Download Windows Admin Center through PowerShell

Invoke-DownloadWacInstaller.ps1

<#PSScriptInfo

.VERSION 2021.03.00

.GUID 0bbe0f49-d3c4-4479-993f-0b7f824f9ace

.AUTHOR Tim Small

.COMPANYNAME Smalls.Online

.COPYRIGHT 2021

.TAGS

.LICENSEURI

.PROJECTURI

.ICONURI

.EXTERNALMODULEDEPENDENCIES 

.REQUIREDSCRIPTS

.EXTERNALSCRIPTDEPENDENCIES

.RELEASENOTES


.PRIVATEDATA

#>

<# 

.DESCRIPTION 
 Download Windows Admin Center through PowerShell. 

#> 
[CmdletBinding()]
param(
    [Parameter(Position = 0, Mandatory)]
    [ValidateNotNullOrEmpty()]
    [string]$OutputDirectory
)

#Resolve the output directory provided and throw a terminating error if it can't be resolved.
$outputResolvedPath = (Resolve-Path -Path $OutputDirectory -ErrorAction "Stop").Path

#Define the generic 'aka.ms' URL for Windows Admin Center.
$wacGenericDownloadUrl = "https://aka.ms/WACDownload"

Write-Verbose "Getting the redirect URL from '$($wacGenericDownloadUrl)'."

#Need to create a HttpClient object with a 'ClientHandler' option for not allowing auto-redirect. This is to prevent the HttpClient from automatically resolving to the redirect-uri from the HTTP response.
$redirectHttpClient = [System.Net.Http.HttpClient]::new(
    [System.Net.Http.HttpClientHandler]@{
        "AllowAutoRedirect" = $false
    },
    $true
)
$redirectHttpClient.DefaultRequestHeaders.ConnectionClose = $true

#Send a HttpRequestMessage for the generic download URL, so we can grab what the redirect-uri is.
$redirectHttpReqMsg = [System.Net.Http.HttpRequestMessage]::new(
    [System.Net.Http.HttpMethod]::Get,
    $wacGenericDownloadUrl
)
$redirectHttpRsp = $redirectHttpClient.Send($redirectHttpReqMsg)

#Test to see if the 'Location' property exists in the header and that the StatusCode is set to 'Moved'.
$redirectLocation = $null
switch (($redirectHttpRsp.Headers.Contains("Location")) -and ($redirectHttpRsp.StatusCode -eq [System.Net.HttpStatusCode]::Moved)) {
    $false {
        $PSCmdlet.ThrowTerminatingError(
            [System.Management.Automation.ErrorRecord]::new(
                [System.Exception]::new("The response was returned with either the header not containing the 'Location' property or the  'StatusCode' was not set to 'Moved'. See the target object in the error record."),
                "FailedToParseHttpHeaders",
                [System.Management.Automation.ErrorCategory]::InvalidData,
                $redirectHttpRsp
            )
        )
    }

    Default {
        $redirectLocation = $redirectHttpRsp.Headers.Location.ToString()
        break
    }
}

$redirectHttpClient.Dispose() #Dispose the HttpClient

Write-Verbose "Redirected URL is '$($redirectLocation)'."

#Perform a regex on the URL that we would have been redirected to. This is to get the filename automatically.
$redirectRegex = [System.Text.RegularExpressions.Regex]::new(
    "(?>https|http):\/\/download\.microsoft\.com[a-zA-Z0-9\/-]+\/(?'fileName'WindowsAdminCenter\d{1,4}\.msi)"
)

#Test to make sure the regex match will be successful.
switch ($redirectRegex.IsMatch($redirectLocation)) {
    $false {
        $PSCmdlet.ThrowTerminatingError(
            [System.Management.Automation.ErrorRecord]::new(
                [System.Exception]::new("The input URL, '$($redirectLocation)' failed the regex match."),
                "FailedToGetFileNameFromUrl",
                [System.Management.Automation.ErrorCategory]::ParserError,
                $redirectLocation
            )
        )
    }
}

#Run the match and get the matched string.
$redirectRegexMatch = $redirectRegex.Match($redirectLocation)
$downloadFileName = $redirectRegexMatch.Groups.Item('fileName').Value

#Join the path of the output directory and the file name it should be.
$downloadPath = Join-Path -Path $outputResolvedPath -ChildPath $downloadFileName
Write-Verbose "File name will be '$($downloadFileName)' and will be saved to '$($outputResolvedPath)'."

#Check to see if the file already exists and if the file, does prompt for overwrite.
Write-Verbose "Testing to see if the file already exists in '$($outputResolvedPath)'."
switch (Test-Path -Path $downloadPath) {
    $true {
        $overwriteFilePrompt = $PSCmdlet.ShouldContinue("File already exists", "Do you want to overwrite '$($downloadPath)'?")
        switch ($overwriteFilePrompt) {
            $false {
                $PSCmdlet.ThrowTerminatingError(
                    [System.Management.Automation.ErrorRecord]::new(
                        [System.Exception]::new("File already exists"),
                        "FileAlreadyExists",
                        [System.Management.Automation.ErrorCategory]::ResourceExists,
                        $downloadPath
                    )
                )
            }

            Default {
                Remove-Item -Path $downloadPath -Force
                break
            }
        }
    }
}

#Create an HttpClient for the download
$downloadHttpClient = [System.Net.Http.HttpClient]::new()
$downloadHttpReqMsg = [System.Net.Http.HttpRequestMessage]::new(
    [System.Net.Http.HttpMethod]::Get,
    $redirectLocation
)

#Download the file.
Write-Verbose "Downloading file."
$downloadHttpRsp = $downloadHttpClient.Send($downloadHttpReqMsg)
$installFileByteArray = $downloadHttpRsp.Content.ReadAsByteArrayAsync().GetAwaiter().GetResult()

$downloadHttpClient.Dispose() #Dispose the HTTP client

$null = [System.IO.File]::WriteAllBytes($downloadPath, $installFileByteArray) #Write the byte array to the output path

$downloadedFile = Get-Item -Path $downloadPath

return $downloadedFile