// JNA JARS
// https://github.com/twall/jna#readme
// you need 2 jars : jna-3.5.1.jar and platform-3.5.1.jar
// from : http://ochafik.com/blog/?p=98 , thanks to the author
// see the comments in the  original article for MACOS, Linux implementation

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.List;
import com.sun.jna.*;
import com.sun.jna.win32.*;

/**
  * Utility method to retrieve the idle time on Windows and sample code to test it.
  * JNA shall be present in your classpath for this to work (and compile).
  * @author ochafik
  */
public class Win32IdleTime {
     public interface Kernel32 extends StdCallLibrary {
         Kernel32 INSTANCE = (Kernel32)Native.loadLibrary("kernel32", Kernel32.class);
         /**
          * Retrieves the number of milliseconds that have elapsed since the system was started.
          * @see http://msdn2.microsoft.com/en-us/library/ms724408.aspx
          * @return number of milliseconds that have elapsed since the system was started.
          */
         public int GetTickCount();
     };

     public interface User32 extends StdCallLibrary {
         User32 INSTANCE = (User32)Native.loadLibrary("user32", User32.class);
         /**
          * Contains the time of the last input.
          * @see http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/keyboardinput/keyboardinputreference/keyboardinputstructures/lastinputinfo.asp
          */
         public static class LASTINPUTINFO extends Structure {
             public int cbSize = 8;
             /// Tick count of when the last input event was received.
             public int dwTime;

            @SuppressWarnings("rawtypes")
            @Override
            protected List getFieldOrder() {
                return Arrays.asList(new String[] { "cbSize", "dwTime" });
            }
         }

         /**
          * Retrieves the time of the last input event.
          * @see http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/keyboardinput/keyboardinputreference/keyboardinputfunctions/getlastinputinfo.asp
          * @return time of the last input event, in milliseconds
          */
         public boolean GetLastInputInfo(LASTINPUTINFO result);
     };

     /**
      * Get the amount of milliseconds that have elapsed since the last input event
      * (mouse or keyboard)
      * @return idle time in milliseconds
      */
     public static int getIdleTimeMillisWin32() {
         User32.LASTINPUTINFO lastInputInfo = new User32.LASTINPUTINFO();
         User32.INSTANCE.GetLastInputInfo(lastInputInfo);
         return Kernel32.INSTANCE.GetTickCount() - lastInputInfo.dwTime;
     }

     enum State {
         UNKNOWN, ONLINE, IDLE, AWAY
     };

     // TEST
     public static void main(String[] args) throws Exception {
         if (!System.getProperty("os.name").contains("Windows")) {
             System.err.println("ERROR: Only implemented on Windows");
             System.exit(1);
         }
         State state = State.UNKNOWN;
         DateFormat dateFormat = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss");
         for (;;) {
             int idleSec = getIdleTimeMillisWin32() / 1000;
             State newState =
                 idleSec < 30 ? State.ONLINE :
                 idleSec > 5 * 60 ? State.AWAY : State.IDLE;
             if (newState != state) {
                 state = newState;
                 System.out.println(dateFormat.format(new Date()) + " # " + state);
                 //
                 // just for fun, if the state is AWAY (screensaver is coming!)
                 // we move the mouse wheel using java.awt.Robot just a little bit to change
                 // the state and prevent the screen saver execution.
                 //
                 if (state == State.AWAY) {
                     System.out.println("Activate the mouse wheel to change state!");
                     java.awt.Robot robot = new java.awt.Robot();
                     robot.mouseWheel(-1);
                     robot.mouseWheel(1);
                 }
             }
             try { Thread.sleep(1000); } catch (Exception ex) {}
         }
     }
}