Add user-portal mapping to database

database/portal.go

@@ -42,7 +42,7 @@ func NewPortalKey(jid, receiver types.WhatsAppID) PortalKey {
 		receiver = jid
 	}
 	return PortalKey{
-		JID: jid,
+		JID:      jid,
 		Receiver: receiver,
 	}
 }
@@ -152,3 +152,26 @@ func (portal *Portal) Delete() {
 		portal.log.Warnfln("Failed to delete %s: %v", portal.Key, err)
 	}
 }
+
+func (portal *Portal) GetUserIDs() []types.MatrixUserID {
+	rows, err := portal.db.Query(`SELECT "user".mxid FROM "user", user_portal
+		WHERE "user".jid=user_portal.user_jid
+			AND user_portal.portal_jid=$1
+			AND user_portal.portal_receiver=$2`,
+		portal.Key.JID, portal.Key.Receiver)
+	if err != nil {
+		portal.log.Debugln("Failed to get portal user ids:", err)
+		return nil
+	}
+	var userIDs []types.MatrixUserID
+	for rows.Next() {
+		var userID types.MatrixUserID
+		err = rows.Scan(&userID)
+		if err != nil {
+			portal.log.Warnln("Failed to scan row:", err)
+			continue
+		}
+		userIDs = append(userIDs, userID)
+	}
+	return userIDs
+}