Red-ink commentary in the line and the head margin

// ═══ Postext Cookbook · Nº 078 · Red-ink commentary in the line and the head margin ═══
// https://postext.dev/en/cookbook/red-ink-commentary
// Code: MIT · Text: 脂硯齋重評石頭記, Jiaxu manuscript, Wikisource (CC BY-SA 4.0) · Pictures: none
// Fonts: Noto Serif TC, LXGW WenKai TC, Noto Sans TC (SIL OFL 1.1) · Needs postext ≥ 1.9.0
// The first chapter of the Stone as a commentary edition: the text set vertically, the
// comments the manuscript writes beside the columns folded into two small red rows inside
// the line, the head-margin comments in red Kai above the columns they gloss.
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, loadVerticalAlternates,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'en'; // @lang: the language of the sample document ('en' | 'es')
const RECIPE = 'red-ink-commentary';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: black ink and vermilion on a warm paper
const palette = {
  ink: '#231d18', // the text: a warm black
  vermilion: '#b0362a', // 朱: every comment, the chapter's kicker; 5.5 : 1 on the paper
  rule: '#b9a78f', // the line under the head margin
  muted: '#6f6356', // folios, the colophon
  paper: '#f7f1e3',
};
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' } })),
  // The engine's defaults link to main-color: aimed at the vermilion, nothing prints blue.
  { id: 'main-color', name: 'vermilion (defaults)',
    value: { hex: palette.vermilion, model: 'hex' } },
];
// #endregion
const [SONG, KAI, HEI] = ['Noto Serif TC', 'LXGW WenKai TC', 'Noto Sans TC']; // 宋, 楷, 黑
const BODY = 12; // pt, 小四: the notes fold to two rows of 6 pt in the same em
const LEAD = 21; // pt between columns, 1.75 × the body

// #region answer: side comments inside the line, head-margin comments above it
const layout = {
  writingMode: 'vertical-rl', // columns down the page, read from the right; bound on the right
  layoutType: 'oneAndHalf', // a text tier and a narrow tier for the comments
  sideColumnRole: 'floats', // no text runs into it: only boxes fenced with span="side"
  sideColumnSide: 'left', // in vertical text 'left' is the top tier: the head margin (天頭)
  sideColumnPercent: 19, // the grid rounds it to 10 characters of the body, 42 mm
  gutterWidth: mm(8), // rounded to 2 characters
  columnRule: { enabled: true, lineWidth: pt(0.5), color: col('rule') },
};
const cjk = {
  grid: { enabled: true, charsPerLine: 36, linesPerPage: 18 }, // 版心: 36 字 × 18 行
  // :warichu[…] folds a side comment into two rows at half the body size, in red
  // and with no brackets, as the manuscripts write their 雙行夾批.
  warichu: { color: col('vermilion') },
};
// A 眉批 is :::callout{type="meipi" span="side"}: span="side" sends it to the head
// margin, level with the column the text has reached at its fence, so the fence goes
// just before the passage it discusses (gotcha: side-box-starts-at-fence).
const meipi = {
  id: 'meipi', backgroundEnabled: false,
  border: { enabled: false }, stripe: { enabled: false },
  padding: { top: pt(0), right: pt(0), bottom: pt(0), left: pt(0) },
  // 17 characters of 7 pt down the 120 pt tier, a column every 10 pt. The next comment
  // starts on a text column at least one body column (21 pt) further on, whatever the margin.
  snapToGrid: false, marginBottom: pt(0),
  body: { fontFamily: KAI, fontSize: pt(7), lineHeight: pt(10), color: col('vermilion'),
    textAlign: 'left', firstLineIndent: pt(0) },
};
// #endregion

// #region opener: the chapter's number and its couplet (回目), set down the first columns
const opener = { enabled: true, minHeight: mm(46), slot: { elements: [
  { kind: 'text', id: 'book', content: '{title}', fontFamily: HEI, fontWeight: 500,
    fontSize: pt(10), letterSpacing: pt(3), color: col('vermilion'), align: 'left',
    placement: { anchor: { to: 'container', edge: 'top-left' } } },
  { kind: 'text', id: 'number', content: '{titleText}', fontFamily: SONG, fontWeight: 700,
    fontSize: pt(30), letterSpacing: pt(6), color: col('ink'), align: 'left',
    placement: { anchor: { to: '#book', edge: 'below' }, offset: { x: em(2), y: mm(4) } } },
  ...['a', 'b'].map((half, i) => ({ kind: 'text', id: `couplet-${half}`,
    content: `{attr.${half}}`, fontFamily: SONG, fontSize: pt(15), letterSpacing: pt(3),
    color: col('ink'), align: 'left',
    placement: { anchor: { to: i ? '#couplet-a' : '#number', edge: 'below' },
      offset: { x: i ? pt(0) : em(4), y: mm(i ? 1.5 : 4) } } })),
] } };
// #endregion

// #region fore-edge: the book's title and the folio down the outer margin
// 'outer' is the margin away from the spine: a recto's left, a verso's right.
const edge = (id, content, edgeOf, y, extra = {}) => ({ kind: 'text', id, content,
  writingMode: 'vertical-rl', fontFamily: HEI, fontWeight: 500, fontSize: pt(9.5),
  letterSpacing: pt(2), color: col('muted'), overflow: 'clip', align: 'left',
  placement: { anchor: { to: 'outer', edge: edgeOf }, offset: { y: em(y) } }, ...extra });
const header = { elements: [
  // Four characters below the head: the book on a verso, the chapter on a recto,
  // never on the opener.
  edge('head-verso', '{title}', 'top', 4, { pages: 'body', parity: 'even' }),
  edge('head-recto', '{chapterTitle}', 'top', 4, { pages: 'body', parity: 'odd' }),
  edge('folio', '{pageNumber}', 'bottom', -5), // 一, 二, 三…: page.pageNumbering below
] };
// #endregion

const config = () => ({ // a factory: the engine caches resolved configs by identity
  locale: 'zh-Hant', // Taiwan conventions: centred full-width marks (gotcha: cjk-locale-tag)
  colorPalette, layout, cjk, header,
  footer: { elements: [] },
  page: {
    sizePreset: 'custom', width: mm(184), height: mm(260), dpi: 150, // 16开
    backgroundColor: col('paper'),
    // Minimums: the grid centres its type area in what they leave. left is the inner
    // margin, which a right-bound recto has on its right.
    margins: { top: mm(16), bottom: mm(22), left: mm(20), right: mm(22), mirror: true },
    pageNumbering: { format: 'trad-chinese-informal' },
  },
  bodyText: {
    fontFamily: SONG, fontSize: pt(BODY), lineHeight: pt(LEAD), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
    textAlign: 'justify', firstLineIndent: em(2), indentAfterHeading: true,
    // A paragraph may open in a page's last column, so every page sets its 18. The
    // orphan rule stays on: a paragraph's last column never stands alone at the head of
    // a page (孤行不成頁).
    avoidWidows: false,
  },
  headings: {
    fontFamily: SONG, color: col('ink'),
    // Restated: any headings object drops the H1 break (gotcha: headings-drop-h1-break).
    levels: [{ level: 1, fontSize: pt(30), breakBefore: { enabled: true, parity: 'any' },
      advancedDesign: opener }],
  },
  paragraphStyles: [
    // The two poems: each line a paragraph, four characters down, never spread.
    { id: 'verse', textAlign: 'left', firstLineIndent: em(4) },
    // The edition's note, two characters lower than the text (低二格), in Kai.
    { id: 'note', fontFamily: KAI, indent: em(2), firstLineIndent: pt(0),
      marginTop: pt(LEAD) },
    // The colophon, in the edition's language: Latin runs sideways down a vertical line.
    { id: 'colophon', fontFamily: HEI, fontWeight: 500, fontSize: pt(7.5),
      lineHeight: pt(LEAD), color: col('muted'), textAlign: 'left', indent: em(2),
      firstLineIndent: pt(0) },
  ],
  calloutStyles: [meipi],
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Markdown sample · 97 lines · content.en.md
title: "脂硯齋重評石頭記"
author: "曹雪芹"
---

# 第一回 {a="甄士隱夢幻識通靈" b="賈雨村風塵懷閨秀"}

列位看官：你道此書從何而來？說起根由雖近荒唐，:warichu[自占地步。]　:warichu[自首荒唐，妙！]細諳則深有趣味。待在下將此來歷註明，方使閱者了然不惑。

:::callout{type="meipi" span="side"}
妙！自謂落墮情根，故無補天之用。
:::

原來女媧氏煉石補天之時，:warichu[補天濟世，勿認真，用常言。]于大荒山:warichu[荒唐也。]無稽崖:warichu[無稽也。]煉成高經十二丈、:warichu[總應十二釵。]方經二十四丈:warichu[照應副十二釵。]頑石三萬六千五百零一塊。媧皇氏只用了三萬六千五百塊，:warichu[合週天之數。]只單單的剩了一塊未用，:warichu[剩了這一塊便生出這許多故事。使當日雖不以此補天，就該去補地之坑陷，使地平坦，而不得有此一部鬼話。]便棄在此山青埂峰下。誰知此石自經煆煉之後，靈性已通，:warichu[煆煉後性方通，甚哉！人生不能學也。]因見衆石俱得補天，獨自己無材不堪入選，遂自怨自嘆，日夜悲號慚愧。

一日，正當嗟悼之際，俄見一僧一道遠遠而來，生得骨格不凡，丰神迥別，說說笑笑來至峰下，坐于石邊高談快論。先是說些雲山霧海神仙玄幻之事，後便說到紅塵中榮華富貴。此石聽了，不覺打動凡心，也想要到人間去享一享這榮華富貴，但自恨粗蠢，不得已，便口吐人言，:warichu[竟有人問口生於何處，其無心肝，可咲可恨之極。]向那僧道說道：「大師，弟子蠢物，:warichu[豈敢豈敢。]不能見禮了。適聞二位談那人世間榮耀繁華，心切慕之。弟子質雖粗蠢，:warichu[豈敢豈敢。]性却稍通，况見二師仙形道體，定非凡品，必有補天濟世之材，利物濟人之德。如蒙發一點慈心，攜帶弟子得入紅塵，在那富貴場中、溫柔鄉裏受享幾年，自當永佩洪恩，萬劫不忘也。」二仙師聽畢，齊憨笑道：「善哉，善哉！那紅塵中有却有些樂事，但不能永遠依恃，况又有『美中不足，好事多魔』八箇字緊相連屬，瞬息間則又樂極悲生，人非物換，究竟是到頭一夢，萬境歸空。:warichu[四句乃一部之總綱。]到不如不去的好。」這石凡心已熾，那里聽得進這話去，乃復苦求再四。二仙知不可強制，乃嘆道：「此亦靜極思動，無中生有之數也。既如此，我們便携你去受享受享，只是到不得意時，切莫後悔。」石道：「自然，自然。」那僧又道：「若說你性靈，却又如此質蠢，並更無奇貴之處，如此也只好踮脚而已。:warichu[煆煉過尚與人踮腳，不學者又當如何？]也罷，我如今大施佛法助你助，待劫終之日，復還本質，以了此案。:warichu[妙！佛法亦湏償還，况世人之償乎？近之賴債者來看此句。所謂遊戲筆墨也。]你道好否？」石頭聽了，感謝不盡。那僧便念咒書符，大展幻:warichu[明點「幻」字。好！]術，將一塊大石登時變成一塊鮮明瑩潔的美玉，且又縮成扇墜大小的可佩可拿。:warichu[奇詭險怪之文，有如髯蘇《石鐘》《赤璧》用幻處。]那僧托于掌上，笑道：「形體到也是個寳物了！:warichu[自愧之語。]還只沒有實在的好處，:warichu[妙極！今之金玉其外敗絮其中者，見此大不歡喜。]湏得在鐫上數字，使人一見便知是奇物方妙。:warichu[世上原宜假，不宜真也。諺云：「一日賣了三千假，三日賣不出一個真。」信哉！]然後好携你到那昌明隆盛之邦，:warichu[伏長安大都。]詩禮簪〔纓〕之族，:warichu[伏榮國府。]花柳繁華地，:warichu[伏大觀園。]溫柔富貴鄉:warichu[伏紫芸軒。]去安身樂業。」:warichu[何不再添一句云「擇個絕世情痴作主人」？]

:::callout{type="meipi" span="side"}
昔子房後謁黃石公，惟見一石。子房當時恨不能隨此石去。余亦恨不能隨此石而去也。聊供閱者一笑。
:::

石頭聽了，喜不能禁，乃問：「不知賜了弟子那幾件奇處，:warichu[可知若果有奇貴之處，自己亦不知者。若自以奇貴而居，究竟是無真奇貴之人。]又不知携了弟子到何地方？望乞明示，使弟子不惑。」那僧笑道：「你且莫問，日後自然明白的。」說着，便袖了這石，同那道人飄然而去，竟不知投奔何方何舍。

後來，不知又過了幾世幾劫，因有個空空道人訪道求仙，忽從這大荒山無稽崖青埂峰下經過，忽見一大石上字跡分明，編述歷歷。空空道人乃從頭一看，原來就是無材補天，幻形入世，:warichu[八字便是作者一生慚恨。]蒙茫茫大士、渺渺真人携入紅塵，歷盡離合悲歡炎凉世態的一叚故事。後面又有一首偈云：

:::paragraphs{style="verse"}
無材可去補蒼天，:warichu[書之本旨。]

枉入紅塵若許年。:warichu[慚愧之言，嗚咽如聞。]

此係身前身後事，

倩誰記去作奇傳？
:::

詩後便是此石墮落之鄉，投胎之處，親自經歷的一叚陳跡故事。其中家庭閨閣瑣事，以及閑情詩詞倒還全備，或:warichu[「或」字謙得好。]可適趣觧悶，然朝代年紀，地輿邦國，却反失落無考。:warichu[若用此套者，胸中必無好文字，手中斷無新筆墨。據余說，卻大有考證。]

空空道人遂向石頭說道：「石兄，你這一叚故事，據你自己說有些趣味，故編寫在此，意欲問世傳奇。據我看來，第一件，無朝代年紀可考，:warichu[先駁得妙。]第二件，並無大賢大忠理朝廷治風俗的善政，:warichu[將世人欲駁之腐言預先代人駁盡。妙！]其中只不過幾箇異樣的女子，或情或痴，或小才微善，亦無班姑蔡女之德能。我總抄去，恐世人不愛看呢。」

石頭笑荅道：「我師何太痴耶！若云無朝代可考，今我師竟假借漢唐等年紀添綴，又有何難？:warichu[所以答的好。]但我想，歷來野史，皆蹈一轍，莫如我這不借此套者，反到新奇別致，不過只取其事體情理罷了，又何必拘拘於朝代年紀哉！再者，世井俗人喜看理治之書者甚少，愛看適趣閒文者特多。歷代野史，或訕謗君相，或貶人妻女，:warichu[先批其大端。]姦滛凶惡，不可勝數。更有一種風月筆墨，其滛穢污臭，塗毒筆墨，壞人子弟，又不可勝數。至若佳人才子等書，則又千部共出一套，且其中終不能不涉于滛濫，以致滿紙潘安子建、西子文君，不過作者要寫出自己的那兩首情詩艶賦來，故假擬出男女二人名姓，又必傍出一小人其間撥亂，亦如劇中之小丑然。且嬛婢開口即者也之乎，非文即理。故逐一看去，悉皆自相矛盾，大不近情理之話。

:::callout{type="meipi" span="side"}
事則實事，然亦叙得有間架、有曲折、有順逆、有映帶、有隱有見、有正有閏，以至草蛇灰線、空谷傳聲、一擊兩鳴、明修棧道、暗度陳倉、雲龍霧雨、兩山對峙、烘雲托月、背面傳粉、千皴萬染諸奇。書中之秘法，亦不復少。余亦于逐回中搜剔刳剖明白注釋以待高明，再批示誤謬。
:::

:::callout{type="meipi" span="side"}
開卷一篇立意，真打破歷來小說窠臼。閱其筆則是《莊子》《離騷》之亞。
:::

:::callout{type="meipi" span="side"}
斯亦太過。
:::

「竟不如我半世親睹親聞的這幾個女子，雖不敢說強似前代書中所有之人，但事跡原委，亦可以消愁破悶，也有幾首歪詩熟話，可以噴飯供酒。至若離合悲歡，興衰際遇，則又追踪攝跡，不敢稍加穿鑿，徒為供人之目而反失其真傳者。今之人，貧者日為衣食所累，富者又懷不足之心，總一時稍閒，又有貪滛戀色、好貸尋愁之事，那里去有工夫看那理治之書？所以我這一叚事，也不愿世人稱奇道妙，也不定要世人喜悅檢讀，:warichu[轉得更好。]只愿他們當那醉餘飽卧之時，或避世去愁之際，把此一玩，豈不省了此壽命筋力？就比那謀虛逐妄，去也省了口舌是非之害，腿脚奔忙之苦。再者，亦令世人換新眼目，不比那些胡牽亂扯，忽離忽遇，滿紙才人淑女、子建文君、紅娘小玉等通共熟套之舊稿。我師意為何如？」:warichu[余代空空道人答曰：「不獨破愁醒盹，且有大益。」]

:::callout{type="meipi" span="side"}
雪芹舊有《風月寳鑑》之書，乃其弟棠村序也。今棠村已逝，余覩新懷舊，故仍因之。
:::

:::callout{type="meipi" span="side"}
若云雪芹披閱增刪，然後開卷至此這一篇楔子又係誰撰？足見作者之筆式狡猾之甚。後文如此處者不少。這正是作者用画家烟雲糢糊處，觀者萬不可被作者瞞蔽了去，方是巨眼。
:::

空空道人聽如此說，思忖半晌，將這《石頭記》:warichu[本名。]再檢閱一遍，:warichu[這空空道人也太小心了，想亦世之一腐儒耳。]因見上面雖有些指奸責佞貶惡誅邪之語，:warichu[亦斷不可少。]亦非傷時罵世之旨，:warichu[要緊句。]及至君仁臣良父慈子孝，凡倫常所關之處，皆是稱功頌德，眷眷無窮，實非別書之可比。雖其中大旨談情，亦不過實錄其事，又非假擬妄稱，:warichu[要緊句。]一味滛邀艶約、私訂偷盟之可比。因毫不干涉時世，:warichu[要緊句。]方從頭至尾抄錄回來，問世傳奇。因空見色，由色生情，傳情入色，自色悟空，遂易名為情僧，改《石頭記》為《情僧錄》。至吳玉峰題曰《紅樓夢》。東魯孔梅溪則題曰《風月寶鑑》。後因曹雪芹于悼紅軒中披閱十載，增刪五次，纂成目錄，分出章回，則題曰《金陵十二釵》，並題一絕云：

:::callout{type="meipi" span="side"}
能觧者方有辛酸之淚，哭成此書。壬午除夕，書未成，芹為淚盡而逝。余嘗哭芹，淚亦待盡。每意覓青埂峯再問石兄，余不遇獺頭和尚何！悵悵！
:::

:::callout{type="meipi" span="side"}
今而後惟愿造化主再出一芹一脂，是書何本，余二人亦大快遂心于九泉矣。甲午八日淚筆。
:::

:::paragraphs{style="verse"}
滿紙荒唐言，一把辛酸淚！

都云作者痴，誰解其中味？:warichu[此是第一首標題詩。]
:::

至脂硯齋甲戌抄閱再評，仍用《石頭記》。

出則既明，且看石上是何故事。按那石上書云：:warichu[以石上所記之文。]

當日地陷東南，這東南一隅有處曰姑蘇，:warichu[是金陵。]有城曰閶門者，最是紅塵中一二等富貴風流之地。:warichu[妙極！是石頭口氣，惜米顛不遇此石。]這閶門外有個十里街，:warichu[開口失云勢利，是伏甄、封二姓之事。]街內有個仁清巷，:warichu[又言人情，總為士隱火後伏筆。]巷內有個古廟，因地方窄狹，:warichu[世路寬平者甚少。亦鑿。]人皆呼作葫蘆廟。:warichu[糊塗也，故假語從此具焉。]

:::callout{type="meipi" span="side"}
真。後之甄寶玉亦借此音，後不注。
:::

廟傍住着一家鄉宦，:warichu[不出榮國大族，先寫鄉宦小家，從小至大，是此書章法。]姓甄，名費，:warichu[廢。]字士隱。:warichu[托言將真事隱去也。]嫡妻封氏，:warichu[風。因風俗來。]情性賢淑，深明禮義。:warichu[八字正是寫日後之香菱，見其根源不凡。]家中雖無甚富貴，然本地便也推他為望族了。:warichu[本地推為望族，寕、榮則天下推為望族，叙事有層落。]只因這甄士隱禀性恬淡，不以功名為念，:warichu[自是羲皇上人，便可作是書之朝代年紀矣。總寫香菱根基，原與正十二釵無異。]每日只以觀花修竹，酌酒吟詩為樂，到是神仙一流人品。只是一件不足：如今年已半百，膝下無兒，:warichu[所謂「美中不足」也。]只有一女，乳名英蓮，:warichu[設云「應怜」也。]年方三歲。

:::paragraphs{style="note"}
本編說明　正文與批語據甲戌本《脂硯齋重評石頭記》第一回，錄文取自維基文庫。朱筆側批改作雙行夾批，排在所批文字之下；眉批仍居天頭，列在所批一段之上。標點從錄文，分段稍有調整。原本空缺之字據他本補入，外加六角括號，如「詩禮簪〔纓〕之族」。字庫未收之異體字，如縂、竒、冩，改用通行字。
:::

:::paragraphs{style="colophon"}
Set in Noto Serif TC, LXGW WenKai TC and Noto Sans TC (SIL OFL) · Text: the Jiaxu manuscript, Wikisource transcription (CC BY-SA 4.0)
:::
`; // content.<lang>.md, inlined by the Cookbook

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = {
  'Noto Serif TC': ['400', '700'], // 宋: the text and the notes in the line; bold 第一回
  'LXGW WenKai TC': ['400'], // 楷: the head-margin comments, the edition's note
  'Noto Sans TC': ['500'], // 黑: the book's title, the folios, the colophon
};

// ─── 4 · Build & show ───────────────────────────────────────────────────────
// #region voices: each face loads the files of the characters it sets
// Song sets the whole sample and its bold only 第一回, Kai the head-margin comments and
// the edition's note, Hei the running heads, the folios and the colophon
// (gotcha: cjk-fonts-slices).
const blocks = (style) => [...markdown.matchAll(
  new RegExp(`:::(?:callout|paragraphs)\\{[^}]*"${style}"[^}]*\\}\\n([^]*?)\\n:::`, 'g'))]
  .map((m) => m[1]).join('');
const numerals = '一二三四五六七八九十';
await loadFonts(FONTS, markdown);
await loadCjkFonts({ [SONG]: ['400'] }, markdown, { vertical: true });
await loadCjkFonts({ [SONG]: ['700'] }, '第一回'); // the bold weight sets three characters
await loadCjkFonts({ [KAI]: FONTS[KAI] }, blocks('meipi') + blocks('note'), { vertical: true });
await loadCjkFonts({ [HEI]: FONTS[HEI] }, `脂硯齋重評石頭記第一回${numerals}${blocks('colophon')}`,
  { vertical: true });
// #endregion
const doc = await buildWithFonts(() => buildDocument({ markdown }, config()), markdown);
showBook(doc, { title: t({ en: 'A red-ink commentary edition',
  es: 'Una edición comentada en rojo' }) });
offerPdf(() => renderToPdf(doc, { fontProvider: cjkPdfProvider }), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, cjk: the same in every recipe · 422 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 goes to fontsourceProvider (the "pdf" block). */
async function cjkPdfProvider(family, weight, style, request) {
  if (!(await isCjkFamily(family))) return fontsourceProvider(family, weight, style);
  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()));
  }));
}

/** 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 ───────────────────────────────────────────────────────────────────────