/*
    * 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.omid;
  
  import java.net.DatagramSocket;
  import java.net.InetAddress;
  import java.net.NetworkInterface;
  import java.net.SocketException;
  import java.util.Collections;
  import java.util.Enumeration;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class NetworkUtils {
  
      private static final Logger LOG = LoggerFactory.getLogger(NetworkUtils.class);
  
      private static final String LINUX_TSO_NET_IFACE_PREFIX = "eth";
      private static final String MAC_TSO_NET_IFACE_PREFIX = "en";
  
      public static String getDefaultNetworkInterface() {
  
          try (DatagramSocket s=new DatagramSocket()) {
              s.connect(InetAddress.getByAddress(new byte[]{1,1,1,1}), 0);
              return NetworkInterface.getByInetAddress(s.getLocalAddress()).getName();
          } catch (Exception e) {
              //fall through
          }
  
          //Fall back to old logic
          try {
              Enumeration<NetworkInterface> networkInterfaces = NetworkInterface.getNetworkInterfaces();
              String fallBackName = null;
              while (networkInterfaces.hasMoreElements()) {
                  NetworkInterface nextElement = networkInterfaces.nextElement();
                  String name = nextElement.getDisplayName();
                  LOG.info("Iterating over network interfaces, found '{}'", name);
                  boolean hasInet = Collections.list(nextElement.getInetAddresses()).size() > 1; // Checking that inet exists, to avoid taking iBridge
                  if (hasInet && fallBackName == null) {
                      fallBackName = name;
                  }
                  if ((name.startsWith(MAC_TSO_NET_IFACE_PREFIX) && hasInet ) ||
                          name.startsWith(LINUX_TSO_NET_IFACE_PREFIX)) {
                    return name;
                  }
              }
              if (fallBackName != null) {
                  return fallBackName;
              }
          } catch (SocketException ignored) {
              throw new RuntimeException("Failed to find any network interfaces", ignored);
          }
  
          throw new IllegalArgumentException(String.format("No network '%s*'/'%s*' interfaces found",
                                                           MAC_TSO_NET_IFACE_PREFIX, LINUX_TSO_NET_IFACE_PREFIX));
      }
  }