#Requires -version 2

## Get the Windows version information
$WinVersion = "{0}.{1}" -f ([System.Environment]::OSVersion.Version).Major,([System.Environment]::OSVersion.Version).Minor
$WinBuild = ([System.Environment]::OSVersion.Version).Build

## Get PowerShell version information
$CurrentVersion = "{0}.{1}" -f $PSVersionTable.PSVersion.Major,$PSVersionTable.PSVersion.Minor

## Check the OS architecture
If ( Test-Path -PathType Container -Path ${env:ProgramFiles(x86)} ) { $Is64bit = $true } Else { $Is64bit = $false }

## Set a variable to make sure the current Windows version is supported
$InstallSupported = $true

Switch ( $WinVersion ) {

    ## Windows Vista
    "6.0" {
        If ( $Is64bit ) { $URL = 'https://download.microsoft.com/download/E/7/6/E76850B8-DA6E-4FF5-8CCE-A24FC513FD16/Windows6.0-KB2506146-x64.msu' }
        Else            { $URL = 'https://download.microsoft.com/download/E/7/6/E76850B8-DA6E-4FF5-8CCE-A24FC513FD16/Windows6.0-KB2506146-x86.msu' }
        $UpgradeVersion = 3.0
    ; break }

    ## Windows 7
    "6.1" {
        ## PowerShell 4.0
        If ( $Is64bit ) { $URL = 'https://download.microsoft.com/download/3/D/6/3D61D262-8549-4769-A660-230B67E15B25/Windows6.1-KB2819745-x64-MultiPkg.msu' }
        Else            { $URL = 'https://download.microsoft.com/download/3/D/6/3D61D262-8549-4769-A660-230B67E15B25/Windows6.1-KB2819745-x86-MultiPkg.msu' }
        $UpgradeVersion = 4.0
    ; break }

    ## Windows 8
    #"6.2" {; break }

    ## Windows 8.1
    #"6.3" {; break }

    ## Windows 10
    #"10.0" {; break }

    ## Not Supported
    default { $InstallSupported = $false ; break }
}

## Make sure installation is supported
If ( ($InstallSupported) -and ($CurrentVersion -lt $UpgradeVersion) ) {

    ## Get the file type so we install it the correct way
    $FileType = ([System.IO.Path]::GetExtension($File)).ToUpper()

    ## Set the destination file for the downloaded package
    $File = "${env:TEMP}\$(Split-Path -Leaf $URL)"
    
    ## Download the installation package
    (New-Object Net.WebClient).DownloadFile($URL,$File)
    
    If ( Test-Path $File ) {

        ## Get the file extension so we use the correct method to install the update
        $FileType = [System.IO.Path]::GetExtension($File)

        ## Write a message so we know what version was upgraded.
        Write-Host "Upgrading PowerShell ${CurrentVersion} to version ${UpgradeVersion}"
    
        ## Install the package
        If ( $FileType -ieq "MSU" ) { Start-Process wusa.exe -ArgumentList "${File} /quiet /norestart" -Wait }
        If ( $FileType -ieq "MSI" ) { Start-Process msiexec.exe -ArgumentList "/i ${File} /qn /norestart" -Wait }

        ## Delete the downloaded package
        Remove-Item -Path $File -Force
    }

} Else { Write-Host "This script cannot upgrade PowerShell on this endpoint." }