feat(player): represents custom data

3 files changed, 143 insertions, 13 deletions

diff --git a/LICENSE.txt b/LICENSE
index 313e689..9718cb2 100644..100755
--- a/LICENSE.txt
+++ b/LICENSE
@@ -1,19 +1,7 @@
-Copyright (c) 2025 
-
-This program is free software: you can redistribute it and/or modify
-it under the terms of the GNU Affero General Public License as published by
-the Free Software Foundation, version 3 of the License, or
-(at your option) any later version.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU Affero General Public License for more details.
-
                     GNU AFFERO GENERAL PUBLIC LICENSE
                        Version 3, 19 November 2007
 
- Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
  Everyone is permitted to copy and distribute verbatim copies
  of this license document, but changing it is not allowed.
 
@@ -629,3 +617,44 @@ Program, unless a warranty or assumption of liability accompanies a
 copy of the Program in return for a fee.
 
                      END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    LifeSteal Copyright (C) <no value>  William Hergès
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<https://www.gnu.org/licenses/>.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e2f233a
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# LifeSteal
+
+LifeSteal is a server-side mod recreating the LifeSteal SMP experience.
diff --git a/src/main/java/world/anhgelus/lifesteal/LifeStealer.java b/src/main/java/world/anhgelus/lifesteal/LifeStealer.java
new file mode 100644
index 0000000..86410de
--- /dev/null
+++ b/src/main/java/world/anhgelus/lifesteal/LifeStealer.java
@@ -0,0 +1,98 @@
+package world.anhgelus.lifesteal;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import net.minecraft.component.DataComponentTypes;
+import net.minecraft.component.type.NbtComponent;
+import net.minecraft.entity.attribute.EntityAttributeModifier;
+import net.minecraft.entity.attribute.EntityAttributes;
+import net.minecraft.item.ItemStack;
+import net.minecraft.item.Items;
+import net.minecraft.nbt.NbtCompound;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.util.Identifier;
+import net.minecraft.util.math.MathHelper;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+
+public class LifeStealer {
+    public static final Identifier HEALTH_MODIFIER = Identifier.of(LifeSteal.MOD_ID, "health_modifier");
+    public static final String PLAYER_KEY = "player";
+
+    private ServerPlayerEntity player;
+    private final UUID uuid;
+    private float healthModifier;
+
+    public LifeStealer(ServerPlayerEntity player, Data data) {
+        this.player = player;
+        this.uuid = player.getUuid();
+        this.healthModifier = data.healthModifier();
+    }
+
+    private void updateHealth() {
+        healthModifier = MathHelper.clamp(healthModifier, -20, 20);
+        final var attr = player.getAttributeInstance(EntityAttributes.MAX_HEALTH);
+        if (attr == null) throw new IllegalStateException("No health attribute assigned to LifeStealer");
+        if (attr.hasModifier(HEALTH_MODIFIER)) attr.removeModifier(HEALTH_MODIFIER);
+        final var modifier = new EntityAttributeModifier(HEALTH_MODIFIER, healthModifier, EntityAttributeModifier.Operation.ADD_VALUE);
+        attr.addTemporaryModifier(modifier);
+    }
+
+    public ItemStack getHeart() {
+        final var nbt = new NbtCompound();
+        nbt.putString(PLAYER_KEY, player.getUuid().toString());
+        final var is = new ItemStack(Items.NETHER_STAR);
+        is.set(DataComponentTypes.CUSTOM_NAME, player.getName());
+        is.set(DataComponentTypes.CUSTOM_DATA, NbtComponent.of(nbt));
+        return is;
+    }
+
+    public void respawn(ServerPlayerEntity newPlayer) {
+        if (!newPlayer.getUuid().equals(uuid)) throw new IllegalArgumentException("Player does not have the same UUID");
+        this.player = newPlayer;
+        updateHealth();
+    }
+
+    public void kill() {
+        healthModifier = MathHelper.clamp(healthModifier + 2, -20, 20);
+        updateHealth();
+    }
+
+    public void killed() {
+        healthModifier = MathHelper.clamp(healthModifier - 2, -20, 20);
+        if (healthModifier <= 0) {
+            //TODO: ban player
+            return;
+        }
+        updateHealth();
+    }
+
+    public float getHealthModifier() {
+        return healthModifier;
+    }
+
+    public record Data(float healthModifier) {
+        public final static String HEALTH_MODIFIER_KEY = "health_modifier";
+        public static final Codec<Data> CODEC = RecordCodecBuilder.create(i -> i.group(
+                Codec.FLOAT.fieldOf(HEALTH_MODIFIER_KEY).forGetter(Data::healthModifier)
+        ).apply(i, Data::new));
+
+        public static Data DEFAULT = new Data(0.0F);
+    }
+
+    public static class Manager {
+        private static final Map<UUID, LifeStealer> players = new HashMap<>();
+
+        public static LifeStealer getLifeStealer(ServerPlayerEntity player) {
+            return players.computeIfAbsent(player.getUuid(), k -> new LifeStealer(player, Data.DEFAULT));
+        }
+
+        @Nullable
+        public static LifeStealer getLifeStealer(UUID uuid) {
+            return players.get(uuid);
+        }
+    }
+}