defmodule QuizGrader do
  require Ami.Gettext
  import Ecto.Query

  alias Ami.{
    Repo,
    Enrollment,
    Quiz,
    User,
    UserAnswer,
    Score,
    Answer,
    Gettext
  }

  def grade(params) do
    enrollment =
      Repo.get(Enrollment, params["enrollment_id"])
      |> Repo.preload([:scores, course_period: [:course]])

    quiz =
      Repo.get(Quiz, params["quiz_id"])
      |> Repo.preload(questions: [answers: from(a in Answer, order_by: [asc: a.id])])

    user =
      Repo.get(User, params["user_id"])
      |> Repo.preload(:profile)

    score = Score.find(quiz.id, enrollment.id)

    if score != nil do
      {
        Gettext.gettext(
          "You have already taken this quiz - Please move on to the activity and next lesson."
        ),
        enrollment,
        quiz,
        user
      }
    else
      user_answers =
        Map.drop(params, [
          "course_id",
          "enrollment_id",
          "lesson_id",
          "quiz_id",
          "user_id",
          "submit_confirmed"
        ])

      correct_answers = correct_answers(user_answers, quiz)
      total_questions = total_questions(quiz)
      quiz_score = score(user_answers, quiz)

      if length(Map.to_list(user_answers)) != total_questions do
        {
          Gettext.gettext("Please answer all the questions to get a grade for this quiz"),
          enrollment,
          quiz,
          user
        }
      else
        user_answers
        |> save_answers(enrollment, quiz, user)

        Score.insert_changeset(%Score{}, %{
          value: quiz_score,
          answers_correct: correct_answers,
          total_questions: total_questions,
          quiz_id: quiz.id,
          user_id: user.id,
          enrollment_id: enrollment.id,
          course_id: enrollment.course_period.course_id,
          course_period_id: enrollment.course_period.id
        })
        |> Repo.insert()

        # Update the enrollment progress binary
        {:ok, enrollment} =
          enrollment
          |> Repo.preload([:scores, course_period: [:course]], force: true)
          |> Enrollment.update_progress()

        {:ok, enrollment} = Enrollment.update_course_flags(enrollment)

        {:ok, enrollment} =
          Ecto.Changeset.change(enrollment, %{updated_at: Timex.now()})
          |> Repo.update()

        {:ok, enrollment} =
          if enrollment.course_started == false do
            Ecto.Changeset.change(enrollment, %{course_started: true, updated_at: Timex.now()})
            |> Repo.update()
          else
            {:ok, enrollment}
          end

        if quiz.title == "Final Exam" do
          {
            Gettext.gettext(
              "Congratulations on completing your final exam! You scored %{score}%. Now, please go to the Final Assignment tab and review, complete and submit your assignment to complete the course.",
              score: quiz_score
            ),
            enrollment,
            quiz,
            user
          }
        else
          {Gettext.gettext("You scored a %{score}% on this quiz.", score: quiz_score), enrollment,
           quiz, user}
        end
      end
    end
  end

  defp save_answers(answers, enrollment, quiz, user) do
    Enum.each(answers, fn {k, v} ->
      question = Enum.find(quiz.questions, &(&1.id == String.to_integer(k)))
      answer = Enum.find(question.answers, &(&1.value == v))

      UserAnswer.changeset(%UserAnswer{}, %{
        user_id: user.id,
        answer_id: answer.id,
        course_period_id: enrollment.course_period.id,
        question_id: question.id,
        quiz_id: quiz.id
      })
      |> Repo.insert()
    end)

    answers
  end

  defp correct_answers(answers, quiz) do
    Enum.filter(answers, fn {k, v} ->
      question = Enum.find(quiz.questions, &(&1.id == String.to_integer(k)))
      correct_answer = Enum.find(question.answers, &(&1.correct_answer == true))
      correct_answer.value == v
    end)
    |> length()
  end

  defp total_questions(quiz), do: length(quiz.questions)

  defp score(answers, quiz) do
    (correct_answers(answers, quiz) * 100 / total_questions(quiz))
    |> Float.round()
    |> Kernel.trunc()
  end
end