From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Fri, 20 Aug 2021 13:03:21 -0700
Subject: [PATCH] Get entity default attributes

== AT ==
public net.minecraft.world.entity.ai.attributes.AttributeSupplier getAttributeInstance(Lnet/minecraft/core/Holder;)Lnet/minecraft/world/entity/ai/attributes/AttributeInstance;

diff --git a/src/main/java/io/papermc/paper/attribute/UnmodifiableAttributeInstance.java b/src/main/java/io/papermc/paper/attribute/UnmodifiableAttributeInstance.java
new file mode 100644
index 0000000000000000000000000000000000000000..12135ffeacd648f6bc4d7d327059ea1a7e8c79c4
--- /dev/null
+++ b/src/main/java/io/papermc/paper/attribute/UnmodifiableAttributeInstance.java
@@ -0,0 +1,30 @@
+package io.papermc.paper.attribute;
+
+import net.minecraft.world.entity.ai.attributes.AttributeInstance;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.attribute.AttributeModifier;
+import org.bukkit.craftbukkit.attribute.CraftAttributeInstance;
+
+import java.util.Collection;
+
+public class UnmodifiableAttributeInstance extends CraftAttributeInstance {
+
+    public UnmodifiableAttributeInstance(AttributeInstance handle, Attribute attribute) {
+        super(handle, attribute);
+    }
+
+    @Override
+    public void setBaseValue(double d) {
+        throw new UnsupportedOperationException("Cannot modify default attributes");
+    }
+
+    @Override
+    public void addModifier(AttributeModifier modifier) {
+        throw new UnsupportedOperationException("Cannot modify default attributes");
+    }
+
+    @Override
+    public void removeModifier(AttributeModifier modifier) {
+        throw new UnsupportedOperationException("Cannot modify default attributes");
+    }
+}
diff --git a/src/main/java/io/papermc/paper/attribute/UnmodifiableAttributeMap.java b/src/main/java/io/papermc/paper/attribute/UnmodifiableAttributeMap.java
new file mode 100644
index 0000000000000000000000000000000000000000..ec9ebd2d539333293c51b7edfa18f18b066d7e43
--- /dev/null
+++ b/src/main/java/io/papermc/paper/attribute/UnmodifiableAttributeMap.java
@@ -0,0 +1,32 @@
+package io.papermc.paper.attribute;
+
+import net.minecraft.world.entity.ai.attributes.AttributeSupplier;
+import org.bukkit.attribute.Attributable;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.attribute.AttributeInstance;
+import org.bukkit.craftbukkit.attribute.CraftAttribute;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public class UnmodifiableAttributeMap implements Attributable {
+
+    private final AttributeSupplier handle;
+
+    public UnmodifiableAttributeMap(@NotNull AttributeSupplier handle) {
+        this.handle = handle;
+    }
+
+    @Override
+    public @Nullable AttributeInstance getAttribute(@NotNull Attribute attribute) {
+        net.minecraft.core.Holder<net.minecraft.world.entity.ai.attributes.Attribute> nmsAttribute = CraftAttribute.bukkitToMinecraftHolder(attribute);
+        if (!this.handle.hasAttribute(nmsAttribute)) {
+            return null;
+        }
+        return new UnmodifiableAttributeInstance(this.handle.getAttributeInstance(nmsAttribute), attribute);
+    }
+
+    @Override
+    public void registerAttribute(@NotNull Attribute attribute) {
+        throw new UnsupportedOperationException("Cannot register new attributes here");
+    }
+}
diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
index bbe66459f29edf0c3de289a8b8a93e926323f82a..c9c18f0e1d7ccb2c7024ed60bf1ac99d30f0104d 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
@@ -570,6 +570,18 @@ public final class CraftMagicNumbers implements UnsafeValues {
     public int getProtocolVersion() {
         return net.minecraft.SharedConstants.getCurrentVersion().getProtocolVersion();
     }
+
+    @Override
+    public boolean hasDefaultEntityAttributes(NamespacedKey bukkitEntityKey) {
+        return net.minecraft.world.entity.ai.attributes.DefaultAttributes.hasSupplier(net.minecraft.core.registries.BuiltInRegistries.ENTITY_TYPE.get(CraftNamespacedKey.toMinecraft(bukkitEntityKey)));
+    }
+
+    @Override
+    public org.bukkit.attribute.Attributable getDefaultEntityAttributes(NamespacedKey bukkitEntityKey) {
+        Preconditions.checkArgument(hasDefaultEntityAttributes(bukkitEntityKey), bukkitEntityKey + " doesn't have default attributes");
+        var supplier = net.minecraft.world.entity.ai.attributes.DefaultAttributes.getSupplier((net.minecraft.world.entity.EntityType<? extends net.minecraft.world.entity.LivingEntity>) net.minecraft.core.registries.BuiltInRegistries.ENTITY_TYPE.get(CraftNamespacedKey.toMinecraft(bukkitEntityKey)));
+        return new io.papermc.paper.attribute.UnmodifiableAttributeMap(supplier);
+    }
     // Paper end
 
     /**
diff --git a/src/test/java/io/papermc/paper/attribute/EntityTypeAttributesTest.java b/src/test/java/io/papermc/paper/attribute/EntityTypeAttributesTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..e8cdfa385230d3de202122e4df5e07f61f80ce75
--- /dev/null
+++ b/src/test/java/io/papermc/paper/attribute/EntityTypeAttributesTest.java
@@ -0,0 +1,39 @@
+package io.papermc.paper.attribute;
+
+import org.bukkit.attribute.Attributable;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.attribute.AttributeInstance;
+import org.bukkit.attribute.AttributeModifier;
+import org.bukkit.entity.EntityType;
+import org.bukkit.support.AbstractTestingBase;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class EntityTypeAttributesTest extends AbstractTestingBase {
+
+    @Test
+    public void testIllegalEntity() {
+        assertFalse(EntityType.EGG.hasDefaultAttributes());
+        assertThrows(IllegalArgumentException.class, () -> EntityType.EGG.getDefaultAttributes());
+    }
+
+    @Test
+    public void testLegalEntity() {
+        assertTrue(EntityType.ZOMBIE.hasDefaultAttributes());
+        EntityType.ZOMBIE.getDefaultAttributes();
+    }
+
+    @Test
+    public void testUnmodifiabilityOfAttributable() {
+        Attributable attributable = EntityType.ZOMBIE.getDefaultAttributes();
+        assertThrows(UnsupportedOperationException.class, () -> attributable.registerAttribute(Attribute.GENERIC_ATTACK_DAMAGE));
+        AttributeInstance instance = attributable.getAttribute(Attribute.GENERIC_FOLLOW_RANGE);
+        assertNotNull(instance);
+        assertThrows(UnsupportedOperationException.class, () -> instance.addModifier(new AttributeModifier("test", 3, AttributeModifier.Operation.ADD_NUMBER)));
+        assertThrows(UnsupportedOperationException.class, () -> instance.setBaseValue(3.2));
+    }
+}