Param(
    [string] [Parameter(Mandatory=$true)] $ResourceGroup,
    [string] [Parameter(Mandatory=$true)] $AppName,
    [string] [Parameter(Mandatory=$true)] $FunctionName,
    [string] [Parameter(Mandatory=$true)] $KeyName,
    [string] [Parameter(Mandatory=$true)] $KeyValue
    )

    function getAuthenticationToken([string]$appName, [string]$resourceGroup)
    {
    $user = az webapp deployment list-publishing-profiles -n $appName -g $resourceGroup `
            --query "[?publishMethod=='MSDeploy'].userName" -o tsv

    $pass = az webapp deployment list-publishing-profiles -n $appName -g $resourceGroup `
            --query "[?publishMethod=='MSDeploy'].userPWD" -o tsv

    $pair = "$($user):$($pass)"
    $encodedCreds = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes($pair))

    $jwt = Invoke-RestMethod -Uri "https://$appName.scm.azurewebsites.net/api/functions/admin/token" -Headers @{Authorization=("Basic {0}" -f $encodedCreds)} -Method GET

    return $jwt
}

function setFunctionKey([string]$appName, [string]$functionName, [string] $keyName, [string]$keyValue, [string]$jwt)
{
    $body = (@{
        "name" = $keyName
        "value" = $keyValue
    } | ConvertTo-Json)

    #Setting the SecurityProtocol is a workaround for calling Azure APIs, I think?
    [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
    try {
        Invoke-RestMethod -Uri "https://$appName.azurewebsites.net/admin/functions/$functionName/keys/$keyName/" `
            -Headers @{Authorization=("Bearer $jwt")} `
            -Method PUT `
            -ContentType "application/json" `
            -Body $body
    } catch {
        $_.Exception | Format-List -Force
    }
}

$jwt = getAuthenticationToken $AppName $ResourceGroup
setFunctionKey $AppName $FunctionName $KeyName $KeyValue $jwt
Write-Host "Specified key '$KeyName' has been added to $FunctionName"

$user = az webapp deployment list-publishing-profiles -n $appName -g $resourceGroup `
                --query "[?publishMethod=='MSDeploy'].userName" -o tsv