/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.shardingsphere.infra.instance.util;

import lombok.AccessLevel;
import lombok.NoArgsConstructor;

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

/**
 * IP utility class.
 */
@NoArgsConstructor(access = AccessLevel.PRIVATE)
public final class IpUtils {
    
    private static volatile String cachedIpAddress;
    
    /**
     * Get localhost IP address.
     *
     * <p>
     * It maybe get IP address of router.
     * Return unknown IP if exception occur.
     * </p>
     *
     * @return IP address of localhost 
     */
    public static String getIp() {
        if (null != cachedIpAddress) {
            return cachedIpAddress;
        }
        Enumeration<NetworkInterface> netInterfaces;
        try {
            netInterfaces = NetworkInterface.getNetworkInterfaces();
        } catch (final SocketException ex) {
            return "UnknownIP";
        }
        String localIpAddress = null;
        while (netInterfaces.hasMoreElements()) {
            NetworkInterface netInterface = netInterfaces.nextElement();
            Enumeration<InetAddress> ipAddresses = netInterface.getInetAddresses();
            while (ipAddresses.hasMoreElements()) {
                InetAddress ipAddress = ipAddresses.nextElement();
                if (isPublicIpAddress(ipAddress)) {
                    String publicIpAddress = ipAddress.getHostAddress();
                    cachedIpAddress = publicIpAddress;
                    return publicIpAddress;
                }
                if (isLocalIpAddress(ipAddress)) {
                    localIpAddress = ipAddress.getHostAddress();
                }
            }
        }
        cachedIpAddress = localIpAddress;
        return localIpAddress;
    }
    
    private static boolean isPublicIpAddress(final InetAddress ipAddress) {
        return !ipAddress.isSiteLocalAddress() && !ipAddress.isLoopbackAddress() && !isV6IpAddress(ipAddress);
    }
    
    private static boolean isLocalIpAddress(final InetAddress ipAddress) {
        return ipAddress.isSiteLocalAddress() && !ipAddress.isLoopbackAddress() && !isV6IpAddress(ipAddress);
    }
    
    private static boolean isV6IpAddress(final InetAddress ipAddress) {
        return ipAddress.getHostAddress().contains(":");
    }
}
