Outputting a file with an Azure Function - powershell

Question

I'm trying to experiment with Azure Functions. Basically my use case is calling the function with a GUID as GET Parameter, having the function download the WIX toolkit DLL and an MSI file, updating a parameter in the MSI file, and the returning that file to the caller of the function (as download prompt for example).
I'm mostly there, just need some help getting the download prompt/send to happen, my code so far:
$urlWix = "http://domain/wix.dll"
$outputWix = "$Env:TEMP\wix.dll"
Invoke-WebRequest -Uri $urlWix -OutFile $outputWix
try{Add-Type -Path $outputWix}catch{$Null}
$urlMSI = "http://domain/file.msi"
$outputFile = "$Env:TEMP\file.msi"
Invoke-WebRequest -Uri $urlMSI -OutFile $outputFile
$oDatabase = New-Object Microsoft.Deployment.WindowsInstaller.Database($outputFile,[Microsoft.Deployment.WindowsInstaller.DatabaseOpenMode]::Direct);
$sSQLQuery = "SELECT * FROM Property WHERE Property= 'MYPROPERTY'"
[Microsoft.Deployment.WindowsInstaller.View]$oView = $oDatabase.OpenView($sSQLQuery)
$oView.Execute()
$oRecord = $oView.Fetch()
$oRecord.SetString("Value","MyCustomValue")
$oView.Modify([Microsoft.Deployment.WindowsInstaller.ViewModifyMode]::Update,$oRecord)
$oView.Close();
$oDatabase.Dispose();
$file = get-item $outputFile
write-output $file

Answer 1

Unfortunately due to content type issues this is not possible in powershell. You can do this via a C#, F#, or Node (isRaw) function. The problem is that you need to specify headers via the JSON response format, which would convert any non-text data into a base64 string.
If you want to sent a text file via powershell it is possible:
$response = ConvertTo-JSON #{
Body="your file data";
Headers=#{
# unfortunately it seems functions does not support 'filename=...'
'Content-Disposition'='attachment';
# you would use application/octet-stream, but because it's converted to JSON you lose binary content
'Content-Type'='text/plain';
};
}
Out-File -Encoding Ascii -FilePath $res -inputObject $response