<#
.SYNOPSIS
	Checks the uptime 
.DESCRIPTION
	This PowerShell script queries the computer's uptime (time between now and last boot up time) and prints it.
.EXAMPLE
	PS> ./check-uptime.ps1
	✅ OfficePC is up for 13 days since 1/25/2024
.LINK
	https://github.com/fleschutz/PowerShell
.NOTES
	Author: Markus Fleschutz | License: CC0
#>

function TimeSpanAsString([TimeSpan]$uptime)
{
	[int]$days = $uptime.Days
	[int]$hours = $days * 24 + $uptime.Hours
	if ($days -gt 2) {
		return "$days days"
	} elseif ($hours -gt 1) {
		return "$hours hours"
	} else {
		return "$($uptime.Minutes)min"
	}
}

function Test-RegistryValue { param([parameter(Mandatory=$true)][ValidateNotNullOrEmpty()]$Path, [parameter(Mandatory=$true)] [ValidateNotNullOrEmpty()]$Value)
	try {
		Get-ItemProperty -Path $Path -Name $Value -EA Stop
		return $true
	} catch {
		return $false
	}
}

try {
	[system.threading.thread]::currentthread.currentculture = [system.globalization.cultureinfo]"en-US"
	if ($IsLinux) {
		$lastBootTime = (Get-Uptime -since)
		$uptime = (Get-Uptime)
	} else {
		$lastBootTime = (Get-CimInstance Win32_OperatingSystem).LastBootUpTime 
		$uptime = New-TimeSpan -Start $lastBootTime -End (Get-Date)
	}
	$status = "✅"
	$pending = ""
	if ($IsLinux) {
		if (Test-Path "/var/run/reboot-required") {
			$status = "⚠️"
			$pending = "with pending reboot (found /var/run/reboot-required)"
		}
	} else {
		$reason = ""
		if (Test-Path -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired") {
			$reason += ", ...\Auto Update\RebootRequired"
		}
		if (Test-Path -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\PostRebootReporting") {
			$reason += ", ...\Auto Update\PostRebootReporting"
		}
		if (Test-Path -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootPending") {
			$reason += ", ...\Component Based Servicing\RebootPending"
		}
		if (Test-Path -Path "HKLM:\SOFTWARE\Microsoft\ServerManager\CurrentRebootAttempts") {
			$reason += ", ...\ServerManager\CurrentRebootAttempts"
		}
		if (Test-RegistryValue -Path "HKLM:\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing" -Value "RebootInProgress") {
			$reason += ", ...\CurrentVersion\Component Based Servicing with 'RebootInProgress'"
		}
		if (Test-RegistryValue -Path "HKLM:\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing" -Value "PackagesPending") {
			$reason += ", '...\CurrentVersion\Component Based Servicing' with 'PackagesPending'"
		}
		if (Test-RegistryValue -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager" -Value "PendingFileRenameOperations2") {
			$reason += ", '...\CurrentControlSet\Control\Session Manager' with 'PendingFileRenameOperations2'"
		}
		if (Test-RegistryValue -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce" -Value "DVDRebootSignal") {
			$reason += ", '...\Windows\CurrentVersion\RunOnce' with 'DVDRebootSignal'"
		}
		if (Test-RegistryValue -Path "HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon" -Value "JoinDomain") {
			$reason += ", '...\CurrentControlSet\Services\Netlogon' with 'JoinDomain'"
		}
		if (Test-RegistryValue -Path "HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon" -Value "AvoidSpnSet") {
			$reason += ", '...\CurrentControlSet\Services\Netlogon' with 'AvoidSpnSet'"
		}
		if ($reason -ne "") {
			$status = "⚠️"
			$pending = "with pending reboot ($($reason.substring(2)) in registry)"
		}
	}
	Write-Host "$status $(hostname) is up for $(TimeSpanAsString $uptime) since $($lastBootTime.ToShortDateString()) $pending"
	exit 0 # success
} catch {
	"⚠️ Error in line $($_.InvocationInfo.ScriptLineNumber): $($Error[0])"
	exit 1
}