examjam-frontend/app/exam/[id]/page.tsx

"use client";

import React, { useEffect, useState, useCallback, useMemo } from "react";
import { useParams, useRouter, useSearchParams } from "next/navigation";
import { useTimer } from "@/context/TimerContext";
import { useExam } from "@/context/ExamContext";
import { API_URL, getToken } from "@/lib/auth";
import Header from "@/components/Header";
import { Bookmark, BookmarkCheck } from "lucide-react";
import { useModal } from "@/context/ModalContext";
import Modal from "@/components/ExamModal";

// Types
interface Question {
  id: number;
  question: string;
  options: Record<string, string>;
}

interface QuestionItemProps {
  question: Question;
  selectedAnswer?: string;
  handleSelect: (questionId: number, option: string) => void;
}

const QuestionItem = React.memo<QuestionItemProps>(
  ({ question, selectedAnswer, handleSelect }) => {
    const [bookmark, setBookmark] = useState(false);

    return (
      <div className="border-[0.5px] border-[#8abdff]/60 rounded-2xl p-4 flex flex-col">
        <h3 className="text-xl font-medium mb-[20px]">
          {question.id}. {question.question}
        </h3>
        <div className="flex justify-between items-center">
          <div></div>
          <button onClick={() => setBookmark(!bookmark)}>
            {bookmark ? (
              <BookmarkCheck size={25} color="#113768" />
            ) : (
              <Bookmark size={25} color="#113768" />
            )}
          </button>
        </div>
        <div className="flex flex-col gap-4 items-start">
          {Object.entries(question.options).map(([key, value]) => (
            <button
              key={key}
              className="flex items-center gap-3"
              onClick={() => handleSelect(question.id, key)}
            >
              <span
                className={`flex items-center rounded-full border px-1.5 ${
                  selectedAnswer === key
                    ? "text-white bg-[#113768] border-[#113768]"
                    : ""
                }`}
              >
                {key.toUpperCase()}
              </span>
              <span className="option-description">{value}</span>
            </button>
          ))}
        </div>
      </div>
    );
  }
);

QuestionItem.displayName = "QuestionItem";

export default function ExamPage() {
  const router = useRouter();
  const { id } = useParams();
  const time = useSearchParams().get("time");
  const { isOpen, close } = useModal();

  const { setInitialTime, stopTimer } = useTimer();
  const {
    currentAttempt,
    setAnswer,
    getAnswer,
    submitExam: submitExamContext,
    setApiResponse,
    isExamStarted,
    isExamCompleted,
    isHydrated,
    isInitialized,
    currentExam,
  } = useExam();

  const [questions, setQuestions] = useState<Question[] | null>(null);
  const [loading, setLoading] = useState(true);
  const [isSubmitting, setIsSubmitting] = useState(false);
  const [submissionLoading, setSubmissionLoading] = useState(false);

  // Initial checks
  useEffect(() => {
    if (!isHydrated || !isInitialized || isSubmitting) return;
    if (!isExamStarted()) return router.push("/unit");
    if (isExamCompleted()) return router.push("/exam/results");
  }, [
    isHydrated,
    isInitialized,
    isExamStarted,
    isExamCompleted,
    isSubmitting,
    router,
  ]);

  // Fetch questions
  useEffect(() => {
    const fetchQuestions = async () => {
      try {
        const response = await fetch(`${API_URL}/mock/${id}`);
        const data = await response.json();
        setQuestions(data.questions);
      } catch (error) {
        console.error("Error fetching questions:", error);
      } finally {
        setLoading(false);
      }
    };
    fetchQuestions();
    if (time) setInitialTime(Number(time));
  }, [id, time, setInitialTime]);

  const handleSelect = useCallback(
    (questionId: number, option: string) => {
      setAnswer(questionId.toString(), option);
    },
    [setAnswer]
  );

  const handleSubmit = async () => {
    if (!currentAttempt) return console.error("No exam attempt found");

    stopTimer();
    setSubmissionLoading(true);
    setIsSubmitting(true);

    const answersForAPI = currentAttempt.answers.reduce(
      (acc, { questionId, answer }) => {
        acc[+questionId] = answer;
        return acc;
      },
      {} as Record<number, string>
    );

    try {
      const response = await fetch(`${API_URL}/submit`, {
        method: "POST",
        headers: {
          "Content-Type": "application/json",
          Authorization: `Bearer ${await getToken()}`,
        },
        body: JSON.stringify({ mock_id: id, data: answersForAPI }),
      });

      if (!response.ok)
        throw new Error((await response.json()).message || "Submission failed");

      const responseData = await response.json();
      submitExamContext();
      setApiResponse(responseData);
      router.push("/exam/results");
    } catch (error) {
      console.error("Error submitting answers:", error);
      setIsSubmitting(false);
    } finally {
      setSubmissionLoading(false);
    }
  };

  const showExitDialog = () => {
    if (window.confirm("Are you sure you want to quit the exam?")) {
      stopTimer();
      router.push("/unit");
    }
  };

  useEffect(() => {
    const handleBeforeUnload = (e: BeforeUnloadEvent) => {
      e.preventDefault();
      e.returnValue = "";
    };

    const handlePopState = (e: PopStateEvent) => {
      e.preventDefault();
      showExitDialog();
    };

    window.addEventListener("beforeunload", handleBeforeUnload);
    window.addEventListener("popstate", handlePopState);

    return () => {
      window.removeEventListener("beforeunload", handleBeforeUnload);
      window.removeEventListener("popstate", handlePopState);
    };
  }, []);

  if (submissionLoading) {
    return (
      <div className="min-h-screen bg-gray-50 flex items-center justify-center">
        <div className="text-center">
          <div className="animate-spin rounded-full h-12 w-12 border-b-2 border-blue-900 mb-4"></div>
          <p className="text-lg font-medium text-gray-900">Submitting...</p>
        </div>
      </div>
    );
  }

  const answeredSet = useMemo(() => {
    if (!currentAttempt) return new Set<string>();
    return new Set(currentAttempt.answers.map((a) => String(a.questionId)));
  }, [currentAttempt]);

  return (
    <div className="min-h-screen bg-gray-50">
      <Header
        examDuration={time}
        displayTabTitle={null}
        image={undefined}
        displayUser={undefined}
        displaySubject={undefined}
      />
      <Modal open={isOpen} onClose={close} title={currentExam?.title}>
        {currentAttempt ? (
          <div>
            <div className="flex gap-4">
              <p className="">Questions: {currentExam?.questions.length}</p>
              <p className="">
                Answers:{" "}
                <span className="text-[#113768] font-bold">
                  {currentAttempt?.answers.length}
                </span>
              </p>
              <p className="">
                Skipped:{" "}
                <span className="text-yellow-600 font-bold">
                  {currentExam?.questions.length -
                    currentAttempt?.answers.length}
                </span>
              </p>

              {/* more details */}
            </div>
            <div className="h-[0.5px] border-[0.5px] border-black/10 w-full my-3"></div>
            <section className="flex flex-wrap gap-4">
              {currentExam?.questions.map((q, idx) => {
                const answered = answeredSet.has(String(q.id)); // ← convert to string

                return (
                  <div
                    key={q.id ?? idx}
                    className={`h-16 w-16 rounded-full flex items-center justify-center
                  text-2xl
                  ${
                    answered
                      ? "bg-[#0E2C53] text-white font-semibold"
                      : "bg-[#E9EDF1] text-black font-normal"
                  }`}
                  >
                    {idx + 1}
                  </div>
                );
              })}
            </section>
          </div>
        ) : (
          <p>No attempt data.</p>
        )}
      </Modal>
      <div className="container mx-auto px-6 py-8">
        {loading ? (
          <div className="flex items-center justify-center min-h-64">
            <div className="animate-spin rounded-full h-12 w-12 border-b-2 border-blue-900"></div>
          </div>
        ) : (
          <div className="space-y-6 mb-20">
            {questions?.map((q) => (
              <QuestionItem
                key={q.id}
                question={q}
                selectedAnswer={getAnswer(q.id.toString())}
                handleSelect={handleSelect}
              />
            ))}
          </div>
        )}

        <div className="fixed bottom-0 left-0 right-0 bg-white border-t border-gray-200 p-4">
          <button
            onClick={handleSubmit}
            disabled={submissionLoading}
            className="w-full bg-blue-900 text-white py-4 px-6 rounded-lg font-bold text-lg hover:bg-blue-800 disabled:opacity-50 disabled:cursor-not-allowed transition-colors"
          >
            Submit
          </button>
        </div>
      </div>
    </div>
  );
}