Method thisUserSub

server/topic.go:1506–1873

User requests or updates a self-subscription to a topic. Called as a result of {sub} or {meta set=sub}. Returns new access mode as *MsgAccessMode if user's access mode has changed, nil otherwise. sess - originating session pkt - client message which triggered this request; {sub} or {set} asUi

(sess *Session, pkt *ClientComMessage, asUid types.Uid, asChan bool, want string,
	private any)

// E. User is accepting ownership transfer (requesting ownership transfer is not permitted).
// In case of a group topic the user may be a reader or a full subscriber.
func (t *Topic) thisUserSub(sess *Session, pkt *ClientComMessage, asUid types.Uid, asChan bool, want string,
	private any) (*MsgAccessMode, error) {

	now := types.TimeNow()
	asLvl := auth.Level(pkt.AuthLvl)

	// Access mode values as they were before this request was processed.
	oldWant := types.ModeNone
	oldGiven := types.ModeNone

	// Parse access mode requested by the user
	modeWant := types.ModeUnset
	if want != "" {
		if err := modeWant.UnmarshalText([]byte(want)); err != nil {
			sess.queueOut(ErrMalformedReply(pkt, now))
			return nil, err
		}
	}

	var err error
	// Check if it's an attempt at a new subscription to the topic / a first connection of a channel reader
	// (channel readers are not permanently cached).
	// It could be an actual subscription (IsJoiner() == true) or a ban (IsJoiner() == false).
	userData, existingSub := t.perUser[asUid]
	if !existingSub || userData.deleted {
		// New subscription or a not yet cached channel reader, either new or existing.

		// Check if the max number of subscriptions is already reached.
		if t.cat == types.TopicCatGrp && !asChan && t.subsCount() >= globals.maxSubscriberCount {
			sess.queueOut(ErrPolicyReply(pkt, now))
			return nil, errors.New("max subscription count exceeded")
		}

		var sub *types.Subscription
		tname := t.name
		if t.cat == types.TopicCatP2P {
			// P2P could be here only if it was previously deleted. I.e. existingSub is always true for P2P.
			if modeWant != types.ModeUnset {
				userData.modeWant = modeWant
			}
			// If no modeWant is provided, leave existing one unchanged.

			// Make sure the user is not asking for unreasonable permissions
			userData.modeWant = (userData.modeWant & globals.typesModeCP2P) | types.ModeApprove
		} else if t.cat == types.TopicCatSys {
			if asLvl != auth.LevelRoot {
				sess.queueOut(ErrPermissionDeniedReply(pkt, now))
				return nil, errors.New("subscription to 'sys' topic requires root access level")
			}

			// Assign default access levels
			userData.modeWant = types.ModeCSys
			userData.modeGiven = types.ModeCSys
			if modeWant != types.ModeUnset {
				userData.modeWant = (modeWant & types.ModeCSys) | types.ModeWrite | types.ModeJoin
			}
		} else if asChan {
			userData.isChan = true