Method AddUser

internal/users/index.go:370–425

AddUser appends a new record to the index file and updates the header.

(userId int, username string)

// AddUser appends a new record to the index file and updates the header.
func (idx *UserIndex) AddUser(userId int, username string) error {
	idx.mu.Lock()
	defer idx.mu.Unlock()

	username = strings.ToLower(username)

	newRecord := IndexUserRecord{
		UserID: int64(userId),
	}
	copy(newRecord.Username[:], username)

	f, err := os.OpenFile(idx.Filename, os.O_RDWR, 0644)
	if err != nil {
		return err
	}
	defer f.Close()

	if _, err := f.Seek(0, io.SeekEnd); err != nil {
		return fmt.Errorf("error seeking to file end: %w", err)
	}

	var recBuf [IndexRecordSizeV1]byte
	copy(recBuf[:80], newRecord.Username[:])
	binary.LittleEndian.PutUint64(recBuf[80:88], uint64(newRecord.UserID))
	recBuf[88] = IndexLineTerminatorV1
	if _, err := f.Write(recBuf[:]); err != nil {
		return fmt.Errorf("error writing record: %w", err)
	}

	if userId > idx.highestUserId {
		idx.highestUserId = userId
	}

	idx.metaData.RecordCount++

	newHeaderBytes, err := idx.metaData.Format()
	if err != nil {
		return fmt.Errorf("error formatting header: %w", err)
	}
	if _, err := f.Seek(0, io.SeekStart); err != nil {
		return fmt.Errorf("error seeking to beginning: %w", err)
	}
	if _, err := f.Write(newHeaderBytes); err != nil {
		return fmt.Errorf("error writing updated header: %w", err)
	}

	if err := f.Sync(); err != nil {
		return fmt.Errorf("error syncing file: %w", err)
	}

	idx.records = append(idx.records, newRecord)
	idx.byUsername[username] = int64(userId)
	idx.byUserId[int64(userId)] = username

	return nil
}

// RemoveByUsername removes the first record matching the username and rewrites the index.