Бэкенд: добавлена проверка в аренду

backend/src/storages/postgres/rent.rs

@@ -11,9 +11,22 @@ pub struct PostgresRentRepository {
 #[async_trait]
 impl RentRepository for PostgresRentRepository {
     async fn create(&self, rent: BindingRent) -> Result<Rent, String> {
+        let query_result = self.connection.query(
+            "SELECT * FROM Rent WHERE car_id=$1 AND time_amount IS NOT NULL",
+            &[&rent.car_id]
+        ).await;
+
+        if let Ok(rows) = query_result {
+            if rows.len() > 0 {
+                return Err("The car is already occupied".to_owned());
+            }
+        } else {
+            return Err("Something gone wrong during checking for existing rents".to_owned());
+        }
+
         let result = self.connection.query(
             "INSERT INTO Rent(time_amount, client_id, car_id) \
-            VALUES ($1, $2, $3, $4) RETURNING *",
+            VALUES ($1, $2, $3) RETURNING *",
             &[&rent.time_amount, &rent.client_id, &rent.car_id]
         ).await;