module RestClient::Payload

def generate(params)
  if params.is_a?(String)
    Base.new(params)
  elsif params
    if params.delete(:multipart) == true || has_file?(params)
      Multipart.new(params)
    else
      UrlEncoded.new(params)
    end
  else
    nil
  end
end

def has_file?(params)
  params.any? do |_, v|
    case v
      when Hash
        has_file?(v)
      else
        v.respond_to?(:path) && v.respond_to?(:read)
    end
  end
end