// 文件路径：src/main/java/com/ruoyi/api/WebSocketServerHandler.java
package com.ruoyi.api;

import org.springframework.stereotype.Component;
import org.springframework.web.socket.*;

import java.io.IOException;
import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * WebSocket 服务处理器
 * 支持：按 userId 建立连接、发送消息、广播、查询在线用户
 */
@Component
public class WebSocketServerHandler implements WebSocketHandler {

    // 存储 userId -> WebSocketSession 映射（线程安全）
    private static final Map<String, WebSocketSession> userSessionMap = new ConcurrentHashMap<>();

    // 存储 session -> userId 映射（便于断开时清理）
    private static final Map<String, String> sessionToUserMap = new ConcurrentHashMap<>();

    /**
     * 广播消息给所有在线用户
     */
    public static void broadcastMessage(String message) {
        Objects.requireNonNull(message, "消息内容不能为空");

        userSessionMap.forEach((userId, session) -> {
            if (session.isOpen()) {
                try {
                    session.sendMessage(new TextMessage(message));
                } catch (IOException e) {
                    System.err.println("广播消息失败 - 用户: " + userId + ", 错误: " + e.getMessage());
                    // 清理失效连接
                    cleanupSession(session, userId);
                }
            }
        });
    }

    /**
     * 发送消息给指定用户
     */
    public static void sendMessageToUser(String userId, String message) {
        Objects.requireNonNull(userId, "userId 不能为空");
        Objects.requireNonNull(message, "消息内容不能为空");

        WebSocketSession session = userSessionMap.get(userId);
        if (session != null && session.isOpen()) {
            try {
                session.sendMessage(new TextMessage(message));
            } catch (IOException e) {
                System.err.println("发送消息失败 - 用户: " + userId + ", 错误: " + e.getMessage());
                cleanupSession(session, userId);
            }
        } else {
            System.out.println("⚠️ 用户未连接或已断开: userId=" + userId);
        }
    }

    /**
     * 获取当前在线用户数
     */
    public static int getOnlineUserCount() {
        return userSessionMap.size();
    }

    /**
     * 获取所有在线用户 ID
     */
    public static Set<String> getOnlineUserIds() {
        return new HashSet<>(userSessionMap.keySet());
    }

    /**
     * 从 WebSocketSession 中提取 userId
     */
    private String extractUserId(WebSocketSession session) {
        URI uri = session.getUri();
        if (uri == null) return null;

        String query = uri.getQuery(); // 格式: userId=123&token=abc
        if (query == null || query.isEmpty()) return null;

        return Arrays.stream(query.split("&"))
                .map(param -> param.split("=", 2))
                .filter(arr -> arr.length == 2)
                .filter(arr -> "userId".equals(arr[0]))
                .map(arr -> arr[1])
                .findFirst()
                .orElse(null);
    }

    /**
     * 清理失效的 session
     */
    private static void cleanupSession(WebSocketSession session, String userId) {
        userSessionMap.remove(userId);
        sessionToUserMap.remove(session.getId());
        try {
            if (session.isOpen()) {
                session.close();
            }
        } catch (IOException e) {
            System.err.println("关闭 session 失败: " + e.getMessage());
        }
    }

    // ========================================
    // WebSocket 回调方法
    // ========================================

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        String userId = extractUserId(session);
        if (userId == null || userId.trim().isEmpty()) {
            System.err.println("❌ 连接拒绝 - 缺少 userId: " + session.getId());
            session.close(CloseStatus.NOT_ACCEPTABLE.withReason("Missing userId"));
            return;
        }

        // 防止重复连接（可选）
        if (userSessionMap.containsKey(userId)) {
            System.out.println("🔄 用户重新连接: userId=" + userId);
            WebSocketSession oldSession = userSessionMap.get(userId);
            if (oldSession.isOpen()) {
                try {
                    oldSession.close();
                } catch (IOException e) {
                    System.err.println("关闭旧连接失败: " + e.getMessage());
                }
            }
        }

        // 保存映射
        userSessionMap.put(userId, session);
        sessionToUserMap.put(session.getId(), userId);

        // 记录日志
        System.out.println("✅ 新用户连接: userId=" + userId + ", sessionId=" + session.getId());

        // 可选：发送欢迎消息
        session.sendMessage(new TextMessage("{\"type\":\"welcome\",\"msg\":\"欢迎, " + userId + "!\"}"));
    }

    @Override
    public void handleMessage(WebSocketSession session, WebSocketMessage<?> message) throws Exception {
        String userId = sessionToUserMap.get(session.getId());
        System.out.println(message);
    }

    @Override
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        String userId = sessionToUserMap.get(session.getId());
        System.err.println("❌ 传输错误 - 用户: " + userId + ", sessionId: " + session.getId() + ", 错误: " + exception.getMessage());
        cleanupSession(session, userId);
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception {
        String userId = sessionToUserMap.get(session.getId());
        if (userId != null) {
            userSessionMap.remove(userId);
            sessionToUserMap.remove(session.getId());
            System.out.println("⏹️ 用户断开: userId=" + userId + ", 原因: " + closeStatus.getReason());
        }
    }

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