Add ability to control playback using command-line flags

backend/app.go

@@ -12,25 +12,22 @@ import (
 	"slices"
 	"time"
 
+	"github.com/dweymouth/supersonic/backend/ipc"
 	"github.com/dweymouth/supersonic/backend/mediaprovider"
 	"github.com/dweymouth/supersonic/backend/player"
 	"github.com/dweymouth/supersonic/backend/player/mpv"
 	"github.com/dweymouth/supersonic/backend/util"
-	"github.com/fsnotify/fsnotify"
 	"github.com/google/uuid"
 
 	"github.com/20after4/configdir"
 	"github.com/zalando/go-keyring"
 )
 
 const (
-	configFile          = "config.toml"
-	portableDir         = "supersonic_portable"
-	sessionDir          = "session"
-	sessionLockFile     = ".lock"
-	sessionActivateFile = ".activate"
-	savedQueueFile      = "saved_queue.json"
-	themesDir           = "themes"
+	configFile     = "config.toml"
+	portableDir    = "supersonic_portable"
+	savedQueueFile = "saved_queue.json"
+	themesDir      = "themes"
 )
 
 var (
@@ -46,6 +43,7 @@ type App struct {
 	LocalPlayer     *mpv.Player
 	UpdateChecker   UpdateChecker
 	MPRISHandler    *MPRISHandler
+	ipcServer       ipc.IPCServer
 
 	// UI callbacks to be set in main
 	OnReactivate func()
@@ -83,26 +81,6 @@ func StartupApp(appName, displayAppName, appVersionTag, latestReleaseURL string)
 	configdir.MakePath(confDir)
 	configdir.MakePath(cacheDir)
 
-	sessionPath := path.Join(confDir, sessionDir)
-	if _, err := os.Stat(path.Join(sessionPath, sessionLockFile)); err == nil {
-		log.Println("Another instance is running. Reactivating it...")
-		reactivateFile := path.Join(sessionPath, sessionActivateFile)
-		if f, err := os.Create(reactivateFile); err == nil {
-			f.Close()
-		}
-		time.Sleep(750 * time.Millisecond)
-		if _, err := os.Stat(reactivateFile); err == nil {
-			log.Println("No other instance responded. Starting as normal...")
-			os.RemoveAll(sessionPath)
-		} else {
-			return nil, ErrAnotherInstance
-		}
-	}
-
-	log.Printf("Starting %s...", appName)
-	log.Printf("Using config dir: %s", confDir)
-	log.Printf("Using cache dir: %s", cacheDir)
-
 	a := &App{
 		appName:       appName,
 		appVersionTag: appVersionTag,
@@ -112,19 +90,24 @@ func StartupApp(appName, displayAppName, appVersionTag, latestReleaseURL string)
 	}
 	a.bgrndCtx, a.cancel = context.WithCancel(context.Background())
 	a.readConfig()
-	a.startConfigWriter(a.bgrndCtx)
 
-	if !a.Config.Application.AllowMultiInstance {
-		log.Println("Creating session lock file")
-		os.MkdirAll(sessionPath, 0770)
-		if f, err := os.Create(path.Join(sessionPath, sessionLockFile)); err == nil {
-			f.Close()
-		} else {
-			log.Printf("error creating session file: %s", err.Error())
+	cli, _ := ipc.Connect()
+	if HaveCommandLineOptions() {
+		if err := a.checkFlagsAndSendIPCMsg(cli); err != nil {
+			// we were supposed to control another instance and couldn't
+			log.Fatalf("error sending IPC message: %s", err.Error())
 		}
-		a.startSessionWatcher(sessionPath)
+		return nil, ErrAnotherInstance
+	} else if cli != nil && !a.Config.Application.AllowMultiInstance {
+		log.Println("Another instance is running. Reactivating it...")
+		cli.Show()
+		return nil, ErrAnotherInstance
 	}
 
+	log.Printf("Starting %s...", appName)
+	log.Printf("Using config dir: %s", confDir)
+	log.Printf("Using cache dir: %s", cacheDir)
+
 	a.UpdateChecker = NewUpdateChecker(appVersionTag, latestReleaseURL, &a.Config.Application.LastCheckedVersion)
 	a.UpdateChecker.Start(a.bgrndCtx, 24*time.Hour)
 
@@ -144,13 +127,28 @@ func StartupApp(appName, displayAppName, appVersionTag, latestReleaseURL string)
 		_, _ = a.ImageManager.GetCoverThumbnail(coverID)
 	})
 
+	// Start IPC server if another not already running in a different instance
+	if cli == nil {
+		ipc.DestroyConn() // cleanup socket possibly orphaned by crashed process
+		listener, err := ipc.Listen()
+		if err == nil {
+			a.ipcServer = ipc.NewServer(a.PlaybackManager, a.callOnReactivate,
+				func() { _ = a.callOnExit() })
+			go a.ipcServer.Serve(listener)
+		} else {
+			log.Printf("error starting IPC server: %s", err.Error())
+		}
+	}
+
 	// OS media center integrations
 	a.setupMPRIS(displayAppName)
 	InitMPMediaHandler(a.PlaybackManager, func(id string) (string, error) {
 		a.ImageManager.GetCoverThumbnail(id) // ensure image is cached locally
 		return a.ImageManager.GetCoverArtUrl(id)
 	})
 
+	a.startConfigWriter(a.bgrndCtx)
+
 	return a, nil
 }
 
@@ -196,26 +194,6 @@ func (a *App) readConfig() {
 	a.Config = cfg
 }
 
-func (a *App) startSessionWatcher(sessionPath string) {
-	if sessionWatch, err := fsnotify.NewWatcher(); err == nil {
-		sessionWatch.Add(sessionPath)
-		go func() {
-			for {
-				select {
-				case <-a.bgrndCtx.Done():
-					return
-				case <-sessionWatch.Events:
-					activatePath := path.Join(sessionPath, sessionActivateFile)
-					if _, err := os.Stat(activatePath); err == nil {
-						os.Remove(path.Join(sessionPath, sessionActivateFile))
-						a.callOnReactivate()
-					}
-				}
-			}
-		}()
-	}
-}
-
 // periodically save config file so abnormal exit won't lose settings
 func (a *App) startConfigWriter(ctx context.Context) {
 	tick := time.NewTicker(2 * time.Minute)
@@ -239,6 +217,17 @@ func (a *App) callOnReactivate() {
 	}
 }
 
+func (a *App) callOnExit() error {
+	if a.OnExit == nil {
+		return errors.New("no quit handler registered")
+	}
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		a.OnExit()
+	}()
+	return nil
+}
+
 func (a *App) initMPV() error {
 	p := mpv.NewWithClientName(a.appName)
 	c := a.Config.LocalPlayback
@@ -314,16 +303,7 @@ func (a *App) setupMPRIS(mprisAppName string) {
 		return a.ImageManager.GetCoverArtUrl(id)
 	}
 	a.MPRISHandler.OnRaise = func() error { a.callOnReactivate(); return nil }
-	a.MPRISHandler.OnQuit = func() error {
-		if a.OnExit == nil {
-			return errors.New("no quit handler registered")
-		}
-		go func() {
-			time.Sleep(10 * time.Millisecond)
-			a.OnExit()
-		}()
-		return nil
-	}
+	a.MPRISHandler.OnQuit = a.callOnExit
 	a.MPRISHandler.Start()
 }
 
@@ -346,6 +326,9 @@ func (a *App) DeleteServerCacheDir(serverID uuid.UUID) error {
 }
 
 func (a *App) Shutdown() {
+	if a.ipcServer != nil {
+		a.ipcServer.Shutdown(a.bgrndCtx)
+	}
 	a.MPRISHandler.Shutdown()
 	a.PlaybackManager.DisableCallbacks()
 	if a.Config.Application.SavePlayQueue {
@@ -362,7 +345,6 @@ func (a *App) Shutdown() {
 	a.cancel()
 	a.LocalPlayer.Destroy()
 	a.Config.WriteConfigFile(a.configFilePath())
-	os.RemoveAll(path.Join(a.configDir, sessionDir))
 }
 
 func (a *App) LoadSavedPlayQueue() error {
@@ -397,6 +379,30 @@ func (a *App) SaveConfigFile() {
 	a.lastWrittenCfg = *a.Config
 }
 
+func (a *App) checkFlagsAndSendIPCMsg(cli *ipc.Client) error {
+	if cli == nil {
+		return errors.New("no IPC connection")
+	}
+	switch {
+	case *FlagPlay:
+		return cli.Play()
+	case *FlagPause:
+		return cli.Pause()
+	case *FlagPlayPause:
+		return cli.PlayPause()
+	case *FlagPrevious:
+		return cli.SeekBackOrPrevious()
+	case *FlagNext:
+		return cli.SeekNext()
+	case VolumeCLIArg >= 0:
+		return cli.SetVolume(VolumeCLIArg)
+	case SeekToCLIArg >= 0:
+		return cli.SeekSeconds(SeekToCLIArg)
+	default:
+		return nil
+	}
+}
+
 func (a *App) configFilePath() string {
 	return path.Join(a.configDir, configFile)
 }

backend/cmdlineoptions.go

@@ -0,0 +1,41 @@
+package backend
+
+import (
+	"flag"
+	"strconv"
+)
+
+var (
+	VolumeCLIArg int     = -1
+	SeekToCLIArg float64 = -1
+
+	FlagPlay      = flag.Bool("play", false, "unpause or begin playback")
+	FlagPause     = flag.Bool("pause", false, "pause playback")
+	FlagPlayPause = flag.Bool("play-pause", false, "toggle play/pause state")
+	FlagPrevious  = flag.Bool("previous", false, "seek to previous track or beginning of current")
+	FlagNext      = flag.Bool("next", false, "seek to next track")
+	FlagVersion   = flag.Bool("version", false, "print app version and exit")
+	FlagHelp      = flag.Bool("help", false, "print command line options and exit")
+)
+
+func init() {
+	flag.Func("volume", "sets the playback volume (0-100)", func(s string) error {
+		v, err := strconv.Atoi(s)
+		VolumeCLIArg = v
+		return err
+	})
+
+	flag.Func("seek-to", "seeks to the given position in seconds in the current file (0.0 - <trackDur>)", func(s string) error {
+		v, err := strconv.ParseFloat(s, 64)
+		SeekToCLIArg = v
+		return err
+	})
+}
+
+func HaveCommandLineOptions() bool {
+	visitedAny := false
+	flag.Visit(func(*flag.Flag) {
+		visitedAny = true
+	})
+	return visitedAny
+}

backend/ipc/api.go

@@ -0,0 +1,29 @@
+package ipc
+
+import "fmt"
+
+const (
+	PingPath      = "/ping"
+	PlayPath      = "/transport/play"
+	PlayPausePath = "/transport/playpause"
+	PausePath     = "/transport/pause"
+	StopPath      = "/transport/stop"
+	PreviousPath  = "/transport/previous"
+	NextPath      = "/transport/next"
+	TimePosPath   = "/transport/timepos" // ?s=<seconds>
+	VolumePath    = "/volume"            // ?v=<vol>
+	ShowPath      = "/window/show"
+	QuitPath      = "/window/quit"
+)
+
+type Response struct {
+	Error string `json:"error"`
+}
+
+func SetVolumePath(vol int) string {
+	return fmt.Sprintf("%s?v=%d", VolumePath, vol)
+}
+
+func SeekToSecondsPath(secs float64) string {
+	return fmt.Sprintf("%s?s=%0.2f", TimePosPath, secs)
+}