(async () => {
  // ===== config =====
  const CLICK_DELAY_MS = 120;   // delay between the two clicks of a pair
  const PAIR_DELAY_MS  = 250;   // delay after a completed pair
  const START_WAIT_MS  = 1500;  // wait for board to appear after clicking start
  const MAX_ITERS      = 500;   // safety stop
  // ==================

  const C = 'color:#7F77DD;font-weight:bold';
  const log  = (m, ...a) => console.log(`%c[Match]%c ${m}`, C, '', ...a);
  const warn = (m, ...a) => console.warn(`%c[Match]%c ${m}`, C, '', ...a);
  const err  = (m, ...a) => console.error(`%c[Match]%c ${m}`, C, '', ...a);
  const sleep = ms => new Promise(r => setTimeout(r, ms));
  const norm = s => (s || '').trim().toLowerCase().replace(/\s+/g, ' ');

  const realClick = (el) => {
    const r = el.getBoundingClientRect();
    const o = { bubbles: true, cancelable: true, view: window,
                clientX: r.left + r.width/2, clientY: r.top + r.height/2 };
    el.dispatchEvent(new PointerEvent('pointerdown', { ...o, pointerType: 'mouse' }));
    el.dispatchEvent(new MouseEvent('mousedown', o));
    el.dispatchEvent(new PointerEvent('pointerup',   { ...o, pointerType: 'mouse' }));
    el.dispatchEvent(new MouseEvent('mouseup', o));
    el.dispatchEvent(new MouseEvent('click', o));
  };

  const isVisible = (el) => {
    if (!el?.isConnected) return false;
    const r = el.getBoundingClientRect();
    if (r.width < 1 || r.height < 1) return false;
    const cs = getComputedStyle(el);
    return cs.visibility !== 'hidden' && cs.display !== 'none' && parseFloat(cs.opacity) > 0.1;
  };

  // 1. extract set id
  const m = location.pathname.match(/^\/(?:[a-z]{2}\/)?(\d+)(?:\/|$)/);
  if (!m) { err('Could not parse set ID from URL'); return; }
  const setId = m[1];
  log(`Set ID: ${setId}`);

  // 2. fetch cards (paginated)
  log('Fetching cards...');
  const cards = [];
  let page = 1, pagingToken = '';
  const perPage = 200;
  while (true) {
    const qs = new URLSearchParams({
      'filters[studiableContainerId]': setId,
      'filters[studiableContainerType]': '1',
      perPage: String(perPage),
      page: String(page),
    });
    if (pagingToken) qs.set('pagingToken', pagingToken);

    const res = await fetch(`https://quizlet.com/webapi/3.4/studiable-item-documents?${qs}`, { credentials: 'include' });
    if (!res.ok) { err(`API returned ${res.status}`); return; }
    const data = await res.json();
    const resp = data?.responses?.[0];
    const items = resp?.models?.studiableItem || [];

    for (const it of items) {
      const term = it.cardSides?.[0]?.media?.find(x => x.plainText)?.plainText;
      const def  = it.cardSides?.[1]?.media?.find(x => x.plainText)?.plainText;
      if (term && def) cards.push({ term, def });
    }

    const total = resp?.paging?.total;
    pagingToken = resp?.paging?.token || '';
    if (items.length < perPage || (total != null && cards.length >= total)) break;
    page++;
  }
  log(`Got ${cards.length} cards`);
  if (!cards.length) { err('No cards fetched'); return; }

  // build pair lookup: each side knows its partner
  const pair = new Map();
  for (const { term, def } of cards) {
    pair.set(norm(term), norm(def));
    pair.set(norm(def), norm(term));
  }

  // 3. click start button inside #__next
  const root = document.getElementById('__next');
  if (!root) { err('#__next not found'); return; }

  const startRx = /spiel beginnen|start game|jouer|commencer|begin game|empezar|iniciar|gioca/i;
  let startBtn = [...root.querySelectorAll('button')].find(b => {
    const lab = (b.getAttribute('aria-label') || '') + ' ' + (b.textContent || '');
    return startRx.test(lab);
  });
  if (!startBtn) startBtn = root.querySelector('button[data-testid="assembly-button-primary"]');

  if (startBtn) {
    log(`Clicking start: "${(startBtn.getAttribute('aria-label') || startBtn.textContent || '').trim()}"`);
    realClick(startBtn);
    await sleep(START_WAIT_MS);
  } else {
    warn('No start button found (assuming game already running)');
  }

  // 4. matching loop
  const getTiles = () => {
    const nodes = root.querySelectorAll('.FormattedText[aria-label]');
    const out = [];
    for (const n of nodes) {
      // FormattedText -> .t1s3w3lt -> .c13hkcga -> tile container
      const tile = n.parentElement?.parentElement?.parentElement;
      if (!tile || !isVisible(tile)) continue;
      out.push({ tile, text: n.getAttribute('aria-label') || '' });
    }
    return out;
  };

  log('Matching started');
  let matched = 0, stuck = 0, prevCount = -1;

  for (let i = 0; i < MAX_ITERS; i++) {
    const tiles = getTiles();

    if (tiles.length === 0) {
      log(`%c✓ Done. Matched ${matched} pairs.`, 'color:#1D9E75;font-weight:bold');
      return;
    }

    if (tiles.length === prevCount) {
      if (++stuck > 3) { err('Stuck. Remaining:', tiles.map(t => t.text)); return; }
    } else { stuck = 0; prevCount = tiles.length; }

    // map normalized text -> DOM tile (for currently visible tiles)
    const visible = new Map();
    for (const t of tiles) {
      const k = norm(t.text);
      if (!visible.has(k)) visible.set(k, t.tile);
    }

    // find first tile whose partner is also visible
    let A, B, aTxt, bTxt;
    for (const t of tiles) {
      const partner = pair.get(norm(t.text));
      if (partner && visible.has(partner) && visible.get(partner) !== t.tile) {
        A = t.tile; aTxt = t.text;
        B = visible.get(partner); bTxt = partner;
        break;
      }
    }

    if (!A) {
      warn('No pair found among visible tiles:', tiles.map(t => t.text));
      await sleep(400);
      continue;
    }

    matched++;
    log(`${matched}. "${aTxt}"  ↔  "${bTxt}"`);
    realClick(A);
    await sleep(CLICK_DELAY_MS);
    realClick(B);
    await sleep(PAIR_DELAY_MS);
  }

  err(`Hit max iterations (${MAX_ITERS})`);
})();