Script that blocks login attempts

$computer='localhost'
$username = gwmi win32_computersystem -comp $computer | select Username
$userstring = [string]$username
$usernamejunk,$adilstu_user = $userstring.Split("=",2)
$usernameonly,$usernamebracket = $adilstu_user.Split("}",2)
$date = (Get-Date).ToString('HH')
$FilePath = 'C:\Users\User\Desktop\restartet.txt'

IF([string]::IsNullOrEmpty($usernameonly)) {

    IF([string]::IsNullOrEmpty((Get-Content $FilePath))) {
        Out-File -FilePath $FilePath -InputObject $date
        Restart-Computer -Force
    }

    else {
        exit
    }

}
else {
    write-host "Benutzer ist noch angemeldet"
}