package com.example.websocket;
import java.io.ByteArrayOutputStream;
import java.net.URI;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import org.springframework.web.socket.BinaryMessage;
import org.springframework.web.socket.CloseStatus;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.AbstractWebSocketHandler;
import com.fasterxml.jackson.databind.ObjectMapper;

public class ChatWebSocketHandler extends AbstractWebSocketHandler {
    private final ConcurrentHashMap<String, Set<WebSocketSession>> userSessions = new ConcurrentHashMap<>();
    private static final ObjectMapper MAPPER = new ObjectMapper();
    private final ConcurrentHashMap<String, StringBuilder> textFragments = new ConcurrentHashMap<>();
    private final ConcurrentHashMap<String, ByteArrayOutputStream> binaryFragments = new ConcurrentHashMap<>();

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        // 驗(yàn)證用戶ID的有效性
        String uid = resolveUserId(session);
        if (uid == null || uid.isEmpty()) {
            session.close(CloseStatus.BAD_DATA);
            return;
        }
        session.getAttributes().put("userId", uid);
        //多會(huì)話管理
        userSessions.computeIfAbsent(uid, k -> ConcurrentHashMap.newKeySet()).add(session);
    }

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        // 分片處理
        String id = session.getId();
        if (!message.isLast()) {
            textFragments.computeIfAbsent(id, k -> new StringBuilder()).append(message.getPayload());
            return;
        }
        StringBuilder sb = textFragments.remove(id);
        String payload = sb != null ? sb.append(message.getPayload()).toString() : message.getPayload();
        routePayload(session, payload);
    }

    @Override
    protected void handleBinaryMessage(WebSocketSession session, BinaryMessage message) throws Exception {
        //二進(jìn)制消息處理
        String id = session.getId();
        ByteBuffer buf = message.getPayload();
        byte[] chunk = new byte[buf.remaining()];
        buf.get(chunk);
        ByteArrayOutputStream acc = binaryFragments.computeIfAbsent(id, k -> new ByteArrayOutputStream());
        acc.write(chunk);
        if (message.isLast()) {
            byte[] all = acc.toByteArray();
            binaryFragments.remove(id);
            String payload = new String(all, StandardCharsets.UTF_8);
            routePayload(session, payload);
        }
    }

    @Override
    public boolean supportsPartialMessages() {
        return true;
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        //  WebSocket 連接關(guān)閉時(shí)的清理邏輯
        Object v = session.getAttributes().get("userId");
        if (v == null) return;
        String uid = String.valueOf(v);
        Set<WebSocketSession> set = userSessions.get(uid);
        if (set != null) {
            set.remove(session);
            if (set.isEmpty()) userSessions.remove(uid);
        }
    }

    /** 從 WebSocket 連接的 URL 查詢參數(shù)中提取用戶ID */
    private String resolveUserId(WebSocketSession session) {
        URI uri = session.getUri();
        if (uri == null) return null;
        String q = uri.getQuery();
        if (q == null || q.isEmpty()) return null;
        String[] parts = q.split("&");
        for (String p : parts) {
            int i = p.indexOf('=');
            if (i > 0) {
                String k = p.substring(0, i);
                String val = p.substring(i + 1);
                if ("userId".equals(k)) return val;
            }
        }
        return null;
    }

    private void routePayload(WebSocketSession session, String payload) throws Exception {
        Object v = session.getAttributes().get("userId");
        if (v == null) return;
        String fromUid = String.valueOf(v);

        // 解析消息
        Message message = new Message();
        message.setFromUserId(fromUid);
        
        try {
            // 嘗試將payload解析為Message對(duì)象
            Message receivedMsg = MAPPER.readValue(payload, Message.class);
            message.setToUserId(receivedMsg.getToUserId());
            message.setContent(receivedMsg.getContent());
            message.setType(receivedMsg.getType());
        } catch (Exception e) {
            // 如果解析失敗，將整個(gè)payload作為content
            message.setContent(payload);
        }

        String toUid = message.getToUserId();
        boolean isP2P = toUid != null && !toUid.isEmpty();
        
        Set<WebSocketSession> targets;
        if (isP2P) {
            targets = userSessions.get(toUid);
        } else {
            targets = userSessions.get(fromUid);
        }
        
        // 序列化消息對(duì)象
        String outStr = MAPPER.writeValueAsString(message);
        TextMessage msg = new TextMessage(outStr);
        
        if (targets == null || targets.isEmpty()) {
            if (session.isOpen()) {
                session.sendMessage(msg);
            }
            return;
        }

        for (WebSocketSession s : targets) {
            if (s.isOpen()) {
                s.sendMessage(msg);
            }
        }
        if (isP2P && session.isOpen()) {
            session.sendMessage(msg);
        }
    }
}

package com.example.websocket;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
import org.springframework.web.socket.server.standard.ServletServerContainerFactoryBean;

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(chatHandler(), "/ws").setAllowedOriginPatterns("*");
    }

    @Bean
    public WebSocketHandler chatHandler() {
        return new ChatWebSocketHandler();
    }

    // 配置 WebSocket 容器參數(shù)（解決消息過大、超時(shí)等問題）
    @Bean
    public ServletServerContainerFactoryBean createWebSocketContainer() {
        ServletServerContainerFactoryBean container = new ServletServerContainerFactoryBean();
        // 文本消息緩沖區(qū)：2MB（解決解碼后消息過大的核心配置）
        container.setMaxTextMessageBufferSize(2 * 1024 * 1024);
        // 二進(jìn)制消息緩沖區(qū)：4MB（按需配置）
        container.setMaxBinaryMessageBufferSize(4 * 1024 * 1024);
        // 會(huì)話空閑超時(shí)：60秒（無交互則關(guān)閉連接）
        container.setMaxSessionIdleTimeout(60_000L);
        return container;
    }
}