Add build support for linking to bibliographical references (#4124)

Refs #2535

This adds support to the Eleventy build system for resolving
bibliographical references within paragraphs in the format `[[ref]]`,
and converting them into links within single brackets instead.

This resolves against both specref.org and the local bibliography
configured in `biblio.js` in this repo.

Note that there are some references that have no resolution in either of
these sources, which is why I'm not marking this as fully resolving the
related issue.

Details at
#2535 (comment)

11ty/CustomLiquid.ts

@@ -8,6 +8,7 @@ import { basename } from "path";
 
 import type { GlobalData } from "eleventy.config";
 
+import { biblioPattern, getBiblio } from "./biblio";
 import { flattenDom, load } from "./cheerio";
 import { generateId } from "./common";
 import { getTermsMap } from "./guidelines";
@@ -21,6 +22,7 @@ const indexPattern = /(techniques|understanding)\/(index|about)\.html$/;
 const techniquesPattern = /\btechniques\//;
 const understandingPattern = /\bunderstanding\//;
 
+const biblio = await getBiblio();
 const termsMap = await getTermsMap();
 const termLinkSelector = "a:not([href])";
 
@@ -89,7 +91,7 @@ export class CustomLiquid extends Liquid {
       const isIndex = indexPattern.test(filepath);
       const isTechniques = techniquesPattern.test(filepath);
       const isUnderstanding = understandingPattern.test(filepath);
-      
+
       if (!isTechniques && !isUnderstanding) return super.parse(html);
 
       const $ = flattenDom(html, filepath);
@@ -507,7 +509,7 @@ export class CustomLiquid extends Liquid {
 				<p>${$el.html()}</p>
 			</div>`);
     });
-    
+
     // Add header to example sections in Key Terms (aside) and Conformance (div)
     $("aside.example, div.example").each((_, el) => {
       const $el = $(el);
@@ -540,6 +542,21 @@ export class CustomLiquid extends Liquid {
       });
     }
 
+    // Link biblio references
+    if (scope.isUnderstanding) {
+      $("p").each((_, el) => {
+        const $el = $(el);
+        const html = $el.html();
+        if (html && biblioPattern.test(html)) {
+          $el.html(
+            html.replace(biblioPattern, (substring, code) =>
+              biblio[code]?.href ? `[<a href="${biblio[code].href}">${code}</a>]` : substring
+            )
+          );
+        }
+      });
+    }
+
     // Allow autogenerating missing top-level section IDs in understanding docs,
     // but don't pick up incorrectly-nested sections in some techniques pages (e.g. H91)
     const sectionSelector = scope.isUnderstanding ? "section" : "section[id]:not(.obsolete)";

11ty/biblio.ts

@@ -0,0 +1,35 @@
+import axios from "axios";
+import { readFile } from "fs/promises";
+import { glob } from "glob";
+import uniq from "lodash-es/uniq";
+
+export const biblioPattern = /\[\[\??([\w-]+)\]\]/g;
+
+/** Compiles URLs from local biblio + specref for linking in Understanding documents. */
+export async function getBiblio() {
+  const localBiblio = eval(
+    (await readFile("biblio.js", "utf8"))
+      .replace(/^respecConfig\.localBiblio\s*=\s*/, "(")
+      .replace("};", "})")
+  );
+
+  const refs: string[] = [];
+  for (const path of await glob(["guidelines/**/*.html", "understanding/*/*.html"])) {
+    const content = await readFile(path, "utf8");
+    let match;
+    while ((match = biblioPattern.exec(content))) if (!localBiblio[match[1]]) refs.push(match[1]);
+  }
+  const uniqueRefs = uniq(refs);
+
+  const response = await axios.get(`https://api.specref.org/bibrefs?refs=${uniqueRefs.join(",")}`);
+  const fullBiblio = {
+    ...response.data,
+    ...localBiblio,
+  };
+
+  const resolvedRefs = Object.keys(fullBiblio);
+  const unresolvedRefs = uniqueRefs.filter((ref) => !resolvedRefs.includes(ref));
+  if (unresolvedRefs.length) console.warn(`Unresolved biblio refs: ${unresolvedRefs.join(", ")}`);
+
+  return fullBiblio;
+}