module RestClient::Payload

def _has_file?(obj)
  case obj
  when Hash, ParamsArray
    obj.any? {|_, v| _has_file?(v) }
  when Array
    obj.any? {|v| _has_file?(v) }
  else
    obj.respond_to?(:path) && obj.respond_to?(:read)
  end
end

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

def has_file?(params)
  unless params.is_a?(Hash)
    raise ArgumentError.new("Must pass Hash, not #{params.inspect}")
  end
  _has_file?(params)
end