Added analytics by transactions

backend/src/repositories/transactions.go

@@ -15,6 +15,7 @@ type TransactionRepository interface {
 	Create(ctx context.Context, transaction *domain.Transaction) error
 	GetByID(ctx context.Context, id int64) (*domain.Transaction, error)
 	List(ctx context.Context, filter domain.TransactionListFilter) ([]*domain.Transaction, error)
+	Analytics(ctx context.Context, filter domain.TransactionAnalyticsFilter) (domain.TransactionAnalytics, error)
 	Update(ctx context.Context, transaction *domain.Transaction, syncReceipt bool) error
 	Delete(ctx context.Context, id int64) error
 }
@@ -188,6 +189,47 @@ func (r *TransactionsSQLRepository) List(ctx context.Context, filter domain.Tran
 	return transactions, rows.Err()
 }
 
+func (r *TransactionsSQLRepository) Analytics(ctx context.Context, filter domain.TransactionAnalyticsFilter) (domain.TransactionAnalytics, error) {
+	var (
+		whereClauses []string
+		args         []any
+	)
+
+	appendFilter := func(condition string, value any) {
+		args = append(args, value)
+		whereClauses = append(whereClauses, fmt.Sprintf(condition, len(args)))
+	}
+
+	appendFilter("datetime >= $%d", filter.DateFrom)
+	appendFilter("datetime <= $%d", filter.DateTo)
+
+	if filter.FamilyID != nil {
+		appendFilter("family_id = $%d", *filter.FamilyID)
+	}
+	if filter.Type != nil {
+		appendFilter("type = $%d", *filter.Type)
+	}
+
+	query := `
+	SELECT
+		COALESCE(SUM(CASE WHEN type = 'expense' THEN amount ELSE 0 END), 0),
+		COALESCE(SUM(CASE WHEN type = 'income' THEN amount ELSE 0 END), 0)
+	FROM transactions
+	`
+
+	if len(whereClauses) > 0 {
+		query += " WHERE " + strings.Join(whereClauses, " AND ")
+	}
+
+	var analytics domain.TransactionAnalytics
+	if err := r.db.QueryRowContext(ctx, query, args...).Scan(&analytics.Expenses, &analytics.Incomes); err != nil {
+		return domain.TransactionAnalytics{}, err
+	}
+	analytics.Total = analytics.Incomes - analytics.Expenses
+
+	return analytics, nil
+}
+
 func (r *TransactionsSQLRepository) Update(ctx context.Context, transaction *domain.Transaction, syncReceipt bool) error {
 	tx, err := r.db.BeginTx(ctx, nil)
 	if err != nil {