Method replyDelMsg

server/topic.go:3173–3293

replyDelMsg deletes (soft or hard) messages in response to del.msg packet.

(sess *Session, asUid types.Uid, asChan bool, msg *ClientComMessage)

// replyDelMsg deletes (soft or hard) messages in response to del.msg packet.
func (t *Topic) replyDelMsg(sess *Session, asUid types.Uid, asChan bool, msg *ClientComMessage) error {
	now := types.TimeNow()

	if asChan {
		// Do not allow channel readers delete messages.
		sess.queueOut(ErrOperationNotAllowedReply(msg, now))
		return errors.New("channel readers cannot delete messages")
	}

	del := msg.Del

	pud := t.perUser[asUid]
	if !(pud.modeGiven & pud.modeWant).IsDeleter() {
		// User must have an R permission: if the user cannot read messages, he has
		// no business of deleting them.
		if !(pud.modeGiven & pud.modeWant).IsReader() {
			sess.queueOut(ErrPermissionDeniedReply(msg, now))
			return errors.New("del.msg: permission denied")
		}

		// User has just the R permission, cannot hard-delete messages, silently
		// switching to soft-deleting
		del.Hard = false
	}

	var err error
	var ranges []types.Range
	if len(del.DelSeq) == 0 {
		err = errors.New("del.msg: no IDs to delete")
	} else {
		count := 0
		for _, dq := range del.DelSeq {
			if dq.LowId > t.lastID || dq.LowId < 0 || dq.HiId < 0 ||
				(dq.HiId > 0 && dq.LowId > dq.HiId) ||
				(dq.LowId == 0 && dq.HiId == 0) {
				err = errors.New("del.msg: invalid entry in list")
				break
			}

			if dq.HiId > t.lastID {
				// Range is inclusive - exclusive [low, hi),
				// to delete all messages hi must be lastId + 1
				dq.HiId = t.lastID + 1
			} else if dq.LowId == dq.HiId || dq.LowId+1 == dq.HiId {
				dq.HiId = 0
			}

			if dq.HiId == 0 {
				count++
			} else {
				count += dq.HiId - dq.LowId
			}

			ranges = append(ranges, types.Range{Low: dq.LowId, Hi: dq.HiId})
		}

		if err == nil {
			// Sort by Low ascending then by Hi descending.