phoenix protobuf gist

config.exs

config :mime, :types, %{
  "application/x-protobuf" => ["protobuf"]
}

decode_protobuf.ex

# in plugs folder

defmodule AppWeb.Plugs.DecodeProtobuf do
  import Plug.Conn

  def init(opts), do: opts

  def call(conn, protobuf_module) do
    with \
      true                <- protobuf_content?(conn),
      {:ok, binary, conn} <- parse_body(conn, ""),
      {:ok, binary, conn} <- decode_body(conn, binary)
    do
      decoded = Jsoorbp.MyPayload.decode(binary)

      conn |> assign(:protobuf, decoded)
    else
      _ ->
        conn
        |> send_resp(400, "")
        |> halt()
    end
  end

  defp protobuf_content?(conn) do
    case get_req_header(conn, "content-type") do
      ["application/x-protobuf" <> _] ->
        true
      _ ->
        false
    end
  end

  def parse_body(%Plug.Conn{} = conn, acc \\ "") do
    case read_body(conn) do
      {:ok, body, next_conn} ->
        {:ok, acc <> body, next_conn}
      {:more, body, next_conn} ->
        parse_body(next_conn, acc <> body)
      other ->
        other
    end
  end

  def decode_body(%Plug.Conn{} = conn, binary) do
    case get_req_header(conn, "content-encoding") do
      ["deflate"] ->
        binary_decoded =  :zlib.uncompress binary
        {:ok, binary_decoded, conn}
      _ ->
        {:ok, binary, conn}
    end
  end
end

definitions.pb.ex

# this will be generated from the schema above

definitions.proto

syntax = "proto2";

package jsoorbp;

message MyPayload {
    required string key = 1;
}

home_controller.ex

  def log(conn, params) do
    send_resp(conn, 200, "")
  end

mix.exs

       {:protobuf, "~> 0.7.1"},
       # Only for files generated from Google's protos.
       # Can be ignored if you don't use Google's protos.
       # Or you can generate the code by yourself.
       {:google_protos, "~> 0.1"},

router.ex

  pipeline :protobuf do                                                                                                                                                  
    plug :accepts, ["protobuf"]
    plug JsoorWeb.Plugs.DecodeProtobuf
  end

  scope "/", JsoorWeb do
    pipe_through [:protobuf]

    post "/log", HomeController, :log
  end