package com.yj.earth.common.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.*;
import java.util.concurrent.*;

/**
 * 网络工具类
 */
public class NetUtils {
    private static final Logger logger = LoggerFactory.getLogger(NetUtils.class);

    // Ping 超时时间（毫秒）
    private static final int PING_TIMEOUT = 500;
    // TCP Ping 端口
    private static final int TCP_PING_PORT = 80;
    // TCP Ping 超时时间（毫秒）
    private static final int TCP_TIMEOUT = 1500;

    private static final ExecutorService PING_EXECUTOR = Executors.newFixedThreadPool(
            Math.min(Runtime.getRuntime().availableProcessors() * 2, 50),
            new ThreadFactory() {
                private int count = 0;
                @Override
                public Thread newThread(Runnable r) {
                    Thread thread = new Thread(r);
                    thread.setName("ping-executor-" + (count++));
                    thread.setDaemon(true);
                    return thread;
                }
            }
    );

    /**
     * 使用 ICMP Echo Request (标准 Ping) 检测主机是否可达
     * @param ipAddress IP地址或主机名
     * @return true if reachable, false otherwise
     */
    public static boolean isReachableByIcmp(String ipAddress) {
        if (ipAddress == null || ipAddress.trim().isEmpty()) {
            return false;
        }
        try {
            InetAddress address = InetAddress.getByName(ipAddress);
            // isReachable 会尝试 ICMP Echo 和 TCP Echo (端口 7)
            return address.isReachable(PING_TIMEOUT);
        } catch (UnknownHostException e) {
            logger.warn("未知的主机: {}", ipAddress);
            return false;
        } catch (IOException e) {
            // 发生 IO 异常、视为不可达
            return false;
        }
    }

    /**
     * 使用 TCP 连接检测主机端口是否开放（模拟 Ping）
     * 当 ICMP 被防火墙禁止时、此方法更有效
     * @param ipAddress IP地址
     * @param port 端口号
     * @return true if port is open, false otherwise
     */
    public static boolean isReachableByTcp(String ipAddress, int port) {
        if (ipAddress == null || ipAddress.trim().isEmpty() || port < 1 || port > 65535) {
            return false;
        }
        Socket socket = null;
        try {
            socket = new Socket();
            socket.connect(new java.net.InetSocketAddress(ipAddress, port), TCP_TIMEOUT);
            return true;
        } catch (IOException e) {
            // 连接失败、端口未开放或主机不可达
            return false;
        } finally {
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    // ignore
                }
            }
        }
    }

    /**
     * 异步并发检测多个IP的可达性
     * @param ips 需要检测的IP列表
     * @return 一个 Map、key 是 IP、value 是 Boolean (是否在线)
     * @throws ExecutionException 执行异常
     * @throws InterruptedException 线程中断异常
     */
    public static Map<String, Boolean> checkReachabilityAsync(Collection<String> ips) throws ExecutionException, InterruptedException {
        if (ips == null || ips.isEmpty()) {
            return Collections.emptyMap();
        }

        List<Callable<Map.Entry<String, Boolean>>> tasks = new ArrayList<>();
        for (String ip : ips) {
            tasks.add(() -> {
                boolean isOnline = isReachableByTcp(ip, TCP_PING_PORT) || isReachableByIcmp(ip);
                return new AbstractMap.SimpleEntry<>(ip, isOnline);
            });
        }

        List<Future<Map.Entry<String, Boolean>>> futures = PING_EXECUTOR.invokeAll(tasks);
        Map<String, Boolean> results = new ConcurrentHashMap<>();
        for (Future<Map.Entry<String, Boolean>> future : futures) {
            Map.Entry<String, Boolean> entry = future.get();
            results.put(entry.getKey(), entry.getValue());
        }
        return results;
    }
}