package imap import ( "sort" "sync" ) type SeqMap struct { lock sync.Mutex // map of IMAP sequence numbers to message UIDs m []uint32 } // Initialize sets the initial seqmap of the mailbox func (s *SeqMap) Initialize(uids []uint32) { s.lock.Lock() s.m = uids s.sort() s.lock.Unlock() } func (s *SeqMap) Size() int { s.lock.Lock() size := len(s.m) s.lock.Unlock() return size } // Get returns the UID of the given seqnum func (s *SeqMap) Get(seqnum uint32) (uint32, bool) { if int(seqnum) > s.Size() || seqnum < 1 { return 0, false } s.lock.Lock() uid := s.m[seqnum-1] s.lock.Unlock() return uid, true } // Put adds a UID to the slice. Put should only be used to add new messages // into the slice func (s *SeqMap) Put(uid uint32) { s.lock.Lock() for _, n := range s.m { if n == uid { // We already have this UID, don't insert it. s.lock.Unlock() return } } s.m = append(s.m, uid) s.sort() s.lock.Unlock() } // Pop removes seqnum from the SeqMap. seqnum must be a valid seqnum, ie // [1:size of mailbox] func (s *SeqMap) Pop(seqnum uint32) (uint32, bool) { if int(seqnum) > s.Size() || seqnum < 1 { return 0, false } s.lock.Lock() uid := s.m[seqnum-1] s.m = append(s.m[:seqnum-1], s.m[seqnum:]...) s.lock.Unlock() return uid, true } // sort sorts the slice in ascending UID order. See: // https://datatracker.ietf.org/doc/html/rfc3501#section-2.3.1.2 func (s *SeqMap) sort() { // Always be sure the SeqMap is sorted sort.Slice(s.m, func(i, j int) bool { return s.m[i] < s.m[j] }) }