Plug 101 - Part 2

plug_authentication.ex

defmodule Authenticate do
  import Plug.Conn
  
  def call(conn, _opts) do
    case get_req_header(conn, "authorization") do
      ["Bearer " <> token] -> authenticate(conn, token)
      _                    -> reject(conn, "Bearer token missing")
    end
  end

  defp authenticate(conn, token) do
    case User.find_by_token(token) do
      nil  -> reject(conn, "Invalid token - user not found")
      user -> assign(conn, :current_user, user)
    end
  end
  
  defp reject(conn, reason) do
    conn
    |> send_resp(401, reason)
    |> halt
  end
end