@Component
public class WebSocketEventListener {
    
    private static final Logger logger = LoggerFactory.getLogger(WebSocketEventListener.class);
    
    @Autowired
    private SimpMessageSendingOperations messagingTemplate;
    
    @EventListener
    public void handleWebSocketConnectListener(SessionConnectedEvent event) {
        logger.info("Received a new web socket connection");
    }
    
    @EventListener
    public void handleWebSocketDisconnectListener(SessionDisconnectEvent event) {
        StompHeaderAccessor headerAccessor = StompHeaderAccessor.wrap(event.getMessage());
        String username = (String) headerAccessor.getSessionAttributes().get("username");
        if(username != null) {
            logger.info("User Disconnected : " + username);
            ChatMessage chatMessage = new ChatMessage();
            chatMessage.setType(ChatMessage.MessageType.LEAVE);
            chatMessage.setSender(username);
            messagingTemplate.convertAndSend("/topic/public", chatMessage);
        }
    }
}