/* ============================================================
   HanziLearn – elearning.js
   Schema fields: kanji, pinyin, sino, vietnamese, topic_name
   ============================================================ */

   (() => {
    const { level, mode, color } = window.LEARN_CONFIG;
  
    /* ── Apply CSS variable for header colour ─────────────── */
    const header = document.getElementById('learnHeader');
    const badge  = document.getElementById('learnBadge');
    if (header) header.style.setProperty('--lc', color);
    if (badge)  badge.style.background = color;
  
    /* ── DOM helpers ─────────────────────────────────────── */
    const $   = id => document.getElementById(id);
    const showPanel = name => $(`${name}Panel`)?.classList.remove('d-none');
    const hidePanel = name => $(`${name}Panel`)?.classList.add('d-none');
  
    function esc(str = '') {
      const d = document.createElement('div');
      d.textContent = str;
      return d.innerHTML;
    }
  
    /* ── Username chip ───────────────────────────────────── */
    document.addEventListener('DOMContentLoaded', () => {
      const username = window.api?.getUsername() || 'Guest';
      const el = $('learnUsername');
      if (el) el.textContent = username;
    });
  
    /* ── Bootstrap entry point ────────────────────────────── */
    document.addEventListener('DOMContentLoaded', () => {
      $('loadingPanel')?.classList.remove('d-none');
      const init = { flashcard: initFlashcard, quiz: initQuiz,
                     fillblank: initFillBlank, leaderboard: initLeaderboard };
      (init[mode] || initFlashcard)();
    });
  
    function hideLoading() { $('loadingPanel')?.classList.add('d-none'); }
  
    /* ══════════════════════════════════════════════════════
       FLASHCARD MODE
    ══════════════════════════════════════════════════════ */
    async function initFlashcard() {
      const json = await fetch(`/api/flashcards/${level}`).then(r => r.json());
      hideLoading();
  
      if (!json.success || !json.data.length) { renderNoData('flashcard'); return; }
  
      let cards   = json.data;
      let index   = 0;
      let flipped = false;
  
      showPanel('flashcard');
  
      /* refs */
      const fcCard    = $('fcCard');
      const fcScene   = $('fcScene');
      const progBar   = $('fcProgressBar');
  
      function renderCard() {
        /* Reset flip state without animation for instant re-render */
        fcCard.style.transition = 'none';
        fcCard.classList.remove('flipped');
        flipped = false;
        /* Force reflow so the removal takes effect before re-enabling transition */
        void fcCard.offsetWidth;
        fcCard.style.transition = '';
  
        const c = cards[index];
        $('fcHanziFront').textContent = c.kanji;
        $('fcHanziBack').textContent  = c.kanji;
        $('fcPinyin').textContent     = c.pinyin;
        $('fcEnglish').textContent    = c.sino;
        $('fcVietnamese').textContent = c.vietnamese;
  
        /* Topic badge on back */
        const topicEl = document.getElementById('fcTopic');
        if (topicEl) topicEl.textContent = c.topic_name || '';
  
        $('fcCurrent').textContent = index + 1;
        $('fcTotal').textContent   = cards.length;
        progBar.style.width = `${((index + 1) / cards.length) * 100}%`;
      }
  
      function flip() {
        flipped = !flipped;
        fcCard.classList.toggle('flipped', flipped);
        if (flipped) window.logActivity?.('flashcard_view', level, 0, { word_id: cards[index].id });
      }
  
      /* Click on scene or Flip button */
      fcScene.addEventListener('click', flip);
      $('fcFlip').addEventListener('click', e => { e.stopPropagation(); flip(); });
  
      $('fcNext').addEventListener('click', () => {
        if (index < cards.length - 1) { index++; renderCard(); }
        else {
          window.logActivity?.('flashcard_complete', level, cards.length);
          showToast(`🎉 Finished all ${cards.length} cards! Reshuffling…`, () => {
            cards = shuffleArr([...json.data]);
            index = 0;
            renderCard();
          });
        }
      });
  
      $('fcPrev').addEventListener('click', () => {
        if (index > 0) { index--; renderCard(); }
      });
  
      $('fcShuffle').addEventListener('click', () => {
        cards = shuffleArr([...cards]);
        index = 0;
        renderCard();
        showToast('Cards shuffled!');
      });
  
      /* Keyboard shortcuts */
      document.addEventListener('keydown', e => {
        if (mode !== 'flashcard') return;
        if (e.key === 'ArrowRight') { e.preventDefault(); $('fcNext').click(); }
        if (e.key === 'ArrowLeft')  { e.preventDefault(); $('fcPrev').click(); }
        if (e.key === ' ')          { e.preventDefault(); flip(); }
      });
  
      renderCard();
    }
  
    /* ══════════════════════════════════════════════════════
       QUIZ MODE
    ══════════════════════════════════════════════════════ */
    async function initQuiz() {
      const json = await fetch(`/api/quiz/${level}?count=10`).then(r => r.json());
      hideLoading();
  
      if (!json.success || !json.data.length) { renderNoData('quiz'); return; }
  
      let questions = json.data;
      let qIndex    = 0;
      let score     = 0;
      let timer     = null;
      let timeLeft  = 30;
      let answered  = false;
  
      showPanel('quiz');
      $('quizResult').classList.add('d-none');
      $('quizGame').classList.remove('d-none');
  
      function renderQuestion() {
        answered = false; timeLeft = 30;
        const q  = questions[qIndex];
  
        $('qNum').textContent    = qIndex + 1;
        $('qTotal').textContent  = questions.length;
        $('qHanzi').textContent  = q.kanji;
        $('qPinyin').textContent = q.pinyin;
        $('qScore').textContent  = `Score: ${score}`;
        $('qProgress').style.width = `${(qIndex / questions.length) * 100}%`;
  
        $('qOptions').innerHTML = q.options.map(opt => `
          <button class="quiz-option" type="button"
                  data-correct="${esc(q.correct)}"
                  data-val="${esc(opt)}">${esc(opt)}</button>
        `).join('');
  
        $('qOptions').querySelectorAll('.quiz-option').forEach(btn =>
          btn.addEventListener('click', () => handleAnswer(btn, q.correct))
        );
  
        startTimer();
      }
  
      function handleAnswer(btn, correct) {
        if (answered) return;
        answered = true;
        clearInterval(timer);
  
        $('qOptions').querySelectorAll('.quiz-option').forEach(b => {
          b.disabled = true;
          if (b.dataset.val === correct) b.classList.add('correct');
        });
  
        if (btn.dataset.val === correct) { btn.classList.add('correct'); score += 10; }
        else                             { btn.classList.add('wrong'); }
  
        $('qScore').textContent = `Score: ${score}`;
        setTimeout(() => { qIndex++; qIndex < questions.length ? renderQuestion() : showResult(); }, 1200);
      }
  
      function startTimer() {
        clearInterval(timer);
        const timerEl = $('quizTimer');
        timerEl.textContent = timeLeft;
        timerEl.classList.remove('urgent');
  
        timer = setInterval(() => {
          timeLeft--;
          timerEl.textContent = timeLeft;
          if (timeLeft <= 10) timerEl.classList.add('urgent');
          if (timeLeft <= 0)  {
            clearInterval(timer);
            if (!answered) {
              answered = true;
              $('qOptions').querySelectorAll('.quiz-option').forEach(b => {
                b.disabled = true;
                if (b.dataset.val === questions[qIndex].correct) b.classList.add('correct');
              });
              setTimeout(() => { qIndex++; qIndex < questions.length ? renderQuestion() : showResult(); }, 1000);
            }
          }
        }, 1000);
      }
  
      function showResult() {
        clearInterval(timer);
        $('quizGame').classList.add('d-none');
        $('quizResult').classList.remove('d-none');
  
        const pct = Math.round((score / (questions.length * 10)) * 100);
        $('resultScore').textContent   = `${score}/${questions.length * 10}`;
        $('resultPercent').textContent = `${pct}%`;
  
        const [emoji, title, msg] =
          pct >= 90 ? ['🏆','Outstanding!','Perfect performance!'] :
          pct >= 70 ? ['🎉','Great job!','Almost perfect!'] :
          pct >= 50 ? ['👍','Good effort!','Keep practicing!'] :
                      ['📚','Keep going!','Review flashcards first.'];
  
        $('resultEmoji').textContent = emoji;
        $('resultTitle').textContent = title;
        $('resultMsg').textContent   = msg;
        window.logActivity?.('quiz_complete', level, score, { percent: pct });
      }
  
      $('quizRetry').addEventListener('click', async () => {
        $('quizResult').classList.add('d-none');
        $('quizGame').classList.remove('d-none');
        $('loadingPanel').classList.remove('d-none');
        hidePanel('quiz');
        const j2 = await fetch(`/api/quiz/${level}?count=10`).then(r => r.json());
        questions = j2.data || questions;
        qIndex = 0; score = 0;
        hideLoading(); showPanel('quiz');
        renderQuestion();
      });
  
      renderQuestion();
    }
  
    /* ══════════════════════════════════════════════════════
       FILL BLANK MODE
    ══════════════════════════════════════════════════════ */
    async function initFillBlank() {
      const json = await fetch(`/api/fillblank/${level}`).then(r => r.json());
      hideLoading();
  
      if (!json.success || !json.data.length) { renderNoData('fillblank'); return; }
  
      const exercises = json.data;
      let index = 0, score = 0, submitted = false;
  
      showPanel('fillblank');
      $('fbTotal').textContent = exercises.length;
  
      function renderExercise() {
        submitted = false;
        const ex  = exercises[index];
        $('fbCurrent').textContent = index + 1;
        $('fbScore').textContent   = score;
        $('fbContext').textContent = ex.context  || 'Complete the sentence';
  
        /* Replace ___ with a styled span */
        const sentence = esc(ex.sentence).replace(/___/g,
          '<span class="fb-blank" id="fbBlankDisplay">___</span>');
        $('fbSentence').innerHTML = sentence;
        $('fbHint').textContent   = ex.hint_pinyin ? `Hint: ${ex.hint_pinyin}` : '';
  
        $('fbFeedback').className    = 'fb-feedback d-none';
        $('fbTranslation').className = 'fb-translation d-none';
        const inp = $('fbInput');
        inp.value = '';
        inp.className = 'form-control fb-input';
        inp.focus();
      }
  
      function checkAnswer() {
        if (submitted) return;
        const inp     = $('fbInput');
        const answer  = inp.value.trim();
        const correct = (exercises[index].answer || '').trim();
  
        if (!answer) { inp.classList.add('is-invalid'); return; }
        inp.classList.remove('is-invalid');
        submitted = true;
  
        const ok = answer === correct || answer.toLowerCase() === correct.toLowerCase();
  
        const blank = document.getElementById('fbBlankDisplay');
        if (blank) { blank.textContent = correct; blank.style.color = ok ? '#4CAF50' : '#F44336'; }
  
        const fb = $('fbFeedback');
        fb.className    = `fb-feedback ${ok ? 'correct' : 'wrong'}`;
        fb.textContent  = ok ? `✓ Correct! "${correct}"` : `✗ Wrong. Answer: "${correct}"`;
  
        const tr = $('fbTranslation');
        tr.className    = 'fb-translation';
        tr.textContent  = exercises[index].translation || '';
  
        if (ok) score += 5;
        $('fbScore').textContent = score;
        window.logActivity?.('fillblank_answer', level, ok ? 5 : 0, { correct: ok });
      }
  
      $('fbSubmit').addEventListener('click', checkAnswer);
      $('fbInput').addEventListener('keydown', e => { if (e.key === 'Enter') checkAnswer(); });
  
      $('fbNext').addEventListener('click', () => {
        if (index < exercises.length - 1) { index++; renderExercise(); }
        else showToast('🎉 All done! Starting over…', () => { index = 0; renderExercise(); });
      });
      $('fbPrev').addEventListener('click', () => {
        if (index > 0) { index--; renderExercise(); }
      });
  
      renderExercise();
    }
  
    /* ══════════════════════════════════════════════════════
       LEADERBOARD MODE
    ══════════════════════════════════════════════════════ */
    async function initLeaderboard() {
      const json = await fetch('/api/leaderboard').then(r => r.json());
      hideLoading();
      showPanel('leaderboard');
  
      const data = json.data || [];
      renderList('topScoresList', data, 'score');
      renderList('mostActiveList', [...data].sort((a,b) => (b.activity_count||0)-(a.activity_count||0)), 'count');
  
      const username = window.api?.getUsername();
      if (username) {
        const me = data.find(d => d.username === username);
        if (me) {
          $('myStats').style.display = 'block';
          $('myStatsRow').innerHTML = `
            <div class="col-4"><div class="my-stat-card">
              <div class="my-stat-val">${me.total_score || 0}</div>
              <div class="my-stat-label">Total Score</div>
            </div></div>
            <div class="col-4"><div class="my-stat-card">
              <div class="my-stat-val">${me.activity_count || 0}</div>
              <div class="my-stat-label">Activities</div>
            </div></div>
            <div class="col-4"><div class="my-stat-card">
              <div class="my-stat-val">#${data.indexOf(me)+1}</div>
              <div class="my-stat-label">Rank</div>
            </div></div>`;
        }
      }
    }
  
    function renderList(containerId, items, metric) {
      const el = $(containerId);
      if (!el) return;
      if (!items.length) { el.innerHTML = '<p class="text-muted text-center py-3">No data yet</p>'; return; }
  
      el.innerHTML = items.slice(0, 10).map((item, i) => {
        const rc  = i === 0 ? 'gold' : i === 1 ? 'silver' : i === 2 ? 'bronze' : '';
        const ri  = i === 0 ? '🥇' : i === 1 ? '🥈' : i === 2 ? '🥉' : i + 1;
        const val = metric === 'score'
          ? `${item.total_score || 0} pts`
          : `${item.activity_count || 0} sessions`;
  
        return `
          <div class="lb-item">
            <div class="lb-rank ${rc}">${ri}</div>
            <div class="lb-avatar">${esc((item.username||'?').charAt(0).toUpperCase())}</div>
            <div class="lb-name">${esc(item.username||'Unknown')}</div>
            <div class="lb-score">${val}</div>
          </div>`;
      }).join('');
    }
  
    /* ── Shared utilities ────────────────────────────────── */
    function shuffleArr(arr) {
      for (let i = arr.length - 1; i > 0; i--) {
        const j = Math.floor(Math.random() * (i + 1));
        [arr[i], arr[j]] = [arr[j], arr[i]];
      }
      return arr;
    }
  
    function renderNoData(name) {
      showPanel(name);
      const p = $(`${name}Panel`);
      if (p) p.innerHTML = `
        <div class="text-center py-5">
          <div style="font-family:var(--hanzi-font);font-size:4rem;opacity:.25">空</div>
          <h5 class="mt-3">No data available</h5>
          <p class="text-muted">No ${name} data for HSK ${level} yet.</p>
        </div>`;
    }
  
    function showToast(msg, callback) {
      const old = document.getElementById('hl-toast');
      if (old) old.remove();
      const t = document.createElement('div');
      t.id = 'hl-toast';
      t.style.cssText = [
        'position:fixed','bottom:2rem','left:50%','transform:translateX(-50%)',
        'background:var(--bg-elevated)','border:1px solid var(--border)',
        'border-radius:999px','padding:.6rem 1.5rem','font-size:.9rem',
        'color:var(--text-primary)','z-index:9999',
        'box-shadow:0 8px 32px rgba(0,0,0,.4)',
        'animation:slideUp .3s cubic-bezier(.4,0,.2,1)'
      ].join(';');
      t.textContent = msg;
  
      if (!document.getElementById('hl-toast-style')) {
        const s = document.createElement('style');
        s.id = 'hl-toast-style';
        s.textContent = `@keyframes slideUp{from{opacity:0;transform:translateX(-50%) translateY(16px)}to{opacity:1;transform:translateX(-50%) translateY(0)}}`;
        document.head.appendChild(s);
      }
  
      document.body.appendChild(t);
      setTimeout(() => { t.remove(); callback?.(); }, 2500);
    }
  })();