<#
    .SYNOPSIS
        Check if there is a pending reboot on a server and reboot

    .DESCRIPTION 
        This script if run as a task it will reboot the server/machine if there is a reboot pending on the host, 
        This script can be used in order to control the reboot schedule for Windows Updates for example. 

    .OUTPUTS
        This script will reboot the machine when there is a pending reboot. 
        
        Errorcodes: 
        n/a

    .EXAMPLE
        Win - Reboot when pending.ps1

    .NOTES
        Author: D.de Kooker <info@dcomputers.nl>
        Source: n/a

    .CHANGELOG
        24-06-2022 - Initial script. 
#>

#region Parameters, functions and global variables
    [CmdletBinding()]
    param(
        # ComputerName is optional. If not specified, localhost is used.
        [ValidateNotNullOrEmpty()]
        [string[]]$ComputerName,
        
        [Parameter()]
        [ValidateNotNullOrEmpty()]
        [pscredential]$Credential
    )

    $ErrorActionPreference = 'Stop'

    $scriptBlock = {
        if ($null -ne $using) {
            # $using is only available if this is being called with a remote session
            $VerbosePreference = $using:VerbosePreference
        }

        function Test-RegistryKey {
            [OutputType('bool')]
            [CmdletBinding()]
            param
            (
                [Parameter(Mandatory)]
                [ValidateNotNullOrEmpty()]
                [string]$Key
            )
        
            $ErrorActionPreference = 'Stop'

            if (Get-Item -Path $Key -ErrorAction Ignore) {
                $true
            }
        }

        function Test-RegistryValue {
            [OutputType('bool')]
            [CmdletBinding()]
            param
            (
                [Parameter(Mandatory)]
                [ValidateNotNullOrEmpty()]
                [string]$Key,

                [Parameter(Mandatory)]
                [ValidateNotNullOrEmpty()]
                [string]$Value
            )
        
            $ErrorActionPreference = 'Stop'

            if (Get-ItemProperty -Path $Key -Name $Value -ErrorAction Ignore) {
                $true
            }
        }

        function Test-RegistryValueNotNull {
            [OutputType('bool')]
            [CmdletBinding()]
            param
            (
                [Parameter(Mandatory)]
                [ValidateNotNullOrEmpty()]
                [string]$Key,

                [Parameter(Mandatory)]
                [ValidateNotNullOrEmpty()]
                [string]$Value
            )
        
            $ErrorActionPreference = 'Stop'

            if (($regVal = Get-ItemProperty -Path $Key -Name $Value -ErrorAction Ignore) -and $regVal.($Value)) {
                $true
            }
        }

        # Added "test-path" to each test that did not leverage a custom function from above since
        # an exception is thrown when Get-ItemProperty or Get-ChildItem are passed a nonexistant key path
        $tests = @(
            { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootPending' }
            { Test-RegistryKey -Key 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootInProgress' }
            { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired' }
            { Test-RegistryKey -Key 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\PackagesPending' }
            { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\PostRebootReporting' }
            #{ Test-RegistryValueNotNull -Key 'HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager' -Value 'PendingFileRenameOperations' }
            #{ Test-RegistryValueNotNull -Key 'HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager' -Value 'PendingFileRenameOperations2' }
            { 
                # Added test to check first if key exists, using "ErrorAction ignore" will incorrectly return $true
                'HKLM:\SOFTWARE\Microsoft\Updates' | Where-Object { test-path $_ -PathType Container } | ForEach-Object {
                    if(Test-Path "$_\UpdateExeVolatile" ){ 
                        (Get-ItemProperty -Path $_ -Name 'UpdateExeVolatile' | Select-Object -ExpandProperty UpdateExeVolatile) -ne 0 
                    }else{ 
                        $false 
                    }
                }
            }
            { Test-RegistryValue -Key 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce' -Value 'DVDRebootSignal' }
            { Test-RegistryKey -Key 'HKLM:\SOFTWARE\Microsoft\ServerManager\CurrentRebootAttempts' }
            { Test-RegistryValue -Key 'HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon' -Value 'JoinDomain' }
            { Test-RegistryValue -Key 'HKLM:\SYSTEM\CurrentControlSet\Services\Netlogon' -Value 'AvoidSpnSet' }
            {
                # Added test to check first if keys exists, if not each group will return $Null
                # May need to evaluate what it means if one or both of these keys do not exist
                ( 'HKLM:\SYSTEM\CurrentControlSet\Control\ComputerName\ActiveComputerName' | Where-Object { test-path $_ } | % { (Get-ItemProperty -Path $_ ).ComputerName } ) -ne 
                ( 'HKLM:\SYSTEM\CurrentControlSet\Control\ComputerName\ComputerName' | Where-Object { Test-Path $_ } | % { (Get-ItemProperty -Path $_ ).ComputerName } )
            }
            {
                # Added test to check first if key exists
                'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Services\Pending' | Where-Object { 
                    (Test-Path $_) -and (Get-ChildItem -Path $_) } | ForEach-Object { $true }
            }
        )

        foreach ($test in $tests) {
            Write-Verbose "Running scriptblock: [$($test.ToString())]"
            if (& $test) {
                $true
                break
            }
        }
    }
#endregion
#region script
# if ComputerName was not specified, then use localhost 
# to ensure that we don't create a Session.
    if ($null -eq $ComputerName) {
        $ComputerName = "localhost"
    }

    foreach ($computer in $ComputerName) {
        try {
            $connParams = @{
                'ComputerName' = $computer
            }
            if ($PSBoundParameters.ContainsKey('Credential')) {
                $connParams.Credential = $Credential
            }

            $output = @{
                ComputerName    = $computer
                IsPendingReboot = $false
            }

            if ($computer -in ".", "localhost", $env:COMPUTERNAME ) {        
                if (-not ($output.IsPendingReboot = Invoke-Command -ScriptBlock $scriptBlock)) {
                    $output.IsPendingReboot = $false
                }
            }
            else {
                $psRemotingSession = New-PSSession @connParams
            
                if (-not ($output.IsPendingReboot = Invoke-Command -Session $psRemotingSession -ScriptBlock $scriptBlock)) {
                    $output.IsPendingReboot = $false
                }
            }
            [pscustomobject]$output.IsPendingReboot
            if ($output.IsPendingReboot -eq $true){Restart-Computer -Force}
        } catch {
            Write-Error -Message $_.Exception.Message
        } finally {
            if (Get-Variable -Name 'psRemotingSession' -ErrorAction Ignore) {
                $psRemotingSession | Remove-PSSession
            }
        }
    }
#endregion