feat: добавить контроллер расходов с базовой функциональностью

finance_app/lib/controllers/expenses_controller.dart

@@ -0,0 +1,76 @@
+import 'dart:async';
+import 'dart:math';
+import 'package:drift/drift.dart' show Value;
+import '../database/database.dart' as db;
+import '../models/category.dart';
+import '../utils/category_utils.dart';
+
+class ExpensesController {
+  final db.AppDatabase database;
+  
+  // State variables
+  int _selectedPieIndex = -1;
+  bool _isPieChartExpanded = true;
+  bool _isFilterVisible = false;
+  String _selectedFilter = 'All';
+
+  ExpensesController(this.database);
+
+  // Getters
+  int get selectedPieIndex => _selectedPieIndex;
+  bool get isPieChartExpanded => _isPieChartExpanded;
+  bool get isFilterVisible => _isFilterVisible;
+  String get selectedFilter => _selectedFilter;
+
+  // Stream that provides transactions based on the selected filter
+  Stream<List<db.Transaction>> watchTransactions() {
+    return database.watchFilteredTransactions(_selectedFilter);
+  }
+
+  // Stream that provides category totals calculated from transactions
+  Stream<List<Category>> watchCategoryTotals() {
+    return database.calculateCategoryTotals();
+  }
+
+  // Handles selection of a pie chart slice
+  void selectPieCategory(int index) {
+    _selectedPieIndex = (_selectedPieIndex == index) ? -1 : index;
+  }
+
+  // Toggles the visibility of the pie chart section
+  void togglePieChartVisibility() {
+    _isPieChartExpanded = !_isPieChartExpanded;
+  }
+
+  // Toggles the visibility of the filter chip row
+  void toggleFilterVisibility() {
+    _isFilterVisible = !_isFilterVisible;
+  }
+
+  // Applies the selected filter to the transaction list
+  void applyFilter(String filter) {
+    _selectedFilter = filter;
+  }
+
+  // Adds a sample transaction for testing/demo
+  Future<void> addSampleTransaction() async {
+    final random = Random();
+    final categories = CategoryUtils.getAllCategoryNames();
+    final randomCategory = categories[random.nextInt(categories.length)];
+    final randomAmount = (random.nextDouble() * 100) + 5;
+    final randomDay = random.nextInt(7);
+    final randomHour = random.nextInt(24);
+    final randomMerchant = [
+      'Amazon', 'Local Cafe', 'Gas Station', 'Online Store', 'Supermarket'
+    ][random.nextInt(5)];
+
+    final newTransaction = db.TransactionsCompanion.insert(
+      categoryName: randomCategory,
+      amount: randomAmount,
+      date: DateTime.now().subtract(Duration(days: randomDay, hours: randomHour)),
+      merchant: randomMerchant,
+    );
+
+    await database.addTransaction(newTransaction);
+  }
+}