/*
    * Copyright 2017-2023 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.software.common;
   
   import java.net.InetAddress;
   import java.net.UnknownHostException;
   import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Locale;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.software.os.NetworkParams;
  import oshi.util.FileUtil;
  import oshi.util.ParseUtil;
  
  /**
   * Common NetworkParams implementation.
   */
  @ThreadSafe
  public abstract class AbstractNetworkParams implements NetworkParams {
  
      private static final String NAMESERVER = "nameserver";
  
      @Override
      public String getDomainName() {
          InetAddress localHost;
          try {
              localHost = InetAddress.getLocalHost();
          } catch (UnknownHostException e) {
              localHost = InetAddress.getLoopbackAddress();
          }
          return localHost.getCanonicalHostName();
      }
  
      @Override
      public String getHostName() {
          InetAddress localHost;
          try {
              localHost = InetAddress.getLocalHost();
          } catch (UnknownHostException e) {
              localHost = InetAddress.getLoopbackAddress();
          }
          String hn = localHost.getHostName();
          int dot = hn.indexOf('.');
          if (dot == -1) {
              return hn;
          }
          return hn.substring(0, dot);
      }
  
      @Override
      public String[] getDnsServers() {
          List<String> resolv = FileUtil.readFile("/etc/resolv.conf");
          String key = NAMESERVER;
          int maxNameServer = 3;
          List<String> servers = new ArrayList<>();
          for (int i = 0; i < resolv.size() && servers.size() < maxNameServer; i++) {
              String line = resolv.get(i);
              if (line.startsWith(key)) {
                  String value = line.substring(key.length()).replaceFirst("^[ \t]+", "");
                  if (value.length() != 0 && value.charAt(0) != '#' && value.charAt(0) != ';') {
                      String val = value.split("[ \t#;]", 2)[0];
                      servers.add(val);
                  }
              }
          }
          return servers.toArray(new String[0]);
      }
  
      /**
       * Convenience method to parse the output of the `route` command. While the command arguments vary between OS's the
       * output is consistently parsable.
       *
       * @param lines output of OS-specific route command
       * @return default gateway
       */
      protected static String searchGateway(List<String> lines) {
          for (String line : lines) {
              String leftTrimmed = line.replaceFirst("^\\s+", "");
              if (leftTrimmed.startsWith("gateway:")) {
                  String[] split = ParseUtil.whitespaces.split(leftTrimmed);
                  if (split.length < 2) {
                      return "";
                  }
                  return split[1].split("%")[0];
              }
          }
          return "";
      }
  
      @Override
      public String toString() {
          return String.format(Locale.ROOT,
                  "Host name: %s, Domain name: %s, DNS servers: %s, IPv4 Gateway: %s, IPv6 Gateway: %s",
                  this.getHostName(), this.getDomainName(), Arrays.toString(this.getDnsServers()),
                  this.getIpv4DefaultGateway(), this.getIpv6DefaultGateway());
 
     }
 }