Remove legacy question storage

internal/store/user.go

@@ -9,12 +9,19 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgconn"
 
 	"plumber/internal/store/sqlc"
 )
 
-// ErrLastAdmin is returned when demoting the only remaining admin.
-var ErrLastAdmin = errors.New("cannot demote the last admin")
+var (
+	// ErrLastAdmin is returned when demoting the only remaining admin.
+	ErrLastAdmin = errors.New("cannot demote the last admin")
+	// ErrDuplicateUsername is returned when inserting an existing username.
+	ErrDuplicateUsername = errors.New("username taken")
+	// ErrDuplicateEmail is returned when inserting or updating an existing email.
+	ErrDuplicateEmail = errors.New("email taken")
+)
 
 // Role is a user privilege level stored in users.role.
 type Role string
@@ -51,6 +58,17 @@ func NormalizeUsername(s string) string {
 	return strings.ToLower(strings.TrimSpace(s))
 }
 
+func mapUniqueViolation(err error) error {
+	var pgErr *pgconn.PgError
+	if errors.As(err, &pgErr) && pgErr.Code == "23505" {
+		if strings.Contains(strings.ToLower(pgErr.ConstraintName), "email") {
+			return ErrDuplicateEmail
+		}
+		return ErrDuplicateUsername
+	}
+	return err
+}
+
 func toUser(db *sql.DB, id, username, name, role, email, avatarURL, state, createdAt, passwordHash string) *User {
 	return &User{
 		ID:           id,