Automatically leave voice channel after some time spent idle

src/main/kotlin/dev/arbjerg/ukulele/UkuleleApplication.kt

@@ -3,9 +3,11 @@ package dev.arbjerg.ukulele
 import org.springframework.boot.autoconfigure.SpringBootApplication
 import org.springframework.boot.context.properties.ConfigurationPropertiesScan
 import org.springframework.boot.runApplication
+import org.springframework.scheduling.annotation.EnableScheduling
 
 @SpringBootApplication
 @ConfigurationPropertiesScan
+@EnableScheduling
 class UkuleleApplication
 
 fun main(args: Array<String>) {

src/main/kotlin/dev/arbjerg/ukulele/audio/Player.kt

@@ -11,22 +11,29 @@ import dev.arbjerg.ukulele.command.NowPlayingCommand
 import dev.arbjerg.ukulele.config.BotProps
 import dev.arbjerg.ukulele.data.GuildProperties
 import dev.arbjerg.ukulele.data.GuildPropertiesService
+import dev.arbjerg.ukulele.features.LeaveOnIdleService
 import net.dv8tion.jda.api.audio.AudioSendHandler
 import net.dv8tion.jda.api.entities.TextChannel
+import net.dv8tion.jda.api.entities.Guild
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import org.springframework.stereotype.Component
 import java.nio.Buffer
 import java.nio.ByteBuffer
 
 
-class Player(val beans: Beans, guildProperties: GuildProperties) : AudioEventAdapter(), AudioSendHandler {
+class Player(
+        private val beans: Beans,
+        guildProperties: GuildProperties,
+        private val guild: Guild
+) : AudioEventAdapter(), AudioSendHandler {
     @Component
     class Beans(
             val apm: AudioPlayerManager,
             val guildProperties: GuildPropertiesService,
             val nowPlayingCommand: NowPlayingCommand,
-            val botProps: BotProps
+            val botProps: BotProps,
+            val leaveOnIdleService: LeaveOnIdleService
     )
 
     private val guildId = guildProperties.guildId
@@ -127,14 +134,24 @@ class Player(val beans: Beans, guildProperties: GuildProperties) : AudioEventAda
         if (beans.botProps.announceTracks) {
             lastChannel?.sendMessage(beans.nowPlayingCommand.buildEmbed(track))?.queue()
         }
+
+        log.debug("onTrackStart called for player in guild {}", guild.idLong)
+        beans.leaveOnIdleService.destroyTimer(guild)
     }
 
     override fun onTrackEnd(player: AudioPlayer, track: AudioTrack, endReason: AudioTrackEndReason) {
+        log.debug("onTrackEnd called for player in guild {}", guild.idLong)
         if (isRepeating && endReason.mayStartNext) {
             queue.add(track.makeClone())
         }
-        val new = queue.take() ?: return
-        player.playTrack(new)
+        val new = queue.take()
+        if (new != null) {
+            player.playTrack(new)
+        }
+
+        if (remainingDuration <= 0) {
+            beans.leaveOnIdleService.onQueueEmpty(guild)
+        }
     }
 
     override fun onTrackException(player: AudioPlayer, track: AudioTrack, exception: FriendlyException) {

src/main/kotlin/dev/arbjerg/ukulele/audio/PlayerRegistry.kt

@@ -1,6 +1,7 @@
 package dev.arbjerg.ukulele.audio
 
 import dev.arbjerg.ukulele.data.GuildProperties
+import dev.arbjerg.ukulele.features.LeaveOnIdleService
 import net.dv8tion.jda.api.entities.Guild
 import org.springframework.stereotype.Service
 
@@ -9,6 +10,6 @@ class PlayerRegistry(val playerBeans: Player.Beans) {
 
     private val players = mutableMapOf<Long, Player>()
 
-    fun get(guild: Guild, guildProperties: GuildProperties) = players.computeIfAbsent(guild.idLong) { Player(playerBeans, guildProperties) }
+    fun get(guild: Guild, guildProperties: GuildProperties) = players.computeIfAbsent(guild.idLong) { Player(playerBeans, guildProperties, guild) }
 
 }

src/main/kotlin/dev/arbjerg/ukulele/config/BotProps.kt

@@ -10,5 +10,6 @@ class BotProps(
         var database: String = "./database",
         var game: String = "",
         var trackDurationLimit: Int = 0,
-        var announceTracks: Boolean = false
-)
+        var announceTracks: Boolean = false,
+        var idleTimeMinutes: Int = 0
+)

src/main/kotlin/dev/arbjerg/ukulele/features/LeaveOnIdleService.kt

@@ -0,0 +1,46 @@
+package dev.arbjerg.ukulele.features
+
+import org.springframework.stereotype.Service
+import dev.arbjerg.ukulele.config.BotProps
+import net.dv8tion.jda.api.entities.Guild
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+import org.springframework.scheduling.TaskScheduler
+import java.time.Instant
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.ScheduledFuture
+
+@Service
+class LeaveOnIdleService(private val scheduler: TaskScheduler, private val botProps: BotProps) {
+    private val log: Logger = LoggerFactory.getLogger(LeaveOnIdleService::class.java)
+    private val timers: ConcurrentHashMap<Long, ScheduledFuture<*>> = ConcurrentHashMap()
+
+    /**
+     * Create a new timer which will start counting from the current moment and cancel any existing timers
+     * associated with this guild.
+     */
+    fun onQueueEmpty(guild: Guild) {
+        if (botProps.idleTimeMinutes <= 0) return
+
+        log.info("Player for guild {} is idle, starting timeout of {} minutes", guild.idLong, botProps.idleTimeMinutes)
+        val instant = Instant.now().plusSeconds(60 * botProps.idleTimeMinutes.toLong())
+        val fut = scheduler.schedule({
+            guild.audioManager.closeAudioConnection()
+        }, instant)
+
+        if (timers.containsKey(guild.idLong)) {
+            timers.replace(guild.idLong, fut)?.cancel(true)
+        } else {
+            timers[guild.idLong] = fut
+        }
+    }
+
+    fun destroyTimer(guild: Guild) {
+        if (botProps.idleTimeMinutes <= 0) return
+
+        timers.remove(guild.idLong)?.let {
+            log.debug("Cleaned up idle timer for guild {}", guild.idLong)
+            it.cancel(true)
+        }
+    }
+}

src/main/kotlin/dev/arbjerg/ukulele/jda/EventHandler.kt

@@ -1,15 +1,17 @@
 package dev.arbjerg.ukulele.jda
 
-import net.dv8tion.jda.api.events.ReadyEvent
+import dev.arbjerg.ukulele.features.LeaveOnIdleService
 import net.dv8tion.jda.api.events.StatusChangeEvent
+import net.dv8tion.jda.api.events.guild.voice.GuildVoiceJoinEvent
+import net.dv8tion.jda.api.events.guild.voice.GuildVoiceLeaveEvent
 import net.dv8tion.jda.api.events.message.guild.GuildMessageReceivedEvent
 import net.dv8tion.jda.api.hooks.ListenerAdapter
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import org.springframework.stereotype.Service
 
 @Service
-class EventHandler(private val commandManager: CommandManager) : ListenerAdapter() {
+class EventHandler(private val commandManager: CommandManager, private val leaveOnIdleService: LeaveOnIdleService) : ListenerAdapter() {
 
     private val log: Logger = LoggerFactory.getLogger(EventHandler::class.java)
 
@@ -22,4 +24,12 @@ class EventHandler(private val commandManager: CommandManager) : ListenerAdapter
         log.info("{}: {} -> {}", event.entity.shardInfo, event.oldStatus, event.newStatus)
     }
 
+    override fun onGuildVoiceJoin(event: GuildVoiceJoinEvent) {
+        log.info("Joining voice channel {} in guild {}", event.channelJoined, event.guild)
+    }
+
+    override fun onGuildVoiceLeave(event: GuildVoiceLeaveEvent) {
+        log.info("Leaving voice channel {} in guild {}", event.channelLeft, event.guild)
+        leaveOnIdleService.destroyTimer(event.guild)
+    }
 }