add PlaylistSearch function

[iconoclasthero]

Something like

type Song struct {
    Fields map[string][]string
}

func PlaylistSearch(conn net.Conn, filter string) ([]Song, error) {
    cmd := fmt.Sprintf("playlistsearch \"(%s)\"\n", filter)

    if _, err := conn.Write([]byte(cmd)); err != nil {
        return nil, err
    }

    reader := bufio.NewReader(conn)

    var songs []Song
    var current *Song

    for {
        line, err := reader.ReadString('\n')
        if err != nil {
            return nil, err
        }

        line = strings.TrimSpace(line)

        if line == "OK" {
            break
        }

        if strings.HasPrefix(line, "ACK") {
            return nil, fmt.Errorf("mpd error: %s", line)
        }

        if line == "" {
            continue
        }

        // New object starts at file:
        if strings.HasPrefix(line, "file: ") {
            if current != nil {
                songs = append(songs, *current)
            }
            current = &Song{
                Fields: make(map[string][]string),
            }
        }

        parts := strings.SplitN(line, ": ", 2)
        if len(parts) == 2 {
            if current == nil {
                current = &Song{
                    Fields: make(map[string][]string),
                }
            }
            key := parts[0]
            value := parts[1]
            current.Fields[key] = append(current.Fields[key], value)
        }
    }

    if current != nil {
        songs = append(songs, *current)
    }

    return songs, nil
}