feat: add syntax highlighting for markdown code blocks

Author: jamesbrink

lib/markdownToHtml.js

@@ -1,8 +1,48 @@
 import remark from 'remark'
 import html from 'remark-html'
 import gfm from 'remark-gfm'
+import { visit } from 'unist-util-visit'
+import prism from 'prismjs'
+
+// Load Prism languages
+require('prismjs/components/prism-bash')
+require('prismjs/components/prism-javascript')
+require('prismjs/components/prism-typescript')
+require('prismjs/components/prism-css')
+require('prismjs/components/prism-jsx')
+require('prismjs/components/prism-json')
+require('prismjs/components/prism-markdown')
+require('prismjs/components/prism-python')
+require('prismjs/components/prism-ruby')
+require('prismjs/components/prism-go')
+require('prismjs/components/prism-rust')
+require('prismjs/components/prism-yaml')
+require('prismjs/components/prism-nix')
+
+// Custom plugin to add syntax highlighting
+function syntaxHighlight() {
+  return (tree) => {
+    visit(tree, 'code', (node) => {
+      const lang = node.lang || '';
+      if (lang && prism.languages[lang]) {
+        node.type = 'html';
+        const highlighted = prism.highlight(
+          node.value,
+          prism.languages[lang],
+          lang
+        );
+        node.value = `<pre class="language-${lang}"><code class="language-${lang}">${highlighted}</code></pre>`;
+      }
+    });
+  };
+}
 
 export default async function markdownToHtml(markdown) {
-  const result = await remark().use(gfm).use(html).process(markdown)
-  return result.toString()
+  const result = await remark()
+    .use(gfm)
+    .use(syntaxHighlight)
+    .use(html, { sanitize: false })
+    .process(markdown);
+  
+  return result.toString();
 }

package.json

@@ -16,11 +16,18 @@
     "date-fns": "2.16.1",
     "gray-matter": "4.0.2",
     "next": "15.2.3",
+    "prismjs": "^1.30.0",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
+    "rehype-prism-plus": "^2.0.0",
+    "rehype-stringify": "^10.0.1",
     "remark": "13.0.0",
     "remark-gfm": "1.0.0",
-    "remark-html": "^13.0.2"
+    "remark-html": "^13.0.2",
+    "remark-parse": "^11.0.0",
+    "remark-rehype": "^11.1.1",
+    "unified": "^11.0.5",
+    "unist-util-visit": "^5.0.0"
   },
   "devDependencies": {
     "autoprefixer": "^10.2.1",

pages/_app.js

@@ -1,4 +1,5 @@
 import '../styles/index.css'
+import '../styles/prism.css'
 
 export default function MyApp({ Component, pageProps }) {
   return <Component {...pageProps} />

styles/prism.css

@@ -0,0 +1,145 @@
+/**
+ * Prism.js syntax highlighting styles
+ * Based on the default theme with some customizations
+ */
+
+code[class*="language-"],
+pre[class*="language-"] {
+  color: #f8f8f2;
+  background: none;
+  text-shadow: 0 1px rgba(0, 0, 0, 0.3);
+  font-family: Consolas, Monaco, 'Andale Mono', 'Ubuntu Mono', monospace;
+  font-size: 1em;
+  text-align: left;
+  white-space: pre;
+  word-spacing: normal;
+  word-break: normal;
+  word-wrap: normal;
+  line-height: 1.5;
+  -moz-tab-size: 4;
+  -o-tab-size: 4;
+  tab-size: 4;
+  -webkit-hyphens: none;
+  -moz-hyphens: none;
+  -ms-hyphens: none;
+  hyphens: none;
+}
+
+/* Code blocks */
+pre[class*="language-"] {
+  padding: 1em;
+  margin: .5em 0;
+  overflow: auto;
+  border-radius: 0.3em;
+}
+
+:not(pre) > code[class*="language-"],
+pre[class*="language-"] {
+  background: #282a36;
+}
+
+/* Inline code */
+:not(pre) > code[class*="language-"] {
+  padding: .1em;
+  border-radius: .3em;
+  white-space: normal;
+}
+
+.token.comment,
+.token.prolog,
+.token.doctype,
+.token.cdata {
+  color: #6272a4;
+}
+
+.token.punctuation {
+  color: #f8f8f2;
+}
+
+.namespace {
+  opacity: .7;
+}
+
+.token.property,
+.token.tag,
+.token.constant,
+.token.symbol,
+.token.deleted {
+  color: #ff79c6;
+}
+
+.token.boolean,
+.token.number {
+  color: #bd93f9;
+}
+
+.token.selector,
+.token.attr-name,
+.token.string,
+.token.char,
+.token.builtin,
+.token.inserted {
+  color: #50fa7b;
+}
+
+.token.operator,
+.token.entity,
+.token.url,
+.language-css .token.string,
+.style .token.string {
+  color: #f8f8f2;
+}
+
+.token.atrule,
+.token.attr-value,
+.token.keyword {
+  color: #ff79c6;
+}
+
+.token.function,
+.token.class-name {
+  color: #8be9fd;
+}
+
+.token.regex,
+.token.important,
+.token.variable {
+  color: #f1fa8c;
+}
+
+.token.important,
+.token.bold {
+  font-weight: bold;
+}
+
+.token.italic {
+  font-style: italic;
+}
+
+.token.entity {
+  cursor: help;
+}
+
+/* Line highlighting */
+.line-highlight {
+  background: rgba(255, 255, 255, 0.1);
+  border-left: 3px solid #ff79c6;
+}
+
+/* Line numbers */
+.line-numbers .line-numbers-rows {
+  border-right: 1px solid #44475a;
+}
+
+.line-numbers-rows > span:before {
+  color: #6272a4;
+}
+
+/* Command line */
+.command-line-prompt {
+  border-right: 1px solid #44475a;
+}
+
+.command-line-prompt > span:before {
+  color: #6272a4;
+}