Replace INT entityId with UUID, which is persistent and does not change between sessions.

src/client/java/com/owlmaddie/ClickHandler.java

@@ -20,6 +20,7 @@ import java.lang.reflect.Type;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Optional;
+import java.util.UUID;
 import java.util.stream.Collectors;
 
 
@@ -43,7 +44,7 @@ public class ClickHandler {
         // Client-side packet handler, message sync
         ClientPlayNetworking.registerGlobalReceiver(ModInit.PACKET_S2C_MESSAGE, (client, handler, buffer, responseSender) -> {
             // Read the data from the server packet
-            int entityId = buffer.readInt();
+            UUID entityId = UUID.fromString(buffer.readString());
             String message = buffer.readString(32767);
             int line = buffer.readInt();
             String status_name = buffer.readString(32767);
@@ -51,10 +52,10 @@ public class ClickHandler {
 
             // Update the chat data manager on the client-side
             client.execute(() -> { // Make sure to run on the client thread
-                Entity entity = client.world.getEntityById(entityId);
+                Entity entity = ClientEntityFinder.getEntityByUUID(client.world, entityId);
                 if (entity != null) {
                     ChatDataManager chatDataManager = ChatDataManager.getClientInstance();
-                    ChatDataManager.EntityChatData chatData = chatDataManager.getOrCreateChatData(entityId);
+                    ChatDataManager.EntityChatData chatData = chatDataManager.getOrCreateChatData(entity.getUuidAsString());
                     if (!message.isEmpty()) {
                         chatData.currentMessage = message;
                     }
@@ -75,7 +76,7 @@ public class ClickHandler {
             Gson GSON = new Gson();
             client.execute(() -> { // Make sure to run on the client thread
                 // Parse JSON and override client chat data
-                Type type = new TypeToken<HashMap<Integer, ChatDataManager.EntityChatData>>(){}.getType();
+                Type type = new TypeToken<HashMap<String, ChatDataManager.EntityChatData>>(){}.getType();
                 ChatDataManager.getClientInstance().entityChatDataMap = GSON.fromJson(chatDataJSON, type);
             });
         });
@@ -149,7 +150,7 @@ public class ClickHandler {
         // Handle the click for the closest entity after the loop
         if (closestEntity != null) {
             // Look-up conversation
-            ChatDataManager.EntityChatData chatData = ChatDataManager.getClientInstance().getOrCreateChatData(closestEntity.getId());
+            ChatDataManager.EntityChatData chatData = ChatDataManager.getClientInstance().getOrCreateChatData(closestEntity.getUuidAsString());
 
             if (chatData.status == ChatDataManager.ChatStatus.NONE) {
                 // Start conversation

src/client/java/com/owlmaddie/ClientEntityFinder.java

+package com.owlmaddie;
+
+import net.minecraft.entity.Entity;
+import net.minecraft.client.world.ClientWorld;
+import java.util.UUID;
+
+// Find Client Entity from UUID
+public class ClientEntityFinder {
+    public static Entity getEntityByUUID(ClientWorld world, UUID uuid) {
+        for (Entity entity : world.getEntities()) {
+            if (entity.getUuid().equals(uuid)) {
+                return entity;
+            }
+        }
+        return null; // Entity not found
+    }
+}

src/client/java/com/owlmaddie/ClientInit.java

@@ -173,7 +173,7 @@ public class ClientInit implements ClientModInitializer {
             }
 
             // Look-up greeting (if any)
-            ChatDataManager.EntityChatData chatData = ChatDataManager.getClientInstance().getOrCreateChatData(entity.getId());
+            ChatDataManager.EntityChatData chatData = ChatDataManager.getClientInstance().getOrCreateChatData(entity.getUuidAsString());
             List<String> lines = chatData.getWrappedLines();
 
             // Set the range of lines to display

src/client/java/com/owlmaddie/ModPackets.java

@@ -13,7 +13,7 @@ public class ModPackets {
 
     public static void sendGenerateGreeting(Entity entity) {
         PacketByteBuf buf = new PacketByteBuf(Unpooled.buffer());
-        buf.writeInt(entity.getId());
+        buf.writeString(entity.getUuidAsString());
 
         // Send C2S packet
         ClientPlayNetworking.send(ModInit.PACKET_C2S_GREETING, buf);
@@ -21,7 +21,7 @@ public class ModPackets {
 
     public static void sendUpdateLineNumber(Entity entity, Integer lineNumber) {
         PacketByteBuf buf = new PacketByteBuf(Unpooled.buffer());
-        buf.writeInt(entity.getId());
+        buf.writeString(entity.getUuidAsString());
         buf.writeInt(lineNumber);
 
         // Send C2S packet
@@ -30,7 +30,7 @@ public class ModPackets {
 
     public static void sendStartChat(Entity entity) {
         PacketByteBuf buf = new PacketByteBuf(Unpooled.buffer());
-        buf.writeInt(entity.getId());
+        buf.writeString(entity.getUuidAsString());
 
         // Send C2S packet
         ClientPlayNetworking.send(ModInit.PACKET_C2S_START_CHAT, buf);
@@ -38,7 +38,7 @@ public class ModPackets {
 
     public static void sendChat(Entity entity, String message) {
         PacketByteBuf buf = new PacketByteBuf(Unpooled.buffer());
-        buf.writeInt(entity.getId());
+        buf.writeString(entity.getUuidAsString());
         buf.writeString(message);
 
         // Send C2S packet

src/main/java/com/owlmaddie/ChatDataManager.java

@@ -6,10 +6,7 @@ import net.minecraft.item.ItemStack;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.util.WorldSavePath;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import com.google.gson.Gson;
@@ -46,7 +43,7 @@ public class ChatDataManager {
     }
 
     // HashMap to associate unique entity IDs with their chat data
-    public HashMap<Integer, EntityChatData> entityChatDataMap;
+    public HashMap<String, EntityChatData> entityChatDataMap;
 
     public static class ChatMessage {
         public String message;
@@ -60,7 +57,7 @@ public class ChatDataManager {
 
     // Inner class to hold entity-specific data
     public static class EntityChatData {
-        public int entityId;
+        public String entityId;
         public String currentMessage;
         public int currentLineNumber;
         public ChatStatus status;
@@ -68,7 +65,7 @@ public class ChatDataManager {
         public String characterSheet;
         public ChatSender sender;
 
-        public EntityChatData(int entityId) {
+        public EntityChatData(String entityId) {
             this.entityId = entityId;
             this.currentMessage = "";
             this.currentLineNumber = 0;
@@ -80,7 +77,7 @@ public class ChatDataManager {
 
         // Light version with no 'previousMessages' attribute
         public class EntityChatDataLight {
-            public int entityId;
+            public String entityId;
             public String currentMessage;
             public int currentLineNumber;
             public ChatStatus status;
@@ -138,7 +135,7 @@ public class ChatDataManager {
             contextData.put("world_time", String.format("%02d:%02d", hours, minutes));
 
             // Get Entity details
-            Entity entity = player.getServerWorld().getEntityById(entityId);
+            Entity entity = ServerEntityFinder.getEntityByUUID(player.getServerWorld(), UUID.fromString(entityId));
             if (entity.getCustomName() == null) {
                 contextData.put("entity_name", "Un-named");
             } else {
@@ -243,7 +240,7 @@ public class ChatDataManager {
     }
 
     // Retrieve chat data for a specific entity, or create it if it doesn't exist
-    public EntityChatData getOrCreateChatData(int entityId) {
+    public EntityChatData getOrCreateChatData(String entityId) {
         return entityChatDataMap.computeIfAbsent(entityId, k -> new EntityChatData(entityId));
     }
 
@@ -284,7 +281,7 @@ public class ChatDataManager {
     public String GetLightChatData() {
         try {
             // Create "light" version of entire chat data HashMap
-            HashMap<Integer, EntityChatData.EntityChatDataLight> lightVersionMap = new HashMap<>();
+            HashMap<String, EntityChatData.EntityChatDataLight> lightVersionMap = new HashMap<>();
             this.entityChatDataMap.forEach((id, entityChatData) -> lightVersionMap.put(id, entityChatData.toLightVersion()));
 
             // Convert light chat data to JSON string
@@ -314,7 +311,7 @@ public class ChatDataManager {
             File loadFile = new File(server.getSavePath(WorldSavePath.ROOT).toFile(), "chatdata.json");
             LOGGER.info("Load chat data from " + loadFile.getAbsolutePath());
             if (loadFile.exists()) {
-                Type type = new TypeToken<HashMap<Integer, EntityChatData>>(){}.getType();
+                Type type = new TypeToken<HashMap<String, EntityChatData>>(){}.getType();
                 try (FileReader reader = new FileReader(loadFile)) {
                     this.entityChatDataMap = GSON.fromJson(reader, type);
                 }

src/main/java/com/owlmaddie/ModInit.java

@@ -17,6 +17,8 @@ import net.minecraft.util.Identifier;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.UUID;
+
 
 public class ModInit implements ModInitializer {
     public static final Logger LOGGER = LoggerFactory.getLogger("mobgpt");
@@ -36,16 +38,16 @@ public class ModInit implements ModInitializer {
 
 		// Handle packet for Greeting
 		ServerPlayNetworking.registerGlobalReceiver(PACKET_C2S_GREETING, (server, player, handler, buf, responseSender) -> {
-			int entityId = buf.readInt();
+			UUID entityId = UUID.fromString(buf.readString());
 
 			// Ensure that the task is synced with the server thread
 			server.execute(() -> {
-				Entity entity = player.getServerWorld().getEntityById(entityId);
+				Entity entity = ServerEntityFinder.getEntityByUUID(player.getServerWorld(), entityId);
 				if (entity != null) {
 					// Slow entity
 					SlowEntity((LivingEntity) entity, 3.5F);
 
-					ChatDataManager.EntityChatData chatData = ChatDataManager.getServerInstance().getOrCreateChatData(entityId);
+					ChatDataManager.EntityChatData chatData = ChatDataManager.getServerInstance().getOrCreateChatData(entity.getUuidAsString());
 					if (chatData.status == ChatDataManager.ChatStatus.NONE ||
 							chatData.status == ChatDataManager.ChatStatus.END) {
 						// Only generate a new greeting if not already doing so
@@ -60,17 +62,17 @@ public class ModInit implements ModInitializer {
 
 		// Handle packet for reading lines of message
 		ServerPlayNetworking.registerGlobalReceiver(PACKET_C2S_READ_NEXT, (server, player, handler, buf, responseSender) -> {
-			int entityId = buf.readInt();
+			UUID entityId = UUID.fromString(buf.readString());
 			int lineNumber = buf.readInt();
 
 			// Ensure that the task is synced with the server thread
 			server.execute(() -> {
-				Entity entity = player.getServerWorld().getEntityById(entityId);
+				Entity entity = ServerEntityFinder.getEntityByUUID(player.getServerWorld(), entityId);
 				if (entity != null) {
 					// Slow entity
 					SlowEntity((LivingEntity) entity, 3.5F);
 
-					ChatDataManager.EntityChatData chatData = ChatDataManager.getServerInstance().getOrCreateChatData(entityId);
+					ChatDataManager.EntityChatData chatData = ChatDataManager.getServerInstance().getOrCreateChatData(entity.getUuidAsString());
 					if (chatData.status == ChatDataManager.ChatStatus.DISPLAY) {
 						// Only set line number if status allows
 						LOGGER.info("Increment read lines to " + lineNumber + " for: " + entity.getType().toString());
@@ -82,11 +84,11 @@ public class ModInit implements ModInitializer {
 
 		// Handle packet for Start Chat
 		ServerPlayNetworking.registerGlobalReceiver(PACKET_C2S_START_CHAT, (server, player, handler, buf, responseSender) -> {
-			int entityId = buf.readInt();
+			UUID entityId = UUID.fromString(buf.readString());
 
 			// Ensure that the task is synced with the server thread
 			server.execute(() -> {
-				Entity entity = player.getServerWorld().getEntityById(entityId);
+				Entity entity = ServerEntityFinder.getEntityByUUID(player.getServerWorld(), entityId);
 				if (entity != null) {
 					// Slow entity, so it does NOT walk away during player typing
 					SlowEntity((LivingEntity) entity, 7F);
@@ -96,17 +98,17 @@ public class ModInit implements ModInitializer {
 
 		// Handle packet for new chat message
 		ServerPlayNetworking.registerGlobalReceiver(PACKET_C2S_SEND_CHAT, (server, player, handler, buf, responseSender) -> {
-			int entityId = buf.readInt();
+			UUID entityId = UUID.fromString(buf.readString());
 			String message = buf.readString(32767);
 
 			// Ensure that the task is synced with the server thread
 			server.execute(() -> {
-				Entity entity = player.getServerWorld().getEntityById(entityId);
+				Entity entity = ServerEntityFinder.getEntityByUUID(player.getServerWorld(), entityId);
 				if (entity != null) {
 					// Slow entity
 					SlowEntity((LivingEntity) entity, 3.5F);
 
-					ChatDataManager.EntityChatData chatData = ChatDataManager.getServerInstance().getOrCreateChatData(entityId);
+					ChatDataManager.EntityChatData chatData = ChatDataManager.getServerInstance().getOrCreateChatData(entity.getUuidAsString());
 					if (chatData.status == ChatDataManager.ChatStatus.END) {
 						// Add new message
 						LOGGER.info("Add new message (" + message + ") to Entity: " + entity.getType().toString());
@@ -152,12 +154,13 @@ public class ModInit implements ModInitializer {
 	// Send new message to all connected players
 	public static void BroadcastPacketMessage(ChatDataManager.EntityChatData chatData) {
 		for (ServerWorld world : serverInstance.getWorlds()) {
-			Entity entity = world.getEntityById(chatData.entityId);
+			UUID entityId = UUID.fromString(chatData.entityId);
+			Entity entity = ServerEntityFinder.getEntityByUUID(world, entityId);
 			if (entity != null) {
 				PacketByteBuf buffer = new PacketByteBuf(Unpooled.buffer());
 
 				// Write the entity's chat updated data
-				buffer.writeInt(entity.getId());
+				buffer.writeString(entity.getUuidAsString());
 				buffer.writeString(chatData.currentMessage);
 				buffer.writeInt(chatData.currentLineNumber);
 				buffer.writeString(chatData.status.toString());

src/main/java/com/owlmaddie/ServerEntityFinder.java

+package com.owlmaddie;
+
+import net.minecraft.entity.Entity;
+import net.minecraft.server.world.ServerWorld;
+import java.util.UUID;
+
+// Find Server Entity from UUID
+public class ServerEntityFinder {
+    public static Entity getEntityByUUID(ServerWorld world, UUID uuid) {
+        for (Entity entity : world.iterateEntities()) {
+            if (entity.getUuid().equals(uuid)) {
+                return entity;
+            }
+        }
+        return null; // Entity not found
+    }
+}
\ No newline at end of file