Refactor response handling

[danschultzer]

I'm not happy with how responses are currently handled. As an example here's how an error response is handled:

ex_oauth2_provider/lib/ex_oauth2_provider/oauth2/authorization.ex

Lines 27 to 34 in 9a8fc6d

	@spec authorize(Schema.t(), map(), keyword()) :: {:ok, binary()} | Response.error() | Response.redirect() | Response.native_redirect()
	def authorize(resource_owner, request, config \\ []) do
	case validate_response_type(request, config) do
	{:error, :invalid_response_type} -> unsupported_response_type(resource_owner, request, config)
	{:error, :missing_response_type} -> invalid_request(resource_owner, request, config)
	{:ok, token_module} -> token_module.authorize(resource_owner, request, config)
	end
	end

ex_oauth2_provider/lib/ex_oauth2_provider/oauth2/authorization.ex

Lines 48 to 49 in 9a8fc6d

	defp unsupported_response_type(resource_owner, request, config),
	do: handle_error_response(resource_owner, request, Error.unsupported_response_type(), config)

ex_oauth2_provider/lib/ex_oauth2_provider/oauth2/authorization.ex

Lines 54 to 59 in 9a8fc6d

	defp handle_error_response(resource_owner, request, error, config) do
	resource_owner
	|> Utils.prehandle_request(request, config)
	|> Error.add_error(error)
	|> Response.error_response(config)
	end

ex_oauth2_provider/lib/ex_oauth2_provider/oauth2/utils/error.ex

Lines 5 to 9 in 9a8fc6d

	@spec add_error({:ok, map()} | {:error, map()}, {:error, map(), atom()}) :: {:error, map()}
	def add_error({:error, params}, _), do: {:error, params}
	def add_error({:ok, params}, {:error, error, http_status}) do
	{:error, Map.merge(params, %{error: error, error_http_status: http_status})}
	end

ex_oauth2_provider/lib/ex_oauth2_provider/oauth2/authorization/utils/response.ex

Lines 13 to 14 in 9a8fc6d

	@spec error_response({:error, map()}, keyword()) :: error() | redirect() | native_redirect()
	def error_response({:error, %{error: error} = params}, config), do: build_response(params, error, config)

ex_oauth2_provider/lib/ex_oauth2_provider/oauth2/authorization/utils/response.ex

Lines 31 to 38 in 9a8fc6d

	defp build_response(%{request: request} = params, payload, config) do
	payload = add_state(payload, request)
	case can_redirect?(params, config) do
	true -> build_redirect_response(params, payload, config)
	_ -> build_standard_response(params, payload)
	end
	end

From the above it's almost impossible to figure what's going on. The code is fragmented and you have to go back and fourth between several files to figure out what's going on. Also the response doesn't make much sense since it's a tuple with a map where an :error key value has been added. Not very helpful.

It should be a lot more compact an easy to read. Something along these lines, almost everything contained within this module:

  def authorize(resource_owner, request, config \\ []) do
    request
    |> validate_response_type(config)
    |> case do
      {:error, error}     -> response_type_validation_error({:error, error}, request, config)
      {:ok, token_module} -> token_authorize(token_module, resource_owner, request, config)
    end
  end

  defp response_type_validation_error({:error, error}, request, config) do
    # Return HTTP error code or build redirect response
  end

  defp token_authorize(Code, resource_owner, request, config), do: Code.authorize(resource_owner, request, config)