#
# This background job automatically locks your Workstation after a specified amount of
# time. It will come in handy if you cannot access the screensaver settings due to policy
# restriction but want to lock your screen after a idle timeout. Or you could just
# press [Win]+[L] everytime you leave your desk ;) .
#
# start with
#       powershell.exe -windowstylpowee hidden -executionpolicy Unrestricted P:\ATH\TO\logoff.ps1
#
# `-windowstyle hidden` will make your PowerShell disappear/run in background
# `-executionpolicy Unrestricted` will enable this PowerShell process to allow non-signed scripts
#

# This is the only setting: How long before locking?
# Alternative Options:
# * -Seconds 10 ( = 10 Seconds)
# * -Minutes 10 ( = 10 Minutes)
# * -Hours 10 ( = 10 Hours)
#
$idle_timeout = New-TimeSpan -Minutes 30
$switch_timeout = New-TimeSpan -Minutes 4
$untouched = New-TimeSpan -Minutes 0

$touch_date = (Get-Date)
$touch_span = New-TimeSpan -Milliseconds 500

# DO NOT CHANGE ANYTHING BELOW THIS LINE
####################################################################################################################################################################

# This snippet is from http://stackoverflow.com/a/15846912
Add-Type @'
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace PInvoke.Win32 {

    public static class UserInput {

        [DllImport("user32.dll", SetLastError=false)]
        private static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

        [StructLayout(LayoutKind.Sequential)]
        private struct LASTINPUTINFO {
            public uint cbSize;
            public int dwTime;
        }

        public static DateTime LastInput {
            get {
                DateTime bootTime = DateTime.UtcNow.AddMilliseconds(-Environment.TickCount);
                DateTime lastInput = bootTime.AddMilliseconds(LastInputTicks);
                return lastInput;
            }
        }

        public static TimeSpan IdleTime {
            get {
                return DateTime.UtcNow.Subtract(LastInput);
            }
        }

        public static int LastInputTicks {
            get {
                LASTINPUTINFO lii = new LASTINPUTINFO();
                lii.cbSize = (uint)Marshal.SizeOf(typeof(LASTINPUTINFO));
                GetLastInputInfo(ref lii);
                return lii.dwTime;
            }
        }
    }
}
'@
#End snippet

Add-Type -AssemblyName System.Windows.Forms

# Helper: Is currently locked?
$locked = 0;

do {
        # 1st: How long is your computer currently idle?
        $idle_time = [PInvoke.Win32.UserInput]::IdleTime
        $now = Get-Date

        # Switch Window only if timeout reached
        if (($locked -eq 0) -And ($idle_time -gt $switch_timeout)) {
                Write-Host (Get-Date -Format HH:mm:ss) -ForegroundColor Green -NoNewline
                $sleep_in = $idle_timeout - $idle_time

                # Elapsed since last auto touch
                $diff = New-Timespan -Start $touch_date -End $now

                if (($diff - $idle_time) -lt $touch_span) {
                        $untouched += $idle_time
                } else {
                        $untouched = $idle_time
                }

                Write-Host " Idle for $idle_time, touched at $touch_date ($diff ago), untouched since $untouched"
                $touch_date = Get-Date

                [System.Windows.Forms.SendKeys]::SendWait("%{TAB}")
        }

        # Your computer is not locked, but idle time is longer than allowed? -> Lock it!
        if (($locked -eq 0) -And ($untouched -gt $idle_timeout)) {
                # Lock it
                rundll32.exe user32.dll,LockWorkStation

                # Setting $locked to 1 will prevent it from relocking every 10 seconds
                $locked = 1;
                $untouched = New-Timespan -Seconds 0;
                Write-Host ("Locking");
        }

        # Your computer is idle for less than the allowed time -> in most cases this means it is unlocked and
        # therefore ready to be locked again!
        if ($idle_time -lt $idle_timeout) {
                $locked = 0;
        }

        # Save the environment. Don't use 100% of a single CPU just for idle checking :)
    Start-Sleep -Seconds 10
}
while (1 -eq 1)