package com.lts.startup;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Enumeration;
import java.util.regex.Pattern;

/**
 * @author Robert HG (254963746@qq.com) on 7/23/14.
 */
public class NetUtils {

    public static final String LOCALHOST = "127.0.0.1";
    public static final String ANYHOST = "0.0.0.0";
    private static final Pattern IP_PATTERN = Pattern.compile("\\d{1,3}(\\.\\d{1,3}){3,5}$");
    private static volatile InetAddress LOCAL_ADDRESS = null;

    private NetUtils() {
    }

    private static boolean isValidAddress(InetAddress address) {
        if (address == null || address.isLoopbackAddress())
            return false;
        String name = address.getHostAddress();
        return (name != null
                && !ANYHOST.equals(name)
                && !LOCALHOST.equals(name)
                && IP_PATTERN.matcher(name).matches());
    }

    public static String getLocalHost() {
        InetAddress address = getLocalAddress();
        return address == null ? LOCALHOST : address.getHostAddress();
    }
    /**
     * 遍历本地网卡，返回第一个合理的IP。
     * @return 本地网卡IP
     */
    public static InetAddress getLocalAddress() {
        if (LOCAL_ADDRESS != null)
            return LOCAL_ADDRESS;
        InetAddress localAddress = getLocalAddress0();
        LOCAL_ADDRESS = localAddress;
        return localAddress;
    }

    private static InetAddress getLocalAddress0() {
        InetAddress localAddress = null;
        try {
            localAddress = InetAddress.getLocalHost();
            if (isValidAddress(localAddress)) {
                return localAddress;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
            if (interfaces != null) {
                while (interfaces.hasMoreElements()) {
                    try {
                        NetworkInterface network = interfaces.nextElement();
                        Enumeration<InetAddress> addresses = network.getInetAddresses();
                        while (addresses.hasMoreElements()) {
                            try {
                                InetAddress address = addresses.nextElement();
                                if (isValidAddress(address)) {
                                    return address;
                                }
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.err.println("Could not get local host ip address, will use 127.0.0.1 instead.");
        return localAddress;
    }
}
