斜めのコマ割りで組むアクションのページ

// ═══ Postext Cookbook · Nº 150 · An action page with slanted gutters ═════════════════
// https://postext.dev/en/cookbook/manga-action-slants
// Code: MIT · Story: written for the recipe (CC BY 4.0) · Pictures: generated with diffusion models
// Fonts: Zen Antique, Comic Neue and six more (SIL OFL 1.1) · Needs postext ≥ 1.21.0
// The last page of a kendo final: slanted panels, a borderless strike, ドン kept in every edition.
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, registerResourceImage,
  loadVerticalAlternates,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'ja'; // @lang: this edition's language; the Japanese original faces it
const RECIPE = 'manga-action-slants';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: black ink on a warm white, one screen-tone grey
const palette = {
  ink: '#151413', // panel borders, balloon outlines, the lettering
  paper: '#fdfcf9', // the page and the balloons
  tone: '#e8e6e1', // the inner-voice box, a light screen tone
  muted: '#6f6b64',
  accent: '#a8322b', // the cover red (the Folio case in recipe.json)
};
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: 'ink (defaults)', value: { hex: palette.ink, model: 'hex' } },
];
// #endregion

// The engine's lettering and sound-effect faces per language (defaultComicFont and
// defaultComicSfxFont), written out so FONTS and the PDF know them.
const EDITIONS = {
  ja: { locale: 'ja', faces: ['Zen Antique', 'Dela Gothic One'] },
  en: { locale: 'en-us', faces: ['Comic Neue', 'Bangers'] },
  es: { locale: 'es', faces: ['Comic Neue', 'Bangers'] },
  ca: { locale: 'ca', faces: ['Comic Neue', 'Bangers'] },
  pt: { locale: 'pt-BR', faces: ['Comic Neue', 'Bangers'] },
  zh: { locale: 'zh-Hans', faces: ['Noto Sans SC', 'ZCOOL KuaiLe'] },
  ar: { locale: 'ar', faces: ['Playpen Sans Arabic', 'Lalezar'] },
};

// #region answer: the slant is in the split; the impact is in the panel and the effect
// The page is split in content.<lang>.md: `* [40~55 | *]` runs the gutter of the third
// tier from 40 % at the top to 55 % at the bottom, so both panels lean into the strike,
// and `24 [58~64 | *]` tilts the last tier the other way. The panel that lands the blow
// is drawn with `border=none`: no frame, so its speed lines run straight to the gutter.
// ドン keeps its Japanese face in every edition (`font=` on the line);
// the translations add a small subtitle under it, the way licensed manga gloss a drawn
// sound effect instead of redrawing it.
const comics = (lang) => ({
  artDirection: 'rtl', // drawn for right-to-left reading: slants and order mirror with it
  mirrorArt: false,
  gutter: { horizontal: mm(4), vertical: mm(2.5) }, // a slanted gutter keeps its width
  panel: { borderWidth: pt(1.1), borderColor: col('ink'), background: col('paper') },
  lettering: {
    fontFamily: EDITIONS[lang].faces[0], color: col('ink'),
    fontSize: pt(['ja', 'zh'].includes(lang) ? 8.5 : 7.5),
    writingMode: lang === 'zh' ? 'vertical' : 'auto',
  },
  balloonStyles: balloons(),
});
// #endregion

// #region balloons: oval speech, a spiky shout, a grey box for the inner voice
const balloons = () => [
  { id: 'speech', fill: col('paper'), stroke: col('ink'), strokeWidth: pt(0.6), roundness: 2 },
  { id: 'shout', fill: col('paper'), stroke: col('ink'), burstPoints: 18, burstDepth: 0.3 },
  { id: 'thought', fill: col('paper'), stroke: col('ink') },
  { id: 'inner', fill: col('tone'), stroke: col('tone'), strokeWidth: pt(0), italic: false },
  { id: 'caption', fill: col('paper'), stroke: col('ink'), strokeWidth: pt(0.5) },
  // white-edged on the art
  { id: 'sfx', color: col('ink'), haloColor: col('paper'), halo: pt(2.2) },
];
// #endregion

const config = () => ({ // a factory: the engine caches resolved configs per object
  // Each edition's language, written out (gotcha: ja-locale-tag); the original is built
  // with 'ja' in every edition (edition('ja') below).
  locale: t({ ja: 'ja', en: 'en-us', es: 'es', ca: 'ca', zh: 'zh-Hans', ar: 'ar', pt: 'pt-BR' }),
  colorPalette,
  page: {
    sizePreset: 'custom', width: mm(128), height: mm(182), dpi: 150, // B6, a tankōbon
    binding: 'right', backgroundColor: col('paper'), // manga open from the right, in any language
    margins: { top: mm(13), bottom: mm(15), left: mm(11), right: mm(11), mirror: true },
  },
  bodyText: {
    fontFamily: 'Zen Antique', fontSize: pt(9), lineHeight: pt(15), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
  },
  headings: { fontFamily: 'Zen Antique', color: col('ink'),
    levels: [{ level: 1, breakBefore: { enabled: true, parity: 'any' } }] }, // the H1 break
  header: { elements: [] }, // comic pages are all panels: no running heads, no folios
  footer: { elements: [] },
  comics: comics(LANG),
});
// Another edition changes the language and the faces; the page and its slants stay.
const edition = (lang) => ({ ...config(), locale: EDITIONS[lang].locale, comics: comics(lang) });

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Markdownの見本 · 22行 · content.ja.md
title: "決勝"
author: "Postext Cookbook"
---

:::page{split="24 / 18 / * [40~55 | *] / 24 [58~64 | *]"}
::panel{art=final}
caption: 決勝戦。
shinpan: 始め！
::panel{art=eyes}
hana{inner}: ……見える
::panel{art=lunge}
sfx{rotate=-12}: ダンッ
rival{shout}: メェェン！
::panel{art=strike border=none}
sfx{at="74% 26%" rotate=-8 size=2.6 font="Dela Gothic One" break}: ドン
hana{shout}: メン！！
::panel{art=coach}
shinpan{tail=top}: 面あり！
mori{thought}: ……ふん。悪くない
::panel{art=stands}
sora{shout break}: 決まったぁぁ！！
:::
`; // content.<lang>.md: this edition's lettering
const original = String.raw`---
Markdownの見本 · 22行 · content.ja.md
title: "決勝"
author: "Postext Cookbook"
---

:::page{split="24 / 18 / * [40~55 | *] / 24 [58~64 | *]"}
::panel{art=final}
caption: 決勝戦。
shinpan: 始め！
::panel{art=eyes}
hana{inner}: ……見える
::panel{art=lunge}
sfx{rotate=-12}: ダンッ
rival{shout}: メェェン！
::panel{art=strike border=none}
sfx{at="74% 26%" rotate=-8 size=2.6 font="Dela Gothic One" break}: ドン
hana{shout}: メン！！
::panel{art=coach}
shinpan{tail=top}: 面あり！
mori{thought}: ……ふん。悪くない
::panel{art=stands}
sora{shout break}: 決まったぁぁ！！
:::
`; // content.ja.md, the original, in every edition
const english = String.raw`---
Markdownの見本 · 23行 · content.en.md
title: "The Final"
author: "Postext Cookbook"
---

:::page{split="24 / 18 / * [40~55 | *] / 24 [58~64 | *]"}
::panel{art=final}
caption: The final.
shinpan: Hajime!
::panel{art=eyes}
hana{inner}: …I can see it.
::panel{art=lunge}
sfx{rotate=-12}: STOMP
rival{shout}: MEEEN!
::panel{art=strike border=none}
sfx{at="74% 26%" rotate=-8 size=2.6 font="Dela Gothic One" vertical break}: ドン
sfx{at="64% 80%" rotate=-8 size=0.9}: WHAM
hana{shout}: MEN!!
::panel{art=coach}
shinpan{tail=top}: Men! Point!
mori{thought}: …Hmph. Not bad.
::panel{art=stands}
sora{shout}: She did it!!
:::
`; // the Japanese edition faces the original with it
// The same panels and speaker ids in every file; only the words change.

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = {
  'Zen Antique': ['400'], 'Dela Gothic One': ['400'], 'Comic Neue': ['400', '700', '400i', '700i'],
  Bangers: ['400'], 'Noto Sans SC': ['400', '700'], 'ZCOOL KuaiLe': ['400'],
  'Playpen Sans Arabic': ['400', '700'], Lalezar: ['400'],
};

// #region art: six panels drawn for the recipe, with each speaker's mouth, head and face marked
const ART = { // fractions of the picture: the same in every language
  final: {
    alt: t({ en: 'The kendo final in a packed gym: two fighters cross swords among three referees.',
      es: 'La final en un pabellón lleno: dos rivales cruzan las espadas entre tres árbitros.',
      ca: 'La final en un pavelló ple: dos rivals creuen les espases entre tres àrbitres.',
      pt: 'A final num ginásio lotado: dois lutadores cruzam as espadas entre três árbitros.',
      zh: '座无虚席的体育馆里的决赛：两名选手在三名裁判之间交剑。',
      ar: 'النهائي في صالة ممتلئة: متباريان يتقاطع سيفاهما بين ثلاثة حكّام.',
      ja: '満員の体育館での決勝。3人の審判の間で2人が剣先を交える。' }),
  safeArea: { x: 0.22, y: 0.44, width: 0.56, height: 0.46 },
  anchors: [{ id: 'hana', x: 0.31, y: 0.51, head: { x: 0.31, y: 0.49 },
    face: { x: 0.28, y: 0.45, width: 0.07, height: 0.1 } },
  { id: 'rival', x: 0.68, y: 0.51, head: { x: 0.68, y: 0.49 },
    face: { x: 0.65, y: 0.46, width: 0.06, height: 0.09 } },
  { id: 'shinpan', x: 0.575, y: 0.585, head: { x: 0.575, y: 0.56 },
    face: { x: 0.56, y: 0.54, width: 0.03, height: 0.06 } }] },
  eyes: {
    alt: t({ en: "Hana's eyes through the bars of her helmet grille.",
      es: 'Los ojos de Hana tras las barras de la rejilla del casco.',
      ca: 'Els ulls de la Hana darrere les barres de la reixa del casc.',
      pt: 'Os olhos de Hana atrás das barras da grade do capacete.',
      zh: '面罩铁栏后花的眼睛。',
      ar: 'عينا هانا خلف قضبان شبكة الخوذة.',
      ja: '面金の向こうの花の目。' }),
  safeArea: { x: 0.22, y: 0.26, width: 0.57, height: 0.38 },
  anchors: [{ id: 'hana', x: 0.5, y: 0.62, head: { x: 0.5, y: 0.4 },
    face: { x: 0.2, y: 0.3, width: 0.6, height: 0.3 } }] },
  lunge: {
    alt: t({ en: 'The opponent lunges at the viewer, speed lines all round.',
      es: 'El rival se lanza hacia el lector entre líneas cinéticas.',
      ca: 'El rival es llança cap al lector entre línies cinètiques.',
      pt: 'O adversário avança contra o leitor entre linhas de velocidade.',
      zh: '对手在速度线中朝读者猛刺过来。',
      ar: 'الخصم يندفع نحو القارئ وسط خطوط السرعة.',
      ja: '集中線の中、こちらへ突いてくる相手。' }),
  safeArea: { x: 0.03, y: 0.01, width: 0.8, height: 0.61 },
  avoid: [{ x: 0.02, y: 0.42, width: 0.23, height: 0.18 }],
  anchors: [{ id: 'rival', x: 0.7, y: 0.2, head: { x: 0.7, y: 0.14 },
    face: { x: 0.63, y: 0.02, width: 0.15, height: 0.24 } }] },
  strike: {
    alt: t({ en: "Hana leaps and strikes the top of the opponent's helmet; the sword bends.",
      es: 'Hana salta y golpea la parte alta del casco del rival; la espada se dobla.',
      ca: 'La Hana salta i colpeja la part alta del casc del rival; l’espasa es doblega.',
      pt: 'Hana salta e acerta o alto do capacete do adversário; a espada se curva.',
      zh: '花跃起击中对手面罩顶部，竹剑弯了起来。',
      ar: 'هانا تقفز وتضرب أعلى خوذة الخصم؛ ينثني السيف.',
      ja: '跳び込んで相手の面を打つ花。竹刀がしなる。' }),
  safeArea: { x: 0.36, y: 0.06, width: 0.42, height: 0.77 },
  avoid: [{ x: 0.52, y: 0.48, width: 0.13, height: 0.16 }],
  anchors: [{ id: 'hana', x: 0.43, y: 0.25, head: { x: 0.43, y: 0.18 },
    face: { x: 0.38, y: 0.07, width: 0.1, height: 0.25 } }, { id: 'sfx', x: 0.75, y: 0.25 }] },
  stands: {
    alt: t({ en: 'Sora jumps up in the stands, fists raised, shouting.',
      es: 'Sora salta en la grada con los puños en alto, gritando.',
      ca: 'En Sora salta a la graderia amb els punys enlaire, cridant.',
      pt: 'Sora pula na arquibancada de punhos erguidos, gritando.',
      zh: '空在看台上跳起来，举着拳头大喊。',
      ar: 'سورا يقفز في المدرّجات رافعًا قبضتيه وهو يصيح.',
      ja: '観客席で拳を突き上げて叫ぶ空。' }),
  safeArea: { x: 0.08, y: 0.07, width: 0.69, height: 0.44 },
  avoid: [{ x: 0.08, y: 0.06, width: 0.12, height: 0.1 },
    { x: 0.64, y: 0.35, width: 0.1, height: 0.12 }],
  anchors: [{ id: 'sora', x: 0.51, y: 0.44, head: { x: 0.5, y: 0.37 },
    face: { x: 0.4, y: 0.3, width: 0.22, height: 0.2 } }] },
  coach: {
    alt: t({ en: 'Mori, arms crossed and eyes closed; behind him the referees raise their flags.',
      es: 'Mori, de brazos cruzados y ojos cerrados; detrás, los árbitros alzan las banderas.',
      ca: 'En Mori, de braços plegats i ulls tancats; darrere, els àrbitres alcen les banderes.',
      pt: 'Mori, de braços cruzados e olhos fechados; atrás, os árbitros erguem as bandeiras.',
      zh: '森老师抱着双臂、闭着眼；身后的裁判举起了旗子。',
      ar: 'موري عاقد الذراعين مغمض العينين، وخلفه يرفع الحكّام راياتهم.',
      ja: '腕を組み目を閉じる森先生。後ろで審判が旗を上げる。' }),
  safeArea: { x: 0.16, y: 0.1, width: 0.76, height: 0.53 },
  avoid: [{ x: 0.55, y: 0.18, width: 0.4, height: 0.17 }],
  anchors: [{ id: 'mori', x: 0.29, y: 0.31, head: { x: 0.29, y: 0.2 },
    face: { x: 0.22, y: 0.1, width: 0.14, height: 0.24 } }] },
};
const panels = () => Promise.all([
  comicPanel('final', asset('match-final.jpg'), ART.final),
  comicPanel('eyes', asset('match-eyes.jpg'), ART.eyes),
  comicPanel('lunge', asset('match-lunge.jpg'), ART.lunge),
  comicPanel('strike', asset('match-strike.jpg'), ART.strike),
  comicPanel('coach', asset('match-coach.jpg'), ART.coach),
  comicPanel('stands', asset('match-stands.jpg'), ART.stands),
]);
// #endregion

// #region fonts: each edition loads its faces with the words they set
const SFX = /^sfx(\{[^}\n]*\})?[ \t]*[:：](.*)$/gm; // sound effects: the second face sets them
async function loadEdition(lang) {
  const text = TEXT[lang];
  const [face, sfx] = EDITIONS[lang].faces;
  const faces = { [face]: FONTS[face], [sfx]: FONTS[sfx] };
  const effects = [...text.matchAll(SFX)];
  for (const [, attrs = '', words] of effects) { // ドン keeps its face in every language
    const family = /font="([^"]+)"/.exec(attrs)?.[1];
    if (!family) continue;
    faces[family] = FONTS[family];
    await loadCjkFonts({ [family]: FONTS[family] }, words, { vertical: true });
  }
  if (['ja', 'zh'].includes(lang)) { // CJK: only the files that hold these characters
    const own = effects.filter(([, attrs = '']) => !attrs.includes('font=')).map((m) => m[2]);
    await loadCjkFonts({ [face]: FONTS[face] }, text.replace(SFX, ''), { vertical: true });
    await loadCjkFonts({ [sfx]: FONTS[sfx] }, own.join(''), { vertical: true });
  }
  if (lang === 'ar') await loadArabicFonts(faces, text);
  await loadComicFonts(faces, text); // the bold and italic the faces do not ship
}
// #endregion

// ─── 4 · Build & show ───────────────────────────────────────────────────────
// #region editions: the original on the right-hand page, this edition's lettering facing it
const FACING = LANG === 'ja' ? 'en' : LANG; // Japanese readers see the English edition
const TEXT = { ja: original, [FACING]: LANG === 'ja' ? english : markdown };
await loadFonts(FONTS, Object.values(TEXT).join('\n'));
const resources = await panels();
const build = async (lang) => { // the same pictures and page; this language's lettering
  await loadEdition(lang);
  return buildWithFonts(() => buildDocument({ markdown: TEXT[lang], resources,
    continuation: { pageIndexOffset: lang === 'ja' ? 1 : 2 } }, edition(lang)), TEXT[lang]);
};
const docs = [await build('ja'), await build(FACING)];
// #endregion
const TITLE = t({
  en: 'An action page with slanted gutters', es: 'Una página de acción con calles inclinadas',
  ca: 'Una pàgina d’acció amb carrers inclinats', zh: '斜向格间的动作页', ar: 'صفحة حركة بفواصل مائلة',
  pt: 'Uma página de ação com sarjetas inclinadas',
  ja: '斜めのコマ割りで組むアクションのページ' });
showBook(docs, { title: TITLE });
offerPdf(() => renderToPdf(docs, { fontProvider: comicPdfProvider, resourceBytes: imageBytes }),
  `${RECIPE}.pdf`);

キット · core, fonts, viewer, pdf, images, cjk, arabic, comics：全レシピ共通 · 722行
// ─── 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 v2 ── the same in every recipe · postext.dev/cookbook
// Postext measures with the loaded faces and caches the widths: load every face
// before the first build, from Fontsource, the files the PDF embeds too.

/** faces = { 'Family Name': ['400', '400i', '700'] }. `text` is the sample:
 *  č ł † α χ also load latin-ext and greek files (kitSubsetsFor). 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',
    greek: 'U+0370-03FF',
  };
  const jobs = [];
  let added = 0;
  for (const [family, specs] of Object.entries(faces)) {
    const id = fontsourceId(family);
    const todo = [...new Set(specs)].map((spec) => [parseInt(spec, 10), spec.endsWith('i') ? 'italic' : 'normal'])
      .filter(([weight, style]) => !hasFace(family, weight, style)); // before any await
    const meta = optional || /[^\0-ÿ]/u.test(text) ? await fontsourceMeta(family) : null;
    const subsets = ['latin', ...kitSubsetsFor(text, meta)];
    for (const [weight, style] of todo) {
      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` and loads any face the pages use that FONTS missed (a regular
 *  one with a warning), then clears the measurement cache and builds 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. */
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' };
}

/** A loaded FontFace covers this family, weight and style (fonts.check() would
 *  also say yes 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;
}

/** The files beyond latin `text` needs that `meta`'s family ships. */
function kitSubsetsFor(text, meta) {
  return [[/[Ā-˿ᴀ-ᶿḀ-ỿ†ℓⱠ-Ɀ꜠-ꟿ]/u, 'latin-ext'], [/[Ͱ-Ͽ]/u, 'greek']]
    .filter(([re, x]) => re.test(text) && meta?.subsets?.includes(x)).map(([, x]) => x);
}

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

/** The family's Fontsource metadata (weights, styles, subsets), 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
/** The pages as spreads on a dark desk, page 1 alone, then verso | recto,
 *  each painted when it scrolls near. */
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 v2 ── the same in every recipe that exports a PDF
/** The Fontsource files the screen used, as TrueType: the nearest weight the
 *  family ships, upright if it has no italic; latin, then what the face's
 *  letters need (kitSubsetsFor). */
async function fontsourceProvider(family, weight, style, request) {
  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 text = String.fromCodePoint(...(request?.codePoints ?? []));
  const more = kitSubsetsFor(text, meta);
  const files = await Promise.all(['latin', ...more].map(async (subset) => {
    const res = await fetch(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-${subset}-${w}-${s}.woff2`);
    if (!res.ok) throw new Error(`Fontsource has no ${family} ${w} ${s} ${subset}`);
    return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
  }));
  return files.length === 1 ? files[0] : files;
}

/** A "Build the PDF" button; then "Open the PDF" (a new tab: CodePen's frame
 *  shows no 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 · images v1 ── recipes with pictures · postext.dev/cookbook
/** Registers a photo or PNG for the canvas and keeps its bytes for the PDF.
 *  fetch → ImageBitmap never taints the canvas (a plain cross-origin <img> would). */
async function loadImage(fileId, url) {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`Image not found (${res.status}): ${url}`);
  const bytes = new Uint8Array(await res.arrayBuffer());
  registerResourceImage(fileId, await createImageBitmap(new Blob([bytes])));
  (loadImage.bytes ??= new Map()).set(fileId, bytes);
}

/** Registers SVG markup (drawn in code, or fetched) as a vector image. */
async function loadSvg(fileId, svg) {
  const img = new Image();
  img.src = `data:image/svg+xml;charset=utf-8,${encodeURIComponent(svg)}`;
  await img.decode();
  registerResourceImage(fileId, img);
  (loadImage.bytes ??= new Map()).set(fileId, new TextEncoder().encode(svg));
}

/** renderToPdf({ resourceBytes: imageBytes }) */
function imageBytes(fileId) { return loadImage.bytes?.get(fileId); }

/** renderToHtml({ resourceImageUrl: imageUrl }) */
function imageUrl(fileId) {
  const bytes = imageBytes(fileId);
  if (!bytes) return undefined;
  imageUrl.urls ??= new Map();
  if (!imageUrl.urls.has(fileId)) {
    const type = /\.svg$/i.test(fileId) ? 'image/svg+xml' : /\.png$/i.test(fileId) ? 'image/png' : 'image/jpeg';
    imageUrl.urls.set(fileId, URL.createObjectURL(new Blob([bytes], { type })));
  }
  return imageUrl.urls.get(fileId);
}

// ─── 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 · arabic v1 ── Arabic-script faces · postext.dev/cookbook
// Fontsource ships an Arabic family as one file per subset and weight: the
// `arabic` file holds the letters, the harakat, the Arabic-Indic digits, the
// Arabic punctuation and the presentation forms; `latin` and `latin-ext`
// hold the rest. loadFonts loads the latin files; this block adds the arabic
// file of every Arabic family, for the canvas and for the PDF, which shapes
// the letters with HarfBuzz from the same bytes.

/** The code points of Fontsource's `arabic` subset, as its stylesheets
 *  declare them (the same unicode-range the browser picks the file by). A
 *  function, not a const: the kit is inlined after the recipe's top-level
 *  awaits, and a const read before its line throws, where a function
 *  declaration is hoisted. */
function arabicRange() {
  return 'U+0600-06FF,U+0750-077F,U+0870-088E,U+0890-0891,U+0897-08E1,U+08E3-08FF,'
    + 'U+200C-200E,U+2010-2011,U+204F,U+2E41,U+FB50-FDFF,U+FE70-FE74,U+FE76-FEFC,U+102E0-102FB,'
    + 'U+10E60-10E7E,U+10EC2-10EC4,U+10EFC-10EFF,U+1EE00-1EEFF';
}

/** Whether code point `cp` is in the arabic file. */
function inArabicRange(cp) {
  inArabicRange.ranges ??= arabicRange().split(',').map((part) => {
    const [lo, hi = lo] = part.slice(2).split('-');
    return [parseInt(lo, 16), parseInt(hi, 16)];
  });
  return inArabicRange.ranges.some(([lo, hi]) => cp >= lo && cp <= hi);
}

/** Whether Fontsource serves `family` with an `arabic` subset. Fails when
 *  the API does not answer: an Arabic face taken for a Latin one would set
 *  its letters in a system face. */
async function isArabicFamily(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?.includes('arabic');
}

/** The arabic file of a face. */
function arabicFileUrl(family, weight, style) {
  const id = fontsourceId(family);
  return `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-arabic-${weight}-${style}.woff2`;
}

/** faces = { Amiri: ['400', '700'] }, as for loadFonts, after it: the whole
 *  FONTS object may be passed, its families without an arabic subset are
 *  left alone. Adds the arabic file of every listed weight of each Arabic
 *  family (the latin files come from loadFonts) and loads it. `text` is
 *  the sample: fails when it holds an Arabic-script character the arabic
 *  file does not cover. List every weight the pages set in Arabic: a weight
 *  left to buildWithFonts gets the latin file only, and its Arabic letters
 *  fall back to a system face. Resolves to the number of files loaded. */
async function loadArabicFonts(faces, text = '') {
  kitStatus('Loading fonts…');
  let loaded = 0;
  try {
    const outside = [...new Set(text)].filter((ch) => /\p{Script=Arabic}/u.test(ch) && !inArabicRange(ch.codePointAt(0)));
    if (outside.length) throw new Error(`Fontsource's arabic files have no ${outside.slice(0, 12).join(' ')}`);
    for (const [family, specs] of Object.entries(faces)) {
      if (!(await isArabicFamily(family))) continue;
      for (const spec of new Set(specs)) {
        const weight = parseInt(spec, 10);
        const style = spec.endsWith('i') ? 'italic' : 'normal';
        const face = new FontFace(family, `url(${arabicFileUrl(family, weight, style)}) format('woff2')`,
          { weight: String(weight), style, unicodeRange: arabicRange() });
        document.fonts.add(await face.load().catch(() => {
          throw new Error(`Fontsource has no arabic file for ${family} ${weight} ${style}`);
        }));
        loaded++;
      }
    }
  } catch (error) {
    kitFail(error);
    throw error;
  }
  return loaded;
}

/** The PDF font provider for recipes with Arabic faces: a family with an
 *  arabic subset gets its arabic file when its pages set Arabic letters
 *  (`request.codePoints`), then its latin file, and its latin-ext file for
 *  the letters beyond latin (transliteration: ā ḥ ʿ). The arabic file comes
 *  first: it also holds the space and the brackets, so a line of Arabic is
 *  shaped as one run and not cut at every space. Any other family goes to
 *  fontsourceProvider (the "pdf" block). */
async function arabicPdfProvider(family, weight, style, request) {
  if (!(await isArabicFamily(family))) return fontsourceProvider(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 wanted = [...(request?.codePoints ?? [])];
  const id = fontsourceId(family);
  const urls = [];
  if (!wanted.length || wanted.some(inArabicRange)) urls.push(arabicFileUrl(family, w, s));
  urls.push(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-${w}-${s}.woff2`);
  if (meta.subsets.includes('latin-ext') && wanted.some((cp) => /[Ā-˿Ḁ-ỿ]/u.test(String.fromCodePoint(cp)))) {
    urls.push(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-ext-${w}-${s}.woff2`);
  }
  return Promise.all(urls.map(async (url) => {
    const res = await fetch(url);
    if (!res.ok) throw new Error(`Fontsource file ${url} (${res.status})`);
    return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
  }));
}

// ─── Kit · comics v1 ── comic pages · postext.dev/cookbook
// The engine letters a comic in a face per language (defaultComicFont:
// Comic Neue, Zen Antique for Japanese, Noto Sans SC, LXGW WenKai TC,
// Playpen Sans Arabic; defaultComicSfxFont: Bangers, Dela Gothic One,
// ZCOOL KuaiLe, Lalezar) and asks for the bold of a shout or a sound effect
// and the italic of an inner voice. Most of these faces ship one weight and
// no italic: this block declares the file Fontsource does ship for those
// variants, so the canvas measures and paints the letters the PDF embeds
// (the providers snap to the shipped file) and not a bold or a slant the
// browser makes up. It also turns the art manifest into panel resources.

/** faces = { 'Comic Neue': ['400', '700'], Bangers: ['400'] }, as for
 *  loadFonts, after it (and after loadCjkFonts or loadArabicFonts for the
 *  faces of those scripts); the whole FONTS object may be passed. List in
 *  FONTS only what Fontsource ships (Bangers: ['400']): loadFonts fails on
 *  the rest. For each family, the regular, bold, italic and bold italic it
 *  lacks are declared with its nearest file (the regular for the bold, the
 *  upright for the italic) and loaded for `text`. A CJK face needs the cjk
 *  block; an Arabic face setting Arabic, the arabic block. Resolves to the
 *  number of variants added. */
async function loadComicFonts(faces, text = '') {
  kitStatus('Loading fonts…');
  let added = 0;
  try {
    for (const family of Object.keys(faces)) {
      const meta = await fontsourceMeta(family);
      if (!meta) throw new Error(`api.fontsource.org did not describe ${family}: reload to try again`);
      const weights = meta.weights?.length ? meta.weights : [400, 700];
      const styles = meta.styles?.length ? meta.styles : ['normal'];
      for (const [weight, style] of [[400, 'normal'], [700, 'normal'], [400, 'italic'], [700, 'italic']]) {
        if ((weights.includes(weight) && styles.includes(style)) || hasFace(family, weight, style)) continue;
        const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
        const s = style === 'italic' && styles.includes('italic') ? 'italic' : 'normal';
        for (const { url, range } of await comicFaceFiles(family, w, s, meta, text)) {
          document.fonts.add(new FontFace(family, `url(${url}) format('woff2')`,
            { weight: String(weight), style, unicodeRange: range }));
        }
        await document.fonts.load(`${style === 'italic' ? 'italic ' : ''}${weight} 16px "${family}"`, text || 'A');
        added++;
      }
    }
  } catch (error) {
    kitFail(error);
    throw error;
  }
  return added;
}

/** The files of a shipped face ({ url, range }): a CJK face's slices (the
 *  cjk block reads them from its stylesheet), else latin, the latin-ext
 *  and greek files `text` needs, and the arabic file when `text` holds
 *  Arabic. */
async function comicFaceFiles(family, weight, style, meta, text) {
  if (meta.subsets?.some((subset) => /^(chinese|japanese|korean)/.test(subset))) {
    if (typeof cjkSlices !== 'function') throw new Error(`${family} is a CJK face: list the cjk kit block`);
    return (await cjkSlices(family, weight, style)).map(({ url, range }) => ({ url, range }));
  }
  const id = fontsourceId(family);
  const file = (subset) => `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-${subset}-${weight}-${style}.woff2`;
  const files = ['latin', ...kitSubsetsFor(text, meta)].map((subset) => ({ url: file(subset), range: comicRange(subset) }));
  if (meta.subsets?.includes('arabic') && /\p{Script=Arabic}/u.test(text)) {
    if (typeof arabicRange !== 'function') throw new Error(`${family} sets Arabic: list the arabic kit block`);
    files.unshift({ url: file('arabic'), range: arabicRange() });
  }
  return files;
}

/** The unicode-range loadFonts gives a Fontsource file. A function, not a
 *  const: the kit is inlined after the recipe's top-level awaits. */
function comicRange(subset) {
  return {
    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',
    greek: 'U+0370-03FF',
  }[subset];
}

/** The PDF font provider of a comic in any script: a CJK face goes to
 *  cjkPdfProvider, an Arabic face to arabicPdfProvider, any other to
 *  fontsourceProvider (the "pdf" block). Each embeds the shipped weight
 *  and style nearest to the one asked for, the file loadComicFonts
 *  declared for the canvas. */
async function comicPdfProvider(family, weight, style, request) {
  const subsets = (await fontsourceMeta(family))?.subsets ?? [];
  if (subsets.some((subset) => /^(chinese|japanese|korean)/.test(subset))) {
    if (typeof cjkPdfProvider !== 'function') throw new Error(`${family} is a CJK face: list the cjk kit block`);
    return cjkPdfProvider(family, weight, style, request);
  }
  if (subsets.includes('arabic') && typeof arabicPdfProvider === 'function') {
    return arabicPdfProvider(family, weight, style, request);
  }
  return fontsourceProvider(family, weight, style, request);
}

/** A panel picture as a resource for art= (and pop=): loads `url`
 *  (write asset('lh-arrive.jpg') in the call, so the lint checks the file)
 *  and declares it with `meta`, its entry in the art manifest:
 *  { width, height, alt, safeArea, anchors, avoid }. The safe area is what
 *  every crop keeps, the anchors the speakers' mouths, heads and faces,
 *  the avoid zones what no balloon covers; all in fractions of the picture,
 *  the same in every language. Without width and height, the picture's own
 *  size. Needs the images block. Resolves to the resource. */
async function comicPanel(id, url, meta = {}) {
  const fileId = decodeURIComponent(url.split('/').pop());
  await loadImage(fileId, url);
  let { width, height } = meta;
  if (!width || !height) {
    const bitmap = await createImageBitmap(new Blob([imageBytes(fileId)]));
    ({ width, height } = bitmap);
    bitmap.close();
  }
  return {
    id, typeId: meta.typeId ?? 'figure', kind: 'bitmap', createdAt: 0, updatedAt: 0,
    bitmap: { fileId, format: /\.png$/i.test(fileId) ? 'png' : 'jpeg', width, height },
    ...(meta.alt && { altText: meta.alt }),
    ...(meta.safeArea && { safeArea: meta.safeArea }),
    ...(meta.anchors?.length && { anchors: meta.anchors }),
    ...(meta.avoid?.length && { avoid: meta.avoid }),
  };
}

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