Update chunk map subscribers implementation

src/main/java/ru/dbotthepony/mc/otm/OverdriveThatMatters.java

@@ -15,7 +15,6 @@ import net.minecraftforge.fml.event.lifecycle.FMLCommonSetupEvent;
 import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.jetbrains.annotations.NotNull;
 import ru.dbotthepony.mc.otm.android.AndroidResearchManager;
 import ru.dbotthepony.mc.otm.android.feature.EnderTeleporterFeature;
 import ru.dbotthepony.mc.otm.block.entity.MatteryBlockEntity;
@@ -47,7 +46,6 @@ import ru.dbotthepony.mc.otm.config.MachinesConfig;
 import ru.dbotthepony.mc.otm.config.ServerCompatConfig;
 import ru.dbotthepony.mc.otm.config.ServerConfig;
 import ru.dbotthepony.mc.otm.config.ToolsConfig;
-import ru.dbotthepony.mc.otm.core.math.Decimal;
 import ru.dbotthepony.mc.otm.item.tool.ExplosiveHammerItem;
 import ru.dbotthepony.mc.otm.item.armor.TritaniumArmorItem;
 import ru.dbotthepony.mc.otm.item.QuantumBatteryItem;
@@ -56,14 +54,12 @@ import ru.dbotthepony.mc.otm.item.PortableCondensationDriveItem;
 import ru.dbotthepony.mc.otm.matter.MatterManager;
 import ru.dbotthepony.mc.otm.network.*;
 import ru.dbotthepony.mc.otm.registry.*;
-import ru.dbotthepony.mc.otm.storage.*;
 import ru.dbotthepony.mc.otm.triggers.KillAsAndroidTrigger;
 import top.theillusivec4.curios.api.CuriosApi;
 
 import static net.minecraftforge.common.MinecraftForge.EVENT_BUS;
 
 import javax.annotation.ParametersAreNonnullByDefault;
-import java.util.Objects;
 
 // The value here should match an entry in the META-INF/mods.toml file
 @Mod(OverdriveThatMatters.MOD_ID)
@@ -147,7 +143,7 @@ public final class OverdriveThatMatters {
 		EVENT_BUS.addListener(EventPriority.HIGHEST, GlobalEventHandlerKt::onServerStopped);
 		EVENT_BUS.addListener(EventPriority.HIGHEST, GlobalEventHandlerKt::onServerStopping);
 		EVENT_BUS.addListener(EventPriority.HIGHEST, GlobalEventHandlerKt::onServerStarting);
-		EVENT_BUS.addListener(EventPriority.LOWEST, GlobalEventHandlerKt::onWorldTick);
+		EVENT_BUS.addListener(EventPriority.LOWEST, GlobalEventHandlerKt::onLevelTick);
 		EVENT_BUS.addListener(EventPriority.LOWEST, GlobalEventHandlerKt::onServerTick);
 
 		EVENT_BUS.addListener(EventPriority.NORMAL, MatteryPlayerCapability.Companion::onPlayerTick);
@@ -180,7 +176,6 @@ public final class OverdriveThatMatters {
 		EVENT_BUS.addListener(EventPriority.NORMAL, MatteryBlockEntity.Companion::onWatch);
 		EVENT_BUS.addListener(EventPriority.NORMAL, MatteryBlockEntity.Companion::onForget);
 		EVENT_BUS.addListener(EventPriority.NORMAL, MatteryBlockEntity.Companion::playerDisconnected);
-		EVENT_BUS.addListener(EventPriority.LOWEST, MatteryBlockEntity.Companion::postLevelTick);
 
 		EVENT_BUS.addListener(EventPriority.LOWEST, KillAsAndroidTrigger.INSTANCE::onKill);
 

src/main/kotlin/ru/dbotthepony/mc/otm/GlobalEventHandler.kt

@@ -15,6 +15,7 @@ import net.minecraftforge.event.server.ServerStoppedEvent
 import net.minecraftforge.event.server.ServerStoppingEvent
 import net.minecraftforge.fml.loading.FMLLoader
 import org.apache.logging.log4j.LogManager
+import ru.dbotthepony.mc.otm.block.entity.MatteryBlockEntity
 import ru.dbotthepony.mc.otm.capability.AbstractProfiledStorage
 import ru.dbotthepony.mc.otm.client.minecraft
 import ru.dbotthepony.mc.otm.core.collect.WeakHashSet
@@ -165,7 +166,7 @@ fun onServerTick(event: ServerTickEvent) {
 	}
 }
 
-fun onWorldTick(event: LevelTickEvent) {
+fun onLevelTick(event: LevelTickEvent) {
 	if (event.phase === TickEvent.Phase.START) {
 		preWorldTick[event.level]?.tick()
 
@@ -176,6 +177,7 @@ fun onWorldTick(event: LevelTickEvent) {
 		}
 	} else {
 		postWorldTick[event.level]?.tick()
+		MatteryBlockEntity.postLevelTick(event)
 	}
 }
 

src/main/kotlin/ru/dbotthepony/mc/otm/block/entity/MatteryBlockEntity.kt

@@ -5,6 +5,7 @@ import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap
 import it.unimi.dsi.fastutil.longs.Long2ObjectFunction
 import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap
 import it.unimi.dsi.fastutil.objects.ObjectArraySet
+import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet
 import it.unimi.dsi.fastutil.objects.Reference2ObjectOpenHashMap
 import mekanism.api.energy.IStrictEnergyHandler
 import net.minecraft.core.BlockPos
@@ -31,7 +32,6 @@ import net.minecraftforge.common.capabilities.ForgeCapabilities
 import net.minecraftforge.common.util.INBTSerializable
 import net.minecraftforge.common.util.LazyOptional
 import net.minecraftforge.energy.IEnergyStorage
-import net.minecraftforge.event.TickEvent
 import net.minecraftforge.event.TickEvent.LevelTickEvent
 import net.minecraftforge.event.entity.player.PlayerEvent
 import net.minecraftforge.event.level.ChunkWatchEvent
@@ -46,7 +46,6 @@ import ru.dbotthepony.mc.otm.compat.mekanism.Mattery2MekanismEnergyWrapper
 import ru.dbotthepony.mc.otm.compat.mekanism.Mekanism2MatteryEnergyWrapper
 import ru.dbotthepony.mc.otm.core.ISubscriptable
 import ru.dbotthepony.mc.otm.core.collect.WeakHashSet
-import ru.dbotthepony.mc.otm.core.forValidRefs
 import ru.dbotthepony.mc.otm.core.get
 import ru.dbotthepony.mc.otm.core.ifPresentK
 import ru.dbotthepony.mc.otm.core.immutableList
@@ -69,7 +68,6 @@ import java.util.function.Predicate
 import java.util.function.Supplier
 import java.util.stream.Stream
 import kotlin.NoSuchElementException
-import kotlin.collections.ArrayList
 import kotlin.properties.ReadWriteProperty
 import kotlin.reflect.KProperty
 import kotlin.reflect.KProperty0
@@ -120,12 +118,11 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 	 */
 	protected val savetablesLevel = Savetables()
 
-	private var tickedOnce = false
-
 	open fun tick() {
 		tickList.tick()
-		tickedOnce = true
-		synchronizeToPlayers(false)
+
+		if (synchronizer.isNotEmpty)
+			synchronizeToPlayers(false)
 	}
 
 	/**
@@ -537,10 +534,12 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 	}
 
 	val synchronizer = FieldSynchronizer {
-		if (isSynchronizing || tickedOnce)
+		if (isSynchronizing || tickList.ticks != 0)
 			return@FieldSynchronizer
 
-		if (!isRemoved && level?.isClientSide == false && (_subCache == null || (_subCache ?: throw ConcurrentModificationException()).players.isNotEmpty())) {
+		if (isRemoved) markSynchronizerClean()
+
+		if (level?.isClientSide == false && (_subCache == null || (_subCache ?: throw ConcurrentModificationException()).players.isNotEmpty())) {
 			ru.dbotthepony.mc.otm.onceServer {
 				synchronizeToPlayers(true)
 			}
@@ -599,6 +598,8 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 	}
 
 	private var _subCache: ChunkSubscribers? = null
+	private val subscription get() = _subCache ?: subscribe()
+	private var playerListUpdated = false
 
 	private fun unsubscribe() {
 		val subCache = _subCache ?: return
@@ -611,7 +612,7 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 			}
 		}
 
-		lastSubscriptionChangeset = -1
+		playerListUpdated = false
 	}
 
 	private fun subscribe(): ChunkSubscribers {
@@ -621,171 +622,106 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 
 		val subs = playerMap
 			.computeIfAbsent(level) { Long2ObjectOpenHashMap() }
-			.computeIfAbsent(ChunkPos(blockPos).toLong(), Long2ObjectFunction { ChunkSubscribers(level = WeakReference(level), chunkPos = ChunkPos(blockPos).toLong()) })
+			.computeIfAbsent(ChunkPos(blockPos).toLong(), Long2ObjectFunction { ChunkSubscribers(level, ChunkPos(blockPos).toLong()) })
 
 		subs.subscribe(this)
 		_subCache = subs
+		playerListUpdated = true
 		return subs
 	}
 
-	private val subscription get() = _subCache ?: subscribe()
-	private var lastSubscriptionChangeset = -1
-
-	fun synchronizeToPlayers() {
-		synchronizeToPlayers(false)
-	}
-
-	protected fun synchronizeToPlayers(calledBySynchronizer: Boolean) {
+	private fun synchronizeToPlayers(calledBySynchronizer: Boolean) {
 		isSynchronizing = true
 
 		try {
-			if (synchronizer.isEmpty || isRemoved) {
-				if (calledBySynchronizer) synchronizer.markClean()
-				return
-			}
-
 			check(level is ServerLevel) { "Invalid realm or Level is null" }
-
 			synchronizer.observe()
-
 			val subscription = subscription
 
-			if (subscription.players.isEmpty() || lastSubscriptionChangeset == subscription.changeset && !synchronizer.hasChanges) {
-				if (calledBySynchronizer) synchronizer.markClean()
-				return
-			}
+			if (subscription.players.isNotEmpty() && (playerListUpdated || synchronizer.isDirty)) {
+				playerListUpdated = false
 
-			lastSubscriptionChangeset = subscription.changeset
+				for (player in subscription.players) {
+					val payload = synchronizer.computeEndpointFor(player).collectNetworkPayload()
 
-			for (player in subscription.players) {
-				val payload = synchronizer.computeEndpointFor(player).collectNetworkPayload()
-
-				if (payload != null) {
-					GenericNetworkChannel.send(player, BlockEntitySyncPacket(blockPos, payload.array, payload.length))
+					if (payload != null) {
+						GenericNetworkChannel.send(player, BlockEntitySyncPacket(blockPos, payload.array, payload.length))
+					}
 				}
-			}
 
-			synchronizer.markClean()
+				synchronizer.markClean()
+			} else if (calledBySynchronizer) {
+				synchronizer.markClean()
+			}
 		} finally {
 			isSynchronizing = false
 		}
 	}
 
-	private data class ChunkSubscribers(
-		val blockEntities: ArrayList<WeakReference<MatteryBlockEntity>> = ArrayList(0),
-		val players: ArrayList<ServerPlayer> = ArrayList(1),
-		val observingBlockEntities: ArrayList<WeakReference<MatteryBlockEntity>> = ArrayList(0),
-		val level: WeakReference<ServerLevel>,
-		val chunkPos: Long,
-		var changeset: Int = 0
-	) {
-		fun cleanUpBlocks() {
-			val listIterator = blockEntities.listIterator()
+	private class ChunkSubscribers(level: ServerLevel, val chunkPos: Long) {
+		val level = WeakReference(level)
+		val blockEntities = WeakHashSet<MatteryBlockEntity>(linked = true, initialCapacity = 0)
+		val players = ObjectLinkedOpenHashSet<ServerPlayer>(0)
+		val blockEntitiesWithObservers = WeakHashSet<MatteryBlockEntity>(linked = true, initialCapacity = 0)
 
-			for (block in listIterator) {
-				if (block.get() == null) {
-					listIterator.remove()
+		operator fun component1() = blockEntities
+		operator fun component2() = players
+
+		val hasObservers: Boolean get() {
+			return blockEntities.any { it.synchronizer.hasObservers }
+		}
+
+		fun subscribe(player: ServerPlayer) {
+			if (players.add(player)) {
+				blockEntities.forEach { it.playerListUpdated = true }
+
+				onceServer(10) {
+					if (!player.hasDisconnected() && player in players) {
+						blockEntities.forEach {
+							it.synchronizeToPlayers(false)
+						}
+					}
 				}
 			}
 		}
 
-		val hasObservers: Boolean get() {
-			val listIterator = blockEntities.listIterator()
-
-			for (value in listIterator) {
-				val ref = value.get()
-
-				if (ref == null) {
-					listIterator.remove()
-				} else if (ref.synchronizer.hasObservers) {
-					return true
+		fun unsubscribe(player: ServerPlayer): Boolean {
+			if (players.remove(player)) {
+				blockEntities.forEach {
+					it.synchronizer.removeEndpointFor(player)
 				}
+
+				return true
 			}
 
 			return false
 		}
 
 		fun subscribe(blockEntity: MatteryBlockEntity) {
-			val iterator = blockEntities.listIterator()
-
-			for (value in iterator) {
-				val ref = value.get()
-
-				if (ref === blockEntity) {
-					return
-				} else if (ref == null) {
-					iterator.remove()
-				}
-			}
-
-			val bref = WeakReference(blockEntity)
-			blockEntities.add(bref)
-			changeset++
+			if (!blockEntities.add(blockEntity)) return
 
 			onceServer {
-				blockEntity.synchronizeToPlayers()
+				blockEntity.synchronizeToPlayers(false)
 			}
 
-			if (blockEntity.synchronizer.hasObservers) {
-				observingBlockEntities.add(bref)
-				val listing = tickingMap.computeIfAbsent(level.get() ?: throw NullPointerException("Level got GCd!")) { ArrayList(1) }
-				val tickerIterator = listing.listIterator()
+			if (blockEntity.synchronizer.hasObservers && blockEntity.tickList.ticks == 0) {
+				blockEntitiesWithObservers.add(blockEntity)
 
-				for (value in tickerIterator) {
-					val ref = value.get()
-
-					if (ref === this) {
-						return
-					} else if (ref == null) {
-						tickerIterator.remove()
-					}
-				}
-
-				listing.add(WeakReference(this))
+				tickingMap
+					.computeIfAbsent(level.get() ?: throw NullPointerException("Level got GCd!")) { WeakHashSet(linked = true, initialCapacity = 2) }
+					.add(this)
 			}
 		}
 
 		fun unsubscribe(blockEntity: MatteryBlockEntity): Boolean {
-			val listIterator = blockEntities.listIterator()
+			blockEntities.remove(blockEntity)
+			blockEntitiesWithObservers.remove(blockEntity)
 
-			for (value in listIterator) {
-				if (value.get() === blockEntity) {
-					listIterator.remove()
-					changeset++
-					break
-				}
-			}
-
-			if (blockEntity.synchronizer.hasObservers) {
-				val tickerIterator = observingBlockEntities.listIterator()
-
-				for (value in tickerIterator) {
-					val ref = value.get()
-
-					if (ref === blockEntity) {
-						tickerIterator.remove()
-						break
-					} else if (ref == null) {
-						tickerIterator.remove()
-					}
-				}
-			}
-
-			if (players.isNotEmpty()) {
-				return false
-			}
-
-			cleanUpBlocks()
-			return blockEntities.isEmpty()
+			return players.isEmpty() && blockEntities.isEmpty()
 		}
 
 		val isEmpty: Boolean get() {
-			if (players.isNotEmpty()) {
-				return false
-			}
-
-			cleanUpBlocks()
-			return blockEntities.isEmpty()
+			return players.isEmpty() && blockEntities.isEmpty()
 		}
 	}
 
@@ -813,7 +749,7 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 		const val LOOT_TABLE_SEED_KEY = RandomizableContainerBlockEntity.LOOT_TABLE_SEED_TAG
 
 		private val playerMap = WeakHashMap<ServerLevel, Long2ObjectOpenHashMap<ChunkSubscribers>>()
-		private val tickingMap = WeakHashMap<ServerLevel, ArrayList<WeakReference<ChunkSubscribers>>>()
+		private val tickingMap = WeakHashMap<ServerLevel, WeakHashSet<ChunkSubscribers>>()
 
 		private val vec2Dir = Int2ObjectOpenHashMap<Direction>()
 
@@ -860,7 +796,7 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 		}
 
 		init {
-			for (dir in Direction.values()) {
+			for (dir in Direction.entries) {
 				vec2Dir[vecKey(dir.normal)] = dir
 			}
 		}
@@ -877,87 +813,47 @@ abstract class MatteryBlockEntity(p_155228_: BlockEntityType<*>, p_155229_: Bloc
 		}
 
 		fun postLevelTick(event: LevelTickEvent) {
-			if (event.phase == TickEvent.Phase.END) {
-				val level = event.level as? ServerLevel ?: return
-				val listing = tickingMap[level] ?: return
-				val listIterator = listing.listIterator()
-				var hitAnyObservers = false
+			val level = event.level as? ServerLevel ?: return
+			val ticking = tickingMap[level] ?: return
 
-				for (value in listIterator) {
-					val ref = value.get()
+			ticking.removeIf {
+				val shouldRemove = it.blockEntitiesWithObservers.isEmpty()
 
-					if (ref == null) {
-						listIterator.remove()
-					} else if (ref.players.isNotEmpty()) {
-						var hitObservers = false
-
-						ref.observingBlockEntities.forValidRefs {
-							hitObservers = true
-							hitAnyObservers = true
-							it.synchronizeToPlayers()
-						}
-
-						if (!hitObservers) {
-							listIterator.remove()
-						}
+				if (!shouldRemove && it.players.isNotEmpty()) {
+					it.blockEntitiesWithObservers.forEach {
+						it.synchronizeToPlayers(false)
 					}
 				}
 
-				if (!hitAnyObservers) {
-					tickingMap.remove(level)
-				}
+				shouldRemove
+			}
+
+			if (ticking.isEmpty()) {
+				tickingMap.remove(level)
 			}
 		}
 
 		fun onWatch(event: ChunkWatchEvent.Watch) {
 			playerMap
 				.computeIfAbsent(event.level) { Long2ObjectOpenHashMap() }
-				.computeIfAbsent(event.pos.toLong(), Long2ObjectFunction { ChunkSubscribers(level = WeakReference(event.level), chunkPos = event.pos.toLong()) })
-			.let {
-				val (blocks, players) = it
-
-				if (event.player !in players) {
-					players.add(event.player)
-					it.changeset++
-
-					onceServer(10) {
-						if (!event.player.hasDisconnected() && event.player in players) {
-							blocks.forValidRefs {
-								it.synchronizeToPlayers(false)
-							}
-						}
-					}
-				}
-			}
+				.computeIfAbsent(event.pos.toLong(), Long2ObjectFunction { ChunkSubscribers(event.level, it) })
+				.subscribe(event.player)
 		}
 
 		fun onForget(event: ChunkWatchEvent.UnWatch) {
-			val subs = playerMap.get(event.level)?.get(event.pos.toLong()) ?: return
+			val levelMap = playerMap[event.level] ?: return
+			val subs = levelMap.get(event.pos.toLong()) ?: return
 
-			if (subs.players.remove(event.player)) {
-				if (subs.isEmpty) {
-					playerMap.get(event.level)?.remove(event.pos.toLong())
-				} else {
-					subs.changeset++
-					subs.blockEntities.forValidRefs {
-						it.synchronizer.removeEndpointFor(event.player)
-					}
-				}
+			if (subs.unsubscribe(event.player) && subs.isEmpty) {
+				levelMap.remove(event.pos.toLong())
 			}
 		}
 
 		fun playerDisconnected(event: PlayerEvent.PlayerLoggedOutEvent) {
 			for (tree in playerMap.values) {
-				val iterator = tree.iterator()
-
-				for (entry in iterator) {
-					if (entry.value.players.remove(event.entity)) {
-						entry.value.changeset++
-
-						if (entry.value.isEmpty) {
-							iterator.remove()
-						}
-					}
+				tree.values.removeIf {
+					it.unsubscribe(event.entity as ServerPlayer)
+					it.isEmpty
 				}
 			}
 		}

src/main/kotlin/ru/dbotthepony/mc/otm/core/collect/WeakHashSet.kt

@@ -1,12 +1,14 @@
 package ru.dbotthepony.mc.otm.core.collect
 
+import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenCustomHashSet
 import it.unimi.dsi.fastutil.objects.ObjectOpenCustomHashSet
+import it.unimi.dsi.fastutil.objects.ObjectSet
 import ru.dbotthepony.mc.otm.core.util.HashedWeakReference
 import java.lang.ref.ReferenceQueue
 
-class WeakHashSet<E : Any> : MutableSet<E> {
+class WeakHashSet<E : Any>(initialCapacity: Int = 16, loadFactor: Float = 0.75f, linked: Boolean = false) : MutableSet<E> {
 	private val queue = ReferenceQueue<E>()
-	private val backing = ObjectOpenCustomHashSet<Any>(ReferenceHashStrategy)
+	private val backing: ObjectSet<Any> = if (linked) ObjectLinkedOpenCustomHashSet(initialCapacity, loadFactor, ReferenceHashStrategy) else ObjectOpenCustomHashSet(initialCapacity, loadFactor, ReferenceHashStrategy)
 
 	private fun purge() {
 		var next = queue.poll()

src/main/kotlin/ru/dbotthepony/mc/otm/network/synchronizer/FieldSynchronizer.kt

@@ -66,10 +66,13 @@ class FieldSynchronizer(private val callback: Runnable, private val alwaysCallCa
 	private var nextFieldID = 0
 
 	val hasObservers: Boolean get() = observers.isNotEmpty()
-	val isEmpty: Boolean get() = fields.isEmpty()
-	val isNotEmpty: Boolean get() = fields.isNotEmpty()
 
-	var hasChanges: Boolean = false
+	var isEmpty: Boolean = true
+		private set
+
+	val isNotEmpty: Boolean get() = !isEmpty
+
+	var isDirty: Boolean = false
 		private set(value) {
 			if (value != field) {
 				field = value
@@ -85,7 +88,7 @@ class FieldSynchronizer(private val callback: Runnable, private val alwaysCallCa
 		}
 
 	fun markClean() {
-		hasChanges = false
+		isDirty = false
 	}
 
 	fun computedByte(getter: () -> Byte) = ComputedField(getter, ByteValueCodec)
@@ -301,7 +304,7 @@ class FieldSynchronizer(private val callback: Runnable, private val alwaysCallCa
 	private var nextEndpointsCleanup = secondTime
 
 	private fun notifyEndpoints(dirtyField: AbstractField<*>) {
-		hasChanges = true
+		isDirty = true
 
 		forEachEndpoint {
 			it.addDirtyField(dirtyField)
@@ -480,6 +483,7 @@ class FieldSynchronizer(private val callback: Runnable, private val alwaysCallCa
 			} else {
 				fields.add(this)
 				id = fields.size
+				isEmpty = false
 			}
 		}
 
@@ -496,6 +500,7 @@ class FieldSynchronizer(private val callback: Runnable, private val alwaysCallCa
 			freeSlots++
 			fields[id - 1] = null
 			observers.remove(this)
+			isEmpty = fields.all { it == null }
 
 			while (fields[fields.size - 1] == null) {
 				fields.removeAt(fields.size - 1)
@@ -1994,7 +1999,7 @@ class FieldSynchronizer(private val callback: Runnable, private val alwaysCallCa
 				}
 
 				lmarkDirty()
-				hasChanges = true
+				this@FieldSynchronizer.isDirty = true
 			}
 
 			override fun onValueAdded(key: K, value: V) {