/* ===== Language detection ===== */
const LANG_OPTIONS = [
  { key: 'nl', label: 'Nederlands', flag: '🇳🇱', data: window.QUESTIONS_NL },
  { key: 'en', label: 'English',    flag: '🇬🇧', data: window.QUESTIONS_EN },
].filter(l => l.data && l.data.length > 0);

let ALL_QUESTIONS = [];

/* ===== Quiz state ===== */
let sessionQ = [];
let currentIdx = 0;
let score = 0;
let wrongIds = [];
let selectedCount = 0;
let answered = false;

let timerInterval = null;
let elapsedSeconds = 0;
let answeredCount = 0;

/* ===== Helpers ===== */
function shuffle(arr) {
  const a = [...arr];
  for (let i = a.length - 1; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    [a[i], a[j]] = [a[j], a[i]];
  }
  return a;
}

function fmtTime(s) {
  return Math.floor(s / 60) + ':' + String(s % 60).padStart(2, '0');
}

function startTimer() {
  stopTimer();
  timerInterval = setInterval(() => { elapsedSeconds++; updateTimerDisplay(); }, 1000);
}

function stopTimer() {
  if (timerInterval) { clearInterval(timerInterval); timerInterval = null; }
}

function updateTimerDisplay() {
  const avg = answeredCount > 0 ? Math.round(elapsedSeconds / answeredCount) + 's' : '—';
  document.getElementById('timer-display').textContent = fmtTime(elapsedSeconds) + '  |  gem. ' + avg;
}

function showScreen(id) {
  document.querySelectorAll('.screen').forEach(s => s.classList.remove('active'));
  document.getElementById(id).classList.add('active');
}

function shuffleQuestion(q) {
  const idx = [0, 1, 2, 3];
  const si = shuffle(idx);
  return {
    exam: q.exam, qnum: q.qnum, q: q.q,
    opts: si.map(i => q.opts[i]),
    correct: si.indexOf(q.correct),
    explanation: si.map(i => q.explanation[i]),
  };
}

/* ===== Language screen ===== */
function initLangScreen() {
  if (LANG_OPTIONS.length === 1) {
    ALL_QUESTIONS = LANG_OPTIONS[0].data;
    initCountButtons();
    showScreen('start');
    return;
  }

  const grid = document.getElementById('lang-grid');
  grid.innerHTML = '';
  LANG_OPTIONS.forEach(lang => {
    const btn = document.createElement('button');
    btn.className = 'lang-btn';
    btn.innerHTML = '<span>' + lang.flag + '</span><span>' + lang.label + '</span>';
    btn.onclick = () => {
      ALL_QUESTIONS = lang.data;
      initCountButtons();
      showScreen('start');
    };
    grid.appendChild(btn);
  });

  showScreen('lang');
}

/* ===== Start screen ===== */
function initCountButtons() {
  const counts = [5, 10, 20, 60, 9999];
  const grid = document.getElementById('count-grid');
  grid.innerHTML = '';
  const total = ALL_QUESTIONS.length;

  counts.forEach(n => {
    const btn = document.createElement('button');
    btn.className = 'count-btn';
    const label = n === 9999 ? 'Alle ' + total : String(n);
    btn.textContent = label;
    btn.dataset.count = n;
    const isDisabled = n !== 9999 && total < n;
    btn.disabled = isDisabled;
    btn.onclick = () => selectCount(n, btn);
    grid.appendChild(btn);
  });

  document.getElementById('start-btn').disabled = true;
  selectedCount = 0;
}

function selectCount(n, btn) {
  selectedCount = Math.min(n, ALL_QUESTIONS.length);
  document.querySelectorAll('.count-btn').forEach(b => b.classList.remove('selected'));
  btn.classList.add('selected');
  document.getElementById('start-btn').disabled = false;
}

function startQuiz() {
  const pool = shuffle(ALL_QUESTIONS.map(shuffleQuestion));
  sessionQ = pool.slice(0, selectedCount);
  currentIdx = 0; score = 0; wrongIds = []; answered = false;
  elapsedSeconds = 0; answeredCount = 0;
  updateTimerDisplay();
  showScreen('quiz');
  renderQuestion();
}

/* ===== Quiz screen ===== */
function renderQuestion() {
  answered = false;
  const q = sessionQ[currentIdx];
  const total = sessionQ.length;
  document.getElementById('progress-fill').style.width = ((currentIdx / total) * 100) + '%';
  document.getElementById('q-meta').textContent = 'Vraag ' + (currentIdx + 1) + ' van ' + total;
  document.getElementById('q-text').textContent = q.q;

  const optDiv = document.getElementById('options');
  optDiv.innerHTML = '';
  ['A', 'B', 'C', 'D'].forEach((ltr, i) => {
    const btn = document.createElement('button');
    btn.className = 'option-btn';
    btn.innerHTML = '<span class="opt-letter">' + ltr + '.</span><span>' + q.opts[i] + '</span>';
    btn.onclick = () => handleAnswer(i);
    optDiv.appendChild(btn);
  });

  document.getElementById('explanation').style.display = 'none';
  document.getElementById('next-btn').style.display = 'none';
  startTimer();
}

function handleAnswer(chosen) {
  if (answered) return;
  answered = true;
  stopTimer();
  answeredCount++;
  updateTimerDisplay();
  const q = sessionQ[currentIdx];
  document.querySelectorAll('.option-btn').forEach((btn, i) => {
    btn.disabled = true;
    if (i === q.correct) btn.classList.add('correct');
    else if (i === chosen && chosen !== q.correct) btn.classList.add('wrong');
  });
  if (chosen === q.correct) score++;
  else wrongIds.push(currentIdx);

  const expDiv = document.getElementById('explanation');
  expDiv.style.display = 'block';
  expDiv.innerHTML =
    '<div class="explanation-source">Proefexamen ' + q.exam + ', vraag ' + q.qnum + '</div>' +
    '<div class="explanation-label">Toelichting</div>' +
    q.explanation.map(e => '<p>' + e + '</p>').join('');

  const nextBtn = document.getElementById('next-btn');
  nextBtn.style.display = 'inline-flex';
  nextBtn.textContent = currentIdx === sessionQ.length - 1 ? 'Bekijk resultaat' : 'Volgende vraag →';
}

function nextQuestion() {
  currentIdx++;
  if (currentIdx >= sessionQ.length) showResult();
  else renderQuestion();
}

/* ===== Result screen ===== */
function showResult() {
  stopTimer();
  showScreen('result');
  const total = sessionQ.length;
  const pct = Math.round((score / total) * 100);
  const circle = document.getElementById('score-circle');
  circle.innerHTML = pct + '%<span>' + (pct >= 60 ? 'Geslaagd' : 'Niet geslaagd') + '</span>';
  circle.className = 'score-circle ' + (pct >= 60 ? 'score-pass' : 'score-fail');
  document.getElementById('result-label').textContent = pct >= 60 ? 'Geslaagd' : 'Niet geslaagd';
  document.getElementById('result-sub').textContent = score + ' van de ' + total + ' vragen goed';
  document.getElementById('stat-correct').textContent = score;
  document.getElementById('stat-wrong').textContent = total - score;
  document.getElementById('stat-time').textContent =
    answeredCount > 0 ? Math.round(elapsedSeconds / answeredCount) + 's' : '—';
  document.getElementById('retry-btn').style.display = wrongIds.length > 0 ? 'inline-flex' : 'none';
}

function goStart() {
  stopTimer();
  document.querySelectorAll('.count-btn').forEach(b => b.classList.remove('selected'));
  document.getElementById('start-btn').disabled = true;
  selectedCount = 0;
  showScreen('start');
}

function retryWrong() {
  sessionQ = shuffle(wrongIds.map(i => shuffleQuestion(sessionQ[i])));
  currentIdx = 0; score = 0; wrongIds = []; answered = false;
  elapsedSeconds = 0; answeredCount = 0;
  updateTimerDisplay();
  showScreen('quiz');
  renderQuestion();
}

/* ===== Boot ===== */
document.addEventListener('DOMContentLoaded', initLangScreen);