[PRTG] Read Date from OID

# note: it's easier if you enter the parameters directly in the script and save it.
# Only the sensor ID should be passed like this in the sensors parameter settings: -sensorid 1234
param(
    $prtgusername  = "<the-username-you-want-to-use>",
    $prtgpasshash  = "<your-prtg-user-passhash>",
    $sensoroid     = <the id of the sensor that retrieves the timestamp>,
    $prtg          = "<the-url-of-your-prtg-server, e.g. http://your-prtg-server>"
)

$prtgurl = ([string]::Format("http://{3}/api/getsensordetails.json?id={0}&username={1}&passhash={2}",$sensoroid,$prtguser,$prtgpass,$prtg))
$result =  ((Invoke-WebRequest -UseBasicParsing $prtgurl) | ConvertFrom-Json).sensordata.lastmessage

[datetime]$timestamp        = [datetime]::ParseExact($result,"yyyy-mm-dd HH:MM:ss",$null)
[datetime]$currentTimeStamp = (Get-Date);

$timediff = (New-TimeSpan -Start $timestamp -End $currentTimeStamp).Seconds
if($timediff -lt 0){ $timediff = $timediff * -1 }

Write-Host ("{0}:Current time offset between PRTG and host: {0} seconds" -f $timediff);