// 9. Разработать программу для обработки и анализа списка финансовых транзакций за месяц. Каждая транзакция включает в себя информацию о дате, типе операции (доход или расход) и сумме. Программа должна подсчитать общий доход и расход за месяц, вычислить итоговый баланс и идентифицировать день с самым большим расходом. В конце работы программа предоставляет подробный отчет.

void main() {
  final transactionManager = TransactionManager();

  transactionManager.addTransaction(
    Transaction(
      date: DateTime(2024, 07, 01),
      operation: Operation.income,
      transactionSum: 1000,
    ),
  );
  transactionManager.addTransaction(
    Transaction(
      date: DateTime(2024, 07, 05),
      operation: Operation.expense,
      transactionSum: 200,
    ),
  );
  transactionManager.addTransaction(
    Transaction(
      date: DateTime(2024, 07, 10),
      operation: Operation.expense,
      transactionSum: 300,
    ),
  );
  transactionManager.addTransaction(
    Transaction(
      date: DateTime(2024, 07, 15),
      operation: Operation.income,
      transactionSum: 1500,
    ),
  );
  transactionManager.addTransaction(
    Transaction(
      date: DateTime(2024, 07, 20),
      operation: Operation.expense,
      transactionSum: 100,
    ),
  );

  final report = transactionManager.report;

  print('Общий доход: ${report.resultIncome}');
  print('Общий расход: ${report.resultExpense}');
  print('Итоговый баланс: ${report.resultBalanse}');
  print('День с самым большим расходом: ${report.mostExpensesDay}');
}

enum Operation { income, expense }

final class Transaction {
  final DateTime date;
  final Operation operation;
  final double transactionSum;

  const Transaction({
    required this.date,
    required this.operation,
    required this.transactionSum,
  });

  @override
  String toString() {
    return 'Transaction{date: $date, operation: $operation, transactionSum: $transactionSum}';
  }
}

final class TransactionManager {
  final List<Transaction> _transactions = [];

  void addTransaction(Transaction transaction) {
    _transactions.add(transaction);
  }

  Report get report => Report(_transactions);
}

final class Report {
  final List<Transaction> _transactions;

  const Report(this._transactions);

  double get resultIncome {
    var resultIncomeVar = 0.0;
    for (final transaction in _transactions) {
      if (transaction.operation == Operation.income) {
        resultIncomeVar += transaction.transactionSum;
      }
    }
    return resultIncomeVar;
  }

  double get resultExpense {
    var resultExpenseVar = 0.0;
    for (final transaction in _transactions) {
      if (transaction.operation == Operation.expense) {
        resultExpenseVar += transaction.transactionSum;
      }
    }
    return resultExpenseVar;
  }

  double get resultBalanse {
    return resultIncome - resultExpense;
  }

  DateTime? get mostExpensesDay {
    if (_transactions.isEmpty) {
      return DateTime.now();
    }

    double maxExpense = 0;
    DateTime? maxExpenseDate;

    for (final transaction in _transactions) {
      if (transaction.operation != Operation.expense) continue;

      final date = DateTime(
        transaction.date.year,
        transaction.date.month,
        transaction.date.day,
      );
      final expense = transaction.transactionSum;

      if (maxExpenseDate == null || expense > maxExpense) {
        maxExpense = expense;
        maxExpenseDate = date;
      }
    }

    return maxExpenseDate;
  }
}