/*
    * Copyright 2017-2023 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.software.os.windows;
   
   import java.nio.charset.StandardCharsets;
   import java.util.ArrayList;
   import java.util.List;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.sun.jna.Memory;
  import com.sun.jna.Native;
  import com.sun.jna.platform.win32.IPHlpAPI;
  import com.sun.jna.platform.win32.IPHlpAPI.FIXED_INFO;
  import com.sun.jna.platform.win32.IPHlpAPI.IP_ADDR_STRING;
  import com.sun.jna.platform.win32.Kernel32;
  import com.sun.jna.platform.win32.Kernel32Util;
  import com.sun.jna.platform.win32.Win32Exception;
  import com.sun.jna.platform.win32.WinError;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.jna.ByRef.CloseableIntByReference;
  import oshi.software.common.AbstractNetworkParams;
  import oshi.util.ExecutingCommand;
  import oshi.util.ParseUtil;
  
  /**
   * WindowsNetworkParams class.
   */
  @ThreadSafe
  final class WindowsNetworkParams extends AbstractNetworkParams {
  
      private static final Logger LOG = LoggerFactory.getLogger(WindowsNetworkParams.class);
  
      private static final int COMPUTER_NAME_DNS_DOMAIN_FULLY_QUALIFIED = 3;
  
      @Override
      public String getDomainName() {
          char[] buffer = new char[256];
          try (CloseableIntByReference bufferSize = new CloseableIntByReference(buffer.length)) {
              if (!Kernel32.INSTANCE.GetComputerNameEx(COMPUTER_NAME_DNS_DOMAIN_FULLY_QUALIFIED, buffer, bufferSize)) {
                  LOG.error("Failed to get dns domain name. Error code: {}", Kernel32.INSTANCE.GetLastError());
                  return "";
              }
          }
          return Native.toString(buffer);
      }
  
      @Override
      public String[] getDnsServers() {
          try (CloseableIntByReference bufferSize = new CloseableIntByReference()) {
              int ret = IPHlpAPI.INSTANCE.GetNetworkParams(null, bufferSize);
              if (ret != WinError.ERROR_BUFFER_OVERFLOW) {
                  LOG.error("Failed to get network parameters buffer size. Error code: {}", ret);
                  return new String[0];
              }
  
              try (Memory buffer = new Memory(bufferSize.getValue())) {
                  ret = IPHlpAPI.INSTANCE.GetNetworkParams(buffer, bufferSize);
                  if (ret != 0) {
                      LOG.error("Failed to get network parameters. Error code: {}", ret);
                      return new String[0];
                  }
                  FIXED_INFO fixedInfo = new FIXED_INFO(buffer);
  
                  List<String> list = new ArrayList<>();
                  IP_ADDR_STRING dns = fixedInfo.DnsServerList;
                  while (dns != null) {
                      // a char array of size 16.
                      // This array holds an IPv4 address in dotted decimal notation.
                      String addr = Native.toString(dns.IpAddress.String, StandardCharsets.US_ASCII);
                      int nullPos = addr.indexOf(0);
                      if (nullPos != -1) {
                          addr = addr.substring(0, nullPos);
                      }
                      list.add(addr);
                      dns = dns.Next;
                  }
                  return list.toArray(new String[0]);
              }
          }
      }
  
      @Override
      public String getHostName() {
          try {
              return Kernel32Util.getComputerName();
          } catch (Win32Exception e) {
              return super.getHostName();
          }
      }
  
      @Override
      public String getIpv4DefaultGateway() {
          return parseIpv4Route();
      }
 
     @Override
     public String getIpv6DefaultGateway() {
         return parseIpv6Route();
     }
 
     private static String parseIpv4Route() {
         List<String> lines = ExecutingCommand.runNative("route print -4 0.0.0.0");
         for (String line : lines) {
             String[] fields = ParseUtil.whitespaces.split(line.trim());
             if (fields.length > 2 && "0.0.0.0".equals(fields[0])) {
                 return fields[2];
             }
         }
         return "";
     }
 
     private static String parseIpv6Route() {
         List<String> lines = ExecutingCommand.runNative("route print -6 ::/0");
         for (String line : lines) {
             String[] fields = ParseUtil.whitespaces.split(line.trim());
             if (fields.length > 3 && "::/0".equals(fields[2])) {
                 return fields[3];
             }
         }
         return "";
     }
 }