Un libro de lectura escolar con furigana en cada kanji

// ═══ Postext Cookbook · Nº 124 · A school reader with furigana: per character, per word ═══
// https://postext.dev/en/cookbook/jukugo-furigana-textbook
// Code: MIT · Text: 新美南吉「ごん狐」(1932), Aozora Bunko 628 (PD); readings: CC BY 4.0
// Fonts: Klee One, Zen Maru Gothic (SIL OFL 1.1) · Needs postext ≥ 1.16.1
import { buildDocument, renderPageToCanvas, clearMeasurementCache } from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'es'; // @lang: the language of the frame; the story is Japanese in both
const RECIPE = 'jukugo-furigana-textbook';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: an autumn reader: ink, the red of the higanbana, a pale straw ground
const palette = {
  ink: '#2a2420', // text: a warm near-black
  red: '#b2402c', // the one accent: the unit badge, the section numbers, the box title
  reading: '#5a4e45', // the furigana, a shade off the ink so the two layers part
  straw: '#f6ecd6', // the opener band and the box
  muted: '#7a6d62', // folios, the series line, the colophon
  paper: '#fffdf8',
};
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = Object.entries({ ...palette, 'main-color': palette.red })
  .map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } }));
// #endregion
const [TEXT, ROUND] = ['Klee One', 'Zen Maru Gothic']; // 教科書体-like text, rounded gothic
const [SIZE, PITCH] = [14, 28]; // pt: a fourth-year reader's size, on a line twice as tall
const [CHARS, LINES] = [28, 21]; // the type area in characters

// #region answer: readings over every kanji: by character, by word, jukugo, JIS 1:2:1
// In a document tagged 'ja' the compact {漢字|かん|じ} (one reading per character) is jukugo
// ruby: each reading stays over its own kanji when it fits, and when one is longer it may run
// onto the next kanji of the same word; a break may fall between the two. {百舌鳥|もず} (one
// reading for the word) is group ruby, spread over the word 1:2:1. :ruby[菜種]{rt="な たね"
// mode=jukugo} says the same as the compact form; mode=mono keeps each reading to its kanji.
const cjk = {
  grid: { enabled: true, charsPerLine: CHARS, linesPerPage: LINES },
  ruby: {
    fontSize: em(0.5), // 7 pt: half the text, the size JLReq gives furigana
    color: col('reading'),
    align: 'jis', // a reading shorter than its base: ½ unit at each end, 1 between (1:2:1)
    overhang: 'kana', // a longer reading may run one ruby character onto a kana, never a kanji
    smallKana: 'keep', // ひょう with its small ょ, as today's books print it
  },
};
// The line gap (28 − 14 = 14 pt) holds a 7 pt reading with room to spare: no line moves for one.
const bodyText = {
  fontFamily: TEXT, fontSize: pt(SIZE), lineHeight: pt(PITCH), color: col('ink'),
  boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
  textAlign: 'justify', firstLineIndent: em(1), indentAfterHeading: true,
  avoidRunts: true, // no paragraph ends on one character
};
// #endregion

// #region opener: a straw band with the unit badge, the title and the author's name in kana
// Design text sets no furigana (gotcha: ruby-not-in-designs): the author's reading is a
// line of its own.
const BAND = 92; // mm from the trim's top
const opener = { enabled: true, minHeight: pt(PITCH * 6), slot: { elements: [
  { kind: 'box', id: 'band', reserve: false, style: { backgroundColor: col('straw') },
    placement: { anchor: { to: 'page', edge: 'top-left' },
      size: { width: 'fill', height: mm(BAND) } } },
  { kind: 'text', id: 'unit', content: '{attr.unit}', fontFamily: ROUND, fontSize: pt(16),
    fontWeight: 700, color: col('paper'), align: 'center', verticalAlign: 'middle',
    overflow: 'clip', box: { backgroundColor: col('red'), borderRadius: mm(6) },
    placement: { anchor: { to: 'container', edge: 'top-left' }, offset: { y: mm(-2) },
      size: { width: mm(12), height: mm(12) } } },
  { kind: 'text', id: 'series', content: '{title}', fontFamily: ROUND, fontSize: pt(9),
    fontWeight: 700, letterSpacing: pt(2), color: col('red'), align: 'left',
    verticalAlign: 'middle', placement: { anchor: { to: 'container', edge: 'top-left' },
      offset: { x: mm(16), y: mm(-2) }, size: { width: mm(80), height: mm(12) } } },
  { kind: 'text', id: 'title', content: '{titleText}', fontFamily: ROUND, fontSize: pt(48),
    lineHeight: 1.1, fontWeight: 700, color: col('ink'), align: 'left',
    placement: { anchor: { to: '#unit', edge: 'below' }, offset: { y: mm(7) } } },
  { kind: 'text', id: 'kana', content: '{attr.kana}', fontFamily: ROUND, fontSize: pt(8),
    letterSpacing: pt(1), color: col('muted'), align: 'left',
    placement: { anchor: { to: '#title', edge: 'below' }, offset: { y: mm(5) } } },
  { kind: 'text', id: 'author', content: '{attr.author}　作', fontFamily: ROUND,
    fontSize: pt(13), fontWeight: 500, color: col('ink'), align: 'left',
    placement: { anchor: { to: '#kana', edge: 'below' }, offset: { y: mm(1) } } },
] } };
// #endregion

// Folios at the outer foot, the series beside them.
const foot = (id, content, parity, edge, x, extra) => ({ kind: 'text', id, content, parity,
  fontFamily: ROUND, fontSize: pt(9), color: col('muted'), align: edge.endsWith('left')
    ? 'left' : 'right', placement: { anchor: { to: 'container', edge }, offset: { x: mm(x),
    y: mm(-12) } }, ...extra });
const folio = { fontWeight: 700, color: col('red') };

const config = () => ({ // a factory: the engine caches resolved configs per object
  locale: 'ja', // written out, never LANG (gotcha: ja-locale-tag)
  colorPalette,
  page: { sizePreset: 'custom', width: mm(182), height: mm(257), dpi: 150, // B5
    backgroundColor: col('paper'),
    // Minimums: the grid centres its 28 × 21 area (138 × 207 mm) in what they leave.
    margins: { top: mm(26), bottom: mm(22), left: mm(20), right: mm(20), mirror: true } },
  layout: { layoutType: 'single' },
  cjk,
  bodyText,
  headings: { fontFamily: ROUND, fontWeight: 700, color: col('red'),
    balancing: { enabled: false }, // nothing added above heads: the grid holds
    levels: [
      // Restated: any headings object drops the H1 break (gotcha: headings-drop-h1-break).
      { level: 1, breakBefore: { enabled: true, parity: 'any' }, advancedDesign: opener },
      { level: 2, fontSize: pt(16), lineSpan: 2 }, // 一, 二…: two lines of the grid
    ] },
  calloutStyles: [{ id: 'words', background: col('straw'), borderRadius: mm(3),
    snapToGrid: false, marginTop: pt(PITCH), marginBottom: pt(0),
    padding: { top: mm(4), right: mm(6), bottom: mm(3), left: mm(6) },
    titleStyle: { fontFamily: ROUND, fontSize: pt(11), fontWeight: 700, color: col('red') },
    body: { fontFamily: TEXT, fontSize: pt(13), lineHeight: pt(28), color: col('ink'),
      firstLineIndent: pt(0), textAlign: 'left' } }],
  paragraphStyles: [{ id: 'colophon', fontFamily: ROUND, fontSize: pt(6.5), lineHeight: pt(9),
    color: col('muted'), firstLineIndent: pt(0), textAlign: 'left', marginTop: mm(4) }],
  header: { elements: [] },
  footer: { elements: [
    foot('v-folio', '{pageNumber}', 'even', 'bottom-left', 0, folio),
    foot('v-series', '{title}', 'even', 'bottom-left', 9),
    foot('r-series', '{chapterTitle}', 'odd', 'bottom-right', -9),
    foot('r-folio', '{pageNumber}', 'odd', 'bottom-right', 0, folio),
  ] },
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Muestra en Markdown · 38 líneas · content.es.md
title: "よみもの　四年"
---

# ごんぎつね {author="新美南吉" kana="にいみ なんきち" unit="4"}

## 一

これは、{私|わたし}が{小|ちい}さいときに、{村|むら}の{茂平|も|へい}というおじいさんからきいたお{話|はなし}です。

むかしは、{私|わたし}たちの{村|むら}のちかくの、{中山|なか|やま}というところに{小|ちい}さなお{城|しろ}があって、{中山|なか|やま}さまというおとのさまが、おられたそうです。

その{中山|なか|やま}から、{少|すこ}しはなれた{山|やま}の{中|なか}に、「ごん{狐|ぎつね}」という{狐|きつね}がいました。ごんは、{一人|ひとり}ぼっちの{小狐|こ|ぎつね}で、:dots[しだ]{style=sesame}の{一|いっ}ぱいしげった{森|もり}の{中|なか}に{穴|あな}をほって{住|す}んでいました。そして、{夜|よる}でも{昼|ひる}でも、あたりの{村|むら}へ{出|で}てきて、いたずらばかりしました。はたけへ{入|はい}って{芋|いも}をほりちらしたり、{菜種|な|たね}:dots[がら]{style=sesame}の、ほしてあるのへ{火|ひ}をつけたり、{百姓家|ひゃく|しょう|や}の{裏手|うら|て}につるしてあるとんがらしをむしりとって、いったり、いろんなことをしました。

{或|ある}{秋|あき}のことでした。{二|に}、{三日|さん|にち}{雨|あめ}がふりつづいたその{間|あいだ}、ごんは、{外|そと}へも{出|で}られなくて{穴|あな}の{中|なか}にしゃがんでいました。

{雨|あめ}があがると、ごんは、ほっとして{穴|あな}からはい{出|で}ました。{空|そら}はからっと{晴|は}れていて、{百舌鳥|もず}の{声|こえ}がきんきん、ひびいていました。

ごんは、{村|むら}の{小川|お|がわ}の{堤|つつみ}まで{出|で}て{来|き}ました。あたりの、すすきの{穂|ほ}には、まだ{雨|あめ}のしずくが{光|ひか}っていました。{川|かわ}は、いつもは{水|みず}が{少|すくな}いのですが、{三日|みっ|か}もの{雨|あめ}で、{水|みず}が、どっとましていました。ただのときは{水|みず}につかることのない、{川|かわ}べりのすすきや、{萩|はぎ}の{株|かぶ}が、{黄|き}いろくにごった{水|みず}に{横|よこ}だおしになって、もまれています。ごんは{川下|かわ|しも}の{方|ほう}へと、ぬかるみみちを{歩|ある}いていきました。

ふと{見|み}ると、{川|かわ}の{中|なか}に{人|ひと}がいて、{何|なに}かやっています。ごんは、{見|み}つからないように、そうっと{草|くさ}の{深|ふか}いところへ{歩|ある}きよって、そこからじっとのぞいてみました。

「{兵十|ひょう|じゅう}だな」と、ごんは{思|おも}いました。{兵十|ひょう|じゅう}はぼろぼろの{黒|くろ}いきものをまくし{上|あ}げて、{腰|こし}のところまで{水|みず}にひたりながら、{魚|さかな}をとる、:dots[はりきり]{style=sesame}という、{網|あみ}をゆすぶっていました。はちまきをした{顔|かお}の{横|よこ}っちょうに、まるい{萩|はぎ}の{葉|は}が{一|いち}まい、{大|おお}きな{黒子|ほくろ}みたいにへばりついていました。

しばらくすると、{兵十|ひょう|じゅう}は、:dots[はりきり]{style=sesame}{網|あみ}の{一|いち}ばんうしろの、{袋|ふくろ}のようになったところを、{水|みず}の{中|なか}からもちあげました。その{中|なか}には、{芝|しば}の{根|ね}や、{草|くさ}の{葉|は}や、くさった{木|き}ぎれなどが、ごちゃごちゃはいっていましたが、でもところどころ、{白|しろ}いものがきらきら{光|ひか}っています。それは、ふとい:dots[うなぎ]{style=sesame}の{腹|はら}や、{大|おお}きな:dots[きす]{style=sesame}の{腹|はら}でした。{兵十|ひょう|じゅう}は、びくの{中|なか}へ、そのうなぎやきすを、ごみと{一|いっ}しょにぶちこみました。そして、また、{袋|ふくろ}の{口|くち}をしばって、{水|みず}の{中|なか}へ{入|い}れました。

{兵十|ひょう|じゅう}はそれから、びくをもって{川|かわ}から{上|あが}りびくを{土手|ど|て}においといて、{何|なに}をさがしにか、{川上|かわ|かみ}の{方|ほう}へかけていきました。

:::callout{type="words" title="ふりがなの つけかた"}
一字に 一つずつ　{村|むら}　{城|しろ}　{森|もり}　{穴|あな}

ことばに 一つ　{百舌鳥|もず}　{一人|ひとり}　{黒子|ほくろ}

一字ずつ、ことばとして　{兵十|ひょう|じゅう}　{小川|お|がわ}　:ruby[菜種]{rt="な たね" mode=jukugo}
:::

:::paragraphs{style="colophon"}
Texto: Niimi Nankichi, «Gon gitsune» (1932), sección 1, de la ficha 628 de Aozora Bunko (texto base 新美南吉童話集, Iwanami Bunko, 1996; transcripción 林裕司, corrección 浜野智), dominio público; lecturas sobre cada kanji añadidas para el Recetario de Postext. Compuesto en Klee One y Zen Maru Gothic (SIL OFL).
:::
`; // content.<lang>.md: the same Japanese page in both

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = { // every face the pages use, loaded before the build (gotcha: fonts-first)
  'Klee One': ['400'], // the text and its readings: the hand of a school textbook
  'Zen Maru Gothic': ['400', '500', '700'], // the title, heads, badge, box title, folios
};

// ─── 4 · Build & show ───────────────────────────────────────────────────────
// Each face loads the files of what it sets (gotcha: cjk-fonts-slices).
const all = (re) => (markdown.match(re) ?? []).join('');
await loadFonts(FONTS, markdown);
await loadCjkFonts({ [TEXT]: FONTS[TEXT] }, markdown);
await loadCjkFonts({ [ROUND]: FONTS[ROUND] },
  `${all(/^#.*$/gm)}${all(/title="[^"]*"/g)}${all(/colophon"\}\n[^\n]*/g)}よみもの四年作0123456789`);
// Page 1 is page 24 of the reader, a verso: the lesson opens on a spread.
const continuation = { pageIndexOffset: 23, pageNumbering: { startAt: 24 } };
const doc = await buildWithFonts(() => buildDocument({ markdown, continuation }, config()),
  markdown);
showPages(doc, { title: t({ en: 'A school reader with furigana',
  es: 'Un libro de lectura con furigana' }) });
offerPdf(() => renderToPdf(doc, { fontProvider: cjkPdfProvider }), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, cjk: igual en todas las recetas · 453 líneas
// ─── Kit ── helpers shared by every Cookbook recipe · postext.dev/cookbook ─────

// ─── Kit · core v1 ── the same in every recipe · postext.dev/cookbook ─────────
function mm(value) { return { value, unit: 'mm' }; }
function pt(value) { return { value, unit: 'pt' }; }
function em(value) { return { value, unit: 'em' }; }
/** The sample language's string: t({ en: 'Figure', es: 'Figura' }). */
function t(strings) { return strings[LANG] ?? Object.values(strings)[0]; }
/** A file in this recipe's assets folder, served from the Postext repo by jsDelivr. */
function asset(file) { return `https://cdn.jsdelivr.net/gh/drnachio/postext@main/cookbook/${RECIPE}/assets/${file}`; }

// ─── Kit · fonts v1 ── the same in every recipe · postext.dev/cookbook ────────
// Postext measures text with the faces the browser has loaded, and caches the
// widths, so every face must be ready before the first build. Faces come from
// Fontsource: the same static files the PDF embeds, so screen and PDF agree.

/** faces = { 'Family Name': ['400', '400i', '700'] }. `text` is the sample:
 *  letters beyond Latin-1 (č, ł, ő…) also load the latin-ext files. With
 *  `optional`, a face Fontsource does not ship is skipped instead of failing.
 *  Resolves to the number of faces added. */
async function loadFonts(faces, text = '', { optional = false } = {}) {
  kitStatus('Loading fonts…');
  const ranges = {
    latin: 'U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,'
      + 'U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD',
    'latin-ext': 'U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,'
      + 'U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF',
  };
  const subsets = /[Ā-˿Ḁ-ỿ]/.test(text) ? ['latin', 'latin-ext'] : ['latin'];
  const jobs = [];
  let added = 0;
  for (const [family, specs] of Object.entries(faces)) {
    const id = fontsourceId(family);
    const meta = optional ? await fontsourceMeta(family) : null;
    for (const spec of new Set(specs)) {
      const weight = parseInt(spec, 10);
      const style = spec.endsWith('i') ? 'italic' : 'normal';
      if (hasFace(family, weight, style)) continue;
      if (optional && !(meta?.weights.includes(weight) && meta.styles.includes(style))) continue;
      for (const subset of subsets) {
        const url = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-${subset}-${weight}-${style}.woff2`;
        const face = new FontFace(family, `url(${url}) format('woff2')`,
          { weight: String(weight), style, unicodeRange: ranges[subset] });
        jobs.push(face.load().then((ready) => { document.fonts.add(ready); added++; }, () => {
          if (subset === 'latin' && !optional) throw new Error(`Fontsource has no ${family} ${weight} ${style}`);
        }));
      }
    }
  }
  await Promise.all(jobs).catch((error) => { kitFail(error); throw error; });
  return added;
}

/** Runs `build` (a buildDocument or buildBundle call) and checks the faces
 *  the pages use. A regular face missing from FONTS is loaded with a warning;
 *  bold and italic variants are loaded when the family ships them. Then the
 *  measurement caches are cleared and the build runs again. */
async function buildWithFonts(build, text = '') {
  const tried = new Set();
  for (let round = 0; round < 3; round++) {
    kitStatus('Laying out…');
    await new Promise(requestAnimationFrame);          // let the status paint first
    const result = await Promise.resolve().then(build).catch((error) => { kitFail(error); throw error; });
    const wanted = { base: {}, variants: {} };
    for (const { font, base } of [result].flat().flatMap(fontStringsOf)) {
      const { family, weight, style } = parseFont(font);
      const key = `${family}|${weight}|${style}`;
      if (tried.has(key) || hasFace(family, weight, style)) continue;
      tried.add(key);
      (wanted[base ? 'base' : 'variants'][family] ??= []).push(`${weight}${style === 'italic' ? 'i' : ''}`);
    }
    if (Object.keys(wanted.base).length) {
      console.warn(`[cookbook] FONTS does not list ${JSON.stringify(wanted.base)}: loading them.`);
    }
    const added = await loadFonts(wanted.base, text) + await loadFonts(wanted.variants, text, { optional: true });
    if (added === 0) return result;
    clearMeasurementCache();
  }
  throw new Error('The fonts did not settle after three builds.');
}

/** Every font string of the layout. `base` marks a block's own face; its
 *  bold, italic and bold-italic variants are listed whether or not used. */
function fontStringsOf(doc) {
  const found = new Map();
  const walk = (node) => {
    if (!node || typeof node !== 'object') return;
    if (Array.isArray(node)) { node.forEach(walk); return; }
    for (const [key, value] of Object.entries(node)) {
      if (typeof value === 'string' && /fontString$/i.test(key)) {
        found.set(value, found.get(value) || key === 'fontString');
      } else if (value && typeof value === 'object') walk(value);
    }
  };
  walk(doc.pages);
  walk(doc.blocks);
  return [...found].map(([font, base]) => ({ font, base }));
}

/** '700 37.5px Open Sans' / 'italic 400 13px "Source Serif 4"' → { family, weight, style }.
 *  A string with no weight ('95.8px Young Serif', from a design text) is 400. */
function parseFont(font) {
  const m = /^(?:(italic|oblique)\s+)?(?:small-caps\s+)?(?:(\d+|bold|normal)\s+)?[\d.]+px\s+(.+)$/.exec(font.trim());
  if (!m) throw new Error(`Unexpected font string: ${font}`);
  const weight = m[2] === 'bold' ? 700 : !m[2] || m[2] === 'normal' ? 400 : Number(m[2]);
  return { family: m[3].replace(/^["']|["']$/g, ''), weight, style: m[1] ? 'italic' : 'normal' };
}

/** True when a loaded FontFace covers exactly this family, weight and style
 *  (document.fonts.check() is also true for families nobody declared). */
function hasFace(family, weight, style) {
  for (const face of document.fonts) {
    if (face.status !== 'loaded' || face.style !== style) continue;
    if (face.family.replace(/^["']|["']$/g, '') !== family) continue;
    const [low, high = low] = face.weight.split(' ').map(Number);
    if (weight >= low && weight <= high) return true;
  }
  return false;
}

/** Fontsource's id for a family: 'Source Serif 4' → 'source-serif-4'. */
function fontsourceId(family) { return family.toLowerCase().replace(/\s+/g, '-'); }

/** The weights and styles a family ships ({ weights: [400, 700], styles: ['normal', 'italic'] }), or null. */
function fontsourceMeta(family) {
  fontsourceMeta.cache ??= new Map();
  const id = fontsourceId(family);
  if (!fontsourceMeta.cache.has(id)) {
    fontsourceMeta.cache.set(id, fetch(`https://api.fontsource.org/v1/fonts/${id}`)
      .then((res) => (res.ok ? res.json() : null), () => null));
  }
  return fontsourceMeta.cache.get(id);
}

// ─── Kit · viewer v1 ── the same in every recipe · postext.dev/cookbook ───────
/** Shows the pages as facing spreads on a dark desk: the first page is a
 *  recto on its own, then verso | recto pairs, as in a bound book. Pages
 *  are painted when they scroll near the screen. */
function showPages(docs, { title, width = 460 } = {}) {
  const root = viewer(title);
  const pages = [docs].flat().flatMap((doc) =>
    doc.pages.map((page) => ({ doc, page, n: (doc.pageIndexOffset ?? 0) + page.index })));
  const spreads = [];
  let verso = null;
  for (const p of pages) {
    if (p.n % 2 === 1) { if (verso) spreads.push([verso, null]); verso = p; }
    else { spreads.push([verso, p]); verso = null; }
  }
  if (verso) spreads.push([verso, null]);
  const density = Math.min(window.devicePixelRatio || 1, 2);
  showPages.painter?.disconnect();
  const painter = new IntersectionObserver((entries) => {
    for (const { isIntersecting, target } of entries) {
      if (!isIntersecting) continue;
      painter.unobserve(target);
      const { doc, page } = target.postext;
      renderPageToCanvas(page, doc, target, { scale: (width * density) / page.width });
    }
  }, { rootMargin: '800px' });
  showPages.painter = painter;
  root.replaceChildren(...spreads.map((pair) => {
    const spread = document.createElement('div');
    spread.className = 'pt-spread';
    for (const p of pair) {
      const figure = document.createElement('figure');
      if (p) {
        const label = p.page.pageLabel || String(p.n + 1);
        const canvas = document.createElement('canvas');
        canvas.postext = p;
        canvas.style.aspectRatio = `${p.page.width} / ${p.page.height}`;
        canvas.setAttribute('role', 'img');
        canvas.setAttribute('aria-label', `Page ${label}`);
        const folio = document.createElement('figcaption');
        folio.textContent = label;
        figure.append(canvas, folio);
        painter.observe(canvas);
      } else figure.className = 'pt-blank';
      spread.append(figure);
    }
    return spread;
  }));
  kitStatus(`${pages.length} ${pages.length === 1 ? 'page' : 'pages'}`);
  document.documentElement.dataset.postext = 'ready';
  return pages.length;
}

/** The desk, the bar and the error reporting, created once. */
function viewer(title) {
  if (!document.getElementById('pt-kit')) {
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit">
      :root { color-scheme: dark; }
      body { margin: 0; background: #0e1014; color: #b9bcc4; font: 13px/1.45 system-ui, sans-serif; }
      #pt-bar { position: sticky; top: 0; z-index: 1; display: flex; flex-wrap: wrap; align-items: center;
        gap: 6px 16px; padding: 10px 16px; background: rgb(14 16 20 / .92); backdrop-filter: blur(6px);
        border-bottom: 1px solid #23262d; }
      #pt-bar strong { color: #f4f1ea; font-weight: 600; }
      #pt-actions { display: flex; gap: 12px; margin-left: auto; }
      #pt-actions a, #pt-actions button { color: #d8a21a; font: inherit; background: none; border: 0; padding: 0; cursor: pointer; }
      #pages { display: grid; justify-items: center; gap: 48px; padding: 32px 16px 72px; }
      .pt-spread { display: flex; }
      .pt-spread figure { margin: 0; width: min(460px, 44vw); }
      .pt-spread canvas { display: block; width: 100%; background: #fff;
        box-shadow: 0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
      .pt-spread figure:first-child canvas { box-shadow: inset -14px 0 14px -14px rgb(0 0 0 / .18), 0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
      .pt-spread figcaption { margin-top: 10px; text-align: center; font: 600 10px/1 system-ui, sans-serif;
        letter-spacing: .18em; text-transform: uppercase; color: #6c7079; }
      .pt-blank { visibility: hidden; }
      @media (max-width: 760px) {
        .pt-spread { flex-direction: column; gap: 32px; }
        .pt-spread figure { width: min(460px, 92vw); }
        .pt-blank { display: none; }
      }
    </style>`);
    document.body.insertAdjacentHTML('afterbegin',
      '<header id="pt-bar"><strong id="pt-title"></strong><span id="pt-status" role="status"></span><span id="pt-actions"></span></header>');
    document.getElementById('pt-title').textContent = document.title || 'Postext';
    addEventListener('error', (event) => kitFail(event.error ?? event.message));
    addEventListener('unhandledrejection', (event) => kitFail(event.reason));
  }
  if (title) document.getElementById('pt-title').textContent = title;
  return document.getElementById('pages')
    ?? document.body.appendChild(Object.assign(document.createElement('main'), { id: 'pages' }));
}

function kitStatus(text) {
  viewer();
  document.getElementById('pt-status').textContent = text;
}

function kitFail(error) {
  document.documentElement.dataset.postext = 'error';
  kitStatus(`Error: ${error?.message ?? error}`);
}

// ─── Kit · pdf v1 ── the same in every recipe that exports a PDF ──────────────
/** postext-pdf embeds TrueType bytes. Fetch the Fontsource file the screen
 *  used, snapping to a weight the family ships and falling back to upright
 *  when it has no italic: the PDF asks for every face a block could use. */
async function fontsourceProvider(family, weight, style) {
  const id = fontsourceId(family);
  const meta = await fontsourceMeta(family);
  const weights = meta?.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && meta && !meta.styles.includes('italic') ? 'normal' : style;
  const res = await fetch(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-${w}-${s}.woff2`);
  if (!res.ok) throw new Error(`Fontsource has no ${family} ${w} ${s} (${res.status})`);
  return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
}

/** A "Build the PDF" button in the bar. Once built: "Open the PDF" (a new
 *  tab, since CodePen's preview frame cannot show PDFs) and a download link. */
function offerPdf(makePdf, filename) {
  viewer();
  const button = Object.assign(document.createElement('button'), { type: 'button', textContent: 'Build the PDF' });
  button.dataset.postextPdf = filename;
  button.addEventListener('click', async () => {
    button.disabled = true;
    button.textContent = 'Building the PDF…';
    try {
      const bytes = await makePdf();
      const url = URL.createObjectURL(new Blob([bytes], { type: 'application/pdf' }));
      const size = `${Math.max(1, Math.round(bytes.length / 1024))} KB`;
      button.replaceWith(
        Object.assign(document.createElement('a'), { href: url, target: '_blank', rel: 'noopener', textContent: 'Open the PDF ↗' }),
        Object.assign(document.createElement('a'), { href: url, download: filename, textContent: `Download ${filename} · ${size}` }));
    } catch (error) {
      button.disabled = false;
      button.textContent = 'Build the PDF';
      kitFail(error);
    }
  });
  document.getElementById('pt-actions').append(button);
}

// ─── Kit · cjk v1 ── Chinese, Japanese and Korean books · postext.dev/cookbook ─
// Fontsource ships a CJK family as about a hundred files per weight, each
// declared in its stylesheet with the unicode-range it covers. The screen
// loads the files the sample touches; the PDF gets the same files for the
// characters its pages set in each face, and embeds each as a subset.
// A book bound on the right (vertical text) is shown with its spreads
// mirrored: page 1 alone on the left of the spine, then [3 | 2].

/** The files of a Fontsource face, read from its stylesheet: { url, range,
 *  ranges }, the last declared first (the order the browser tries them in). */
function cjkSlices(family, weight, style) {
  cjkSlices.cache ??= new Map();
  const id = fontsourceId(family);
  const css = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/${weight}${style === 'italic' ? '-italic' : ''}.css`;
  if (!cjkSlices.cache.has(css)) {
    cjkSlices.cache.set(css, fetch(css)
      .then((res) => {
        if (!res.ok) throw new Error(`Fontsource has no ${family} ${weight} ${style} (${res.status})`);
        return res.text();
      })
      .then((text) => [...text.matchAll(/@font-face\s*{([^}]*)}/g)].map(([, rule]) => {
        const range = /unicode-range:\s*([^;]+);/.exec(rule)?.[1].trim() ?? 'U+0-10FFFF';
        const ranges = range.split(',').map((part) => {
          const [lo, hi = lo] = part.trim().slice(2).split('-');
          return [parseInt(lo, 16), parseInt(hi, 16)];
        });
        return { url: new URL(/url\(([^)]+?\.woff2)\)/.exec(rule)[1], css).href, range, ranges };
      }).reverse()));
  }
  return cjkSlices.cache.get(css);
}

/** The file of `slices` that holds code point `cp`, if any. */
function cjkSliceFor(slices, cp) {
  return slices.find((slice) => slice.ranges.some(([lo, hi]) => cp >= lo && cp <= hi));
}

/** Whether Fontsource serves `family` as a Chinese, Japanese or Korean
 *  family (its subsets name the script). Fails when the API does not
 *  answer: a CJK face taken for a Latin one would paint in a system face. */
async function isCjkFamily(family) {
  const meta = await fontsourceMeta(family);
  if (!meta) throw new Error(`api.fontsource.org did not describe ${family}: reload to try again`);
  return !!meta.subsets?.some((subset) => /^(chinese|japanese|korean)/.test(subset));
}

/** faces = { 'Noto Serif TC': ['400', '700'] }, as for loadFonts: the
 *  whole FONTS object may be passed, its other families are left to
 *  loadFonts. Adds one FontFace per file of each CJK face with its
 *  unicodeRange, then loads the files `text` touches. `text` is what the
 *  faces set: the sample for the text face; a book in several voices calls
 *  it once per voice (loadCjkFonts({ 'LXGW WenKai TC': ['400'] }, quotes)),
 *  so the heading and quotation faces fetch and check only their own
 *  characters. Fails when a character of `text` is in no file of a face.
 *  List every weight the pages use: a weight left to buildWithFonts gets
 *  the latin file only. With { vertical: true } it also loads each
 *  family's vertical forms (brackets, quotes, pause marks) for the canvas,
 *  which needs loadVerticalAlternates imported from postext. Resolves to
 *  the number of files loaded. */
async function loadCjkFonts(faces, text, { vertical = false } = {}) {
  kitStatus('Loading fonts…');
  let loaded = 0;
  try {
    if (vertical && typeof loadVerticalAlternates !== 'function') {
      throw new Error('loadCjkFonts(…, { vertical: true }) needs loadVerticalAlternates imported from postext');
    }
    for (const [family, specs] of Object.entries(faces)) {
      if (!(await isCjkFamily(family))) continue;
      const twin = [];
      for (const spec of new Set(specs)) {
        const weight = parseInt(spec, 10);
        const style = spec.endsWith('i') ? 'italic' : 'normal';
        const slices = await cjkSlices(family, weight, style);
        const missing = [...new Set(text)].filter((ch) => /\S/.test(ch) && !cjkSliceFor(slices, ch.codePointAt(0)));
        if (missing.length) {
          throw new Error(`${family} ${spec} has no file for ${missing.slice(0, 12).join(' ')}: `
            + `give each face the text it sets (loadCjkFonts({ '${family}': ['${spec}'] }, text))`);
        }
        for (const slice of slices) {
          document.fonts.add(new FontFace(family, `url(${slice.url}) format('woff2')`,
            { weight: String(weight), style, unicodeRange: slice.range }));
          twin.push({ source: slice.url, weight: String(weight), style, unicodeRange: slice.range });
        }
        const font = `${style === 'italic' ? 'italic ' : ''}${weight} 16px "${family}"`;
        loaded += (await document.fonts.load(font, text)).length;
        if (!document.fonts.check(font, text)) throw new Error(`${family} ${spec} did not load for the sample`);
      }
      // The same files under a twin name with the `vert` feature on: the
      // canvas paints the punctuation of vertical lines with it.
      if (vertical && twin.length) await loadVerticalAlternates(family, twin);
    }
  } catch (error) {
    kitFail(error);
    throw error;
  }
  return loaded;
}

/** The PDF font provider for recipes with CJK faces: a family whose
 *  Fontsource subsets are Chinese, Japanese or Korean gets the files that
 *  hold the characters its pages set (`request.codePoints`); any other
 *  family gets the latin file fontsourceProvider fetches (the "pdf" block)
 *  and, when the face sets letters only latin-ext has, that file too. */
async function cjkPdfProvider(family, weight, style, request) {
  if (!(await isCjkFamily(family))) return cjkLatinPdfFiles(family, weight, style, request);
  const meta = await fontsourceMeta(family);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const slices = await cjkSlices(family, w, s);
  const picked = new Set();
  for (const cp of request?.codePoints ?? []) {
    const slice = cjkSliceFor(slices, cp);
    if (slice) picked.add(slice);
  }
  if (!picked.size) picked.add(slices[0]);
  return Promise.all(slices.filter((slice) => picked.has(slice)).map(async (slice) => {
    const res = await fetch(slice.url);
    if (!res.ok) throw new Error(`Fontsource file ${slice.url} (${res.status})`);
    return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
  }));
}

/** A Latin family set next to the CJK faces: its latin file, then its
 *  latin-ext file when the face sets letters only latin-ext has (ō ū in
 *  Hepburn rōmaji, ǎ in pinyin), the file loadFonts adds on screen for
 *  them. Latin comes first: postext-pdf draws a character from the first
 *  file that has it, as the browser takes a character both files hold from
 *  latin. A face Fontsource ships without latin-ext, or whose file does
 *  not come, gets latin alone, and the PDF names the letters it lacks. */
async function cjkLatinPdfFiles(family, weight, style, request) {
  const meta = await fontsourceMeta(family);
  const beyond = [...(request?.codePoints ?? [])].some(cjkLatinExtOnly);
  if (!beyond || !meta?.subsets?.includes('latin-ext')) return fontsourceProvider(family, weight, style);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const id = fontsourceId(family);
  const url = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-ext-${w}-${s}.woff2`;
  const [latin, ext] = await Promise.all([fontsourceProvider(family, weight, style), fetch(url)
    .then(async (res) => (res.ok ? decompressWoff2(new Uint8Array(await res.arrayBuffer())) : null), () => null)]);
  return ext ? [latin, ext] : latin;
}

/** Whether code point `cp` is in Fontsource's latin-ext file and not in
 *  its latin file: Latin Extended-A and -B, IPA, the spacing modifiers and
 *  Latin Extended Additional (loadFonts's test for latin-ext), less the
 *  few latin holds too (ı Œ œ ʻ ʼ ˆ ˚ ˜). */
function cjkLatinExtOnly(cp) {
  if (!((cp >= 0x100 && cp <= 0x2ff) || (cp >= 0x1e00 && cp <= 0x1eff))) return false;
  return ![0x131, 0x152, 0x153, 0x2bb, 0x2bc, 0x2c6, 0x2da, 0x2dc].includes(cp);
}

/** showPages for a book bound on either edge. A right-bound book (the
 *  document says so: doc.binding is 'right' for page.binding 'right' and
 *  for vertical text) lies on the desk as it opens: page 1 alone on the
 *  left of the spine, then [3 | 2], the spine shade on each page's inner
 *  edge. `binding` ('left' | 'right') overrides the document's. */
function showBook(docs, { binding, ...options } = {}) {
  const count = showPages(docs, options);
  const right = (binding ?? [docs].flat()[0]?.binding) === 'right';
  if (!document.getElementById('pt-kit-cjk')) {
    // The pages keep direction ltr: a canvas draws text in the direction its
    // element inherits, and under rtl each run would end where the engine
    // starts it, its brackets mirrored.
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit-cjk">
      .pt-spread[dir="rtl"] canvas { direction: ltr; }
      .pt-spread[dir="rtl"] figure:first-child canvas { box-shadow: inset 14px 0 14px -14px rgb(0 0 0 / .18),
        0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
    </style>`);
  }
  // Each pair stays [verso, recto] in the page; right to left, the verso
  // sits on the right. Phones stack the pages in reading order either way.
  for (const spread of document.querySelectorAll('#pages > .pt-spread')) spread.dir = right ? 'rtl' : 'ltr';
  document.getElementById('pages').dataset.binding = right ? 'right' : 'left';
  return count;
}

// ─── /Kit ───────────────────────────────────────────────────────────────────────