Add combat tracker API (#11853)

paper-server/src/main/java/io/papermc/paper/PaperServerInternalAPIBridge.java

@@ -1,10 +1,21 @@
 package io.papermc.paper;
 
+import io.papermc.paper.world.damagesource.CombatEntry;
+import io.papermc.paper.world.damagesource.FallLocationType;
+import io.papermc.paper.world.damagesource.PaperCombatEntryWrapper;
+import io.papermc.paper.world.damagesource.PaperCombatTrackerWrapper;
+import net.minecraft.Optionull;
+import net.minecraft.world.damagesource.FallLocation;
 import org.bukkit.block.Biome;
 import org.bukkit.craftbukkit.block.CraftBiome;
 import org.bukkit.craftbukkit.damage.CraftDamageEffect;
+import org.bukkit.craftbukkit.damage.CraftDamageSource;
+import org.bukkit.craftbukkit.entity.CraftLivingEntity;
 import org.bukkit.damage.DamageEffect;
+import org.bukkit.damage.DamageSource;
+import org.bukkit.entity.LivingEntity;
 import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 @NullMarked
 public class PaperServerInternalAPIBridge implements InternalAPIBridge {
@@ -22,4 +33,42 @@ public class PaperServerInternalAPIBridge implements InternalAPIBridge {
         }
         return Holder.LEGACY_CUSTOM;
     }
+
+    @Override
+    public CombatEntry createCombatEntry(final LivingEntity entity, final DamageSource damageSource, final float damage) {
+        final net.minecraft.world.entity.LivingEntity mob = ((CraftLivingEntity) entity).getHandle();
+        final FallLocation fallLocation = FallLocation.getCurrentFallLocation(mob);
+        return createCombatEntry(
+            ((CraftDamageSource) damageSource).getHandle(),
+            damage,
+            fallLocation,
+            (float) mob.fallDistance
+        );
+    }
+
+    @Override
+    public CombatEntry createCombatEntry(
+        final DamageSource damageSource,
+        final float damage,
+        @Nullable final FallLocationType fallLocationType,
+        final float fallDistance
+    ) {
+        return createCombatEntry(
+            ((CraftDamageSource) damageSource).getHandle(),
+            damage,
+            Optionull.map(fallLocationType, PaperCombatTrackerWrapper::paperToMinecraft),
+            fallDistance
+        );
+    }
+
+    private CombatEntry createCombatEntry(
+        final net.minecraft.world.damagesource.DamageSource damageSource,
+        final float damage,
+        final net.minecraft.world.damagesource.@Nullable FallLocation fallLocation,
+        final float fallDistance
+    ) {
+        return new PaperCombatEntryWrapper(new net.minecraft.world.damagesource.CombatEntry(
+            damageSource, damage, fallLocation, fallDistance
+        ));
+    }
 }

paper-server/src/main/java/io/papermc/paper/world/damagesource/PaperCombatEntryWrapper.java

@@ -0,0 +1,32 @@
+package io.papermc.paper.world.damagesource;
+
+import net.minecraft.Optionull;
+import org.bukkit.craftbukkit.damage.CraftDamageSource;
+import org.bukkit.damage.DamageSource;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+@NullMarked
+public record PaperCombatEntryWrapper(net.minecraft.world.damagesource.CombatEntry handle) implements CombatEntry {
+
+    @Override
+    public DamageSource getDamageSource() {
+        return new CraftDamageSource(this.handle.source());
+    }
+
+    @Override
+    public float getDamage() {
+        return this.handle.damage();
+    }
+
+    @Override
+    public @Nullable FallLocationType getFallLocationType() {
+        return Optionull.map(this.handle.fallLocation(), PaperCombatTrackerWrapper::minecraftToPaper);
+    }
+
+    @Override
+    public float getFallDistance() {
+        return this.handle.fallDistance();
+    }
+
+}

paper-server/src/main/java/io/papermc/paper/world/damagesource/PaperCombatTrackerWrapper.java

@@ -0,0 +1,110 @@
+package io.papermc.paper.world.damagesource;
+
+import com.google.common.collect.BiMap;
+import com.google.common.collect.HashBiMap;
+import io.papermc.paper.adventure.PaperAdventure;
+import java.util.ArrayList;
+import java.util.List;
+import net.kyori.adventure.text.Component;
+import net.minecraft.Util;
+import net.minecraft.world.damagesource.FallLocation;
+import org.bukkit.entity.LivingEntity;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+@NullMarked
+public record PaperCombatTrackerWrapper(
+    net.minecraft.world.damagesource.CombatTracker handle
+) implements CombatTracker {
+
+    @Override
+    public LivingEntity getEntity() {
+        return this.handle.mob.getBukkitLivingEntity();
+    }
+
+    @Override
+    public List<CombatEntry> getCombatEntries() {
+        final List<CombatEntry> combatEntries = new ArrayList<>(this.handle.entries.size());
+        this.handle.entries.forEach(combatEntry -> combatEntries.add(new PaperCombatEntryWrapper(combatEntry)));
+        return combatEntries;
+    }
+
+    @Override
+    public void setCombatEntries(final List<CombatEntry> combatEntries) {
+        this.handle.entries.clear();
+        combatEntries.forEach(combatEntry -> this.handle.entries.add(((PaperCombatEntryWrapper) combatEntry).handle()));
+    }
+
+    @Override
+    public @Nullable CombatEntry computeMostSignificantFall() {
+        final net.minecraft.world.damagesource.CombatEntry combatEntry = this.handle.getMostSignificantFall();
+        return combatEntry == null ? null : new PaperCombatEntryWrapper(combatEntry);
+    }
+
+    @Override
+    public boolean isInCombat() {
+        return this.handle.inCombat;
+    }
+
+    @Override
+    public boolean isTakingDamage() {
+        return this.handle.takingDamage;
+    }
+
+    @Override
+    public int getCombatDuration() {
+        return this.handle.getCombatDuration();
+    }
+
+    @Override
+    public void addCombatEntry(final CombatEntry combatEntry) {
+        final net.minecraft.world.damagesource.CombatEntry entry = ((PaperCombatEntryWrapper) combatEntry).handle();
+        this.handle.recordDamageAndCheckCombatState(entry);
+    }
+
+    @Override
+    public Component getDeathMessage() {
+        return PaperAdventure.asAdventure(this.handle.getDeathMessage());
+    }
+
+    @Override
+    public void resetCombatState() {
+        this.handle.resetCombatState();
+    }
+
+    @Override
+    public FallLocationType calculateFallLocationType() {
+        final FallLocation fallLocation = FallLocation.getCurrentFallLocation(this.handle().mob);
+        return fallLocation == null ? FallLocationType.GENERIC : PaperCombatTrackerWrapper.minecraftToPaper(fallLocation);
+    }
+
+    private static final BiMap<FallLocation, FallLocationType> FALL_LOCATION_MAPPING = Util.make(() -> {
+        final BiMap<FallLocation, FallLocationType> map = HashBiMap.create(8);
+        map.put(FallLocation.GENERIC, FallLocationType.GENERIC);
+        map.put(FallLocation.LADDER, FallLocationType.LADDER);
+        map.put(FallLocation.VINES, FallLocationType.VINES);
+        map.put(FallLocation.WEEPING_VINES, FallLocationType.WEEPING_VINES);
+        map.put(FallLocation.TWISTING_VINES, FallLocationType.TWISTING_VINES);
+        map.put(FallLocation.SCAFFOLDING, FallLocationType.SCAFFOLDING);
+        map.put(FallLocation.OTHER_CLIMBABLE, FallLocationType.OTHER_CLIMBABLE);
+        map.put(FallLocation.WATER, FallLocationType.WATER);
+        return map;
+    });
+
+    public static FallLocation paperToMinecraft(final FallLocationType fallLocationType) {
+        final FallLocation fallLocation = FALL_LOCATION_MAPPING.inverse().get(fallLocationType);
+        if (fallLocation == null) {
+            throw new IllegalArgumentException("Unknown fall location type: " + fallLocationType.id());
+        }
+        return fallLocation;
+    }
+
+    public static FallLocationType minecraftToPaper(final FallLocation fallLocation) {
+        final FallLocationType fallLocationType = FALL_LOCATION_MAPPING.get(fallLocation);
+        if (fallLocationType == null) {
+            throw new IllegalArgumentException("Unknown fall location: " + fallLocation.id());
+        }
+        return fallLocationType;
+    }
+
+}