From 2a16dcba5a31a45a12853a15254719c357baae6d Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fischer@muhq.space>
Date: Wed, 31 May 2023 20:53:12 +0200
Subject: use an atomic pointer to track the current song

Also fix showing finished songs as current playing on new
clients.
---
 main.go         |  6 +++++-
 player.go       |  4 ++--
 web/client.html | 10 ++++++++--
 wrms.go         | 17 +++++++++--------
 4 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/main.go b/main.go
index 0539e1a..53dc440 100644
--- a/main.go
+++ b/main.go
@@ -232,7 +232,11 @@ func wsEndpoint(w http.ResponseWriter, r *http.Request) {
 
 	initialCmds := [][]byte{}
 	if wrms.Playing {
-		data, err := json.Marshal(newEvent("play", []Song{wrms.CurrentSong}))
+		var songs []Song
+		if currentSong := wrms.CurrentSong.Load(); currentSong != nil {
+			songs = []Song{*currentSong}
+		}
+		data, err := json.Marshal(newEvent("play", songs))
 		if err != nil {
 			llog.Error("Encoding the play event failed with %s", err)
 			return
diff --git a/player.go b/player.go
index db1936a..db4457c 100644
--- a/player.go
+++ b/player.go
@@ -68,12 +68,12 @@ func (player *Player) runMpv() {
 		llog.Fatal("Mpv failed with: %s", err.Error())
 	}
 
-	wrms := player.wrms
+	currentSong := wrms.CurrentSong.Load()
 
 	llog.Info("mpv finished. Resetting mpv, and calling next")
 	player.mpv = nil
 
-	player.Backends[wrms.CurrentSong.Source].OnSongFinished(&wrms.CurrentSong)
+	player.Backends[currentSong.Source].OnSongFinished(currentSong)
 	wrms.Next()
 }
 
diff --git a/web/client.html b/web/client.html
index 91ce11d..c0aef1f 100644
--- a/web/client.html
+++ b/web/client.html
@@ -202,9 +202,15 @@
         playing = document.getElementById("playing").innerHTML = "";
       }
 
-      function handlePlay(currentSong) {
+      function handlePlay(_currentSongs) {
         {{if .IsAdmin}} document.getElementById("ppbutton").innerHTML = 'Pause'; {{end}}
 
+        if (_currentSongs == null || _currentSongs.length == 0) {
+          return;
+        }
+
+        const currentSong = _currentSongs[0]
+
         idx = -1;
         songs.forEach(function(s, i, a) { if (s.uri == currentSong.uri) idx = i; });
         if (idx != -1) {
@@ -251,7 +257,7 @@
             handleStop()
             break;
           case "play":
-            handlePlay(cmd.songs[0])
+            handlePlay(cmd.songs)
             break;
           case "upvoted":
             handleVotes("up", cmd.songs)
diff --git a/wrms.go b/wrms.go
index 0a844cb..fd1d10f 100644
--- a/wrms.go
+++ b/wrms.go
@@ -112,7 +112,7 @@ type Wrms struct {
 	Connections sync.Map
 	Songs       []Song
 	queue       Playlist
-	CurrentSong Song
+	CurrentSong atomic.Pointer[Song]
 	Player      Player
 	Playing     bool
 	Config      Config
@@ -149,12 +149,13 @@ func (wrms *Wrms) Broadcast(ev Event) {
 }
 
 func (wrms *Wrms) startPlaying() {
-	wrms.Broadcast(newEvent("play", []Song{wrms.CurrentSong}))
-	wrms.Player.Play(&wrms.CurrentSong)
+	currentSong := wrms.CurrentSong.Load()
+	wrms.Broadcast(newEvent("play", []Song{*currentSong}))
+	wrms.Player.Play(currentSong)
 }
 
 func (wrms *Wrms) AddSong(song Song) {
-	startPlayingAgain := wrms.Playing && wrms.CurrentSong.Uri == ""
+	startPlayingAgain := wrms.Playing && wrms.CurrentSong.Load() == nil
 	wrms.Songs = append(wrms.Songs, song)
 	s := &wrms.Songs[len(wrms.Songs)-1]
 	wrms.queue.Add(s)
@@ -187,17 +188,17 @@ func (wrms *Wrms) Next() {
 
 	next := wrms.queue.PopSong()
 	if next == nil {
-		wrms.CurrentSong.Uri = ""
+		wrms.CurrentSong.Store(nil)
 		wrms.Broadcast(newNotification("stop"))
 		return
 	}
 
-	wrms.CurrentSong = *next
+	wrms.CurrentSong.Store(next)
 
 	llog.Info("popped next song and removing it from the song list %v", next)
 
 	for i, s := range wrms.Songs {
-		if s.Uri == wrms.CurrentSong.Uri {
+		if s.Uri == next.Uri {
 			wrms.Songs[i] = wrms.Songs[len(wrms.Songs)-1]
 			wrms.Songs = wrms.Songs[:len(wrms.Songs)-1]
 			break
@@ -213,7 +214,7 @@ func (wrms *Wrms) PlayPause() {
 	wrms.Playing = !wrms.Playing
 
 	if wrms.Playing {
-		if wrms.CurrentSong.Uri == "" {
+		if wrms.CurrentSong.Load() == nil {
 			llog.Info("No song currently playing play the next")
 			wrms.Next()
 		} else {
-- 
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