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<#
.DESCRIPTION
Replaces a credspec template with actual credspec and deploys to EKS cluster.

.SYNOPSIS
Creates a webhook deployment config yaml for an EKS kubernetes cluster

.PARAMETER Namespace
The kubernetes namespace to target

.PARAMETER ServiceAccount
The application service account

.PARAMETER CredSpecName
The name of the Credspec

.PARAMETER CredSpecFile
The file path to the Credential spec json file generated from Active Directory

.PARAMETER CredSpecTemplate
The path to the Credential Spec Template json file to deploy to kubernetes cluster

.PARAMETER CredSpecClusterRole
The path to the credential Spec cluster role template file to
configure cluster role to enable RBAC on specific GMSA credential specs

.PARAMETER DryRun
A switch that, when enabled, will generate the artifacts and pre-requisites for
deploying the credspec, but will return the config yaml content
rather than applying it to the cluster

#>

[CmdLetBinding()]
Param (
    [Parameter(Mandatory = $true)]
    [ValidateNotNullOrEmpty()]
    [string]$Namespace,
    
    [Parameter(Mandatory = $true)]
    [ValidateNotNullOrEmpty()]
    [string]$ServiceAccount,

    [Parameter(Mandatory = $true)]
    [ValidateNotNullOrEmpty()]
    [string]$CredSpecName,

    [Parameter(Mandatory = $true)]
    [ValidateScript({Test-Path -Path $_})]
    [string]$CredSpecFile,

    [Parameter(Mandatory = $false)]
    [ValidateScript({Test-Path -Path $_})]
    [string]$CredSpecTemplate = 'gmsa-credspec-template.json',

    [Parameter(Mandatory = $false)]
    [ValidateScript({Test-Path -Path $_})]
    [string]$CredSpecClusterRole = 'credspec-cluster-role-template.yaml',

    [Parameter(Mandatory = $false)]
    [switch]$DryRun
)

$ErrorActionPreference = 'Stop'
Set-StrictMode -Version Latest

if (!(Get-Command -Name 'kubectl' -ErrorAction:SilentlyContinue)) {
    throw 'kubectl not found'
}

Write-Output "Checking namespace : $Namespace"
$result = Invoke-Expression -command "kubectl get namespaces --field-selector metadata.name==$Namespace -o json" | Out-String | ConvertFrom-Json

if ($result.items.length -eq 0) {
    Write-Verbose "Creating namespace $Namespace"
    Invoke-Expression -Command "kubectl create namespace $Namespace"
}

Write-Output "Checking Serviceaccount:$ServiceAccount in namespace : $Namespace"
$result = Invoke-Expression -command "kubectl get serviceaccount -n $Namespace --field-selector metadata.name==$ServiceAccount -o json" | Out-String | ConvertFrom-Json

if ($result.items.length -eq 0) {
    Write-Verbose "Creating Serviceaccount $ServiceAccount"
    Invoke-Expression -Command "kubectl create serviceaccount $ServiceAccount -n $Namespace"
}

$credSpecContent = Get-Content -Path $CredSpecFile

$newCredSpec = Get-Content -Path $CredSpecTemplate | ForEach-Object {
    $_ -replace '\${CREDSPEC}', $credSpecContent `
       -replace '\${CREDSPECNAME}', $CredSpecName `
       -replace '\${NAMESPACE}', $Namespace
}

if ($DryRun) {
    Write-Output ($newCredSpec | Out-String)
} else {
    $tempOutFile = "newcredspec.json"
    Out-File -FilePath $tempOutFile -InputObject $newCredSpec -Force
    Invoke-Expression -Command "kubectl apply -f $tempOutFile"
    Remove-Item -Path $tempOutFile -Force
}

Write-Verbose "Assign role to service accounts to use specific GMSA credspecs"
$clusterRole = (Get-Content -Path $CredSpecClusterRole) | Foreach-Object {
    $_ -replace '\${CREDSPECNAME}', $CredSpecName `
        -replace '\${NAMESPACE}', $Namespace `
        -replace '\${SERVICEACCOUNTNAME}', $ServiceAccount
}

$tempOutFile = "newclusterrole.yaml"
Out-File -FilePath $tempOutFile -InputObject $clusterRole -Force

if ($DryRun) {
    Write-Output ("Cluster role file for credspec :{0} is generated at : {1}" -f $CredSpecName, $tempOutFile)
} else {
    Invoke-Expression -Command "kubectl apply -f $tempOutFile"
    Remove-Item -Path $tempOutFile -Force
}