Listens for new alarms from a Milestone XProtect VMS installation

Trace-VmsAlarms.ps1

function Trace-VmsAlarms {
    <#
    .SYNOPSIS
        Polls a Milestone XProtect Event Server for new alarmline entries
    .DESCRIPTION
        Starts a polling loop to ask for new alarmline entries from a Milestone XProtect Event
        Server. The InitialStartTime is "now" by default, so only new alarms are returned. You
        can either pipe the alarms to a Foreach-Object and process them there, or provide a
        scriptblock which will be invoked once for each alarm returned.
    .EXAMPLE
        PS C:\> Trace-VmsAlarms -PollingInterval (New-TimeSpan -Seconds 1) -ScriptBlock { param($Alarm) Write-Output "Alarm received at $($Alarm.Timestamp) from $($Alarm.SourceName)" }
        Explanation of what the example does
    #>
    [CmdletBinding()]
    [OutputType([VideoOS.Platform.Proxy.Alarm.AlarmLine])]
    param(
        # Specifies an optional scriptblock to be called when an alarm is received. The scriptblock will be invoked with an [VideoOS.Platform.Proxy.Alarm.AlarmLine] object as a parameter. If no scriptblock is provided, the alarm will be returned to the pipeline instead.
        [Parameter()]
        [scriptblock]
        $ScriptBlock,

        # Specifies the timestamp for the first alarm to be detected. The default is to only return new alarms.
        [Parameter()]
        [datetime]
        $InitialStartTime = (Get-Date).ToUniversalTime(),

        # Specifies the interval between calls to Get-AlarmLine. Default is 2 seconds.
        [Parameter()]
        [timespan]
        $PollingInterval = (New-TimeSpan -Seconds 2),

        # Specifies the time at which the function should quit. By default the command runs indefinitely and must be interrupted by CTRL+C or ending the process.
        [Parameter()]
        [datetime]
        $EndTrace = [datetime]::MaxValue
    )

    process {
        $ascendingOrder = New-AlarmOrder -Target Timestamp -Order Ascending
        $startTimeCondition = New-AlarmCondition -Target Timestamp -Operator GreaterThan -Value $InitialStartTime.ToUniversalTime()
        while ($true) {
            Get-AlarmLine -Conditions $startTimeCondition -SortOrders $ascendingOrder | ForEach-Object {
                if ($_.Timestamp -gt $startTimeCondition.Value) {
                    $startTimeCondition.Value = $_.Timestamp
                }
                if ($null -eq $ScriptBlock) {
                    Write-Output $_
                }
                else {
                    try {
                        $ScriptBlock.Invoke($_)
                    }
                    catch {
                        Write-Error -Message "An error was thrown within the provided scriptblock. Error: $($_.Exception.Message)"
                    }
                    
                }
            }
            if ((Get-Date) -ge $EndTrace) {
                break
            }
            Start-Sleep -Seconds $PollingInterval.TotalSeconds
        }    
    }
}