Implement attribute instances

src/main/java/net/minestom/server/attribute/Attribute.java

@@ -1,53 +1,69 @@
 package net.minestom.server.attribute;
 
+import java.util.HashMap;
+import java.util.Map;
+
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-public enum Attribute {
+public class Attribute {
 
-    MAX_HEALTH("generic.max_health", 20, 1024),
+	private static final Map<String, Attribute> ATTRIBUTES = new HashMap<>();
-    FOLLOW_RANGE("generic.follow_range", 32, 2048),
-    KNOCKBACK_RESISTANCE("generic.knockback_resistance", 0, 1),
-    MOVEMENT_SPEED("generic.movement_speed", 0.25f, 1024),
-    ATTACK_DAMAGE("generic.attack_damage", 2, 2048),
-    ATTACK_SPEED("generic.attack_speed", 4, 1024),
-    FLYING_SPEED("generic.flying_speed", 0.4f, 1024),
-    ARMOR("generic.armor", 0, 30),
-    ARMOR_TOUGHNESS("generic.armor_toughness", 0, 20),
-    ATTACK_KNOCKBACK("generic.attack_knockback", 0, 5),
-    LUCK("generic.luck", 0, 1024),
-    HORSE_JUMP_STRENGTH("horse.jump_strength", 0.7f, 2),
-    ZOMBIE_SPAWN_REINFORCEMENTS("zombie.spawn_reinforcements", 0, 1);
 
-    private final String key;
+	private final String key;
-    private final float defaultValue;
+	private final float defaultValue;
-    private final float maxVanillaValue;
+	private final float maxValue;
+	private final boolean shareWithClient;
 
-    Attribute(@NotNull String key, float defaultValue, float maxVanillaValue) {
+	public Attribute(@NotNull String key, float defaultValue, float maxValue) {
-        this.key = key;
+		this(key, false, defaultValue, maxValue);
-        this.defaultValue = defaultValue;
+	}
-        this.maxVanillaValue = maxVanillaValue;
-    }
 
-    @NotNull
+	public Attribute(@NotNull String key, boolean shareWithClient, float defaultValue, float maxValue) {
-    public String getKey() {
+		if (defaultValue > maxValue) {
-        return key;
+			throw new IllegalArgumentException("Default value cannot be greater than the maximum allowed");
-    }
+		}
+		this.key = key;
+		this.shareWithClient = shareWithClient;
+		this.defaultValue = defaultValue;
+		this.maxValue = maxValue;
+	}
 
-    public float getDefaultValue() {
+	@NotNull
-        return defaultValue;
+	public String getKey() {
-    }
+		return key;
+	}
 
-    public float getMaxVanillaValue() {
+	public float getDefaultValue() {
-        return maxVanillaValue;
+		return defaultValue;
-    }
+	}
 
-    @Nullable
+	public float getMaxValue() {
-    public static Attribute fromKey(@NotNull String key) {
+		return maxValue;
-        for (Attribute attribute : values()) {
+	}
-            if (attribute.getKey().equals(key))
+
-                return attribute;
+	public boolean isShared() {
-        }
+		return shareWithClient;
-        return null;
+	}
-    }
+
+	@NotNull
+	public Attribute register() {
+		ATTRIBUTES.put(key, this);
+		return this;
+	}
+
+	@Nullable
+	public static Attribute fromKey(@NotNull String key) {
+		return ATTRIBUTES.get(key);
+	}
+
+	@NotNull
+	public static Attribute[] values() {
+		return ATTRIBUTES.values().toArray(new Attribute[0]);
+	}
+
+	@NotNull
+	public static Attribute[] sharedAttributes() {
+		return ATTRIBUTES.values().stream().filter(Attribute::isShared).toArray(Attribute[]::new);
+	}
 }

src/main/java/net/minestom/server/attribute/AttributeInstance.java

@@ -0,0 +1,94 @@
+package net.minestom.server.attribute;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.util.function.Consumer;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public class AttributeInstance {
+
+	private final Attribute attribute;
+	private final Map<UUID, AttributeModifier> modifiers = new HashMap<>();
+	private final Consumer<AttributeInstance> propertyChangeListener;
+	private float baseValue;
+	private boolean dirty = true;
+	private float cachedValue = 0.0f;
+
+	public AttributeInstance(@NotNull Attribute attribute, @Nullable Consumer<AttributeInstance> listener) {
+		this.attribute = attribute;
+		this.propertyChangeListener = listener;
+		this.baseValue = attribute.getDefaultValue();
+	}
+
+	@NotNull
+	public Attribute getAttribute() {
+		return attribute;
+	}
+
+	public float getBaseValue() {
+		return baseValue;
+	}
+
+	private void setDirty() {
+		if (!dirty) {
+			dirty = true;
+			if (propertyChangeListener != null) {
+				propertyChangeListener.accept(this);
+			}
+		}
+	}
+
+	public void setBaseValue(float baseValue) {
+		if (this.baseValue != baseValue) {
+			this.baseValue = baseValue;
+			setDirty();
+		}
+	}
+
+	public void addModifier(@NotNull AttributeModifier modifier) {
+		if (modifiers.putIfAbsent(modifier.getId(), modifier) == null) {
+			setDirty();
+		}
+	}
+
+	public void removeModifier(@NotNull AttributeModifier modifier) {
+		if (modifiers.remove(modifier.getId()) != null) {
+			setDirty();
+		}
+	}
+
+	public Collection<AttributeModifier> getModifiers() {
+		return modifiers.values();
+	}
+
+	public float getValue() {
+		if (dirty) {
+			cachedValue = processModifiers();
+			dirty = false;
+		}
+		return cachedValue;
+	}
+
+	protected float processModifiers() {
+		float base = getBaseValue();
+
+		for (var modifier : modifiers.values().stream().filter(mod -> mod.getOperation() == AttributeOperation.ADDITION).toArray(AttributeModifier[]::new)) {
+			base += modifier.getAmount();
+		}
+
+		float result = base;
+
+		for (var modifier : modifiers.values().stream().filter(mod -> mod.getOperation() == AttributeOperation.MULTIPLY_BASE).toArray(AttributeModifier[]::new)) {
+			result += (base * modifier.getAmount());
+		}
+		for (var modifier : modifiers.values().stream().filter(mod -> mod.getOperation() == AttributeOperation.MULTIPLY_TOTAL).toArray(AttributeModifier[]::new)) {
+			result *= (1.0f + modifier.getAmount());
+		}
+
+		return Math.min(result, getAttribute().getMaxValue());
+	}
+}

src/main/java/net/minestom/server/attribute/AttributeModifier.java

@@ -0,0 +1,45 @@
+package net.minestom.server.attribute;
+
+import java.util.UUID;
+
+import io.netty.util.internal.ThreadLocalRandom;
+import net.minestom.server.utils.UniqueIdUtils;
+import org.jetbrains.annotations.NotNull;
+
+public class AttributeModifier {
+
+	private final float amount;
+	private final String name;
+	private final AttributeOperation operation;
+	private final UUID id;
+
+	public AttributeModifier(@NotNull String name, float amount, @NotNull AttributeOperation operation) {
+		this(UniqueIdUtils.createRandomUUID(ThreadLocalRandom.current()), name, amount, operation);
+	}
+
+	public AttributeModifier(@NotNull UUID id, @NotNull String name, float amount, @NotNull AttributeOperation operation) {
+		this.id = id;
+		this.name = name;
+		this.amount = amount;
+		this.operation = operation;
+	}
+
+	@NotNull
+	public UUID getId() {
+		return id;
+	}
+
+	@NotNull
+	public String getName() {
+		return name;
+	}
+
+	public float getAmount() {
+		return amount;
+	}
+
+	@NotNull
+	public AttributeOperation getOperation() {
+		return operation;
+	}
+}

src/main/java/net/minestom/server/attribute/Attributes.java

@@ -0,0 +1,18 @@
+package net.minestom.server.attribute;
+
+public final class Attributes
+{
+    public static final Attribute MAX_HEALTH = (new Attribute("generic.max_health", true, 20, 1024)).register();
+    public static final Attribute FOLLOW_RANGE = (new Attribute("generic.follow_range", true, 32, 2048)).register();
+    public static final Attribute KNOCKBACK_RESISTANCE = (new Attribute("generic.knockback_resistance", true, 0, 1)).register();
+    public static final Attribute MOVEMENT_SPEED = (new Attribute("generic.movement_speed", true, 0.25f, 1024)).register();
+    public static final Attribute ATTACK_DAMAGE = (new Attribute("generic.attack_damage", true, 2, 2048)).register();
+    public static final Attribute ATTACK_SPEED = (new Attribute("generic.attack_speed", true, 4, 1024)).register();
+    public static final Attribute FLYING_SPEED = (new Attribute("generic.flying_speed", true, 0.4f, 1024)).register();
+    public static final Attribute ARMOR = (new Attribute("generic.armor", true, 0, 30)).register();
+    public static final Attribute ARMOR_TOUGHNESS = (new Attribute("generic.armor_toughness", true, 0, 20)).register();
+    public static final Attribute ATTACK_KNOCKBACK = (new Attribute("generic.attack_knockback", true, 0, 5)).register();
+    public static final Attribute LUCK = (new Attribute("generic.luck", true, 0, 1024)).register();
+    public static final Attribute HORSE_JUMP_STRENGTH = (new Attribute("horse.jump_strength", true, 0.7f, 2)).register();
+    public static final Attribute ZOMBIE_SPAWN_REINFORCEMENTS = (new Attribute("zombie.spawn_reinforcements", true, 0, 1)).register();
+}

src/main/java/net/minestom/server/entity/EntityCreature.java

@@ -3,7 +3,7 @@ package net.minestom.server.entity;
 import com.extollit.gaming.ai.path.HydrazinePathFinder;
 import com.extollit.gaming.ai.path.model.IPath;
 import net.minestom.server.MinecraftServer;
-import net.minestom.server.attribute.Attribute;
+import net.minestom.server.attribute.Attributes;
 import net.minestom.server.entity.ai.GoalSelector;
 import net.minestom.server.entity.ai.TargetSelector;
 import net.minestom.server.entity.pathfinding.PFPathingEntity;
@@ -134,7 +134,7 @@ public abstract class EntityCreature extends LivingEntity {
                 this.path = pathFinder.updatePathFor(pathingEntity);
 
                 if (path != null) {
-                    final float speed = getAttributeValue(Attribute.MOVEMENT_SPEED);
+                    final float speed = getAttributeValue(Attributes.MOVEMENT_SPEED);
                     final Position targetPosition = pathingEntity.getTargetPosition();
                     moveTowards(targetPosition, speed);
                 } else {

src/main/java/net/minestom/server/entity/LivingEntity.java

@@ -1,6 +1,8 @@
 package net.minestom.server.entity;
 
 import net.minestom.server.attribute.Attribute;
+import net.minestom.server.attribute.AttributeInstance;
+import net.minestom.server.attribute.Attributes;
 import net.minestom.server.collision.BoundingBox;
 import net.minestom.server.entity.damage.DamageType;
 import net.minestom.server.event.entity.EntityDamageEvent;
@@ -26,9 +28,12 @@ import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.HashMap;
+import java.util.Map;
 import java.util.Set;
 import java.util.function.Consumer;
 
+//TODO: Default attributes registration (and limitation ?)
 public abstract class LivingEntity extends Entity implements EquipmentHandler {
 
     // Item pickup
@@ -44,7 +49,7 @@ public abstract class LivingEntity extends Entity implements EquipmentHandler {
     // Bounding box used for items' pickup (see LivingEntity#setBoundingBox)
     protected BoundingBox expandedBoundingBox;
 
-    private final float[] attributeValues = new float[Attribute.values().length];
+    private final Map<String, AttributeInstance> attributeModifiers = new HashMap<>(Attribute.values().length);
 
     private boolean isHandActive;
     private boolean offHand;
@@ -369,41 +374,48 @@ public abstract class LivingEntity extends Entity implements EquipmentHandler {
     }
 
     /**
-     * Gets the entity max health from {@link #getAttributeValue(Attribute)} {@link Attribute#MAX_HEALTH}.
+     * Gets the entity max health from {@link #getAttributeValue(Attribute)} {@link Attributes#MAX_HEALTH}.
      *
      * @return the entity max health
      */
     public float getMaxHealth() {
-        return getAttributeValue(Attribute.MAX_HEALTH);
+        return getAttributeValue(Attributes.MAX_HEALTH);
     }
 
     /**
      * Sets the heal of the entity as its max health.
      * <p>
-     * Retrieved from {@link #getAttributeValue(Attribute)} with the attribute {@link Attribute#MAX_HEALTH}.
+     * Retrieved from {@link #getAttributeValue(Attribute)} with the attribute {@link Attributes#MAX_HEALTH}.
      */
     public void heal() {
-        setHealth(getAttributeValue(Attribute.MAX_HEALTH));
+        setHealth(getAttributeValue(Attributes.MAX_HEALTH));
     }
 
     /**
-     * Changes the specified attribute value to {@code value}.
+     * Retrieves the attribute instance and its modifiers.
      *
-     * @param attribute The attribute to change
+     * @param attribute the attribute instance to get
-     * @param value     the new value of the attribute
+     * @return the attribute instance
      */
-    public void setAttribute(@NotNull Attribute attribute, float value) {
+    @NotNull
-        this.attributeValues[attribute.ordinal()] = value;
+    public AttributeInstance getAttribute(@NotNull Attribute attribute) {
+        if (!attributeModifiers.containsKey(attribute.getKey())) {
+            attributeModifiers.put(attribute.getKey(), new AttributeInstance(attribute, this::onAttributeChanged));
+        }
+        return attributeModifiers.get(attribute.getKey());
     }
 
+    protected void onAttributeChanged(@NotNull AttributeInstance instance) { }
+
     /**
-     * Retrieves the attribute value set by {@link #setAttribute(Attribute, float)}.
+     * Retrieves the attribute value.
      *
      * @param attribute the attribute value to get
      * @return the attribute value
      */
     public float getAttributeValue(@NotNull Attribute attribute) {
-        return this.attributeValues[attribute.ordinal()];
+        AttributeInstance instance = attributeModifiers.get(attribute.getKey());
+        return (instance != null) ? instance.getValue() : attribute.getDefaultValue();
     }
 
     /**
@@ -488,15 +500,16 @@ public abstract class LivingEntity extends Entity implements EquipmentHandler {
         EntityPropertiesPacket propertiesPacket = new EntityPropertiesPacket();
         propertiesPacket.entityId = getEntityId();
 
-        final int length = Attribute.values().length;
+        AttributeInstance[] instances = attributeModifiers.values().stream()
-        EntityPropertiesPacket.Property[] properties = new EntityPropertiesPacket.Property[length];
+                .filter(i -> i.getAttribute().isShared())
-        for (int i = 0; i < length; i++) {
+                .toArray(AttributeInstance[]::new);
+        EntityPropertiesPacket.Property[] properties = new EntityPropertiesPacket.Property[instances.length];
+        for (int i = 0; i < properties.length; ++i) {
             EntityPropertiesPacket.Property property = new EntityPropertiesPacket.Property();
 
-            final Attribute attribute = Attribute.values()[i];
+            final float value = instances[i].getBaseValue();
-            final float value = getAttributeValue(attribute);
 
-            property.attribute = attribute;
+            property.attribute = instances[i].getAttribute();
             property.value = value;
 
             properties[i] = property;
@@ -511,7 +524,7 @@ public abstract class LivingEntity extends Entity implements EquipmentHandler {
      */
     private void setupAttributes() {
         for (Attribute attribute : Attribute.values()) {
-            setAttribute(attribute, attribute.getDefaultValue());
+            attributeModifiers.put(attribute.getKey(), new AttributeInstance(attribute, this::onAttributeChanged));
         }
     }
 

src/main/java/net/minestom/server/entity/Player.java

@@ -3,6 +3,8 @@ package net.minestom.server.entity;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.advancements.AdvancementTab;
 import net.minestom.server.attribute.Attribute;
+import net.minestom.server.attribute.AttributeInstance;
+import net.minestom.server.attribute.Attributes;
 import net.minestom.server.bossbar.BossBar;
 import net.minestom.server.chat.ChatParser;
 import net.minestom.server.chat.ColoredText;
@@ -288,7 +290,7 @@ public class Player extends LivingEntity implements CommandSender {
 
     @Override
     public float getAttributeValue(@NotNull Attribute attribute) {
-        if (attribute == Attribute.MOVEMENT_SPEED) {
+        if (attribute == Attributes.MOVEMENT_SPEED) {
             return walkingSpeed;
         }
         return super.getAttributeValue(attribute);
@@ -1020,9 +1022,8 @@ public class Player extends LivingEntity implements CommandSender {
     }
 
     @Override
-    public void setAttribute(@NotNull Attribute attribute, float value) {
+    protected void onAttributeChanged(@NotNull final AttributeInstance instance) {
-        super.setAttribute(attribute, value);
+        if (instance.getAttribute().isShared() && playerConnection != null)
-        if (playerConnection != null)
             playerConnection.sendPacket(getPropertiesPacket());
     }
 

src/main/java/net/minestom/server/entity/pathfinding/PFPathingEntity.java

@@ -4,7 +4,7 @@ import com.extollit.gaming.ai.path.model.Gravitation;
 import com.extollit.gaming.ai.path.model.IPathingEntity;
 import com.extollit.gaming.ai.path.model.Passibility;
 import com.extollit.linalg.immutable.Vec3d;
-import net.minestom.server.attribute.Attribute;
+import net.minestom.server.attribute.Attributes;
 import net.minestom.server.entity.EntityCreature;
 import net.minestom.server.utils.Position;
 
@@ -26,7 +26,7 @@ public class PFPathingEntity implements IPathingEntity {
 
     public PFPathingEntity(EntityCreature entity) {
         this.entity = entity;
-        this.searchRange = entity.getAttributeValue(Attribute.FOLLOW_RANGE);
+        this.searchRange = entity.getAttributeValue(Attributes.FOLLOW_RANGE);
     }
 
     public Position getTargetPosition() {
@@ -113,7 +113,7 @@ public class PFPathingEntity implements IPathingEntity {
         return new Capabilities() {
             @Override
             public float speed() {
-                return entity.getAttributeValue(Attribute.MOVEMENT_SPEED);
+                return entity.getAttributeValue(Attributes.MOVEMENT_SPEED);
             }
 
             @Override

src/main/java/net/minestom/server/network/packet/server/play/EntityPropertiesPacket.java

@@ -1,6 +1,10 @@
 package net.minestom.server.network.packet.server.play;
 
+import java.util.Collection;
+
 import net.minestom.server.attribute.Attribute;
+import net.minestom.server.attribute.AttributeInstance;
+import net.minestom.server.attribute.AttributeModifier;
 import net.minestom.server.network.packet.server.ServerPacket;
 import net.minestom.server.network.packet.server.ServerPacketIdentifier;
 import net.minestom.server.utils.binary.BinaryWriter;
@@ -30,9 +34,14 @@ public class EntityPropertiesPacket implements ServerPacket {
 
         public Attribute attribute;
         public double value;
+        public AttributeInstance instance;
 
         private void write(BinaryWriter writer) {
-            float maxValue = attribute.getMaxVanillaValue();
+            if (instance != null) {
+                attribute = instance.getAttribute();
+                value = instance.getBaseValue();
+            }
+            float maxValue = attribute.getMaxValue();
 
             // Bypass vanilla limit client-side if needed (by sending the max value allowed)
             final double v = value > maxValue ? maxValue : value;
@@ -40,8 +49,16 @@ public class EntityPropertiesPacket implements ServerPacket {
             writer.writeSizedString(attribute.getKey());
             writer.writeDouble(v);
 
-            // TODO support for AttributeOperation
+            {
-            writer.writeVarInt(0);
+                Collection<AttributeModifier> modifiers = instance.getModifiers();
+                writer.writeVarInt(modifiers.size());
+
+                for (var modifier : modifiers) {
+                    writer.writeUuid(modifier.getId());
+                    writer.writeDouble(modifier.getAmount());
+                    writer.writeByte((byte) modifier.getOperation().getId());
+                }
+            }
         }
     }
 

src/main/java/net/minestom/server/utils/UniqueIdUtils.java

@@ -1,5 +1,6 @@
 package net.minestom.server.utils;
 
+import java.util.Random;
 import java.util.UUID;
 import java.util.regex.Pattern;
 
@@ -20,4 +21,11 @@ public final class UniqueIdUtils {
         return input.matches(UNIQUE_ID_PATTERN.pattern());
     }
 
+    public static UUID createRandomUUID(Random random) {
+        long most = random.nextLong() & -61441L | 16384L;
+        long least = random.nextLong() & 4611686018427387903L | Long.MAX_VALUE;
+
+        return new UUID(most, least);
+    }
+
 }

src/test/java/demo/entity/ChickenCreature.java

@@ -1,6 +1,6 @@
 package demo.entity;
 
-import net.minestom.server.attribute.Attribute;
+import net.minestom.server.attribute.Attributes;
 import net.minestom.server.entity.LivingEntity;
 import net.minestom.server.entity.ai.goal.RandomStrollGoal;
 import net.minestom.server.entity.damage.DamageType;
@@ -37,7 +37,7 @@ public class ChickenCreature extends EntityChicken {
         //targetSelectors.add(new ClosestEntityTarget(this, 15, LivingEntity.class));
 
 
-        setAttribute(Attribute.MOVEMENT_SPEED, 0.1f);
+        getAttribute(Attributes.MOVEMENT_SPEED).setBaseValue(0.1f);
 
         addEventCallback(EntityAttackEvent.class, event -> {
             //System.out.println("CALL ATTACK");