'use strict';
/* ──────────────────────────────────────────────────────────────────
   Exam 9 — Math 2025 renderer
   Variants loaded into window.VARIANTS by /js/exam9/variants/vNN.js
   ────────────────────────────────────────────────────────────────── */

const STORAGE_KEY  = 'exam9_progress_v1';
let   currentVariant = null;
let   katexLoaded    = false;

/* ── KaTeX bootstrap ────────────────────────────────────────────── */
function onKatexLoad() {
  katexLoaded = true;
  if (currentVariant !== null) runKatex(document.getElementById('ex-main'));
}

function runKatex(el) {
  if (!katexLoaded || !el) return;
  try {
    renderMathInElement(el, {
      delimiters: [
        { left: '$$', right: '$$', display: true  },
        { left: '$',  right: '$',  display: false },
      ],
      throwOnError: false,
    });
  } catch {}
}

/* ── Progress in localStorage ───────────────────────────────────── */
function loadProgress() {
  try { return JSON.parse(localStorage.getItem(STORAGE_KEY) || '{}'); }
  catch { return {}; }
}
function saveProgress(p) {
  try { localStorage.setItem(STORAGE_KEY, JSON.stringify(p)); } catch {}
}
function markSolutionViewed(variantNum, taskIdx) {
  const p = loadProgress();
  p[variantNum] = p[variantNum] || [];
  if (!p[variantNum].includes(taskIdx)) {
    p[variantNum].push(taskIdx);
    saveProgress(p);
  }
}

/* ── Variant picker ─────────────────────────────────────────────── */
function buildGrid() {
  const grid = document.getElementById('variant-grid');
  const progress = loadProgress();
  grid.innerHTML = '';
  Object.keys(VARIANTS).sort((a, b) => Number(a) - Number(b)).forEach(n => {
    const v = VARIANTS[n];
    const total = (v.tasks || []).length;
    const viewed = (progress[n] || []).length;
    let cls = '';
    if (viewed === total && total > 0) cls = ' done';
    else if (viewed > 0)                cls = ' partial';
    const isActive = Number(n) === currentVariant ? ' active' : '';

    const btn = document.createElement('button');
    btn.className = 'vg-btn' + cls + isActive;
    btn.textContent = n;
    btn.title = `${v.label}${viewed === total ? ' ✓' : viewed > 0 ? ` (${viewed}/${total})` : ''}`;
    btn.onclick = () => { selectVariant(Number(n)); closePicker(); };
    grid.appendChild(btn);
  });
}

function togglePicker() {
  const overlay = document.getElementById('picker-overlay');
  const btn     = document.getElementById('picker-btn');
  if (overlay.classList.contains('visible')) closePicker();
  else {
    buildGrid();
    overlay.classList.add('visible');
    btn.classList.add('open');
    document.addEventListener('keydown', onEsc);
  }
}

function closePicker() {
  document.getElementById('picker-overlay').classList.remove('visible');
  document.getElementById('picker-btn').classList.remove('open');
  document.removeEventListener('keydown', onEsc);
}

function onOverlayClick(e) {
  if (e.target === document.getElementById('picker-overlay')) closePicker();
}
function onEsc(e) { if (e.key === 'Escape') closePicker(); }

/* ── Task rendering ─────────────────────────────────────────────── */
function buildOpts(opts) {
  const isLong = opts.some(([, t]) => t.length > 40 && !t.startsWith('$'));
  const cls = isLong ? 'opts-vertical' : 'opts';
  return `<div class="${cls}">` +
    opts.map(([l, t]) =>
      `<span class="opt"><span class="opt-lbl">${l})</span><span>${t}</span></span>`
    ).join('') + `</div>`;
}

const SOL_ICON_CLOSED = `<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round"><polyline points="9 18 15 12 9 6"/></svg>`;

function renderVariant(num) {
  const main = document.getElementById('ex-main');
  const v = VARIANTS[num];
  if (!v) {
    main.innerHTML = '<div class="ex-empty">Вариант не найден</div>';
    return;
  }

  main.innerHTML =
    `<div class="variant-title">${v.label}<small>${v.tasks.length} заданий</small></div>` +
    v.tasks.map((t, i) => `
      <div class="task-card">
        <div class="task-header">
          <div class="task-num">${i + 1}</div>
          <div class="task-label">Задание ${i + 1}</div>
        </div>
        <div class="task-body">
          <div class="task-text">${t.text}</div>
          ${t.figure ? `<div class="task-figure">${t.figure}</div>` : ''}
          ${t.opts ? buildOpts(t.opts) : ''}
        </div>
        ${t.sol ? `<div class="sol-wrap">
          <button class="sol-btn" data-task="${i}" onclick="toggleSol(this, ${num}, ${i})">
            ${SOL_ICON_CLOSED}<span>Показать решение</span>
          </button>
          <div class="sol-panel">${t.sol}</div>
        </div>` : ''}
      </div>`
    ).join('');

  runKatex(main);
}

function toggleSol(btn, variantNum, taskIdx) {
  const panel = btn.nextElementSibling;
  const open  = panel.classList.contains('visible');
  panel.classList.toggle('visible', !open);
  btn.classList.toggle('open', !open);
  btn.querySelector('span').textContent = open ? 'Показать решение' : 'Скрыть решение';
  if (!open) {
    if (!panel.dataset.k) { runKatex(panel); panel.dataset.k = '1'; }
    markSolutionViewed(variantNum, taskIdx);
  }
}

function selectVariant(num) {
  currentVariant = num;
  document.getElementById('picker-label').textContent = VARIANTS[num].label;
  document.querySelectorAll('.vg-btn').forEach(b => {
    b.classList.toggle('active', Number(b.textContent) === num);
  });
  renderVariant(num);
  // Persist last opened variant
  try { localStorage.setItem('exam9_last_variant', String(num)); } catch {}
  window.scrollTo({ top: 0, behavior: 'smooth' });
}

/* ── Boot ───────────────────────────────────────────────────────── */
(function boot() {
  const keys = Object.keys(VARIANTS);
  if (!keys.length) {
    document.getElementById('ex-main').innerHTML = '<div class="ex-empty">Варианты не загружены</div>';
    return;
  }
  // Resume last opened variant or open first one
  let initial = Number(keys[0]);
  try {
    const last = Number(localStorage.getItem('exam9_last_variant'));
    if (last && VARIANTS[last]) initial = last;
  } catch {}
  selectVariant(initial);
})();