feat(nuldoc): implement syntax highlight

1 files changed, 31 insertions, 0 deletions

diff --git a/nuldoc-src/docbook/to_html.ts b/nuldoc-src/docbook/to_html.ts
index 64d3492..24be139 100644
--- a/nuldoc-src/docbook/to_html.ts
+++ b/nuldoc-src/docbook/to_html.ts
@@ -1,3 +1,5 @@
+import hljs from "hljs/highlight.min.js";
+import hljsPhp from "hljs/languages/php.min.js";
 import { Document } from "./document.ts";
 import { DocBookError } from "../errors.ts";
 import {
@@ -31,6 +33,7 @@ export default function toHtml(doc: Document): Document {
   transformNoteElement(doc);
   setDefaultLangAttribute(doc);
   traverseFootnotes(doc);
+  highlightPrograms(doc);
   return doc;
 }
 
@@ -277,3 +280,31 @@ function traverseFootnotes(doc: Document) {
     n.children = [];
   });
 }
+
+function highlightPrograms(doc: Document) {
+  forEachChildRecursively(doc.root, (n) => {
+    if (n.kind !== "element" || n.name !== "pre") {
+      return;
+    }
+    const preClass = n.attributes.get("class") || "";
+    if (!preClass.includes("highlight")) {
+      return;
+    }
+    const codeElement = findFirstChildElement(n, "code");
+    if (!codeElement) {
+      return;
+    }
+    const language = n.attributes.get("language");
+    if (!language) {
+      return;
+    }
+    const sourceCode = codeElement.children[0].content;
+
+    const validLanguage = hljs.getLanguage(language) ? language : "plaintext";
+    const highlighted =
+      hljs.highlight(sourceCode, { language: validLanguage }).value;
+
+    codeElement.children[0].content = highlighted;
+    codeElement.attributes.set("class", "highlight");
+  });
+}