Add implementation for data watcher dedicated to hologram

nms/interface/src/main/java/de/epiceric/shopchest/nms/FakeArmorStand.java

@@ -0,0 +1,17 @@
+package de.epiceric.shopchest.nms;
+
+import org.bukkit.Location;
+
+public interface FakeArmorStand {
+
+    int getEntityId();
+
+    void sendData(String name);
+
+    void remove();
+
+    void setLocation(Location location);
+
+    void spawn();
+
+}

nms/interface/src/main/java/de/epiceric/shopchest/nms/Platform.java

@@ -0,0 +1,7 @@
+package de.epiceric.shopchest.nms;
+
+public interface Platform {
+
+    FakeArmorStand createFakeArmorStand();
+
+}

nms/v1_17_R1/pom.xml

@@ -23,6 +23,10 @@
             <artifactId>spigot</artifactId>
             <classifier>remapped-mojang</classifier>
         </dependency>
+        <dependency>
+            <groupId>de.epiceric</groupId>
+            <artifactId>shopchest-nms-interface</artifactId>
+        </dependency>
     </dependencies>
 
     <build>

nms/v1_17_R1/src/main/java/de/epiceric/shopchest/nms/v1_17_R1/FakeArmorStandImpl.java

@@ -0,0 +1,104 @@
+package de.epiceric.shopchest.nms.v1_17_R1;
+
+import de.epiceric.shopchest.nms.FakeArmorStand;
+import net.minecraft.network.chat.Component;
+import net.minecraft.network.protocol.game.ClientboundSetEntityDataPacket;
+import net.minecraft.network.syncher.EntityDataAccessor;
+import net.minecraft.network.syncher.SynchedEntityData;
+import net.minecraft.world.entity.Entity;
+import org.bukkit.Location;
+
+import java.lang.reflect.Field;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class FakeArmorStandImpl implements FakeArmorStand {
+
+    private final static byte INVISIBLE_FLAG = 0b100000;
+    private final static AtomicInteger ENTITY_COUNTER;
+    protected static final EntityDataAccessor<Byte> DATA_SHARED_FLAGS_ID;
+    private static final EntityDataAccessor<Boolean> DATA_NO_GRAVITY;
+    private static final EntityDataAccessor<Optional<Component>> DATA_CUSTOM_NAME;
+    private static final EntityDataAccessor<Boolean> DATA_CUSTOM_NAME_VISIBLE;
+    private static final EntityDataAccessor<Boolean> DATA_SILENT;
+    private final static Field packedItemField;
+
+    static {
+        try {
+            final Field entityCounterField = Entity.class.getDeclaredField("b"); // ENTITY_COUNTER
+            ENTITY_COUNTER = (AtomicInteger) entityCounterField.get(null);
+            final Field dataSharedFlagsId = Entity.class.getDeclaredField("Z"); // DATA_SHARED_FLAGS_ID
+            DATA_SHARED_FLAGS_ID = forceCast(dataSharedFlagsId.get(null));
+            final Field dataNoGravityField = Entity.class.getDeclaredField("aM"); // DATA_NO_GRAVITY
+            DATA_NO_GRAVITY = forceCast(dataNoGravityField.get(null));
+            final Field dataCustomNameField = Entity.class.getDeclaredField("aJ"); // DATA_CUSTOM_NAME
+            DATA_CUSTOM_NAME = forceCast(dataCustomNameField.get(null));
+            final Field dataCustomNameVisibleField = Entity.class.getDeclaredField("aK"); // DATA_CUSTOM_NAME_VISIBLE
+            DATA_CUSTOM_NAME_VISIBLE = forceCast(dataCustomNameVisibleField.get(null));
+            final Field dataSilentField = Entity.class.getDeclaredField("aL"); // DATA_SILENT
+            DATA_SILENT = forceCast(dataSilentField.get(null));
+            packedItemField = ClientboundSetEntityDataPacket.class.getDeclaredField("b"); // packedItems
+        } catch (ReflectiveOperationException e){
+            throw new RuntimeException(e);
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static <T> T forceCast(Object o){
+        return (T) o;
+    }
+
+    private final int entityId;
+
+    public FakeArmorStandImpl() {
+        entityId = ENTITY_COUNTER.incrementAndGet();
+    }
+
+    @Override
+    public int getEntityId() {
+        return entityId;
+    }
+
+    @Override
+    public void sendData(String name) {
+        // Create packet
+        final SynchedEntityData entityData = new SynchedEntityData(null);
+        final ClientboundSetEntityDataPacket dataPacket = new ClientboundSetEntityDataPacket(entityId, entityData, false);
+        final List<SynchedEntityData.DataItem<?>> packedItems = new ArrayList<>(5);
+
+        // Setup data
+        packedItems.add(new SynchedEntityData.DataItem<>(DATA_SHARED_FLAGS_ID, INVISIBLE_FLAG));
+        packedItems.add(new SynchedEntityData.DataItem<>(DATA_NO_GRAVITY, true));
+        packedItems.add(new SynchedEntityData.DataItem<>(DATA_CUSTOM_NAME, Optional.ofNullable(Component.Serializer.fromJson(
+                "" // TODO Use chat-api to serialize the name
+        ))));
+        packedItems.add(new SynchedEntityData.DataItem<>(DATA_CUSTOM_NAME_VISIBLE, true));
+        packedItems.add(new SynchedEntityData.DataItem<>(DATA_SILENT, true));
+
+        try {
+            packedItemField.set(dataPacket, packedItems);
+        } catch (IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+
+        // Send packet
+
+    }
+
+    @Override
+    public void remove() {
+
+    }
+
+    @Override
+    public void setLocation(Location location) {
+
+    }
+
+    @Override
+    public void spawn() {
+
+    }
+}

nms/v1_17_R1/src/main/java/de/epiceric/shopchest/nms/v1_17_R1/PlatformImpl.java

@@ -0,0 +1,13 @@
+package de.epiceric.shopchest.nms.v1_17_R1;
+
+import de.epiceric.shopchest.nms.FakeArmorStand;
+import de.epiceric.shopchest.nms.Platform;
+
+public class PlatformImpl implements Platform {
+
+    @Override
+    public FakeArmorStand createFakeArmorStand() {
+        return new FakeArmorStandImpl();
+    }
+
+}