stream-tools/music/music.go

package music

import (
	"context"
	"embed"
	"fmt"
	"io"
	"log"
	"net/http"
	"strings"
	"time"

	"codeberg.org/arimelody/ari-stream-tools/broadcast"
	"github.com/gin-gonic/gin"
	"github.com/godbus/dbus/v5"
)

const (
	MPRIS_ART_URL = "mpris:artUrl"
	MPRIS_LENGTH = "mpris:length"
	MPRIS_TRACK_ID = "mpris:trackid"
	XESAM_TITLE = "xesam:title"
	XESAM_ALBUM = "xesam:album"
	XESAM_ARTISTS = "xesam:artist"

	DBUS_STRAWBERRY = "org.mpris.MediaPlayer2.strawberry"
)

//go:embed public
var publicFS embed.FS
//go:embed pages
var pagesFS embed.FS

type (
	trackMetadata struct {
		ArtworkURL string
		Length int64
		Title string
		Album string
		Artists []string
	}

	Service struct {
		track *trackMetadata
		nextTrack chan *trackMetadata
		nextTrackBroadcast broadcast.BroadcastChannel[*trackMetadata]
		playing bool
		nextPlaying chan bool
		playingBroadcast broadcast.BroadcastChannel[bool]
	}
)

func New(ctx context.Context) *Service {
	nextTrack := make(chan *trackMetadata)
	nextPlaying := make(chan bool)

	srv := &Service{
		track: nil,
		nextTrack: nextTrack,
		nextTrackBroadcast: broadcast.NewBroadcastChannel(ctx, nextTrack),
		playing: false,
		nextPlaying: nextPlaying,
		playingBroadcast: broadcast.NewBroadcastChannel(ctx, nextPlaying),
	}

	return srv
}

func (srv *Service) BindRoutes(group *gin.RouterGroup) {
	group.GET("/public/*path", func(ctx *gin.Context) {
		path := strings.TrimPrefix(ctx.Request.URL.Path, "/music/")
		http.ServeFileFS(ctx.Writer, ctx.Request, publicFS, path)
	})

	group.GET("/sse", func(ctx *gin.Context) {
		ctx.Header("connection", "keep-alive")

		nextTrack := srv.nextTrackBroadcast.Subscribe()
		nextPlaying := srv.playingBroadcast.Subscribe()

		if srv.track == nil { <-nextTrack }

		ctx.SSEvent("music", gin.H{
			"title": srv.track.Title,
			"artist": artistString(srv.track),
		})
		ctx.SSEvent("music-state", gin.H{ "playing": srv.playing })

		ticker := time.NewTicker(10 * time.Millisecond)
		ctx.Stream(func(w io.Writer) bool {
			select {
			case track := <-nextTrack:
				ctx.SSEvent("music", gin.H{
					"title": track.Title,
					"artist": artistString(track),
				})
			case playing := <-nextPlaying:
				ctx.SSEvent("music-state", gin.H{ "playing": playing })
			case <-ticker.C:
			}
			return true
		})

		srv.nextTrackBroadcast.Cancel(nextTrack)
		srv.playingBroadcast.Cancel(nextPlaying)
	})

	group.GET("/artwork", func(ctx *gin.Context) {
		ctx.Header("cache-control", "no-cache")

		if srv.track == nil || srv.track.ArtworkURL == "" {
			http.ServeFileFS(ctx.Writer, ctx.Request, publicFS, "public/default-cover-art.png")
			return
		}

		artworkPath := strings.TrimPrefix(srv.track.ArtworkURL, "file://")
		http.ServeFile(ctx.Writer, ctx.Request, artworkPath)
	})

	group.GET("/", func(ctx *gin.Context) {
		http.ServeFileFS(ctx.Writer, ctx.Request, pagesFS, "pages/music.html")
	})
}

func (srv *Service) Run(ctx context.Context) {
	var err error

	conn, err := dbus.ConnectSessionBus()
	if err != nil {
		log.Fatalf("Failed to connect to session bus: %v", err)
	}
	defer conn.Close()

	var data map[string]dbus.Variant
	obj := conn.Object(DBUS_STRAWBERRY, "/org/mpris/MediaPlayer2")
	if err := obj.Call(
		"org.freedesktop.DBus.Properties.GetAll",
		0,
		"org.mpris.MediaPlayer2.Player",
	).Store(&data); err != nil {
		log.Fatalf("Failed to query media player data: %v", err)
	}
	
	metadata, ok := data["Metadata"].Value().(map[string]dbus.Variant)
	if !ok { log.Fatalf("Could not cast metadata to map[string]dbus.Variant") }
	
	playbackStatus, ok := data["PlaybackStatus"].Value().(string)
	if !ok { log.Fatalf("Could not cast metadata to string") }

	// on first run, mpris:artUrl returns a temporary strawberry player artwork
	// located in /tmp. this is gone by the time we attempt to read, so we need
	// a way to pull the real artwork filepath at runtime.
	// TODO: figure out how to pull real (not /tmp) track artwork
	if srv.track, err = parseTrackMetadata(metadata); err == nil {
		log.Printf("Now playing: %s - %s", artistString(srv.track), srv.track.Title)
	} else {
		log.Printf("Failed to parse track metadata: %v", err)
	}
	srv.playing = playbackStatus == "Playing"

	var dbusChan chan *dbus.Signal
	dbusChan, err = setupPlayerListener(conn)
	if err != nil {
		log.Fatalf("Failed to connect to session bus: %v", err)
	}

	failed := make(chan error)
	go func() {
		for {
			for signal := range dbusChan {
				data, ok := signal.Body[1].(map[string]dbus.Variant)
				if !ok { continue }
				
				if _, ok := data["PlaybackStatus"]; ok {
					playbackStatus, ok := data["PlaybackStatus"].Value().(string)
					if ok {
						if playbackStatus == "Playing" {
							srv.playing = true
							log.Print("Music playing")
						} else {
							srv.playing = false
							log.Print("Music paused")
						}
						srv.nextPlaying<-srv.playing
					}

				} else if _, ok := data["Metadata"]; ok {
					metadata, ok := data["Metadata"].Value().(map[string]dbus.Variant)
					if !ok { continue }

					nextTrack, err := parseTrackMetadata(metadata)
					if err != nil {
						log.Printf("Failed to parse track metadata: %v", err)
						continue
					}
					/*
					if nextTrack.Title == srv.track.Title &&
					slices.Compare(nextTrack.Artists, srv.track.Artists) == 0 {
						continue
					}
					*/
					srv.track = nextTrack
					srv.nextTrack<-nextTrack

					log.Printf("Now playing: %s - %s", artistString(nextTrack), nextTrack.Title)

				}
			}

			log.Printf("Session bus connection lost. Reconnecting...")
			conn, err = dbus.ConnectSessionBus()
			dbusChan, err = setupPlayerListener(conn)
			if err != nil {
				log.Fatalf("Failed to connect to session bus: %v", err)
			}

			time.Sleep(1 * time.Second)
		}
	}()

	select {
	case err := <-failed:
		log.Fatalf("MPRIS/D-Bus error: %v", err)
	case <-ctx.Done():
	}
}

func parseTrackMetadata(metadata map[string]dbus.Variant) (*trackMetadata, error) {
	if _, exists := metadata[MPRIS_LENGTH]; !exists {
		return nil, fmt.Errorf("Metadata does not contain %s", MPRIS_LENGTH)
	}
	length, ok := metadata[MPRIS_LENGTH].Value().(int64)
	if !ok { return nil, fmt.Errorf("Failed to cast %s to int64", MPRIS_LENGTH) }

	var artUrl string
	if _, exists := metadata[MPRIS_ART_URL]; exists {
		artUrl, ok = metadata[MPRIS_ART_URL].Value().(string)
		if !ok { return nil, fmt.Errorf("Failed to cast %s to string", MPRIS_ART_URL) }
	}

	if _, exists := metadata[XESAM_TITLE]; !exists {
		return nil, fmt.Errorf("Metadata does not contain %s", XESAM_TITLE)
	}
	title, ok := metadata[XESAM_TITLE].Value().(string)
	if !ok { return nil, fmt.Errorf("Failed to cast %s to string", XESAM_TITLE) }

	var album string
	if _, exists := metadata[XESAM_ALBUM]; exists {
		album, ok = metadata[XESAM_ALBUM].Value().(string)
		if !ok { return nil, fmt.Errorf("Failed to cast %s to string", XESAM_ALBUM) }
	}

	var artists []string
	if _, exists := metadata[XESAM_ARTISTS]; exists {
		artists, ok = metadata[XESAM_ARTISTS].Value().([]string)
		if !ok { return nil, fmt.Errorf("Failed to cast %s to []string", XESAM_ARTISTS) }
	}

	trackMetadata := &trackMetadata{
		ArtworkURL: artUrl,
		Length: length,
		Title: title,
		Album: album,
		Artists: artists,
	}

	return trackMetadata, nil
}

func artistString(track *trackMetadata) string {
	artists := ""
	if len(track.Artists) == 0 { return "Unknown Artist" }
	if len(track.Artists) == 1 { return track.Artists[0] }
	artists += strings.Join(track.Artists[:len(track.Artists)-2], ", ")
	artists += " & " + track.Artists[len(track.Artists) - 1]
	return artists
}

func setupPlayerListener(conn *dbus.Conn) (chan *dbus.Signal, error) {
	if err := conn.AddMatchSignal(
		dbus.WithMatchObjectPath("/org/mpris/MediaPlayer2"),
		dbus.WithMatchInterface("org.freedesktop.DBus.Properties"),
		dbus.WithMatchSender(DBUS_STRAWBERRY),
	); err != nil {
		return nil, fmt.Errorf("Failed to configure D-Bus signal listener: %v", err)
	}

	c := make(chan *dbus.Signal)
	conn.Signal(c)

	return c, nil
}