antikythera

# Copyright(c) 2015-2019 ACCESS CO., LTD. All rights reserved.

use Croma

defmodule AntikytheraCore.Handler.CowboyReq do
  alias Croma.Result, as: R
  alias Antikythera.{Time, GearName, PathInfo, Conn, Context}
  alias Antikythera.Http.{Method, QueryParams, Body}
  alias Antikythera.Request.PathMatches
  alias Antikythera.Context.GearEntryPoint
  alias AntikytheraCore.Conn, as: CoreConn
  alias AntikytheraCore.Handler.{GearError, BodyParser, HelperModules}
  alias AntikytheraCore.GearLog.{ContextHelper, Writer}

  @type result(a)    :: {:ok, a} | {:error, :cowboy_req.req}
  @type routing_info :: {GearName.t, nil | GearEntryPoint.t, Method.t, PathInfo.t, PathMatches.t}

  defun method(req :: :cowboy_req.req) :: result(Method.t) do
    try do
      :cowboy_req.method(req) |> Method.from_string() |> R.pure()
    rescue
      FunctionClauseError -> {:error, :cowboy_req.reply(400, req)}
    end
  end

  defun path_info(%{path: encoded_path_string, path_info: decoded_path_info} :: :cowboy_req.req) :: PathInfo.t do
    case byte_size(encoded_path_string) do
      0   -> []
      len ->
        case binary_part(encoded_path_string, len - 1, 1) do # Avoid `String.last/1` as it takes O(length_of_string)
          "/" -> decoded_path_info ++ [""] # append "" due to trailing '/'; See also: `GearAction.split_path_to_segments/1`
          _   -> decoded_path_info
        end
    end
  end

  defun query_params(req :: :cowboy_req.req, routing_info :: routing_info) :: result(QueryParams.t) do
    try do
      :cowboy_req.parse_qs(req)
      |> Map.new(fn
        {k, true} -> {k, ""}
        kv_pair   -> kv_pair
      end)
      |> R.pure()
    catch
      :exit, {:request_error, :qs, _message} -> {:error, with_conn(req, routing_info, %{}, &GearError.bad_request/1)}
    end
  end

  defun request_body_pair(req1           :: :cowboy_req.req,
                          routing_info   :: routing_info,
                          qparams        :: v[QueryParams.t],
                          helper_modules :: v[HelperModules.t]) :: result({:cowboy_req.req, {binary, Body.t}}) do
    case BodyParser.parse(req1) do
      {:ok, req2, raw, parsed}      -> {:ok, {req2, {raw, parsed}}}
      {:error, :invalid_body, req2} -> {:error, with_conn(req2, routing_info, qparams, &GearError.bad_request/1)}
      {:error, :timeout}            -> {:error, with_conn(req1, routing_info, qparams, &bad_request_with_body_timeout_logging(&1, helper_modules))}
    end
  end

  defunp bad_request_with_body_timeout_logging(%Conn{context: %Context{context_id: context_id}} = conn,
                                               %HelperModules{logger: logger}) :: Conn.t do
    Writer.info(logger, Time.now(), context_id, "timeout in receiving request body: something is wrong with the client?")
    GearError.bad_request(conn)
  end

  defun with_conn(req          :: :cowboy_req.req,
                  routing_info :: routing_info,
                  qparams      :: v[QueryParams.t],
                  body_pair    :: {binary, Body.t} \\ {"", ""},
                  f            :: (Conn.t -> Conn.t)) :: :cowboy_req.req do
    conn = CoreConn.make_from_cowboy_req(req, routing_info, qparams, body_pair)
    ContextHelper.set(conn)
    f.(conn) |> CoreConn.reply_as_cowboy_res(req)
  end
end