(() => {
  const sourceLine = document.getElementById('source-line');
  const codeDisplay = document.getElementById('code-display');
  const input = document.getElementById('typing-input');
  const statWpm = document.getElementById('stat-wpm');
  const statAcc = document.getElementById('stat-acc');
  const statKps = document.getElementById('stat-kps');
  const statTime = document.getElementById('stat-time');
  const restartBtn = document.getElementById('restart-btn');
  const gameCard = document.getElementById('game-card');
  const helpBtn = document.getElementById('help-btn');
  const closeHelp = document.getElementById('close-help');
  const helpModal = document.getElementById('help-modal');

  let snippets = [];
  let target = '';
  let startTime = null;
  let finished = false;
  let totalKeystrokes = 0;
  let correctKeystrokes = 0;
  let tickHandle = null;
  let resultBanner = null;

  function escapeHtml(s) {
    return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
  }

  function pickSnippet() {
    return snippets[Math.floor(Math.random() * snippets.length)];
  }

  function loadSnippet() {
    const s = pickSnippet();
    // Tabs shown as two spaces so the player never needs to press Tab --
    // a plain textarea's default Tab behavior is "move focus," and
    // preventDefault-ing that just to insert a literal tab is more
    // fragile (IME/mobile edge cases) than sidestepping it entirely.
    target = s.code.replace(/\t/g, '  ');
    sourceLine.innerHTML = `typing: <span class="accent">${escapeHtml(s.repo)}/${escapeHtml(s.file)}</span>`;

    startTime = null;
    finished = false;
    totalKeystrokes = 0;
    correctKeystrokes = 0;
    input.value = '';
    if (resultBanner) { resultBanner.remove(); resultBanner = null; }
    render();
    input.disabled = false;
    input.focus();
    stopTick();
    startTick();
  }

  function render() {
    const typed = input.value;
    let html = '';
    for (let i = 0; i < target.length; i++) {
      const targetChar = target[i] === '\n' ? '\n' : target[i];
      let cls = 'char-pending';
      if (i < typed.length) {
        cls = typed[i] === target[i] ? 'char-correct' : 'char-incorrect';
      } else if (i === typed.length) {
        cls = 'char-pending char-cursor';
      }
      html += `<span class="${cls}">${escapeHtml(targetChar)}</span>`;
    }
    codeDisplay.innerHTML = html;
    updateStats();
  }

  function elapsedSeconds() {
    if (startTime === null) return 0;
    return (performance.now() - startTime) / 1000;
  }

  function updateStats() {
    const typed = input.value;
    let correctSoFar = 0;
    for (let i = 0; i < typed.length && i < target.length; i++) {
      if (typed[i] === target[i]) correctSoFar++;
    }
    const secs = elapsedSeconds();
    const mins = secs / 60;
    const wpm = mins > 0 ? Math.round((correctSoFar / 5) / mins) : 0;
    const acc = totalKeystrokes > 0 ? Math.round((correctKeystrokes / totalKeystrokes) * 100) : 100;
    const kps = secs > 0 ? (totalKeystrokes / secs) : 0;

    statWpm.textContent = wpm;
    statAcc.textContent = `${acc}%`;
    statKps.textContent = kps.toFixed(1);
    statTime.textContent = `${secs.toFixed(1)}s`;
  }

  function startTick() {
    tickHandle = setInterval(() => { if (!finished) updateStats(); }, 200);
  }
  function stopTick() {
    if (tickHandle) clearInterval(tickHandle);
    tickHandle = null;
  }

  function finish() {
    finished = true;
    input.disabled = true;
    stopTick();
    updateStats();
    resultBanner = document.createElement('div');
    resultBanner.className = 'result-banner';
    resultBanner.textContent = `Done — ${statWpm.textContent} wpm, ${statAcc.textContent} accuracy, ${statTime.textContent}. Nice.`;
    gameCard.insertBefore(resultBanner, gameCard.querySelector('.actions'));
  }

  input.addEventListener('keydown', (e) => {
    if (finished) return;
    const isBackspace = e.key === 'Backspace';
    const isNewline = e.key === 'Enter';
    const isChar = e.key.length === 1;
    if (!isBackspace && !isNewline && !isChar) return; // ignore Shift/Control/Arrow/Tab/etc

    if (startTime === null && !isBackspace) startTime = performance.now();

    totalKeystrokes++;
    if (!isBackspace) {
      const expected = target[input.value.length];
      const pressed = isNewline ? '\n' : e.key;
      if (expected !== undefined && pressed === expected) correctKeystrokes++;
    }
  });

  input.addEventListener('input', () => {
    render();
    if (input.value === target) finish();
  });

  // mousedown + preventDefault, not click -- a click handler runs after the
  // browser's own default-focus behavior has already fired, which was
  // stealing focus away from the hidden textarea whenever this had a
  // native tabindex. preventDefault on mousedown stops that entirely, so
  // our explicit focus() call is the only thing that happens.
  codeDisplay.addEventListener('mousedown', (e) => {
    e.preventDefault();
    if (!finished) input.focus();
  });
  restartBtn.addEventListener('click', loadSnippet);

  helpBtn.addEventListener('click', () => { helpModal.hidden = false; });
  closeHelp.addEventListener('click', () => { helpModal.hidden = true; });
  helpModal.addEventListener('click', (e) => { if (e.target === helpModal) helpModal.hidden = true; });

  fetch('snippets.json')
    .then(r => r.json())
    .then(data => {
      snippets = data;
      loadSnippet();
    })
    .catch(() => {
      sourceLine.textContent = 'Could not load snippets.';
    });
})();