first commit

backend/src/main/java/com/xuezhanmaster/ws/service/GameMessagePublisher.java

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+package com.xuezhanmaster.ws.service;
+
+import com.xuezhanmaster.game.event.GameEvent;
+import com.xuezhanmaster.ws.dto.PrivateActionMessage;
+import com.xuezhanmaster.ws.dto.PrivateTeachingMessage;
+import com.xuezhanmaster.ws.dto.PublicGameMessage;
+import org.springframework.messaging.simp.SimpMessagingTemplate;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+
+@Service
+public class GameMessagePublisher {
+
+    private final SimpMessagingTemplate messagingTemplate;
+
+    public GameMessagePublisher(SimpMessagingTemplate messagingTemplate) {
+        this.messagingTemplate = messagingTemplate;
+    }
+
+    public void publishPublicEvent(GameEvent event) {
+        messagingTemplate.convertAndSend(
+                "/topic/games/" + event.gameId() + "/events",
+                new PublicGameMessage(
+                        event.gameId(),
+                        event.eventType().name(),
+                        event.seatNo(),
+                        event.payload(),
+                        event.createdAt()
+                )
+        );
+    }
+
+    public void publishPrivateActionRequired(String gameId, String userId, List<String> availableActions, int currentSeatNo) {
+        messagingTemplate.convertAndSend(
+                "/topic/users/" + userId + "/actions",
+                new PrivateActionMessage(gameId, userId, availableActions, currentSeatNo)
+        );
+    }
+
+    public void publishPrivateTeaching(String gameId, String userId, String teachingMode, String recommendedAction, String explanation) {
+        messagingTemplate.convertAndSend(
+                "/topic/users/" + userId + "/teaching",
+                new PrivateTeachingMessage(gameId, userId, teachingMode, recommendedAction, explanation)
+        );
+    }
+}