Add mutex and context for better playlist handling

bot.go

@@ -5,6 +5,7 @@ import (
 	"log"
 	"os"
 	"os/signal"
+	"sync"
 	"syscall"
 	"time"
 
@@ -43,6 +44,9 @@ func init() {
 	if err != nil {
 		log.Fatal(err)
 	}
+
+	app.plmutex = &sync.Mutex{}
+
 	log.Println("bot.go done.")
 }
 
@@ -50,11 +54,9 @@ type App struct {
 	discord  *discordgo.Session
 	voice    *discordgo.VoiceConnection
 	youtube  *youtube.Service
-	queue    *Queue
 	ambiance beep.Mixer
 	curamb   Ambiance
 	events   events.EventEmmiter
-	next     bool
 	db       *pgx.Conn
 	router   *httprouter.Router
 	active   []string
@@ -63,6 +65,8 @@ type App struct {
 	mpdc     context.CancelFunc
 	mpdw     *mpd.Watcher
 	mpd      *mpd.Client
+	plmutex  *sync.Mutex
+	plcancel context.CancelFunc
 }
 
 func main() {

events.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"dndmusicbot/opus"
 	discordspeaker "dndmusicbot/speaker"
 	"encoding/json"
@@ -305,7 +306,12 @@ func (app *App) songInfo(payload ...interface{}) {
 func (app *App) stop(payload ...interface{}) {
 	log.Println("stop event received")
 
+	app.plmutex.Lock()
+	if app.plcancel != nil {
+		app.plcancel()
+	}
 	app.mpd.Stop()
+	app.plmutex.Unlock()
 
 	msg := make(map[string]interface{})
 	msg["event"] = "stop"
@@ -315,7 +321,9 @@ func (app *App) stop(payload ...interface{}) {
 
 func (app *App) prevSong(payload ...interface{}) {
 	log.Println("prev_song event received")
+	app.plmutex.Lock()
 	err := app.mpd.Previous()
+	app.plmutex.Unlock()
 	if err != nil {
 		log.Println(err)
 	}
@@ -323,7 +331,10 @@ func (app *App) prevSong(payload ...interface{}) {
 
 func (app *App) nextSong(payload ...interface{}) {
 	log.Println("next_song event received")
+
+	app.plmutex.Lock()
 	err := app.mpd.Next()
+	app.plmutex.Unlock()
 	if err != nil {
 		log.Println(err)
 	}
@@ -431,12 +442,23 @@ func (app *App) loadPlaylist(payload ...interface{}) {
 		log.Println("Unable to shuffle playlist")
 		return
 	}
-
+	app.plmutex.Lock()
+	if app.plcancel != nil {
+		app.plcancel()
+	}
 	app.mpd.Stop()
 	app.mpd.Clear()
+	app.plmutex.Unlock()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	app.plcancel = cancel
 
 	go func() {
+		defer cancel()
+
 		for _, vid := range list {
+			log.Printf("Adding %s", vid)
+
 			ytinfo, err := app.Video(vid)
 			if err != nil {
 				log.Println(err)
@@ -455,43 +477,60 @@ func (app *App) loadPlaylist(payload ...interface{}) {
 				continue
 			}
 
+			// Run as a local function so we can defer the mutex unlock incase one of these errors.
+			ok := func() (ok bool) {
+				app.plmutex.Lock()
+				defer app.plmutex.Unlock()
+
+				if ctx.Err() != nil {
+					return false
+				}
+
+				ok = true
+
 				// state:stop
 				songid, err := app.mpd.AddID(string(yt), 0)
 				if err != nil {
 					log.Println(err)
-				continue
+					return
 				}
 
 				mpdcmd := app.mpd.Command("%s %d %s %s", mpd.Quoted("addtagid"), songid, mpd.Quoted("artist"), ytinfo.Channel)
 				err = mpdcmd.OK()
 				if err != nil {
 					log.Println(err)
-				continue
+					return
 				}
 
 				mpdcmd = app.mpd.Command("%s %d %s %s", mpd.Quoted("addtagid"), songid, mpd.Quoted("title"), ytinfo.Title)
 				err = mpdcmd.OK()
 				if err != nil {
 					log.Println(err)
-				continue
+					return
 				}
 
 				mpdcmd = app.mpd.Command("%s %d %s %s", mpd.Quoted("addtagid"), songid, mpd.Quoted("location"), vid)
 				err = mpdcmd.OK()
 				if err != nil {
 					log.Println(err)
-				continue
+					return
 				}
 
 				mpdcmd = app.mpd.Command("%s %d %s %s", mpd.Quoted("addtagid"), songid, mpd.Quoted("album"), pl.Id.String())
 				err = mpdcmd.OK()
 				if err != nil {
 					log.Println(err)
-				continue
+					return
 				}
 
 				app.mpd.Play(-1)
 
+				return
+			}()
+
+			if !ok {
+				break
+			}
 		}
 	}()
 }