/*
 * Copyright (c) 2017 Baidu, Inc. All Rights Reserve.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.baidu.fsg.uid.utils;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;

/**
 * NetUtils
 *
 * @author yutianbao
 */
public final class NetUtils {
    /**
     * Pre-loaded local address
     */
    private static InetAddress localAddress;

    static {
        try {
            localAddress = getLocalInetAddress();
        } catch (SocketException e) {
            throw new RuntimeException("fail to get local ip.", e);
        }
    }

    private NetUtils() {
    }

    /**
     * Retrieve the first validated local ip address(the Public and LAN ip addresses are validated).
     *
     * @return the local address
     * @throws SocketException the socket exception
     */
    public static InetAddress getLocalInetAddress() throws SocketException {
        // enumerates all network interfaces
        Enumeration<NetworkInterface> enu = NetworkInterface.getNetworkInterfaces();

        while (enu.hasMoreElements()) {
            NetworkInterface ni = enu.nextElement();
            if (ni.isLoopback()) {
                continue;
            }

            Enumeration<InetAddress> addressEnumeration = ni.getInetAddresses();
            while (addressEnumeration.hasMoreElements()) {
                InetAddress address = addressEnumeration.nextElement();

                // ignores all invalidated addresses
                if (address.isLinkLocalAddress() || address.isLoopbackAddress() || address.isAnyLocalAddress()) {
                    continue;
                }

                return address;
            }
        }

//        throw new RuntimeException("No validated local address!");
        return null;
    }

    /**
     * Retrieve local address
     *
     * @return the string local address
     */
    public static String getLocalAddress() {
        return localAddress != null ? localAddress.getHostAddress() : "127.0.0.1";
    }

}
