Function isArgExist ($hostname) { 
 if ([string]::IsNullOrEmpty($hostname)) {
     Write-Output("you should pass the hostname, Exit")
     exit 
  } 
} 

Function isResolvable ($puppetServer) {
  $checkResolution =  Resolve-DnsName -Name $puppetServer -ErrorAction SilentlyContinue
  if ($checkResolution -eq $null) {
     Write-Output "$puppetServer is not resolvable, Exit"
     exit
  }
}

Function downloadPuppetClient ($tempPath, $executableFileName, $downloadURL ) {
	$installer=-join($tempPath, $executableFileName)
	if(![System.IO.File]::Exists($installer)){
		Write-Output("Download puppet Client ")
		Write-Output($installer)	
		Invoke-WebRequest $downloadURL -OutFile $installer -UseBasicParsing
	} 
}

Function ispuppetClientinstalled {
   $isInstalled=(Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\* | Where { $_.DisplayName -like '*puppet*' }) -ne $null
   if ($isInstalled) {
	    Write-Output("puppet client is already installed, Exit")
        exit
   }
}

Function installpuppetClient($tempPath, $executableFileName, $puppetServer, $hostname) {
    $installer=-join($tempPath, $executableFileName)
    Write-Output("installing puppet Client and sending the certification request to puppet Server...")
    Start-Process -FilePath "msiexec.exe" -ArgumentList "/qn /norestart /i $installer PUPPET_MASTER_SERVER=$puppetServer PUPPET_AGENT_CERTNAME=$hostname" -Wait 
    $puppetClientIsInstalled = (Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\* | Where { $_.DisplayName -like '*puppet*' }) -ne $null
    if(-Not $puppetClientIsInstalled) {
        Write-Output "Failed to install puppet Client, Exit";
        exit
    } else {
	Write-Output "puppet Client is now installed ";
    }
    Set-Service -Name puppet -StartupType Automatic
}

Function addpuppetExtIP () {
    $fileInput="C:\windows\system32\drivers\etc\hosts"
    $searchresults= Select-String -Path $fileInput  -Pattern "cmdbsrv"
    if ($searchresults -eq $null) {
       ADD-Content -path $fileInput -value "78.142.176.122                  cmdbsrv.kopi.org "
    }
}

##########################################
###### Global variables declaration
$hostname = $args[0]
$tempPath = $env:temp
$downloadURL = "https://www.progmag.com/telechargements/puppet7/puppet-agent-x64-latest.msi"
$executableFileName = "\puppet-agent-x64-latest.msi"
$puppetClientInstallationPath = -join($Env:Programfiles,"\Puppet Labs")
$puppetServer = "cmdbsrv.kopi.org"

##########################################
###### Main #########
## add Puppet external IP to hosts file
addpuppetExtIP
######## check puppet client is installed
ispuppetClientinstalled
######## check hostname is passed
isArgExist $hostname
######## check a puppet server is resolvable
isResolvable $puppetServer
######## download puppet client
downloadPuppetClient $tempPath $executableFileName $downloadURL
######## install puppet client and send certification request to the server
installpuppetClient $tempPath $executableFileName $puppetServer $hostname