Lady’s Gitweb - GitWikiWeb/blob - build.js

   1 // 🐙🕸️ GitWikiWeb ∷ build.js
   2 // ====================================================================
   3 //
   4 // Copyright © 2023 Lady [@ Lady’s Computer].
   5 //
   6 // This Source Code Form is subject to the terms of the Mozilla Public
   7 // License, v. 2.0. If a copy of the MPL was not distributed with this
   8 // file, You can obtain one at <https://mozilla.org/MPL/2.0/>.
   9 //
  10 // --------------------------------------------------------------------
  11 //
  12 // A script for generating static wiki pages from a git repository.
  13 //
  14 // First, clone this repository to your machine in an accessible
  15 // location (for example, `/srv/git/GitWikiWeb`). A bare repository is
  16 // fine; customize the templates and stylesheets as you like. Then, use
  17 // this file as the post‐receive hook for your wiki as follows :—
  18 //
  19 //     #!/usr/bin/env -S sh
  20 //     export GITWIKIWEB=/srv/git/GitWikiWeb
  21 //     git archive --remote=$GITWIKIWEB HEAD build.js \
  22 //       | tar -xO \
  23 //       | deno run -A - ~/public/wiki $GITWIKIWEB
  24 //
  25 // The directory `~/public/wiki` (or whatever you specify as the first
  26 // argument to `deno run -A -`) **will be deleted** and a new static
  27 // wiki will be generated in its place. This script is not very smart
  28 // (yet) and cannot selectively determine which pages will need
  29 // updating. It just wipes and regenerates the whole thing.
  30 //
  31 // This script will make a number of requests to `$GITWIKIWEB` to
  32 // download the latest templates, stylesheets, ⁊·c from this
  33 // repository. Consequently, it is best that you set it to a repository
  34 // you control and can ensure uptime for—ideally one local to the
  35 // computer hosting the wiki.
  36
  37 import {
  38   emptyDir,
  39   ensureDir,
  40 } from "https://deno.land/std@0.195.0/fs/mod.ts";
  41 import djot from "npm:@djot/djot@0.2.3";
  42 import { Parser } from "npm:htmlparser2@9.0.0";
  43 import { DomHandler, Element, Text } from "npm:domhandler@5.0.3";
  44 import * as domutils from "npm:domutils@3.1.0";
  45 import domSerializer from "npm:dom-serializer@2.0.0";
  46
  47 const DESTINATION = Deno.args[0] ?? "~/public/wiki";
  48 const REMOTE = Deno.args[1] ?? "/srv/git/GitWikiWeb";
  49
  50 const READ_ONLY = {
  51   configurable: false,
  52   enumerable: true,
  53   writable: false,
  54 };
  55
  56 const rawBlock = (strings, ...substitutions) => ({
  57   tag: "raw_block",
  58   format: "html",
  59   text: String.raw(strings, substitutions),
  60 });
  61 const rawInline = (strings, ...substitutions) => ({
  62   tag: "raw_inline",
  63   format: "html",
  64   text: String.raw(strings, substitutions),
  65 });
  66 const str = (strings, ...substitutions) => ({
  67   tag: "str",
  68   text: String.raw(strings, substitutions),
  69 });
  70
  71 const getDOM = (source) => {
  72   let result;
  73   const handler = new DomHandler((error, dom) => {
  74     if (error) {
  75       throw new Error("GitWikiWeb: Failed to process DOM.", {
  76         cause: error,
  77       });
  78     } else {
  79       result = dom;
  80     }
  81   });
  82   const parser = new Parser(handler);
  83   parser.write(source);
  84   parser.end();
  85   return result;
  86 };
  87
  88 const getRemoteContent = async (pathName) => {
  89   const getArchive = new Deno.Command("git", {
  90     args: ["archive", `--remote=${REMOTE}`, "HEAD", pathName],
  91     stdout: "piped",
  92     stderr: "piped",
  93   }).spawn();
  94   const untar = new Deno.Command("tar", {
  95     args: ["-xO"],
  96     stdin: "piped",
  97     stdout: "piped",
  98     stderr: "piped",
  99   }).spawn();
 100   getArchive.stdout.pipeTo(untar.stdin);
 101   const [
 102     err1,
 103     getArchiveStatus,
 104     result,
 105     err2,
 106     untarStatus,
 107   ] = await Promise.allSettled([
 108     new Response(getArchive.stderr).text(),
 109     getArchive.status,
 110     new Response(untar.stdout).text(),
 111     new Response(untar.stderr).text(),
 112     untar.status,
 113   ]).then(logErrorsAndCollectResults);
 114   if (err1 || err2) {
 115     console.error(err1 + err2);
 116   } else {
 117     /* do nothing */
 118   }
 119   if (!getArchiveStatus.success) {
 120     throw new Error(
 121       `GitWikiWeb: git archive returned nonzero exit code: ${getArchiveStatus.code}.`,
 122     );
 123   } else if (!untarStatus.success) {
 124     throw new Error(
 125       `GitWikiWeb: tar returned nonzero exit code: ${untarStatus.code}.`,
 126     );
 127   } else {
 128     return result || "";
 129   }
 130 };
 131
 132 const logErrorsAndCollectResults = (results) =>
 133   results.map(({ value, reason }) => {
 134     if (reason) {
 135       console.error(reason);
 136       return undefined;
 137     } else {
 138       return value;
 139     }
 140   });
 141
 142 const getReferenceFromPath = (path) =>
 143   /Sources\/([A-Z][0-9A-Za-z]*\/[A-Z][0-9A-Za-z]*)\.djot$/u.exec(path)
 144     ?.[1]?.replace?.("/", ":");
 145
 146 const listOfInternalLinks = (references, wrapper = ($) => $) => ({
 147   tag: "bullet_list",
 148   tight: true,
 149   style: "*",
 150   children: Array.from(
 151     references,
 152     (reference) => {
 153       const [namespace, pageName] = splitReference(reference);
 154       return {
 155         tag: "list_item",
 156         children: [{
 157           tag: "para",
 158           children: [wrapper({
 159             tag: "link",
 160             attributes: {
 161               "data-realm": "internal",
 162               "data-pagename": pageName,
 163               "data-namespace": namespace,
 164             },
 165             reference,
 166             children: [],
 167           })],
 168         }],
 169       };
 170     },
 171   ),
 172 });
 173
 174 const diffReferences = async (hash) => {
 175   const diff = new Deno.Command("git", {
 176     args: [
 177       "diff-tree",
 178       "-r",
 179       "-z",
 180       "--name-only",
 181       "--no-renames",
 182       "--diff-filter=AM",
 183       hash,
 184     ],
 185     stdout: "piped",
 186     stderr: "piped",
 187   }).spawn();
 188   const [diffNames] = await Promise.allSettled([
 189     new Response(diff.stdout).text(),
 190     new Response(diff.stderr).text(),
 191   ]).then(logErrorsAndCollectResults);
 192   return references(diffNames.split("\0")); // returns an iterable
 193 };
 194
 195 function* references(paths) {
 196   for (const path of paths) {
 197     const reference = getReferenceFromPath(path);
 198     if (reference) {
 199       yield reference;
 200     } else {
 201       /* do nothing */
 202     }
 203   }
 204 }
 205
 206 const splitReference = (reference) => {
 207   const colonIndex = reference.indexOf(":");
 208   return [
 209     reference.substring(0, colonIndex),
 210     reference.substring(colonIndex + 1),
 211   ];
 212 };
 213
 214 class GitWikiWebPage {
 215   #internalLinks = new Set();
 216   #externalLinks = new Map();
 217
 218   constructor(namespace, name, ast, source) {
 219     const internalLinks = this.#internalLinks;
 220     const externalLinks = this.#externalLinks;
 221     const sections = Object.create(null);
 222     djot.applyFilter(ast, () => {
 223       let titleSoFar = null; // used to collect strs from headings
 224       return {
 225         doc: {
 226           enter: (_) => {},
 227           exit: (e) => {
 228             const links_section = [];
 229             if (internalLinks.size || externalLinks.size) {
 230               links_section.push(
 231                 rawBlock`<footer>`,
 232                 rawBlock`<nav id="links">`,
 233                 {
 234                   tag: "heading",
 235                   level: 2,
 236                   children: [str`this page contains links`],
 237                 },
 238               );
 239               if (internalLinks.size) {
 240                 links_section.push(
 241                   rawBlock`<details open="">`,
 242                   rawBlock`<summary>on this wiki</summary>`,
 243                   listOfInternalLinks(internalLinks),
 244                   rawBlock`</details>`,
 245                 );
 246               } else {
 247                 /* do nothing */
 248               }
 249               if (externalLinks.size) {
 250                 links_section.push(
 251                   rawBlock`<details open="">`,
 252                   rawBlock`<summary>elsewhere on the Web</summary>`,
 253                   {
 254                     tag: "bullet_list",
 255                     tight: true,
 256                     style: "*",
 257                     children: Array.from(
 258                       externalLinks,
 259                       ([destination, text]) => ({
 260                         tag: "list_item",
 261                         children: [{
 262                           tag: "para",
 263                           children: [{
 264                             tag: "link",
 265                             attributes: { "data-realm": "external" },
 266                             destination,
 267                             children: text
 268                               ? [
 269                                 rawInline`<cite>`,
 270                                 str`${text}`,
 271                                 rawInline`</cite>`,
 272                               ]
 273                               : [
 274                                 rawInline`<code>`,
 275                                 str`${destination}`,
 276                                 rawInline`</code>`,
 277                               ],
 278                           }],
 279                         }],
 280                       }),
 281                     ),
 282                   },
 283                   rawBlock`</details>`,
 284                 );
 285               } else {
 286                 /* do nothing */
 287               }
 288               links_section.push(
 289                 rawBlock`</nav>`,
 290                 rawBlock`</footer>`,
 291               );
 292             } else {
 293               /* do nothing */
 294             }
 295             e.children.push(...links_section);
 296           },
 297         },
 298         hard_break: {
 299           enter: (_) => {
 300             if (titleSoFar != null) {
 301               titleSoFar += " ";
 302             } else {
 303               /* do nothing */
 304             }
 305           },
 306           exit: (_) => {},
 307         },
 308         heading: {
 309           enter: (_) => {
 310             titleSoFar = "";
 311           },
 312           exit: (e) => {
 313             e.attributes ??= {};
 314             const { attributes } = e;
 315             attributes.title ??= titleSoFar;
 316             titleSoFar = null;
 317           },
 318         },
 319         link: {
 320           enter: (e) => {
 321             e.attributes ??= {};
 322             const { attributes, reference, destination } = e;
 323             if (
 324               /^(?:[A-Z][0-9A-Za-z]*|[@#])?:(?:[A-Z][0-9A-Za-z]*)?$/u
 325                 .test(reference ?? "")
 326             ) {
 327               const [namespacePrefix, pageName] = splitReference(
 328                 reference,
 329               );
 330               const expandedNamespace = {
 331                 "": "Page",
 332                 "@": "Editor",
 333                 "#": "Category",
 334               }[namespacePrefix] ?? namespacePrefix;
 335               const resolvedReference = pageName == ""
 336                 ? `Namespace:${expandedNamespace}`
 337                 : `${expandedNamespace}:${pageName}`;
 338               this.#internalLinks.add(resolvedReference);
 339               e.reference = resolvedReference;
 340               attributes["data-realm"] = "internal";
 341               attributes["data-pagename"] = pageName;
 342               attributes["data-namespace"] = expandedNamespace;
 343             } else {
 344               attributes["data-realm"] = "external";
 345               const remote = destination ??
 346                 ast.references[reference]?.destination;
 347               if (remote) {
 348                 externalLinks.set(remote, attributes?.title);
 349               } else {
 350                 /* do nothing */
 351               }
 352             }
 353           },
 354         },
 355         non_breaking_space: {
 356           enter: (_) => {
 357             if (titleSoFar != null) {
 358               titleSoFar += "\xA0";
 359             } else {
 360               /* do nothing */
 361             }
 362           },
 363           exit: (_) => {},
 364         },
 365         section: {
 366           enter: (_) => {},
 367           exit: (e) => {
 368             e.attributes ??= {};
 369             const { attributes, children } = e;
 370             const heading = children.find(({ tag }) =>
 371               tag == "heading"
 372             );
 373             const title = (() => {
 374               if (heading?.attributes?.title) {
 375                 const result = heading.attributes.title;
 376                 delete heading.attributes.title;
 377                 return result;
 378               } else {
 379                 return heading.level == 1
 380                   ? `${namespace}:${name}`
 381                   : "untitled section";
 382               }
 383             })();
 384             const variantTitles = Object.create(null);
 385             for (const attr in attributes) {
 386               if (attr.startsWith("v-")) {
 387                 Object.defineProperty(
 388                   variantTitles,
 389                   attr.substring(2),
 390                   { ...READ_ONLY, value: attributes[attr] },
 391                 );
 392                 delete attributes[attr];
 393               } else {
 394                 continue;
 395               }
 396             }
 397             const definition = Object.create(null, {
 398               title: { ...READ_ONLY, value: title },
 399               variantTitles: {
 400                 ...READ_ONLY,
 401                 value: Object.preventExtensions(variantTitles),
 402               },
 403             });
 404             if (heading.level == 1 && !("main" in sections)) {
 405               attributes.id = "main";
 406               heading.attributes ??= {};
 407               heading.attributes.class = "main";
 408             } else {
 409               /* do nothing */
 410             }
 411             try {
 412               Object.defineProperty(
 413                 sections,
 414                 attributes.id,
 415                 {
 416                   ...READ_ONLY,
 417                   writable: true,
 418                   value: Object.preventExtensions(definition),
 419                 },
 420               );
 421             } catch (cause) {
 422               throw new Error(
 423                 `GitWikiWeb: A section with the provided @id already exists: ${attributes.id}`,
 424                 { cause },
 425               );
 426             }
 427           },
 428         },
 429         soft_break: {
 430           enter: (_) => {
 431             if (titleSoFar != null) {
 432               titleSoFar += " ";
 433             } else {
 434               /* do nothing */
 435             }
 436           },
 437           exit: (_) => {},
 438         },
 439         str: {
 440           enter: ({ text }) => {
 441             if (titleSoFar != null) {
 442               titleSoFar += text;
 443             } else {
 444               /* do nothing */
 445             }
 446           },
 447           exit: (_) => {},
 448         },
 449       };
 450     });
 451     Object.defineProperties(this, {
 452       ast: { ...READ_ONLY, value: ast },
 453       namespace: { ...READ_ONLY, value: namespace },
 454       name: { ...READ_ONLY, value: name },
 455       sections: {
 456         ...READ_ONLY,
 457         value: Object.preventExtensions(sections),
 458       },
 459       source: { ...READ_ONLY, value: source },
 460     });
 461   }
 462
 463   *externalLinks() {
 464     yield* this.#externalLinks;
 465   }
 466
 467   *internalLinks() {
 468     yield* this.#internalLinks;
 469   }
 470 }
 471
 472 {
 473   const ls = new Deno.Command("git", {
 474     args: ["ls-tree", "-rz", "live"],
 475     stdout: "piped",
 476     stderr: "piped",
 477   }).spawn();
 478   const [
 479     objects,
 480     lserr,
 481     lsstatus,
 482   ] = await Promise.allSettled([
 483     new Response(ls.stdout).text().then((lsout) =>
 484       lsout
 485         .split("\0")
 486         .slice(0, -1) // drop the last entry; it is empty
 487         .map(($) => $.split(/\s+/g))
 488     ),
 489     new Response(ls.stderr).text(),
 490     ls.status,
 491   ]).then(logErrorsAndCollectResults);
 492   if (lserr) {
 493     console.error(lserr);
 494   } else {
 495     /* do nothing */
 496   }
 497   if (!lsstatus.success) {
 498     throw new Error(
 499       `GitWikiWeb: git ls-tree returned nonzero exit code: ${lsstatus.code}.`,
 500     );
 501   } else {
 502     const requiredButMissingPages = new Map([
 503       ["Special:FrontPage", "front page"],
 504       ["Special:NotFound", "not found"],
 505       ["Special:RecentlyChanged", "recently changed"],
 506     ]);
 507     const pages = new Map();
 508     const promises = [emptyDir(DESTINATION)];
 509     for (const object of objects) {
 510       const hash = object[2];
 511       const path = object[3];
 512       const reference = getReferenceFromPath(path);
 513       if (reference == null) {
 514         continue;
 515       } else {
 516         const [namespace, pageName] = splitReference(reference);
 517         const cat = new Deno.Command("git", {
 518           args: ["cat-file", "blob", hash],
 519           stdout: "piped",
 520           stderr: "piped",
 521         }).spawn();
 522         const promise = Promise.allSettled([
 523           new Response(cat.stdout).text(),
 524           new Response(cat.stderr).text(),
 525           cat.status,
 526         ]).then(logErrorsAndCollectResults).then(
 527           ([source, caterr, catstatus]) => {
 528             if (caterr) {
 529               console.error(caterr);
 530             } else {
 531               /* do nothing */
 532             }
 533             if (!catstatus.success) {
 534               throw new Error(
 535                 `GitWikiWeb: git cat-file returned nonzero exit code: ${catstatus.code}.`,
 536               );
 537             } else {
 538               const page = new GitWikiWebPage(
 539                 namespace,
 540                 pageName,
 541                 djot.parse(source, {
 542                   warn: ($) =>
 543                     console.warn(`Djot(${reference}): ${$.render()}`),
 544                 }),
 545                 source,
 546               );
 547               const reference = `${namespace}:${pageName}`;
 548               pages.set(reference, page);
 549               requiredButMissingPages.delete(reference);
 550             }
 551           },
 552         );
 553         promises.push(promise);
 554       }
 555     }
 556     for (const [reference, defaultTitle] of requiredButMissingPages) {
 557       const [namespace, pageName] = splitReference(reference);
 558       const source = `# ${defaultTitle}\n`;
 559       const page = new GitWikiWebPage(
 560         namespace,
 561         pageName,
 562         djot.parse(source, {
 563           warn: ($) =>
 564             console.warn(`Djot(${reference}): ${$.render()}`),
 565         }),
 566         source,
 567       );
 568       pages.set(reference, page);
 569     }
 570     await Promise.allSettled(promises).then(
 571       logErrorsAndCollectResults,
 572     );
 573     const [template, recentlyChanged] = await Promise.allSettled([
 574       getRemoteContent("template.html"),
 575       (async () => {
 576         const dateParse = new Deno.Command("git", {
 577           args: ["rev-parse", "--after=1 week ago"],
 578           stdout: "piped",
 579           stderr: "piped",
 580         }).spawn();
 581         const [maxAge] = await Promise.allSettled([
 582           new Response(dateParse.stdout).text(),
 583           new Response(dateParse.stderr).text(),
 584         ]).then(logErrorsAndCollectResults);
 585         let commit;
 586         if (!maxAge) {
 587           /* do nothing */
 588         } else {
 589           const revList = new Deno.Command("git", {
 590             args: ["rev-list", maxAge, "--reverse", "HEAD"],
 591             stdout: "piped",
 592             stderr: "piped",
 593           }).spawn();
 594           [commit] = await Promise.allSettled([
 595             new Response(revList.stdout).text().then((list) =>
 596               list.split("\n")[0]
 597             ),
 598             new Response(revList.stderr).text(),
 599           ]).then(logErrorsAndCollectResults);
 600         }
 601         if (!commit) {
 602           const revList2 = new Deno.Command("git", {
 603             args: ["rev-list", "--max-count=1", "HEAD^"],
 604             stdout: "piped",
 605             stderr: "piped",
 606           }).spawn();
 607           [commit] = await Promise.allSettled([
 608             new Response(revList2.stdout).text().then((list) =>
 609               list.trim()
 610             ),
 611             new Response(revList2.stderr).text(),
 612           ]).then(logErrorsAndCollectResults);
 613         } else {
 614           /* do nothing */
 615         }
 616         const results = new Array(6);
 617         const seen = new Set();
 618         let recency = 5;
 619         let current;
 620         do {
 621           const show = new Deno.Command("git", {
 622             args: [
 623               "show",
 624               "-s",
 625               "--format=%H%x00%cI%x00%cD",
 626               recency ? `HEAD~${5 - recency}` : commit,
 627             ],
 628             stdout: "piped",
 629             stderr: "piped",
 630           }).spawn();
 631           const [
 632             [hash, dateTime, humanReadable],
 633           ] = await Promise.allSettled([
 634             new Response(show.stdout).text().then((rev) =>
 635               rev.trim().split("\0")
 636             ),
 637             new Response(show.stderr).text(),
 638           ]).then(logErrorsAndCollectResults);
 639           const refs = [];
 640           current = hash;
 641           for (const ref of (await diffReferences(current))) {
 642             if (seen.has(ref)) {
 643               /* do nothing */
 644             } else {
 645               refs.push(ref);
 646               seen.add(ref);
 647             }
 648           }
 649           results[recency] = { dateTime, humanReadable, refs };
 650         } while (recency-- > 0 && current && current != commit);
 651         return results;
 652       })(),
 653       ...Array.from(
 654         pages.keys(),
 655         (name) => ensureDir(`${DESTINATION}/${name}`),
 656       ),
 657       ["style.css"].map((dependency) =>
 658         getRemoteContent(dependency).then((source) =>
 659           Deno.writeTextFile(
 660             `${DESTINATION}/${dependency}`,
 661             source,
 662             { createNew: true },
 663           )
 664         )
 665       ),
 666     ]).then(logErrorsAndCollectResults);
 667     promises.length = 0;
 668     const redLinks = (() => {
 669       const result = new Set();
 670       for (const page of pages.values()) {
 671         for (const link of page.internalLinks()) {
 672           if (pages.has(link)) {
 673             continue;
 674           } else {
 675             result.add(link);
 676           }
 677         }
 678       }
 679       return result;
 680     })();
 681     for (
 682       const [pageRef, { ast, namespace, sections, source }] of pages
 683     ) {
 684       const title = sections.main?.title ?? pageRef;
 685       djot.applyFilter(ast, () => {
 686         let isNavigationPage = true;
 687         return {
 688           doc: {
 689             enter: (e) => {
 690               const { content, navigation } = (() => {
 691                 const navigation = [];
 692                 if (pageRef == "Special:RecentlyChanged") {
 693                   navigation.push({
 694                     tag: "bullet_list",
 695                     attributes: { class: "recent-changes" },
 696                     tight: true,
 697                     style: "*",
 698                     children: Array.from(function* () {
 699                       for (
 700                         const [index, result] of recentlyChanged
 701                           .entries()
 702                       ) {
 703                         if (result != null) {
 704                           const {
 705                             dateTime,
 706                             humanReadable,
 707                             refs,
 708                           } = result;
 709                           yield* listOfInternalLinks(refs, (link) => ({
 710                             tag: index ? "strong" : "span",
 711                             attributes: { "data-recency": `${index}` },
 712                             children: [
 713                               link,
 714                               str` `,
 715                               rawInline`<small>(<time dateTime="${dateTime}">`,
 716                               str`${humanReadable}`,
 717                               rawInline`</time>)</small>`,
 718                             ],
 719                           })).children;
 720                         } else {
 721                           /* do nothing */
 722                         }
 723                       }
 724                     }()).reverse(),
 725                   });
 726                 } else {
 727                   isNavigationPage = false;
 728                   return { content: e.children, navigation };
 729                 }
 730                 return {
 731                   content: [
 732                     {
 733                       tag: "heading",
 734                       attributes: {
 735                         class: "main",
 736                         generated: "", // will be removed later
 737                       },
 738                       level: 1,
 739                       children: [str`${title}`],
 740                     },
 741                     rawBlock`<details id="navigation-about" open="">`,
 742                     rawBlock`<summary>about this listing</summary>`,
 743                     rawBlock`<article>`,
 744                     ...e.children,
 745                     rawBlock`</article>`,
 746                     rawBlock`</details>`,
 747                   ],
 748                   navigation: [
 749                     rawBlock`<nav id="navigation">`,
 750                     ...navigation,
 751                     rawBlock`</nav>`,
 752                   ],
 753                 };
 754               })();
 755               e.children = [
 756                 rawBlock`<article>`,
 757                 ...content,
 758                 ...navigation,
 759                 rawBlock`</article>`,
 760               ];
 761             },
 762             exit: (_) => {},
 763           },
 764           heading: {
 765             enter: (e) => {
 766               const attributes = e.attributes ?? Object.create(null);
 767               if (
 768                 isNavigationPage && e.level == 1 &&
 769                 attributes?.class == "main"
 770               ) {
 771                 if ("generated" in attributes) {
 772                   delete attributes.generated;
 773                 } else {
 774                   return { stop: [] };
 775                 }
 776               } else {
 777                 /* do nothing */
 778               }
 779             },
 780             exit: (e) => {
 781               if (e.level == 1 && e.attributes?.class == "main") {
 782                 return [
 783                   rawBlock`<header class="main">`,
 784                   e,
 785                   { tag: "verbatim", text: pageRef },
 786                   rawBlock`</header>`,
 787                 ];
 788               } else {
 789                 /* do nothing */
 790               }
 791             },
 792           },
 793           link: {
 794             enter: (_) => {},
 795             exit: (e) => {
 796               e.attributes ??= {};
 797               const { attributes, children, reference } = e;
 798               if (attributes["data-realm"] == "internal") {
 799                 delete e.reference;
 800                 if (redLinks.has(reference)) {
 801                   e.destination =
 802                     `/Special:NotFound?path=/${reference}`;
 803                   attributes["data-notfound"] = "";
 804                 } else {
 805                   e.destination = `/${reference}`;
 806                 }
 807                 if (children.length == 0) {
 808                   const section =
 809                     pages.get(reference)?.sections?.main ??
 810                       Object.create(null);
 811                   const { v } = attributes;
 812                   if (v == null) {
 813                     children.push(
 814                       str`${section.title ?? reference}`,
 815                     );
 816                   } else {
 817                     delete attributes.v;
 818                     children.push(
 819                       str`${
 820                         section.variantTitles?.[v] ?? section.title ??
 821                           reference
 822                       }`,
 823                     );
 824                   }
 825                 }
 826               } else {
 827                 if (children.length == 0 && "title" in attributes) {
 828                   children.push(
 829                     rawInline`<cite>`,
 830                     str`${attributes.title}`,
 831                     rawInline`</cite>`,
 832                   );
 833                 }
 834               }
 835               if (
 836                 (attributes.class ?? "").split(/\s/gu).includes("sig")
 837               ) {
 838                 return {
 839                   tag: "span",
 840                   attributes: { class: "sig" },
 841                   children: [str`—${"\xA0"}`, e],
 842                 };
 843               } else {
 844                 /* do nothing */
 845               }
 846             },
 847           },
 848           section: {
 849             enter: (_) => {},
 850             exit: (e) => {
 851               if (e.children.length < 1) {
 852                 // The heading for this section was removed and it had
 853                 // no other children.
 854                 return [];
 855               } else {
 856                 /* do nothing */
 857               }
 858             },
 859           },
 860         };
 861       });
 862       const doc = getDOM(template);
 863       const result = getDOM(`${djot.renderHTML(ast)}`);
 864       const headElement = domutils.findOne(
 865         (node) => node.name == "head",
 866         doc,
 867       );
 868       const titleElement = domutils.findOne(
 869         (node) => node.name == "title",
 870         headElement,
 871       );
 872       const contentElement = domutils.findOne(
 873         (node) => node.name == "gitwikiweb-content",
 874         doc,
 875       );
 876       if (headElement == null) {
 877         throw new Error(
 878           "GitWikiWeb: Template must explicitly include a <head> element.",
 879         );
 880       } else {
 881         domutils.appendChild(
 882           headElement,
 883           new Element("link", {
 884             rel: "source",
 885             type: "text/x.djot",
 886             href: `/${pageRef}/source.djot`,
 887           }),
 888         );
 889         if (titleElement == null) {
 890           domutils.prependChild(
 891             headElement,
 892             new Element("title", {}, [new Text(title)]),
 893           );
 894         } else {
 895           domutils.prependChild(titleElement, new Text(`${title} | `));
 896         }
 897       }
 898       if (contentElement == null) {
 899         throw new Error(
 900           "GitWikiWeb: Template did not include a <gitwikiweb-content> element.",
 901         );
 902       } else {
 903         for (const node of result) {
 904           domutils.prepend(contentElement, node);
 905         }
 906         domutils.removeElement(contentElement);
 907       }
 908       promises.push(
 909         Deno.writeTextFile(
 910           `${DESTINATION}/${pageRef}/index.html`,
 911           domSerializer(doc, {
 912             emptyAttrs: true,
 913             encodeEntities: "utf8",
 914             selfClosingTags: true,
 915             xmlMode: false,
 916           }),
 917           { createNew: true },
 918         ),
 919       );
 920       promises.push(
 921         Deno.writeTextFile(
 922           `${DESTINATION}/${pageRef}/source.djot`,
 923           source,
 924           { createNew: true },
 925         ),
 926       );
 927     }
 928     await Promise.allSettled(promises).then(
 929       logErrorsAndCollectResults,
 930     );
 931     console.log(`GitWikiWeb: Wrote ${pages.size} page(s).`);
 932   }
 933 }