mobux 0.1.4

import { TerminalCore } from './terminal-core.js';
import { ReaderView } from './reader-view.js';
import { createGestureRecognizer } from './touch.js';
import { createInputBar } from './input-bar.js';
import { applyTheme, getStoredThemeId } from './themes.js';

const session = window.MOBUX_SESSION;
const termEl = document.getElementById("terminal");
const readerEl = document.getElementById("reader");
const overlay = document.getElementById("touchOverlay");
const loadquote = document.getElementById("loadquote");
const paneIndicator = document.getElementById("paneIndicator");
const cmdPickList = document.getElementById("cmdPickList");
const cmdOverlayBg = document.getElementById("cmdOverlayBg");
const cmdCloseBtn = document.getElementById("cmdCloseBtn");

// ── Loading screen quotes ───────────────────────────────────────────
const quotes = [
  ["Simplicity is prerequisite for reliability.", "Edsger W. Dijkstra"],
  ["If debugging is the process of removing bugs, then programming must be the process of putting them in.", "Edsger W. Dijkstra"],
  ["The Analytical Engine weaves algebraical patterns just as the Jacquard loom weaves flowers and leaves.", "Ada Lovelace"],
  ["We can only see a short distance ahead, but we can see plenty there that needs to be done.", "Alan Turing"],
  ["Those who can imagine anything, can create the impossible.", "Alan Turing"],
  ["The most dangerous phrase in the language is: we\u2019ve always done it this way.", "Grace Hopper"],
  ["The best way to predict the future is to invent it.", "Alan Kay"],
  ["Premature optimization is the root of all evil.", "Donald Knuth"],
  ["Talk is cheap. Show me the code.", "Linus Torvalds"],
  ["Controlling complexity is the essence of computer programming.", "Brian Kernighan"],
  ["Any sufficiently advanced technology is indistinguishable from magic.", "Arthur C. Clarke"],
  ["Information is the resolution of uncertainty.", "Claude Shannon"],
  ["Looking back, we were the luckiest people in the world; there was no choice but to be pioneers.", "Margaret Hamilton"],

  // Contemporary craft
  ["Any fool can write code that a computer can understand. Good programmers write code that humans can understand.", "Martin Fowler"],
  ["Truth can only be found in one place: the code.", "Robert C. Martin"],
  ["I'm not a great programmer; I'm just a good programmer with great habits.", "Kent Beck"],
  ["Duplication is far cheaper than the wrong abstraction.", "Sandi Metz"],
  ["It's harder to read code than to write it.", "Joel Spolsky"],
  ["I call it my billion-dollar mistake.", "Tony Hoare, on null"],
  ["Programmers know the value of everything and the cost of nothing.", "Rich Hickey"],
  ["Fancy algorithms are slow when n is small, and n is usually small.", "Rob Pike"],
  ["There are only two kinds of programming languages: the ones people complain about and the ones nobody uses.", "Bjarne Stroustrup"],
  ["Ruby is designed to make programmers happy.", "Yukihiro Matsumoto"],
  ["The three chief virtues of a programmer are: laziness, impatience, and hubris.", "Larry Wall"],
  ["If you're not failing every now and again, it's a sign you're not doing anything very innovative.", "John Carmack"],
];
{
  const [text, author] = quotes[Math.floor(Math.random() * quotes.length)];
  document.getElementById("quote").textContent = text;
  document.getElementById("qauthor").textContent = "\u2014 " + author;
}

// ── External links ──────────────────────────────────────────────────
// In a TWA (Trusted Web Activity, package id `io.github.mvhenten.mobux`),
// external links should open in the user's system default browser (e.g.
// Firefox, Chrome, whatever the user has configured), not Chrome Custom
// Tabs. Android's intent:// URL scheme with action=VIEW and no package=
// attribute forces the system to resolve through the default browser.
//
// TWA detection: document.referrer starts with 'android-app://' when
// running inside the TWA shell.
//
// On desktop / regular browsers, this uses the standard anchor-click
// new-tab behavior.

// Helper for navigation - exposed for test stubbing
function navigateToUrl(url) {
  window.location.assign(url);
}

function openExternal(url) {
  const isTWA = document.referrer.startsWith('android-app://');
  
  if (isTWA && /^https?:\/\//.test(url)) {
    // Build an intent:// URL that opens the link in the system default
    // browser. Format:
    // intent://<url>#Intent;action=android.intent.action.VIEW;scheme=<scheme>;S.browser_fallback_url=<url>;end;
    const urlObj = new URL(url);
    const intentUrl = `intent://${urlObj.host}${urlObj.pathname}${urlObj.search}${urlObj.hash}#Intent;action=android.intent.action.VIEW;scheme=${urlObj.protocol.replace(':', '')};S.browser_fallback_url=${encodeURIComponent(url)};end;`;
    window.__mobuxNavigateToUrl(intentUrl);
    return;
  }
  
  // Non-TWA or non-http(s) URLs: use anchor-click fallback
  const a = document.createElement('a');
  a.href = url;
  a.target = '_blank';
  a.rel = 'noopener noreferrer';
  a.style.display = 'none';
  document.body.appendChild(a);
  a.click();
  a.remove();
}
// Expose for tests
window.__mobuxNavigateToUrl = navigateToUrl;
// Expose for smoke tests (mirrors `window.__mobuxView` etc.).
window.__mobuxOpenExternal = openExternal;

// ── Core ────────────────────────────────────────────────────────────
// `coarse` pointer = touch primary (phones + tablets). Width fallback
// catches devices that misreport pointer capability. Desktops with a
// mouse stay `false` and skip the on-screen input bar.
const isMobile = window.matchMedia('(pointer: coarse)').matches || window.innerWidth < 620;
const core = new TerminalCore({ session, host: termEl });

// Apply the stored theme to all three layers. terminal-core.js already
// picked the matching palette + Ace theme at construction; this call
// pushes the --ansi-* vars onto #reader for tokenized reader output.
// Only the sterk backend has an Ace editor under the hood; xterm has none.
const getEditor = () => core.term?._sterk?.renderer?.getEditor?.();
applyTheme(getStoredThemeId(), { editor: getEditor() });

// Live swap when the settings page (or another tab) changes the theme.
// `storage` only fires in OTHER documents — same-doc swaps go through
// `mobux:theme` (dispatched by the picker).
function onThemeChange() {
  applyTheme(getStoredThemeId(), { editor: getEditor() });
}
window.addEventListener('storage', (e) => {
  if (e.key === 'mobux:theme') onThemeChange();
});
window.addEventListener('mobux:theme', onThemeChange);

// Enable overlay for touch devices
if ('ontouchstart' in window || navigator.maxTouchPoints > 0) {
  overlay.style.pointerEvents = 'auto';
}

// ── Pane indicator ──────────────────────────────────────────────────
function updatePaneUI() {
  const { panes, activeIndex } = core;
  if (panes.length <= 1) {
    paneIndicator.textContent = panes.length === 1 ? panes[0].title : "";
  } else {
    const current = panes[activeIndex];
    paneIndicator.textContent = `${current ? current.title : "?"} (${activeIndex + 1}/${panes.length})`;
  }
}
core.addEventListener('panes', () => {
  updatePaneUI();
  pruneViewPrefs();
  applyStoredViewForActiveWindow();
});

// ── Command pick list ───────────────────────────────────────────────
function showCmdList() {
  cmdPickList.classList.add('visible');
  cmdOverlayBg.classList.add('visible');
  overlay.style.pointerEvents = 'none';
}

function hideCmdList() {
  cmdPickList.classList.remove('visible');
  cmdOverlayBg.classList.remove('visible');
  if ('ontouchstart' in window || navigator.maxTouchPoints > 0) {
    overlay.style.pointerEvents = 'auto';
  }
}

cmdPickList.addEventListener('click', (e) => {
  const cmdItem = e.target.closest('[data-cmd]');
  if (cmdItem) { core.runTmuxCmd(cmdItem.dataset.cmd); hideCmdList(); return; }
});
cmdCloseBtn.addEventListener('click', hideCmdList);
cmdOverlayBg.addEventListener('click', hideCmdList);

// ── Touch gestures ──────────────────────────────────────────────────
function scrollByPixels(dy) {
  const lines = Math.round(dy / core.cellSize().height);
  if (lines !== 0) core.scrollLines(lines);
}

createGestureRecognizer(overlay, {
  onScroll: scrollByPixels,
  onReconnect: () => core.reconnect(),
  getFontSize: () => core.getFontSize(),

  onPinch(scale, startSize) {
    const newSize = Math.round(Math.max(8, Math.min(32, startSize * scale)));
    core.setFontSize(newSize);
  },

  onTwoPullMove(pull, vh) {
    if (pull > vh * 0.08) paneIndicator.textContent = '↻ Release to reload';
    else if (pull > vh * 0.03) paneIndicator.textContent = '↓ Pull to reload...';
  },

  onTwoPullEnd(pull, vh) {
    if (pull > vh * 0.08) location.reload(true);
    else updatePaneUI();
  },

  onTap(x, y) {
    // Detect URLs in terminal text at tap position and open them.
    // WebLinksAddon uses hover-based links which don't work on mobile,
    // so we read the buffer text directly.
    const cell = core.cellSize();
    const rect = termEl.getBoundingClientRect();
    const col = Math.floor((x - rect.left) / cell.width);
    const row = Math.floor((y - rect.top) / cell.height);
    const buffer = core.getActiveBuffer();
    const bufferRow = buffer.viewportY + row;
    const line = buffer.getLine(bufferRow);
    if (!line) return;
    const text = line.translateToString(true);
    const urlRe = /https?:\/\/[^\s)"'>]+/g;
    let match;
    while ((match = urlRe.exec(text)) !== null) {
      if (col >= match.index && col < match.index + match[0].length) {
        openExternal(match[0]);
        return;
      }
    }
  },

  onDoubleTap(x, y) {
    if (inputBar) {
      inputBar.show();
      return;
    }
    overlay.style.pointerEvents = 'none';
    setTimeout(() => { overlay.style.pointerEvents = 'auto'; }, 500);
    const el = document.elementFromPoint(x, y);
    if (el) {
      el.dispatchEvent(new MouseEvent('mousedown', { bubbles: true, clientX: x, clientY: y }));
      el.dispatchEvent(new MouseEvent('mouseup', { bubbles: true, clientX: x, clientY: y }));
      el.dispatchEvent(new MouseEvent('click', { bubbles: true, clientX: x, clientY: y }));
    }
  },

  onHSwipe: (dir) => core.switchWindow(dir),

  onLongPress: showCmdList,
  onSwipeUp: showCmdList,
});

// ReaderView uses fully synthetic scroll: native overflow scrolling
// on mobile WebViews has been unreliable (engaged-only-after-fresh-touch
// on iOS, locked-state on Android with large scrollbacks). We feed the
// gesture recogniser's onScroll/fling output straight into reader's
// translateY transform.
let readerGestures = null;
function mountReaderGestures() {
  if (readerGestures) return;
  readerGestures = createGestureRecognizer(readerEl, {
    onReconnect: () => core.reconnect(),
    onLongPress: showCmdList,
    onSwipeUp: showCmdList,
    onHSwipe: (dir) => core.switchWindow(dir),
    onTap: () => {},
    // Double-tap in reader mode is for typing, but the reader has no
    // cursor / no live editing affordance — opening the keyboard
    // there is confusing. Drop back to xterm first, then show the
    // input bar so the keystrokes have somewhere to land.
    onDoubleTap: () => { swapView('xterm'); if (inputBar) inputBar.show(); },
    onScroll: (dy) => reader.scrollBy(dy),
    onTwoPullMove(pull, vh) {
      if (pull > vh * 0.08) paneIndicator.textContent = '↻ Release to reload';
      else if (pull > vh * 0.03) paneIndicator.textContent = '↓ Pull to reload...';
    },
    onTwoPullEnd(pull, vh) {
      if (pull > vh * 0.08) location.reload(true);
      else updatePaneUI();
    },
  }, { passiveScroll: false });
}
function unmountReaderGestures() {
  if (!readerGestures) return;
  readerGestures.destroy();
  readerGestures = null;
}

// ── Reveal on first output ──────────────────────────────────────────
// Fire on the first `data` event, not on settle. The previous
// implementation reset an 800 ms timer per event, which never
// settled when the attached session pumped continuous output (e.g.
// a TUI like Claude Code), leaving the loading splash up forever.
let revealScheduled = false;
function scheduleReveal() {
  if (revealScheduled) return;
  if (!loadquote || !loadquote.parentNode) return;
  revealScheduled = true;
  setTimeout(() => {
    core.scrollToBottom();
    loadquote.style.opacity = '0';
    setTimeout(() => { if (loadquote.parentNode) loadquote.remove(); }, 300);
  }, 200);
}
core.addEventListener('data', scheduleReveal);

// ── Mobile input bar ────────────────────────────────────────────────
let inputBar = null;
if (isMobile) {
  inputBar = createInputBar(core.term, (d) => core.send(d));
}

// ── View swap (xterm <-> reader) ────────────────────────────────────
const reader = new ReaderView({ host: readerEl, core, overlay });
let currentView = 'xterm';

const VIEW_DEFAULT_KEY = 'mobux.view.default';
const viewPrefKey = (windowId) => `mobux.view.${session}.${windowId}`;

function activeWindowId() {
  const p = core.panes[core.activeIndex];
  return p?.id || null;
}

function storedDefaultView() {
  try { return localStorage.getItem(VIEW_DEFAULT_KEY) || 'xterm'; }
  catch (_) { return 'xterm'; }
}

function storedViewFor(windowId) {
  if (!windowId) return null;
  try { return localStorage.getItem(viewPrefKey(windowId)); }
  catch (_) { return null; }
}

function updateToggleLabel() {
  const btn = document.getElementById('viewToggleBtn');
  if (!btn) return;
  if (currentView === 'reader') {
    btn.textContent = '▣';
    btn.title = 'Switch to terminal view';
  } else {
    btn.textContent = '📖';
    btn.title = 'Switch to reader view';
  }
}

function applyView(mode, { persist = true } = {}) {
  if (mode !== 'xterm' && mode !== 'reader') return;
  if (mode === currentView) { updateToggleLabel(); return; }
  if (mode === 'reader') {
    termEl.classList.add('hidden');
    // Reader has its own gesture recogniser on #reader. Disable the
    // xterm overlay so it doesn't sit on top and eat every touch.
    overlay.style.pointerEvents = 'none';
    reader.mount();
    mountReaderGestures();
  } else {
    unmountReaderGestures();
    reader.unmount();
    termEl.classList.remove('hidden');
    if ('ontouchstart' in window || navigator.maxTouchPoints > 0) {
      overlay.style.pointerEvents = 'auto';
    }
    setTimeout(() => core.resize(), 0);
  }
  currentView = mode;
  if (persist) {
    try {
      localStorage.setItem(VIEW_DEFAULT_KEY, mode);
      const wid = activeWindowId();
      if (wid) localStorage.setItem(viewPrefKey(wid), mode);
    } catch (_) {}
  }
  updateToggleLabel();
  window.dispatchEvent(new CustomEvent('mobux:viewchange', { detail: mode }));
}

function swapView(mode) { applyView(mode, { persist: true }); }

// Ribbon view-toggle button (mobile input bar).
const viewToggleBtn = document.getElementById('viewToggleBtn');
if (viewToggleBtn) {
  viewToggleBtn.addEventListener('mousedown', (e) => e.preventDefault());
  viewToggleBtn.addEventListener('click', (e) => {
    e.preventDefault();
    swapView(currentView === 'xterm' ? 'reader' : 'xterm');
  });
}

function applyStoredViewForActiveWindow() {
  const wid = activeWindowId();
  const stored = storedViewFor(wid);
  const mode = stored || storedDefaultView();
  applyView(mode, { persist: false });
}

function pruneViewPrefs() {
  const live = new Set(core.panes.map((p) => p.id).filter(Boolean));
  const prefix = `mobux.view.${session}.`;
  try {
    for (let i = localStorage.length - 1; i >= 0; i--) {
      const k = localStorage.key(i);
      if (k?.startsWith(prefix) && !live.has(k.slice(prefix.length))) {
        localStorage.removeItem(k);
      }
    }
  } catch (_) {}
}

window.__mobuxView = {
  swap: swapView,
  get current() { return currentView; },
  send: (d) => core.send(d),
  test: {
    // Test injections close the WS first so tmux can't race/clobber
    // the injected content (e.g. by re-asserting alt-screen mode).
    inject: (str) => {
      // Mark the close intentional so auto-reconnect doesn't reopen the
      // WS and let tmux clobber the injected content.
      core.intentionalClose = true;
      try { core.ws?.close(); } catch (_) {}
      return new Promise((resolve) =>
        core.term.write('\x1b[?1049l' + str.replace(/\n/g, '\r\n'), resolve));
    },
    injectLines: (n, prefix = 'inject') => {
      core.intentionalClose = true;
      try { core.ws?.close(); } catch (_) {}
      let s = '\x1b[?1049l';
      for (let i = 0; i < n; i++) s += `${prefix} ${i}\r\n`;
      return new Promise((resolve) => core.term.write(s, resolve));
    },
    // Like injectLines but WITHOUT the \x1b[?1049l (alt-screen exit)
    // prefix. Use this in tests that care about sticky-to-bottom
    // behaviour after incremental content growth: the alt-screen exit
    // sequence causes sterk to reset the buffer, which races with the
    // test's scroll-geometry probe.
    injectLinesPlain: (n, prefix = 'inject') => {
      try { core.ws?.close(); } catch (_) {}
      let s = '';
      for (let i = 0; i < n; i++) s += `${prefix} ${i}\r\n`;
      return new Promise((resolve) => core.term.write(s, resolve));
    },
    // Returns a Promise that resolves after the reader's next _render()
    // call has committed updated scroll geometry (maxScroll, scrollY).
    // Safe to call from page.evaluate() — Playwright serialises the
    // resolved value via structured-clone, so callers should not await
    // a non-serialisable payload.
    readerAwaitRender: () => reader.awaitNextRender(),
    bufferLength: () => core.getActiveBuffer().length,
    isAlternate: () => {
      // sterk: compare alternate vs active buffer references
      if (core.term?._sterk?.buffer) {
        return core.term._sterk.buffer.alternate === core.term._sterk.buffer.active;
      }
      // xterm: the BufferNamespace exposes `active.type` ('normal' | 'alternate')
      const t = core.term?.buffer?.active?.type;
      return t === 'alternate';
    },
    readerAtBottom: () => reader._atBottom,
    readerForceScrollTop: () => { reader._atBottom = false; reader._scrollY = 0; reader._applyTransform?.(); },
    terminalRows: () => core.term.rows,
    cols: () => core.term.cols,
    rows: () => core.term.rows,
    viewportY: () => core.getActiveBuffer().viewportY,
    scrollToBottom: () => core.scrollToBottom(),
    wsReady: () => core.ws?.readyState === WebSocket.OPEN,
    // Simulate an *unexpected* server-side drop: close the socket
    // WITHOUT marking the close intentional, so the core's onclose
    // backoff fires exactly as it would for a real network/server blip.
    // Used by the auto-reconnect test.
    forceDrop: () => {
      core.intentionalClose = false;
      try { core.ws?.close(); } catch (_) {}
    },
    oscDetected: () => !!core.oscDetected,
    readerScrollY: () => reader.scrollY,
    readerMaxScroll: () => reader.maxScroll,
    readerInnerHeight: () => reader.innerHeight,
    readerScrollBy: (dy) => reader.scrollBy(dy),
    readerStickToBottom: () => reader.stickToBottom(),
    // Force a synchronous re-render. Used by tests that need to assert
    // post-render invariants (e.g. that rb-speaking re-applies after
    // _inner.replaceChildren wipes the icon DOM) without racing the
    // 50ms render throttle.
    readerForceRender: () => reader._render(),
    switchWindow: (dir) => core.switchWindow(dir),
    statusBarOffsetHeight: () => document.querySelector('.reader-statusbar')?.offsetHeight ?? 0,
    statusBarFilled: () => document.querySelector('.reader-statusbar')?.classList.contains('reader-statusbar--filled') ?? false,
  },
};

// Apply stored default at boot so the user lands in their preferred
// view even before the first /panes refresh resolves. Per-window
// override (if any) is applied later in the panes listener.
const bootDefault = storedDefaultView();
if (bootDefault === 'reader') {
  setTimeout(() => applyView('reader', { persist: false }), 0);
}

updateToggleLabel();

// ── Notification deep-link ─────────────────────────────────────────
// A push notification's URL embeds ?w={window_index} for the tmux
// window that fired the alert-bell hook. On boot we honor that, and
// on a click into an already-open tab the SW posts `mobux-navigate`
// so we can switch without a reload.
function selectWindow(windowIndex) {
  if (windowIndex == null || windowIndex === '') return;
  window.MobuxMesh.apiFetch(
    `/api/sessions/${encodeURIComponent(session)}/panes/${encodeURIComponent(windowIndex)}/select`,
    { method: 'POST' },
  ).then(() => {
    core.clear();
    core.scrollToBottom();
    setTimeout(() => { core.refreshPanes(); core.reloadHistory(); }, 300);
  }).catch(() => {});
}

function windowFromUrl(href) {
  try { return new URL(href, location.origin).searchParams.get('w'); }
  catch (_) { return null; }
}

if ('serviceWorker' in navigator) {
  navigator.serviceWorker.addEventListener('message', (ev) => {
    if (ev.data?.type === 'mobux-navigate') {
      selectWindow(windowFromUrl(ev.data.url));
    }
  });
}

// ── Boot ────────────────────────────────────────────────────────────
// `booted` gates the page-level auto-reconnect listeners below: until
// boot's own connect() has run there's nothing to reconnect, and firing
// reconnect() while `core.ws` is still null would open a competing
// socket that boot then immediately replaces.
let booted = false;
(async () => {
  await core.reloadHistory();
  core.connect();
  booted = true;
  const w = windowFromUrl(location.href);
  if (w != null) {
    // Brief wait so the WS attach completes before we ask tmux to
    // switch windows; refreshPanes after the switch then sees the new
    // active window.
    setTimeout(() => selectWindow(w), 500);
  }
})();

window.addEventListener("resize", () => core.resize());
setTimeout(() => core.resize(), 100);
setInterval(() => core.refreshPanes(), 5000);

// ── Auto-reconnect ──────────────────────────────────────────────────
// Renderer-agnostic. The tmux session persists server-side, so
// re-establishing the WS resumes cleanly. `core.reconnect()` is
// idempotent (no-ops if the socket is already OPEN), so wiring several
// triggers is safe — whichever fires first reconnects, the rest no-op.
//
// The core's own `ws.onclose` handler does capped exponential backoff
// for the "server bounced / network blip" case; these page-level
// listeners are the "user came back to the app" fast paths that
// reconnect immediately instead of waiting out the backoff window. The
// existing touch-based reconnect (touch.js onTouchStart → onReconnect)
// stays as a manual fallback.

function autoReconnect() {
  if (!booted) return;
  core.reconnect();
}

// Primary path: screen/tab is visible again → reconnect now.
document.addEventListener('visibilitychange', () => {
  if (document.visibilityState === 'visible') autoReconnect();
});
// Network came back.
window.addEventListener('online', autoReconnect);
// Android bfcache restore (app swapped back into the foreground).
window.addEventListener('pageshow', autoReconnect);

// A real navigation away / unload is an intentional teardown — mark it
// so the socket's onclose doesn't arm a (pointless) backoff retry on a
// page that's going away.
window.addEventListener('pagehide', () => { core.intentionalClose = true; });

// ── Soft keyboard (visualViewport) handler ──────────────────────────
// Renderer-agnostic. On Android Chrome (the TWA target) the soft
// keyboard does NOT shrink the layout viewport — `window.innerHeight`
// and the `100vh`/`100dvh` units used by `.term-body` stay at full
// screen — but `window.visualViewport.height` does shrink. Without
// this handler the bottom rows of the terminal (typically the tmux
// status line + active prompt) end up rendered behind the keyboard.
//
// We shrink the body to the visual viewport height so the flex
// children (#terminal, #reader, #inputBar) reflow into the visible
// area. Then we dispatch a `resize` so both backends recompute their
// (cols, rows) from the new host clientHeight. input-bar.js still
// owns its show/hide auto-restore on viewport grow-back — this handler
// only handles the body height tracking, which must work whether the
// input bar is mounted or not (the bug also reproduces when the
// renderer's native textarea gets focus directly).
if (window.visualViewport) {
  const vv = window.visualViewport;
  let lastH = vv.height;
  const trackKeyboard = () => {
    const shrunk = vv.height < window.innerHeight - 1;
    document.body.style.height = shrunk ? `${vv.height}px` : '';
    if (Math.abs(vv.height - lastH) > 0.5) {
      lastH = vv.height;
      // Synchronous resize so both backends recompute cols/rows from
      // the freshly-laid-out host height in the same task — no visible
      // jump on the next frame.
      window.dispatchEvent(new Event('resize'));
    }
  };
  vv.addEventListener('resize', trackKeyboard);
  vv.addEventListener('scroll', trackKeyboard);
}

// ── Tap-to-snap-to-bottom ───────────────────────────────────────────
// Renderer-agnostic. When the user is parked mid-scrollback and TAPS
// the terminal to type, the soft keyboard comes up but the viewport
// stays parked in scrollback — so what they type lands somewhere they
// can't see (issue #99). Snap to the live screen on a genuine tap so
// keystrokes always land in view.
//
// We discriminate a TAP from a SWIPE using pointer events, NOT focus.
// PR #100 hooked `focusin` and snapped on every touch — but focusin
// fires on tap-to-scroll too, so swiping up to read scrollback
// immediately snapped back to bottom and broke incremental scrolling.
// That PR was reverted in #102. Here we only snap when the pointer
// barely moved (< TAP_MOVE_PX) and was down only briefly
// (< TAP_MAX_MS): a real tap, not a swipe or a long-press-drag.
//
// Both backends mount under `#terminal` (xterm: `.xterm-helper-textarea`,
// sterk: `.ace_text-input`), so listening on the host element keeps
// this renderer-agnostic. This coexists with the visualViewport
// handler above (PR #98) — that one tracks keyboard height, this one
// tracks the viewport scroll position. Both stay.
{
  const TAP_MOVE_PX = 10; // max pointer travel for a tap (vs. swipe)
  const TAP_MAX_MS = 250; // max press duration for a tap (vs. drag)
  let downX = 0;
  let downY = 0;
  let downT = 0;
  let tracking = false;

  termEl.addEventListener('pointerdown', (e) => {
    downX = e.clientX;
    downY = e.clientY;
    downT = e.timeStamp;
    tracking = true;
  });

  termEl.addEventListener('pointerup', (e) => {
    if (!tracking) return;
    tracking = false;
    const moved = Math.hypot(e.clientX - downX, e.clientY - downY);
    const elapsed = e.timeStamp - downT;
    if (moved < TAP_MOVE_PX && elapsed < TAP_MAX_MS) {
      core.scrollToBottom();
    }
  });

  // A canceled pointer (e.g. the gesture recogniser claims it for a
  // scroll/pinch) is never a tap — drop tracking so the next pointerup
  // can't be misread.
  termEl.addEventListener('pointercancel', () => { tracking = false; });
}