slayer plugin: better support multikills

This observes deaths of tagged npcs each tick and will use those if
available instead of assuming one kill per xpdrop

runelite-client/src/main/java/net/runelite/client/plugins/slayer/SlayerPlugin.java

@@ -30,11 +30,14 @@ import com.google.inject.Provides;
 import java.awt.Color;
 import java.awt.image.BufferedImage;
 import java.io.IOException;
+import static java.lang.Integer.max;
 import java.time.Duration;
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -44,18 +47,22 @@ import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.Setter;
 import lombok.extern.slf4j.Slf4j;
+import net.runelite.api.Actor;
 import net.runelite.api.ChatMessageType;
 import net.runelite.api.Client;
 import net.runelite.api.GameState;
+import net.runelite.api.Hitsplat;
 import net.runelite.api.ItemID;
 import net.runelite.api.MessageNode;
 import net.runelite.api.NPC;
 import net.runelite.api.NPCComposition;
 import static net.runelite.api.Skill.SLAYER;
 import net.runelite.api.coords.WorldPoint;
+import net.runelite.api.events.ActorDeath;
 import net.runelite.api.events.ChatMessage;
 import net.runelite.api.events.GameStateChanged;
 import net.runelite.api.events.GameTick;
+import net.runelite.api.events.HitsplatApplied;
 import net.runelite.api.events.NpcDespawned;
 import net.runelite.api.events.NpcSpawned;
 import net.runelite.api.events.StatChanged;
@@ -174,6 +181,10 @@ public class SlayerPlugin extends Plugin
 	@Getter(AccessLevel.PACKAGE)
 	private List<NPC> highlightedTargets = new ArrayList<>();
 
+	private final Set<NPC> taggedNpcs = new HashSet<>();
+	private int taggedNpcsDiedPrevTick;
+	private int taggedNpcsDiedThisTick;
+
 	@Getter(AccessLevel.PACKAGE)
 	@Setter(AccessLevel.PACKAGE)
 	private int amount;
@@ -237,6 +248,7 @@ public class SlayerPlugin extends Plugin
 		overlayManager.remove(targetMinimapOverlay);
 		removeCounter();
 		highlightedTargets.clear();
+		taggedNpcs.clear();
 		cachedXp = -1;
 
 		chatCommandManager.unregisterCommand(TASK_COMMAND_STRING);
@@ -260,6 +272,7 @@ public class SlayerPlugin extends Plugin
 				amount = 0;
 				loginFlag = true;
 				highlightedTargets.clear();
+				taggedNpcs.clear();
 				break;
 			case LOGGED_IN:
 				if (config.amount() != -1
@@ -299,6 +312,7 @@ public class SlayerPlugin extends Plugin
 	public void onNpcDespawned(NpcDespawned npcDespawned)
 	{
 		NPC npc = npcDespawned.getNpc();
+		taggedNpcs.remove(npc);
 		highlightedTargets.remove(npc);
 	}
 
@@ -391,6 +405,9 @@ public class SlayerPlugin extends Plugin
 				removeCounter();
 			}
 		}
+
+		taggedNpcsDiedPrevTick = taggedNpcsDiedThisTick;
+		taggedNpcsDiedThisTick = 0;
 	}
 
 	@Subscribe
@@ -541,20 +558,49 @@ public class SlayerPlugin extends Plugin
 			return;
 		}
 
-		final Task task = Task.getTask(taskName);
-
-		// null tasks are technically valid, it only means they arent explicitly defined in the Task enum
-		// allow them through so that if there is a task capture failure the counter will still work
-		final int taskKillExp = task != null ? task.getExpectedKillExp() : 0;
-
-		// Only count exp gain as a kill if the task either has no expected exp for a kill, or if the exp gain is equal
-		// to the expected exp gain for the task.
-		if (taskKillExp == 0 || taskKillExp == slayerExp - cachedXp)
-		{
-			killedOne();
-		}
-
+		final int delta = slayerExp - cachedXp;
 		cachedXp = slayerExp;
+
+		log.debug("Slayer xp change delta: {}, killed npcs: {}", delta, taggedNpcsDiedPrevTick);
+
+		final Task task = Task.getTask(taskName);
+		if (task != null && task.getExpectedKillExp() > 0)
+		{
+			// Only decrement a kill if the xp drop matches the expected drop. This is just for Tzhaar tasks.
+			if (task.getExpectedKillExp() == delta)
+			{
+				killed(1);
+			}
+		}
+		else
+		{
+			// This is at least one kill, but if we observe multiple tagged NPCs dieing on the previous tick, count them
+			// instead.
+			killed(max(taggedNpcsDiedPrevTick, 1));
+		}
+	}
+
+	@Subscribe
+	public void onHitsplatApplied(HitsplatApplied hitsplatApplied)
+	{
+		Actor actor = hitsplatApplied.getActor();
+		Hitsplat hitsplat = hitsplatApplied.getHitsplat();
+		if (hitsplat.getHitsplatType() == Hitsplat.HitsplatType.DAMAGE_ME && highlightedTargets.contains(actor))
+		{
+			// If the actor is in highlightedTargets it must be an NPC and also a task assignment
+			taggedNpcs.add((NPC) actor);
+		}
+	}
+
+	@Subscribe
+	public void onActorDeath(ActorDeath actorDeath)
+	{
+		Actor actor = actorDeath.getActor();
+		if (taggedNpcs.contains(actor))
+		{
+			log.debug("Tagged NPC {} has died", actor.getName());
+			++taggedNpcsDiedThisTick;
+		}
 	}
 
 	@Subscribe
@@ -576,16 +622,17 @@ public class SlayerPlugin extends Plugin
 	}
 
 	@VisibleForTesting
-	void killedOne()
+	void killed(int amt)
 	{
 		if (amount == 0)
 		{
 			return;
 		}
 
-		amount--;
+		amount -= amt;
 		if (doubleTroubleExtraKill())
 		{
+			assert amt == 1;
 			amount--;
 		}