param (
  [string]$path,
  [string]$first_name,
  [string]$last_name,
  [string]$user_name,
  [string]$password
)

function CreateUser {
  param (
    [string]$path,
    [string]$first_name,
    [string]$last_name,
    [string]$user_name,
    [string]$password
  )
  echo "Creating: $first_name $last_name - $user_name
  $securepassword = ConvertTo-SecureString $password -AsPlainText -Force
  New-AdUser -Name $user_name -GivenName $first_name -Surname $last_name -AccountPassword $securepassword
}

If($path) {
  $file = Get-Content $path {
  foreach($line in $file) {
    $user = $line.Split(",");
    createUser @user
  }
} else {
  createUser($first_name, $last_name, $user_name, $password)
}