/*
    * Copyright 2020-2023 The OSHI Project Contributors
    * SPDX-License-Identifier: MIT
    */
   package oshi.driver.linux;
   
   import static oshi.jna.platform.unix.CLibrary.LOGIN_PROCESS;
   import static oshi.jna.platform.unix.CLibrary.USER_PROCESS;
   import static oshi.util.Util.isSessionValid;
  
  import java.nio.charset.Charset;
  import java.util.ArrayList;
  import java.util.List;
  
  import com.sun.jna.Native;
  
  import oshi.annotation.concurrent.ThreadSafe;
  import oshi.jna.platform.linux.LinuxLibc;
  import oshi.jna.platform.linux.LinuxLibc.LinuxUtmpx;
  import oshi.software.os.OSSession;
  import oshi.util.ParseUtil;
  
  /**
   * Utility to query logged in users.
   */
  @ThreadSafe
  public final class Who {
  
      private static final LinuxLibc LIBC = LinuxLibc.INSTANCE;
  
      private Who() {
      }
  
      /**
       * Query {@code getutxent} to get logged in users.
       *
       * @return A list of logged in user sessions
       */
      public static synchronized List<OSSession> queryUtxent() {
          List<OSSession> whoList = new ArrayList<>();
          LinuxUtmpx ut;
          // Rewind
          LIBC.setutxent();
          try {
              // Iterate
              while ((ut = LIBC.getutxent()) != null) {
                  if (ut.ut_type == USER_PROCESS || ut.ut_type == LOGIN_PROCESS) {
                      String user = Native.toString(ut.ut_user, Charset.defaultCharset());
                      String device = Native.toString(ut.ut_line, Charset.defaultCharset());
                      String host = ParseUtil.parseUtAddrV6toIP(ut.ut_addr_v6);
                      long loginTime = ut.ut_tv.tv_sec * 1000L + ut.ut_tv.tv_usec / 1000L;
                      // Sanity check. If errors, default to who command line
                      if (!isSessionValid(user, device, loginTime)) {
                          return oshi.driver.unix.Who.queryWho();
                      }
                      whoList.add(new OSSession(user, device, loginTime, host));
                  }
              }
          } finally {
              // Close
              LIBC.endutxent();
          }
          return whoList;
      }
  }