Kanji numerals, counters and dates in vertical text

// ═══ Postext Cookbook · Nº 129 · Kanji numerals, counters and dates in vertical text ═══
// https://postext.dev/en/cookbook/kanji-numerals-and-dates
// Code: MIT · Text: written for the recipe (CC BY 4.0)
// Fonts: Noto Serif JP, Noto Sans JP, Zen Maru Gothic (SIL OFL 1.1) · Needs postext ≥ 1.16.1
// A neighbourhood newsletter set vertically: every way Japanese writes a number.
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, loadVerticalAlternates,
  formatNumeral,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'en'; // @lang: the language of the frame; the newsletter is Japanese in both
const RECIPE = 'kanji-numerals-and-dates';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: ink, the green of young leaves, its tint, a festival red and its blush
const palette = {
  ink: '#1f2420', // the text
  leaf: '#2f6b3f', // masthead band, section numbers (6.4:1 on the paper)
  tint: '#e4efdf', // the calendar's marked days, the receipt
  red: '#b4362b', // the receipt's amount
  blush: '#f4d4cc', // the festival days in the calendar
  muted: '#5f665f', // folios, the colophon
  paper: '#fdfdf9',
};
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = [
  ...Object.entries(palette).map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } })),
  { id: 'main-color', name: 'leaf (defaults)', value: { hex: palette.leaf, model: 'hex' } },
];
// #endregion

const MINCHO = 'Noto Serif JP'; // the text
const GOTHIC = 'Noto Sans JP'; // section heads, labels, the calendar
const ROUND = 'Zen Maru Gothic'; // the masthead's title
const [BODY, LEAD] = [11, 20]; // pt: large print for every age on the street
const [CHARS, LINES] = [44, 20];
const PT = 25.4 / 72; // mm in a point
const TRIM = { w: 182, h: 257 }; // mm, B5
const LINE = CHARS * BODY * PT; // mm: 170.7, the length of a line
const HEAD = 30 + (TRIM.h - 30 - 24 - LINE) / 2; // mm: the head of the type area

// #region answer: one number, four spellings, chosen by where it stands
// formatNumeral is the counter the engine numbers pages, lists and headings with.
const ISSUE = 120;
const kan = (n) => formatNumeral(n, 'japanese-informal'); // 120 → 百二十: counted
const pos = (n) => formatNumeral(n, 'cjk-decimal'); // 2026 → 二〇二六: digit by digit
const daiji = (n) => formatNumeral(n, 'japanese-formal'); // 12000 → 壱萬弐阡: on money
// {{daiji:12000}} in the text: the amount of a receipt in the hard-to-alter daiji.
const withDaiji = (md) => md.replace(/\{\{daiji:(\d+)\}\}/g, (_, n) => daiji(Number(n)));
const cjk = {
  grid: { enabled: true, charsPerLine: CHARS, linesPerPage: LINES },
  uprightDigits: 2, // 8月22日: one or two Arabic digits stand in one cell (the default)
};
// Sections 一、二、三、, items （一）（二）, then イ ロ ハ and あ い う beneath them.
const sectionLevel = { level: 2, numberingTemplate: '{2:一}、', numberSeparator: '',
  fontFamily: GOTHIC, fontWeight: 700, fontSize: pt(12), color: col('leaf'), lineSpan: 2 }; // 二行取り
const level = (n, numberFormat, prefix, separator) => ({ level: n, numberFormat, prefix,
  separator }); // each level starts where the text of the one above starts
const orderedLists = {
  fontFamily: GOTHIC, color: col('leaf'), fontWeight: 700, gap: em(0.5),
  marginTop: pt(0), marginBottom: pt(0), itemSpacing: pt(0),
  levels: [level(1, 'japanese-informal', '（', '）'), level(2, 'katakana-iroha', '', ''),
    level(3, 'hiragana', '', '、')],
};
// #endregion

// #region masthead: a green band down the right edge, the issue and the date in kanji
const BAND = 46; // mm from the right trim edge
const at = (x, y, extra = {}) => ({ anchor: { to: 'page', edge: 'top-left' },
  offset: { x: mm(x), y: mm(y) }, ...extra }); // x down the sheet, y leftward from its right
const onBand = { color: col('paper'), overflow: 'wrap', align: 'left' };
const masthead = {
  id: 'masthead', numbered: false, toc: false, runningChapter: false,
  breakBefore: { enabled: true, parity: 'any' },
  advancedDesign: { enabled: true, minHeight: mm(BAND - 15), slot: { elements: [
    { kind: 'box', id: 'band', style: { backgroundColor: col('leaf') },
      placement: { anchor: { to: 'bleed', edge: 'top-left' }, size: { height: mm(BAND) } } },
    { kind: 'text', id: 'title', content: '{titleText}', ...onBand, fontFamily: ROUND,
      fontWeight: 700, fontSize: pt(36), lineHeight: 1.1, letterSpacing: pt(3),
      placement: at(HEAD, 9) },
    { kind: 'text', id: 'issue', content: `第${kan(ISSUE)}号`, ...onBand, fontFamily: GOTHIC,
      fontWeight: 700, fontSize: pt(12), letterSpacing: pt(2), placement: at(HEAD, 26) },
    { kind: 'text', id: 'date', content: `${pos(2026)}年（令和${kan(8)}年）${kan(8)}月${kan(1)}日発行`,
      ...onBand, fontFamily: GOTHIC, fontSize: pt(10), align: 'right',
      placement: at(HEAD, 26, { size: { width: mm(LINE) } }) },
    { kind: 'text', id: 'publisher', content: '{author}', ...onBand, fontFamily: GOTHIC,
      fontSize: pt(10), align: 'right', placement: at(HEAD, 33, { size: { width: mm(LINE) } }) },
    { kind: 'text', id: 'latin', content: '{attr.latin}', ...onBand, fontFamily: GOTHIC,
      fontSize: pt(7.5), placement: at(HEAD, 40) },
  ] } },
};
// #endregion

// #region calendar: August 2026 as a table, the festival and the duties marked
const DAYS = { 2: '訓練', 9: '清掃', 13: 'お盆', 18: '練習会', 19: '練習会',
  22: '夏祭り', 23: '夏祭り', 30: '役員会' };
const day = (d) => (d ? { content: `**${d}**\n${DAYS[d] ?? '\u00a0'}`, align: 'center',
  ...(DAYS[d] ? { background: col(d === 22 || d === 23 ? 'blush' : 'tint') } : {}) }
  : { content: '' });
const weeks = []; // 1 August 2026 is a Saturday
for (let d = -5; d <= 31; d += 7) weeks.push([0, 1, 2, 3, 4, 5, 6].map((k) => day(d + k > 0
  && d + k <= 31 ? d + k : 0)));
const calendar = { id: 'calendar', typeId: 'table', kind: 'table', createdAt: 0, updatedAt: 0,
  // An upright table takes every line of the vertical page it stands on (gap:
  // vertical-tables): the calendar is the back page, cited at the end of the text.
  placement: { position: 'top', span: 'page' },
  caption: '八月の行事。13日から16日まではごみの収集がありません。',
  table: { model: { headerRowCount: 1, rows: [[...'日月火水木金土'].map((c) => ({ content: c,
    isHeader: true, align: 'center' })), ...weeks] } } };
const resourceTypes = [{ id: 'table', name: '表', shortLabel: '表', captionPrefix: '表',
  numberingTemplate: '{n}', counterFormat: '一', resetOn: 'never' }]; // 表一, 表二…
// #endregion

const config = () => ({ // a factory: the engine caches resolved configs per object
  locale: 'ja', // written out, never LANG (gotcha: ja-locale-tag)
  colorPalette,
  resourceTypes,
  page: {
    sizePreset: 'custom', width: mm(TRIM.w), height: mm(TRIM.h), dpi: 150,
    backgroundColor: col('paper'),
    margins: { top: mm(30), bottom: mm(24), left: mm(16), right: mm(18), mirror: true },
    pageNumbering: { format: 'japanese-informal' },
  },
  layout: { layoutType: 'single', writingMode: 'vertical-rl' },
  cjk,
  bodyText: {
    fontFamily: MINCHO, fontSize: pt(BODY), lineHeight: pt(LEAD), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
    textAlign: 'justify', firstLineIndent: em(1), indentAfterHeading: true,
  },
  headings: { fontFamily: GOTHIC, color: col('ink'),
    levels: [{ level: 1, breakBefore: { enabled: true, parity: 'any' } }, sectionLevel] },
  headingStyles: [masthead],
  orderedLists,
  paragraphStyles: [
    { id: 'item', firstLineIndent: em(0), indent: em(1), hangingIndent: em(3) },
    { id: 'chronicle', firstLineIndent: em(0), hangingIndent: em(14) },
    { id: 'colophon', fontFamily: GOTHIC, fontSize: pt(7), color: col('muted'),
      textAlign: 'left', firstLineIndent: em(0), marginTop: pt(LEAD) },
  ],
  calloutStyles: [{ id: 'receipt', title: '領収証（記入例）', background: col('tint'),
    padding: { top: mm(4), right: mm(4), bottom: mm(4), left: mm(4) },
    marginTop: pt(LEAD / 2), marginBottom: pt(0), // the next heading's 行取り gives it room
    titleStyle: { fontFamily: GOTHIC, fontSize: pt(12), fontWeight: 700, color: col('leaf') },
    body: { fontFamily: MINCHO, color: col('ink'), boldColor: col('red'), textAlign: 'left',
      firstLineIndent: em(0) } }],
  tableStyle: { rules: 'horizontal', borderColor: col('leaf'), borderWidth: pt(0.5),
    headerBackground: col('leaf'), headerColor: col('paper'), headerFontFamily: GOTHIC,
    headerFontSize: pt(12), bodyFontFamily: GOTHIC, bodyFontSize: pt(11), bodyColor: col('ink'),
    cellPadding: mm(3.2) },
  // 表一　八月の行事: label and number solid, then U+3000 (the ja default)
  captionStyle: { fontFamily: GOTHIC, fontSize: pt(10), color: col('ink'),
    labelColor: col('leaf') },
  header: { elements: [{ kind: 'text', id: 'folio', content: '{pageNumber}', pages: 'body',
    fontFamily: GOTHIC, fontSize: pt(8), color: col('muted'), align: 'center',
    placement: { anchor: { to: 'page', edge: 'bottom' }, offset: { y: mm(-12) } } }] },
  footer: { elements: [] },
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = withDaiji(String.raw`---
Markdown sample · 74 lines · content.en.md
title: "東若葉台だより"
author: "東若葉台二丁目町会　広報部"
---

# 東若葉台だより {style="masthead" latin="Higashi-Wakabadai News, the newsletter of a neighbourhood association (fiction)"}

暑い日が続いています。今号は夏祭りの案内を中心に、八月の行事、町会費と協賛金のお願い、それに町会の歩みをお届けします。

## 夏祭りのお知らせ

今年の夏祭りは第三十二回になります。平成七年に公民館の駐車場で始まった小さな盆踊りが、昨年は二日間で延べ二千四百人が訪れる行事になりました。今年も子ども会、婦人部、消防団の皆さんが準備を進めています。

:::paragraphs{style="item"}
日時　8月22日（土）・23日（日）　午後4時から9時まで

会場　若葉台第二公園（雨の場合は公民館ホール）
:::

1. 盆踊り
   1. 練習会　8月18日（火）・19日（水）の午後7時から、公民館ホールで行います。浴衣でなくてもかまいません。
   2. 本番　両日とも午後6時半から。太鼓は今年も若葉台中学校の和太鼓部が務めます。
2. 屋台
   1. 子ども会　焼きそば、かき氷
   2. 婦人部　おでん、冷やしきゅうり
   3. 消防団　ラムネ、射的
3. 子ども神輿
   1. 対象　小学生。保護者の方の付き添いをお願いします。
   2. 出発　23日（日）午後4時、公民館前。若葉通りを回り、5時半に戻ります。
   3. 持ち物
      1. 帽子
      2. 水筒
      3. タオル

「雨が降ったら中止!?」という問い合わせを、毎年この時期にいただきます。小雨なら公園で行い、強い雨のときは公民館ホールに移します。中止にするのは警報が出たときだけで、その場合は当日の正午までに町会の掲示板でお知らせします。

## 八月の行事

八月の行事は、裏表紙の表一にまとめました。お盆の13日から16日までは、ごみの収集がありません。15日の朝、集積所にごみを出さないようにお願いします。

## 町会費と協賛金のお願い

今年度の町会費は、一世帯あたり年額三千六百円です。九月の班長会までに、各班の班長さんへお納めください。

夏祭りには、毎年たくさんの商店と個人の方から協賛金をいただいています。協賛金には領収証をお渡しします。金額は、書き換えを防ぐために大字（だいじ）で書きます。

:::callout{type="receipt"}
若葉台商店会　様

金　**{{daiji:12000}}**　円也

但し　第三十二回夏祭り協賛金として

二〇二六年八月一日　東若葉台二丁目町会　会計　中村　節子
:::

## 町会の歩み

:::paragraphs{style="chronicle"}
一九六〇年（昭和三十五年）　町会ができる。このときの世帯数は八十四。

一九七二年（昭和四十七年）　公民館が完成する。

一九九五年（平成七年）　　　第一回の夏祭りを公民館の駐車場で開く。

二〇一一年（平成二十三年）　若葉台第二公園に防災倉庫を置く。

二〇二六年（令和八年）　　　世帯数は三百十二になった。
:::

:::paragraphs{style="colophon"}
Set in Noto Serif JP, Noto Sans JP and Zen Maru Gothic (SIL OFL) · The association, its people and its events are fiction written for this recipe, CC BY 4.0
:::

::resource{id="calendar"}
`); // content.<lang>.md, amounts filled in

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = { 'Noto Serif JP': ['400', '700'], 'Noto Sans JP': ['400', '700'],
  'Zen Maru Gothic': ['700'] };
// #region voices: each face loads the files of the characters it sets
const heads = (markdown.match(/^#+ .*$/gm) ?? []).join('');
const gothicText = `${heads}${markdown}第号年月日発行令和${kan(ISSUE)}${pos(2026)}${
  calendar.caption}日月火水木金土${Object.values(DAYS).join('')}領収証（記入例）表一`;
// #endregion

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadFonts(FONTS, markdown);
await loadCjkFonts({ [MINCHO]: FONTS[MINCHO] }, markdown, { vertical: true });
await loadCjkFonts({ [GOTHIC]: FONTS[GOTHIC] }, gothicText, { vertical: true });
await loadCjkFonts({ [ROUND]: FONTS[ROUND] }, heads, { vertical: true });
const doc = await buildWithFonts(
  () => buildDocument({ markdown, resources: [calendar] }, config()), markdown);
showBook(doc, { title: t({ en: 'A newsletter in kanji numerals',
  es: 'Un boletín con numerales kanji' }) });
offerPdf(() => renderToPdf(doc, { fontProvider: cjkPdfProvider }), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, cjk: the same in every recipe · 453 lines
// ─── 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 ───────────────────────────────────────────────────────────────────────