Second checkpoint

internal/repository/postgres/errors.go

@@ -0,0 +1,35 @@
+package postgres
+
+import (
+	"errors"
+	"fmt"
+
+	"gis/internal/domain"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+)
+
+// mapError translates pgx/Postgres errors into domain sentinel errors so the
+// service and transport layers stay decoupled from the driver.
+func mapError(err error) error {
+	if err == nil {
+		return nil
+	}
+	if errors.Is(err, pgx.ErrNoRows) {
+		return domain.ErrNotFound
+	}
+
+	var pgErr *pgconn.PgError
+	if errors.As(err, &pgErr) {
+		switch pgErr.Code {
+		case "23503": // foreign_key_violation
+			return fmt.Errorf("%w: %s", domain.ErrConflict, pgErr.ConstraintName)
+		case "23505": // unique_violation
+			return fmt.Errorf("%w: %s", domain.ErrConflict, pgErr.ConstraintName)
+		case "23514": // check_violation
+			return fmt.Errorf("%w: %s", domain.ErrValidation, pgErr.ConstraintName)
+		}
+	}
+	return err
+}