select(database.barTabs)
      ..where((tab) => tab.status.equals('open'))
      ..orderBy([
            (tab) => OrderingTerm.desc(tab.openedAt),
      ]);

    final tabRows = await query.get();

    final tabs = <BarTab>[];

    for (final tabRow in tabRows) {
      final items = await _getItemsForTab(tabRow.id);

      tabs.add(_mapTabRow(tabRow, items));
    }

    return tabs;
  }

  @override
  Future<BarTab?> getTabById(String id) async {
    final query = database.select(database.barTabs)
      ..where((tab) => tab.id.equals(id));

    final tabRow = await query.getSingleOrNull();

    if (tabRow == null) {
      return null;
    }

    final items = await _getItemsForTab(tabRow.id);

    return _mapTabRow(tabRow, items);
  }

  @override
  Future<BarTab> createTab({
    required String customerName,
  }) async {
    final id = _uuid.v4();

    await database.into(database.barTabs).insert(
      BarTabsCompanion.insert(
        id: id,
        customerName: customerName,
        status: const Value('open'),
        openedAt: DateTime.now(),
      ),
    );

    final tab = await getTabById(id);

    if (tab == null) {
      throw Exception('Could not create tab.');
    }

    return tab;
  }

  @override
  Future<void> addProductToTab({
    required String tabId,
    required Product product,
  }) async {
    await database.transaction(() async {
      final existingItemQuery = database.select(database.tabItems)
        ..where(
              (item) =>
          item.tabId.equals(tabId) &
          item.productId.equals(product.id),
        );

      final existingItem = await existingItemQuery.getSingleOrNull();

      if (existingItem != null) {
        final updateQuery = database.update(database.tabItems)
          ..where((item) => item.id.equals(existingItem.id));

        await updateQuery.write(
          TabItemsCompanion(
            quantity: Value(existingItem.quantity + 1),
          ),
        );

        return;
      }

      await database.into(database.tabItems).insert(
        TabItemsCompanion.insert(
          id: _uuid.v4(),
          tabId: tabId,
          productId: product.id,
          productName: product.name,
          quantity: 1,
          unitPriceInCents: product.priceInCents,
          createdAt: DateTime.now(),
        ),
      );
    });
  }

  @override
  Future<void> updateTabItemQuantity({
    required String tabItemId,
    required int quantity,
  }) async {
    if (quantity <= 0) {
      final deleteQuery = database.delete(database.tabItems)
        ..where((item) => item.id.equals(tabItemId));

      await deleteQuery.go();
      return;
    }

    final updateQuery = database.update(database.tabItems)
      ..where((item) => item.id.equals(tabItemId));

    await updateQuery.write(
      TabItemsCompanion(
        quantity: Value(quantity),
      ),
    );
  }

  @override
  Future<void> closeTab(String tabId) async {
    final updateQuery = database.update(database.barTabs)
      ..where((tab) => tab.id.equals(tabId));

    await updateQuery.write(
      BarTabsCompanion(
        status: const Value('closed'),
        closedAt: Value(DateTime.now()),
      ),
    );
  }
}