From f0aa00b9321d44b4150976edfbeb3c8240834704 Mon Sep 17 00:00:00 2001
From: "Alexander \"Arav\" Andreev" <me@arav.su>
Date: Sun, 8 Oct 2023 02:52:37 +0400
Subject: [PATCH] Added a fallback song option. Altered a PlaylistNext() header
 to use it.

---
 cmd/dwelling-radio/main.go   |  3 +-
 internal/http/dj_handlers.go | 64 ++++++++++++++++++++----------------
 2 files changed, 38 insertions(+), 29 deletions(-)

diff --git a/cmd/dwelling-radio/main.go b/cmd/dwelling-radio/main.go
index 55bc9be..6d78962 100644
--- a/cmd/dwelling-radio/main.go
+++ b/cmd/dwelling-radio/main.go
@@ -20,6 +20,7 @@ var (
 	listenAddress        = flag.String("listen", "/var/run/dwelling-radio/sock", "listen address (ip:port|unix_path)")
 	filelistPath         = flag.String("filelist", "/mnt/data/appdata/radio/filelist.html", "path to a filelist.html file")
 	playlist             = flag.String("playlist", "", "path to a playlist")
+	fallbackSong         = flag.String("fallback-song", "", "path to a fallbacl song")
 	mostListenedSongPath = flag.String("mls-file", "/mnt/data/appdata/radio/mostlistenedsong", "path to a file that stores info about the most listened song")
 	songListLen          = flag.Int("list-length", 10, "number of songs to show in last N songs table")
 
@@ -65,7 +66,7 @@ func main() {
 
 	r.ServeStatic("/assets/*filepath", web.Assets())
 
-	djh := ihttp.NewDJHandlers(lstnrs, plylst, songList, &mostListenedSong)
+	djh := ihttp.NewDJHandlers(lstnrs, plylst, songList, &mostListenedSong, *fallbackSong)
 
 	s := r.Sub("/api/listener")
 	s.Handler(http.MethodGet, "/", djh.ListenersGet)
diff --git a/internal/http/dj_handlers.go b/internal/http/dj_handlers.go
index 1f79778..180c8b9 100644
--- a/internal/http/dj_handlers.go
+++ b/internal/http/dj_handlers.go
@@ -11,14 +11,17 @@ import (
 )
 
 type DJHandlers struct {
-	listeners *radio.ListenerCounter
-	playlist  *radio.Playlist
-	songList  *radio.SongList
-	mostLSong *radio.MostListenedSong
+	listeners    *radio.ListenerCounter
+	playlist     *radio.Playlist
+	songList     *radio.SongList
+	mostLSong    *radio.MostListenedSong
+	fallbackSong string
 }
 
-func NewDJHandlers(l *radio.ListenerCounter, p *radio.Playlist, sl *radio.SongList, mls *radio.MostListenedSong) *DJHandlers {
-	return &DJHandlers{listeners: l, playlist: p, songList: sl, mostLSong: mls}
+func NewDJHandlers(l *radio.ListenerCounter, p *radio.Playlist,
+	sl *radio.SongList, mls *radio.MostListenedSong, fS string) *DJHandlers {
+	return &DJHandlers{listeners: l, playlist: p, songList: sl,
+		mostLSong: mls, fallbackSong: fS}
 }
 
 func (dj *DJHandlers) ListenersGet(w http.ResponseWriter, _ *http.Request) {
@@ -51,29 +54,34 @@ func (dj *DJHandlers) PlaylistNext(w http.ResponseWriter, _ *http.Request) {
 	nxt := dj.playlist.Next()
 	if nxt == "" {
 		log.Println("the end of a playlist has been reached")
-	} else {
-		go func() {
-			oggf, err := oggtag.NewOggFile(nxt)
-			if err != nil {
-				log.Println("cannot read an OGG file", nxt, ":", err)
-				http.Error(w, "cannot read an OGG file", http.StatusInternalServerError)
-				return
-			}
-
-			song := radio.Song{
-				Artist:       oggf.GetTag("artist"),
-				Title:        oggf.GetTag("title"),
-				Duration:     oggf.GetDuration(),
-				MaxListeners: dj.listeners.Current(),
-				StartAt:      time.Now()}
-
-			if dj.songList.Current() != nil {
-				dj.mostLSong.Update(*dj.songList.Current())
-			}
-
-			dj.songList.Add(song)
-		}()
+		if nxt = dj.fallbackSong; nxt == "" {
+			log.Println("a fallback song is not set")
+			http.Error(w, "a playlist is empty and a fallback song is not set", http.StatusNotFound)
+			return
+		}
 	}
+
+	go func() {
+		oggf, err := oggtag.NewOggFile(nxt)
+		if err != nil {
+			log.Println("cannot read an OGG file", nxt, ":", err)
+			http.Error(w, "cannot read an OGG file", http.StatusInternalServerError)
+			return
+		}
+
+		song := radio.Song{
+			Artist:       oggf.GetTag("artist"),
+			Title:        oggf.GetTag("title"),
+			Duration:     oggf.GetDuration(),
+			MaxListeners: dj.listeners.Current(),
+			StartAt:      time.Now()}
+
+		if dj.songList.Current() != nil {
+			dj.mostLSong.Update(*dj.songList.Current())
+		}
+
+		dj.songList.Add(song)
+	}()
 	fmt.Fprintln(w, nxt)
 }