(() => {
  'use strict';
  const $ = (id) => document.getElementById(id);
  const sleep = (ms) => new Promise((r) => window.setTimeout(r, ms));
  const pad3 = (n) => String(n).padStart(3, '0');
  const hostClock = () => new Date().toLocaleTimeString('zh-TW', { hour12: false });
  const HOST_RE = /^[a-z0-9][a-z0-9-]*\.hf\.space$/i;
  const chips = () => Array.from(document.querySelectorAll('#chips .chip'));

  $('clock').textContent = hostClock();
  window.setInterval(() => { $('clock').textContent = hostClock(); }, 1000);

  let vm;
  let ready = false;
  let asking = false;
  let bootTimer;
  let asked = 0, answered = 0;
  let llmAnswer = '';              // reply captured by the bridge from the Gradio stream
  let currentQuestion = '';
  let toastTimer;

  function toast(text) {
    $('toast').textContent = text; $('toast').classList.add('show');
    window.clearTimeout(toastTimer); toastTimer = window.setTimeout(() => $('toast').classList.remove('show'), 2200);
  }
  function logRow(src, text, cls = '') {
    const log = $('log'); const empty = log.querySelector('.log-empty'); if (empty) empty.remove();
    const row = document.createElement('div'); row.className = `log-row ${cls}`;
    for (const [c, t] of [['t', hostClock()], ['src', src], ['msg', text]]) {
      const s = document.createElement('span'); s.className = c; s.textContent = t; row.append(s);
    }
    log.append(row); while (log.children.length > 200) log.firstElementChild.remove();
    log.scrollTop = log.scrollHeight;
  }
  function setButtons(enabled, label) {
    $('askButton').disabled = !enabled; $('askButton').innerHTML = label;
    chips().forEach((c) => { c.disabled = !enabled; });
  }
  async function gunzipBase64(b64) {
    const bin = Uint8Array.from(atob(b64), (c) => c.charCodeAt(0));
    return new Response(new Blob([bin]).stream().pipeThrough(new DecompressionStream('gzip'))).arrayBuffer();
  }
  // XiaoMao Chinese puts the VGA into a graphics mode and keeps the 80x25 text (char, attribute pairs) in a shadow
  // buffer at VGA plane offset 0x8000 (patched: A800:0000). Before it loads, the normal text screen is used.
  function screenLines() {
    const vga = vm.v86.cpu.devices.vga;
    if (vga && vga.graphical_mode) {
      const m = vga.vga_memory; const rows = [];
      for (let r = 0; r < 25; r++) {
        const b = new Uint8Array(80);
        for (let c = 0; c < 80; c++) b[c] = m[0x8000 + (r * 80 + c) * 2];
        rows.push(window.Big5.decode(b).replace(/\s+$/, ''));
      }
      return rows;
    }
    return vm.screen_adapter.get_text_screen().map((l) => l.replace(/\s+$/, ''));
  }
  const screenText = () => screenLines().join('\n');
  const lastLine = () => { const l = screenLines().filter((x) => x.trim() !== ''); return l.length ? l[l.length - 1] : ''; };
  const atPrompt = () => /^[A-Z]:\\>$/.test(lastLine().trim());
  async function typeLine(text) { await vm.keyboard_send_text(`${text}\n`, 25); await sleep(250); }

  // ---- screen presentation -------------------------------------------------------------------------------
  // Before XiaoMao loads (first ~2 s) v86 shows an 80x25 DOM text layer; scale it to the card width with CSS.
  function fitText() {
    const stage = $('stage'); const text = $('screen').firstElementChild;
    if (!stage.clientWidth || !text || !text.offsetWidth) return;
    const k = stage.clientWidth / text.offsetWidth;
    text.style.transformOrigin = '0 0'; text.style.transform = `scale(${k})`; stage.style.height = `${Math.round(text.offsetHeight * k)}px`;
  }
  // With XiaoMao the VGA is in a 640x400 graphics mode and v86 draws it on its own canvas, whose CSS size it sets from
  // devicePixelRatio. Scaling that canvas with CSS (the first version) broke on HiDPI screens (shown 2x too large and cropped) and
  // gave uneven strokes at fractional scales. So v86's canvas is hidden and its pixels are presented here, in device pixels:
  //   - integer scale in device pixels: nearest neighbour (perfectly sharp)
  //   - otherwise: nearest-neighbour up to the next integer, then smooth down ("sharp bilinear"): even strokes, no shimmer
  let zoom = (window.localStorage && localStorage.getItem('dosllm.zoom')) || 'fit';
  let aspect43 = !(window.localStorage && localStorage.getItem('dosllm.aspect') === '0');
  const view = $('view'); const vctx = view.getContext('2d');
  const off = document.createElement('canvas'); const octx = off.getContext('2d');
  window.presentInfo = {};
  function present() {
    if (!vm) return;
    const stage = $('stage'); const host = $('screen'); const src = host.querySelector('canvas'); const vga = vm.v86.cpu.devices.vga;
    const graphical = !!(vga && vga.graphical_mode && src && src.width > 0 && src.height > 0);
    host.classList.toggle('hidden', graphical); view.style.display = graphical ? 'block' : 'none';
    if (!graphical) { stage.classList.remove('scroll'); fitText(); return; }
    const dpr = window.devicePixelRatio || 1; const avail = stage.clientWidth; if (!avail) return;
    const nw = src.width, nh = src.height;
    let sx; let sy;                                   // CSS pixels per source pixel
    if (zoom === 'crisp') { sx = Math.max(1, Math.floor(avail * dpr / nw)) / dpr; sy = sx; }        // integer device pixels, square
    else {
      sx = zoom === 'big' ? 2 : avail / nw;
      sy = sx * (aspect43 ? (nw / nh) / (4 / 3) : 1);  // 640x400 shown as 4:3 like a real VGA monitor: rows 1.2x taller
    }
    let pw = Math.round(nw * sx * dpr); let ph = Math.round(nh * sy * dpr);
    const area = pw * ph; if (area > 16e6) { const f = Math.sqrt(16e6 / area); pw = Math.round(pw * f); ph = Math.round(ph * f); }   // keep memory sane
    if (view.width !== pw || view.height !== ph) { view.width = pw; view.height = ph; }
    const cw = pw / dpr; const chh = ph / dpr; view.style.width = `${cw}px`; view.style.height = `${chh}px`;
    stage.style.height = `${Math.round(chh)}px`; stage.classList.toggle('scroll', cw > avail + 1);
    const kx = Math.ceil(pw / nw); const ky = Math.ceil(ph / nh);
    if (pw === nw * kx && ph === nh * ky) { vctx.imageSmoothingEnabled = false; vctx.drawImage(src, 0, 0, pw, ph); }
    else {
      const ow = nw * Math.min(kx, 8); const oh = nh * Math.min(ky, 8);
      if (off.width !== ow || off.height !== oh) { off.width = ow; off.height = oh; }
      octx.imageSmoothingEnabled = false; octx.drawImage(src, 0, 0, ow, oh);
      vctx.imageSmoothingEnabled = true; vctx.imageSmoothingQuality = 'high'; vctx.drawImage(off, 0, 0, pw, ph);
    }
    window.presentInfo = { dpr, avail, native: [nw, nh], css: [Math.round(cw), Math.round(chh)], device: [pw, ph], scaleDevice: [+(pw / nw).toFixed(3), +(ph / nh).toFixed(3)], zoom, aspect43 };
  }
  window.addEventListener('resize', present);

  // What G.EXE prints: a line "A> ..." followed by indented continuation lines (Chinese text wraps anywhere).
  const CJK = /[\u3000-\u9fff\uff00-\uffef]/;
  function dosAnswer() {
    let out = []; let on = false;
    for (const l of screenLines()) {
      if (/^A> /.test(l)) { out = [l.slice(3).trim()]; on = true; }
      else if (on && /^ {3}\S/.test(l)) out.push(l.trim());
      else if (on) on = false;
    }
    return out.reduce((acc, line) => (acc === '' ? line : (CJK.test(acc.slice(-1)) || CJK.test(line[0]) ? acc + line : `${acc} ${line}`)), '');
  }
  // G.EXE can only print what Big5 can show and joins lines with single spaces: apply the same to the LLM's reply.
  const expectedOnDos = (s) => window.Big5.displayable(s).replace(/[\r\n]+/g, ' ').replace(/\s+/g, ' ').trim();
  const squash = (s) => s.replace(/\s+/g, '');   // wrapping may add or drop a space at line breaks

  function watchBoot() {
    window.clearInterval(bootTimer);
    bootTimer = window.setInterval(() => {
      const text = screenText();
      const ip = /IPADDR\s+([\d.]+)/.exec(text); if (ip) $('ip').textContent = `IP ${ip[1]}`;
      if (/TCP\/IP is up/.test(text)) {
        window.clearInterval(bootTimer); ready = true; asking = false;
        $('netText').textContent = 'DOS NET UP'; $('liveDot').classList.add('on');
        $('dosState').textContent = 'NET UP'; $('dosState').classList.add('on'); $('bootTag').textContent = 'FREEDOS READY';
        setButtons(true, '<span class="button-icon">▶</span>問 DOS');
        $('note').textContent = 'DOS 已取得 DHCP 位址。按「問 DOS」會在 DOS 提示字元輸入 G <問題>，答案會印在 DOS 畫面上。';
      }
    }, 400);
  }

  async function boot() {
    const assets = window.DOSLLM_ASSETS;
    if (!window.V86 || !assets || !window.GradioBridge || !window.Big5) {
      $('netText').textContent = 'LOAD ERROR'; $('note').textContent = 'v86 或資產載入失敗，請重新整理頁面。'; return;
    }
    if (typeof DecompressionStream !== 'function') {
      $('netText').textContent = 'UNSUPPORTED'; $('note').textContent = '這個瀏覽器不支援 DecompressionStream，請改用較新的 Chrome / Edge / Safari / Firefox。'; return;
    }
    if (!window.Big5.available) logRow('SYS', '這個瀏覽器的 TextDecoder 不支援 big5：只能用英文提問', 'err');
    window.GradioBridge.install();
    window.GradioBridge.onEvent = (_m, text) => {
      if (text.startsWith('Gradio answer: ')) { llmAnswer = text.slice('Gradio answer: '.length); logRow('LLM', llmAnswer, 'ok'); }
      else logRow('BRIDGE', text, 'bridge');
    };
    const [wasm, bios, vga, img] = await Promise.all(['wasm', 'bios', 'vga', 'img'].map((k) => gunzipBase64(assets[k])));
    const wasmModule = await WebAssembly.compile(wasm);
    vm = new window.V86({
      wasm_fn: async (imports) => (await WebAssembly.instantiate(wasmModule, imports)).exports,
      memory_size: 16 * 1024 * 1024, vga_memory_size: 2 * 1024 * 1024,
      screen_container: $('screen'),
      bios: { buffer: bios }, vga_bios: { buffer: vga }, fda: { buffer: img },
      net_device: { type: 'ne2k', relay_url: window.GradioBridge.relayUrl('dos'), dns_method: 'doh' },
      autostart: true, disable_speaker: true,
    });
    window.dosVm = vm;   // handy for tests: window.dosVm.screen_adapter.get_text_screen()
    vm.add_listener('screen-set-size', () => window.setTimeout(present, 50));
    vm.keyboard_set_status(false);
    const focus = () => { vm.keyboard_set_status(true); $('stage').classList.add('focus'); };
    $('stage').addEventListener('mousedown', focus);
    $('stage').addEventListener('touchstart', focus, { passive: true });
    watchBoot();
  }

  const hex = (bytes) => Array.from(bytes, (b) => b.toString(16).padStart(2, '0')).join('').toUpperCase();
  async function ask(fixedQuestion) {
    if (!ready || asking) return;
    const host = $('host').value.trim();
    const raw = typeof fixedQuestion === 'string' ? fixedQuestion : $('question').value;
    // DOS shell / JSON metacharacters out, control characters out
    let text = raw.replace(/[\u0000-\u001f\u007f"\\%&|<>^!]/g, ' ').replace(/\s+/g, ' ').trim();
    let enc = window.Big5.encode(text);
    while (enc.bytes.length > 120) { text = Array.from(text).slice(0, -1).join(''); enc = window.Big5.encode(text); }   // G.EXE keeps 120 bytes
    if (!HOST_RE.test(host)) { toast('主機必須是 *.hf.space 網域'); return; }
    if (!text) { toast('請輸入問題（中文或英文）'); return; }
    if (!atPrompt()) { toast('DOS 尚未回到提示字元（上一個程式還在執行）'); return; }
    const chinese = enc.bytes.some((b) => b >= 0x80);
    if (chinese && !window.Big5.available) { toast('這個瀏覽器不支援 Big5 轉碼，請用英文提問'); return; }
    if (enc.lost.length) { toast(`DOS 無法顯示這些字，已改成 ?：${Array.from(new Set(enc.lost)).join('')}（Big5 沒有簡體字）`); logRow('SYS', `無法用 Big5 表示：${enc.lost.join('')}`, 'err'); }
    $('question').value = text;
    asking = true; llmAnswer = ''; currentQuestion = window.Big5.displayable(text); asked += 1; $('askCount').textContent = pad3(asked);
    setButtons(false, '<span class="button-icon">◌</span>DOS 等待回答…');
    $('matchTag').textContent = 'WAITING'; $('answerBox').hidden = true;
    logRow('SYS', `host ${host}  ${chinese ? '中文' : 'English'} question "${text}"`);
    await typeLine(`SET GRADIO_HOST=${host}`);
    if (chinese) {
      // The page cannot type Zhuyin, so the Big5 bytes travel as hex in GQ1..GQ4 and G.EXE decodes them.
      const h = hex(enc.bytes);
      for (let i = 0; i < 4; i += 1) await typeLine(`SET GQ${i + 1}=${h.slice(i * 60, i * 60 + 60)}`);
      await typeLine('CLS');
      await typeLine('G');
    } else {
      await typeLine('CLS');
      await typeLine(`G ${text}`);
    }
    const deadline = Date.now() + 190000;                         // DNS + two HTTP exchanges + model time
    await sleep(1500);
    while (Date.now() < deadline && asking && !atPrompt()) await sleep(400);
    await sleep(500);
    if (asking) finish();
  }

  function finish() {
    asking = false;
    setButtons(true, '<span class="button-icon">▶</span>再問一次');
    const dos = dosAnswer(); const expected = expectedOnDos(llmAnswer);
    if (!dos) { logRow('DOS', 'DOS 畫面上沒有看到答案（G.EXE 可能出錯或逾時，可按「重新開機」再試）', 'err'); $('matchTag').textContent = 'NO ANSWER'; return; }
    answered += 1; $('ansCount').textContent = pad3(answered);
    logRow('DOS', `畫面印出：${dos}`, 'ok');
    const same = expected !== '' && squash(dos) === squash(expected);
    const lossy = expected !== '' && expected !== llmAnswer.replace(/[\r\n]+/g, ' ').replace(/\s+/g, ' ').trim();
    $('matchTag').textContent = same ? 'DOS = LLM' : 'DIFFERENT';
    logRow('CHECK', same ? `DOS 畫面上的答案與 LLM 回傳的答案相同${lossy ? '（LLM 用了 Big5 沒有的字，DOS 顯示為 ?）' : '（逐字）'}` : `與 LLM 回傳不同。LLM（DOS 能顯示的部分）：${expected || '(bridge 沒有擷取到)'}`, same ? 'ok' : 'err');
    const box = $('answerBox'); box.hidden = false; box.textContent = '';
    for (const [k, v] of [['Q', currentQuestion], ['DOS 印出', dos], ['LLM 回傳', llmAnswer]]) {
      const b = document.createElement('b'); b.textContent = `${k}  `; box.append(b, document.createTextNode(`${v}\n`));
    }
  }

  // Ctrl+Space toggles XiaoMao's Zhuyin input. The key events need human-like timing: sent in one burst, the BIOS has not
  // yet seen Ctrl when Space arrives and the toggle is missed.
  async function toggleIme() {
    if (!vm || !ready) return;
    vm.keyboard_set_status(true); $('stage').classList.add('focus');
    vm.keyboard_send_scancodes([0x1D]); await sleep(250);
    vm.keyboard_send_scancodes([0x39]); await sleep(150);
    vm.keyboard_send_scancodes([0xB9]); await sleep(150);
    vm.keyboard_send_scancodes([0x9D]);
    toast('已切換注音／英數（畫面最下列會顯示 [注音] 或 [英數]）');
  }

  function reboot() {
    if (!vm) return;
    asking = false; ready = false;
    $('netText').textContent = 'REBOOTING'; $('liveDot').classList.remove('on');
    $('dosState').textContent = 'REBOOT'; $('dosState').classList.remove('on'); $('bootTag').textContent = 'REBOOTING FREEDOS';
    setButtons(false, '<span class="button-icon">◌</span>DOS 重新開機中…');
    vm.restart(); watchBoot(); logRow('SYS', 'DOS 重新開機');
  }

  $('askButton').addEventListener('click', () => ask());
  $('question').addEventListener('keydown', (e) => { if (e.key === 'Enter') ask(); });
  chips().forEach((c) => c.addEventListener('click', () => ask(c.textContent)));
  $('rebootButton').addEventListener('click', reboot);
  $('imeButton').addEventListener('click', toggleIme);
  window.setInterval(present, 66);                                    // ~15 fps is plenty for a text screen
  $('zoomSel').value = zoom; $('aspect').checked = aspect43; $('aspectLabel').style.display = zoom === 'crisp' ? 'none' : '';
  $('zoomSel').addEventListener('change', () => { zoom = $('zoomSel').value; try { localStorage.setItem('dosllm.zoom', zoom); } catch (e) { /* private mode */ } $('aspectLabel').style.display = zoom === 'crisp' ? 'none' : ''; present(); });
  $('aspect').addEventListener('change', () => { aspect43 = $('aspect').checked; try { localStorage.setItem('dosllm.aspect', aspect43 ? '1' : '0'); } catch (e) { /* private mode */ } present(); });
  boot().catch((e) => { $('netText').textContent = 'BOOT ERROR'; $('note').textContent = `啟動失敗：${e && e.message ? e.message : e}`; console.error(e); });
})();