fix: shortlink generation logic update/create

internal/api/repository/shortlink.go

@@ -139,3 +139,28 @@ func (r *ShortLinkRepository) UpdateShortLink(shortLink *models.ShortLink) error
 
 	return nil
 }
+
+// GetActiveShortLinkByPatientAndStudy retrieves an active (unexpired, not revoked) shortlink
+// for the given patient ID and study UID
+func (r *ShortLinkRepository) GetActiveShortLinkByPatientAndStudy(patientID string, studyUID string) (*models.ShortLink, error) {
+	var dbShortLink DBShortLink
+
+	query := `SELECT * FROM shortlink 
+		WHERE Shortlink_PatientID = ? 
+		AND Shortlink_Study_IUID = ? 
+		AND ShortlinkExpiredAt > NOW() 
+		AND ShortlinkIsRevoked = FALSE 
+		ORDER BY ShortlinkExpiredAt DESC 
+		LIMIT 1`
+
+	err := database.DB.Get(&dbShortLink, query, patientID, studyUID)
+
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("database error getting active shortlink: %w", err)
+	}
+
+	return dbShortLink.ToShortLink(), nil
+}