package com.lanremote.watch;

import android.content.Context;
import android.net.wifi.WifiManager;

import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.InterfaceAddress;
import java.net.NetworkInterface;
import java.util.Collections;
import java.util.List;

/**
 * 安卓侧的自动发现包装。
 *
 * 真正干活的是 {@link DiscoveryCore}（纯 Java，可桌面联调）。这里多做两件事：
 *   1. 抓 WifiManager.MulticastLock（部分手表息屏/省电时会过滤广播）
 *   2. 算出**本网段的定向广播地址**，这是广播探测能不能收到回复的关键
 */
public final class Discovery {

    public static final int PORT = DiscoveryCore.PORT;

    private Discovery() {
    }

    /** 本机在某张网卡上的 IPv4 与前缀长度。 */
    public static class LocalNet {
        public final String ip;
        public final int prefix;
        public final String iface;

        LocalNet(String ip, int prefix, String iface) {
            this.ip = ip;
            this.prefix = prefix;
            this.iface = iface;
        }

        public String broadcast() {
            return DiscoveryCore.directedBroadcast(ip, prefix);
        }

        @Override
        public String toString() {
            return iface + " " + ip + "/" + prefix;
        }
    }

    /** 取当前可用的局域网 IPv4（优先 wlan*）。 */
    public static LocalNet localNet() {
        try {
            LocalNet fallback = null;
            for (NetworkInterface ni : Collections.list(NetworkInterface.getNetworkInterfaces())) {
                if (!ni.isUp() || ni.isLoopback()) {
                    continue;
                }
                String name = ni.getName() == null ? "" : ni.getName();
                if (name.startsWith("p2p") || name.startsWith("dummy")) {
                    continue;                       // WiFi Direct / 占位网卡
                }
                for (InterfaceAddress ia : ni.getInterfaceAddresses()) {
                    InetAddress addr = ia.getAddress();
                    if (!(addr instanceof Inet4Address) || addr.isLoopbackAddress()) {
                        continue;
                    }
                    int prefix = ia.getNetworkPrefixLength();
                    if (prefix <= 0 || prefix > 32) {
                        continue;
                    }
                    LocalNet net = new LocalNet(addr.getHostAddress(), prefix, name);
                    if (name.startsWith("wlan")) {
                        return net;                 // wlan 最优，直接返回
                    }
                    if (fallback == null) {
                        fallback = net;
                    }
                }
            }
            return fallback;
        } catch (Exception e) {
            return null;
        }
    }

    /** 本网段定向广播地址，如 192.168.10.255。 */
    public static String directedBroadcast() {
        LocalNet net = localNet();
        return net == null ? null : net.broadcast();
    }

    /** 广播搜索（自动带上本网段定向广播）。 */
    public static List<DiscoveryCore.Found> search(Context context, int timeoutMs) {
        WifiManager.MulticastLock lock = acquireLock(context);
        try {
            return DiscoveryCore.search(timeoutMs, directedBroadcast());
        } finally {
            releaseLock(lock);
        }
    }

    /**
     * 子网 TCP 扫描 —— 广播被拦时的兜底。
     * 注意：会阻塞，必须在后台线程调用。
     */
    public static List<String> scanSubnet(Context context, int port, int connectTimeoutMs) {
        LocalNet net = localNet();
        if (net == null || net.prefix > 30) {
            return new java.util.ArrayList<String>();
        }
        WifiManager.MulticastLock lock = acquireLock(context);
        try {
            return DiscoveryCore.scanSubnet(net.ip, net.prefix, port,
                    connectTimeoutMs, 300);
        } finally {
            releaseLock(lock);
        }
    }

    /**
     * 请电脑打开「网络自检」。
     * 返回电脑名；没收到回应返回 null。
     */
    public static String requestSelfCheck(Context context, int timeoutMs) {
        WifiManager.MulticastLock lock = acquireLock(context);
        try {
            return DiscoveryCore.requestSelfCheck(directedBroadcast(), timeoutMs);
        } finally {
            releaseLock(lock);
        }
    }

    public static DiscoveryCore.Found probeHost(String host, int timeoutMs) {
        return DiscoveryCore.probeHost(host, timeoutMs);
    }

    public static boolean ping(String host, int port, int timeoutMs) {
        return DiscoveryCore.ping(host, port, timeoutMs);
    }

    private static WifiManager.MulticastLock acquireLock(Context context) {
        try {
            WifiManager manager = (WifiManager) context.getApplicationContext()
                    .getSystemService(Context.WIFI_SERVICE);
            if (manager == null) {
                return null;
            }
            WifiManager.MulticastLock lock = manager.createMulticastLock("lanremote");
            lock.setReferenceCounted(false);
            lock.acquire();
            return lock;
        } catch (Exception e) {
            return null;
        }
    }

    private static void releaseLock(WifiManager.MulticastLock lock) {
        if (lock == null) {
            return;
        }
        try {
            if (lock.isHeld()) {
                lock.release();
            }
        } catch (Exception ignored) {
            // 释放失败不影响结果
        }
    }
}