feat: self-sufficient grading client

Author: polvalente

modules/grading_client/config/config.exs

@@ -7,29 +7,8 @@ defmodule GradingClient do
   Checks the answer to a question.
   """
 
-  @spec check_answer(any() | String.t(), integer(), integer()) :: :ok | {:error, String.t()}
-  def check_answer(answer, module_id, question_id) when not is_binary(answer) do
-    check_answer(module_id, question_id, "#{inspect(answer)}")
-  end
-
+  @spec check_answer(any(), any(), any()) :: :correct | {:incorrect, String.t() | nil}
   def check_answer(answer, module_id, question_id) do
-    # TODO: Make this configurable
-    url = "http://localhost:4000/api/answers/check"
-
-    headers = [
-      {"Content-Type", "application/json"}
-    ]
-
-    json = Jason.encode!(%{module_id: module_id, question_id: question_id, answer: answer})
-
-    %{body: body, status_code: 200} = HTTPoison.post!(url, json, headers)
-
-    %{"correct" => is_correct, "help_text" => help_text} = Jason.decode!(body)
-
-    if is_correct do
-      :ok
-    else
-      {:error, help_text}
-    end
+    GradingClient.Answers.check(module_id, question_id, answer)
   end
 end

modules/grading_client/lib/grading_client.ex

@@ -0,0 +1,11 @@
+defmodule GradingClient.Answer do
+  @enforce_keys [:question_id, :module_id, :answer, :help_text]
+  defstruct [:question_id, :module_id, :answer, :help_text]
+
+  @type t :: %__MODULE__{
+          module_id: term(),
+          question_id: term(),
+          answer: term(),
+          help_text: term()
+        }
+end

modules/grading_client/lib/grading_client/answer.ex

@@ -0,0 +1,56 @@
+defmodule GradingClient.Answers do
+  @moduledoc """
+  This module is responsible for checking if an answer is correct.
+  It uses the `AnswerStore` to fetch the answer and compares if it is correct or not.
+  """
+  use GenServer
+
+  alias GradingClient.Answer
+
+  @table :answer_store
+
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  @impl true
+  def init(opts) do
+    :ets.new(@table, [:set, :named_table])
+
+    filename = opts[:filename]
+
+    {answers, _} = Code.eval_file(filename)
+
+    Enum.each(answers, fn answer ->
+      :ets.insert(@table, {{answer.module_id, answer.question_id}, answer})
+    end)
+
+    {:ok, nil}
+  end
+
+  @doc """
+  Checks if the given answer is correct.
+  """
+  @spec check(integer(), integer(), String.t()) :: :correct | {:incorrect, String.t()}
+  def check(module_id, question_id, answer) do
+    GenServer.call(__MODULE__, {:check, module_id, question_id, answer})
+  end
+
+  @impl true
+  def handle_call({:check, module_id, question_id, answer}, _from, state) do
+    result =
+      case :ets.lookup(@table, {module_id, question_id}) do
+        [] ->
+          {:incorrect, "Question not found"}
+
+        [{_id, %Answer{answer: correct_answer, help_text: help_text}}] ->
+          if answer == correct_answer do
+            :correct
+          else
+            {:incorrect, help_text}
+          end
+      end
+
+    {:reply, result, state}
+  end
+end

modules/grading_client/lib/grading_client/answers.ex

@@ -2,9 +2,14 @@ defmodule GradingClient.Application do
   use Application
 
   def start(_type, _args) do
-    Kino.SmartCell.register(GradingClient.GradingCell)
+    Kino.SmartCell.register(GradingClient.GradedCell)
 
-    children = []
+    default_filename = Path.join(:code.priv_dir(:grading_client), "answers.exs")
+
+    children = [
+      {GradingClient.Answers,
+       filename: Application.get_env(:grading_client, :answers_file, default_filename)}
+    ]
 
     opts = [strategy: :one_for_one, name: GradingClient.Supervisor]
     Supervisor.start_link(children, opts)

modules/grading_client/lib/grading_client/application.ex

@@ -1,7 +1,7 @@
-defmodule GradingClient.GradingCell do
+defmodule GradingClient.GradedCell do
   use Kino.JS
   use Kino.JS.Live
-  use Kino.SmartCell, name: "Graded"
+  use Kino.SmartCell, name: "Graded Cell"
 
   @impl true
   def init(attrs, ctx) do

modules/grading_client/lib/grading_client/grading_cell.ex

@@ -22,9 +22,6 @@ defmodule GradingClient.MixProject do
   # Run "mix help deps" to learn about dependencies.
   defp deps do
     [
-      {:grading_server, path: "#{__DIR__}/../../grading_server"},
-      {:httpoison, "~> 2.1"},
-      {:jason, "~> 1.4"},
       {:kino, "~> 0.10"}
     ]
   end

modules/grading_client/mix.exs

@@ -0,0 +1,24 @@
+alias GradingClient.Answer
+
+to_answers = fn module_name, answers ->
+  Enum.map(answers, fn data ->
+    %Answer{
+      module_id: module_name,
+      question_id: data.question_id,
+      answer: data.answer,
+      help_text: data[:help_text]
+    }
+  end)
+end
+
+owasp_questions = [
+  %{
+    question_id: 1,
+    answer: "A",
+    help_text: "A"
+  }
+]
+
+List.flatten([
+  to_answers.(OWASP, owasp_questions)
+])