feat: added cache for css

eleventy.config.js

@@ -4,8 +4,26 @@ const markdownItFootnote = require("markdown-it-footnote");
 const markdownItMermaid = require('markdown-it-mermaid').default
 const syntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
 const fs = require("fs");
+const crypto = require("crypto");
+const path = require("path");
 const { DateTime } = require("luxon");
 
+const cssHashCache = {};
+const getCssHash = (cssFile) => {
+  if (cssHashCache[cssFile]) return cssHashCache[cssFile];
+  
+  const cssPath = path.join(__dirname, "css", cssFile);
+  try {
+    const content = fs.readFileSync(cssPath, "utf-8");
+    const hash = crypto.createHash("md5").update(content).digest("hex").slice(0, 8);
+    cssHashCache[cssFile] = hash;
+    return hash;
+  } catch (e) {
+    console.warn(`Could not hash CSS file: ${cssFile}`);
+    return null;
+  }
+};
+
 const extractTags = (content, mdInstance) => {
   if (!content) return [];
   
@@ -220,7 +238,36 @@ module.exports = (eleventyConfig) => {
     return tagMap;
   });
 
-  eleventyConfig.addPassthroughCopy("css");
+  // Cache busting filter: returns hashed CSS filename
+  eleventyConfig.addFilter("cssHash", (cssFile) => {
+    const hash = getCssHash(cssFile);
+    const ext = path.extname(cssFile);
+    const base = path.basename(cssFile, ext);
+    return `/css/${base}.${hash}${ext}`;
+  });
+
+  eleventyConfig.on("eleventy.before", async () => {
+    const cssDir = path.join(__dirname, "css");
+    const outputCssDir = path.join(__dirname, "_site", "css");
+    
+    if (!fs.existsSync(outputCssDir)) {
+      fs.mkdirSync(outputCssDir, { recursive: true });
+    }
+    
+    const cssFiles = fs.readdirSync(cssDir).filter(f => f.endsWith(".css"));
+    for (const cssFile of cssFiles) {
+      const hash = getCssHash(cssFile);
+      const ext = path.extname(cssFile);
+      const base = path.basename(cssFile, ext);
+      const hashedName = `${base}${hash == null ? '' : `.${hash}`}${ext}`;
+      
+      fs.copyFileSync(
+        path.join(cssDir, cssFile),
+        path.join(outputCssDir, hashedName)
+      );
+    }
+  });
+
   eleventyConfig.addPassthroughCopy("robots.txt");
 
   eleventyConfig.ignores.add("README.md");