let questions = [];
let currentIndex = 0;
let userAnswers = [];
let startTime;

document.getElementById('start-session').addEventListener('click', async () => {
    const file = document.getElementById('file').value;
    if (!file) return alert("Please select a file");

    const response = await fetch('/load_questions', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ file_name: file })
    });

    questions = await response.json();
    userAnswers = Array(questions.length).fill([]);
    startQuiz();
});

function startQuiz() {
    document.getElementById('file-selection').style.display = 'none';
    document.getElementById('quiz-container').style.display = 'block';
    startTime = Date.now();
    displayQuestion();
    setInterval(updateTimer, 1000);
}

function displayQuestion() {
    const question = questions[currentIndex];
    document.getElementById('question').innerText = question.question;
    const optionsDiv = document.getElementById('options');
    optionsDiv.innerHTML = '';
    question.options.forEach((option, i) => {
        const btn = document.createElement('button');
        btn.innerText = option;
        btn.className = userAnswers[currentIndex].includes(i) ? 'selected' : '';
        btn.addEventListener('click', () => selectAnswer(i));
        optionsDiv.appendChild(btn);
    });
}

function selectAnswer(optionIndex) {
    const currentAnswers = userAnswers[currentIndex];
    if (currentAnswers.includes(optionIndex)) {
        userAnswers[currentIndex] = currentAnswers.filter(i => i !== optionIndex);
    } else {
        userAnswers[currentIndex].push(optionIndex);
    }
    displayQuestion();
}

document.getElementById('next').addEventListener('click', () => {
    currentIndex = Math.min(currentIndex + 1, questions.length - 1);
    displayQuestion();
});

document.getElementById('prev').addEventListener('click', () => {
    currentIndex = Math.max(currentIndex - 1, 0);
    displayQuestion();
});

document.getElementById('end-session').addEventListener('click', async () => {
    const response = await fetch('/submit_results', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ questions, user_answers: userAnswers })
    });
    const result = await response.json();
    document.getElementById('quiz-container').style.display = 'none';
    document.getElementById('results-container').style.display = 'block';
    document.getElementById('score').innerText = `Your score: ${result.score.toFixed(2)}%`;
});

function updateTimer() {
    const elapsedTime = Math.floor((Date.now() - startTime) / 1000);
    document.getElementById('timer').innerText = `Time: ${elapsedTime}s`;
}