feat: add missing lib file

lib/blog.ts

@@ -0,0 +1,35 @@
+import { readFileSync } from "fs";
+import { glob } from "glob";
+import matter from "gray-matter";
+import path from "path";
+
+const postsDirectory = path.join(process.cwd(), "posts");
+
+export function getAllTagsAndYears() {
+  const fileNames = glob.sync(`${postsDirectory}/**/*.md`);
+  const yearsSet = new Set<string>();
+  const tagsSet = new Set<string>();
+
+  fileNames.forEach((fileName) => {
+    const [id] = fileName.split("/").slice(-1);
+    const [year] = id.split("-");
+
+    // add year
+    yearsSet.add(year);
+
+    const filePath = path.join(postsDirectory, id);
+    const fileContents = readFileSync(filePath, "utf8");
+
+    const matterResult = matter(fileContents);
+
+    matterResult.data.tags.forEach((tag: string) => {
+      // add tag
+      tagsSet.add(tag);
+    });
+  });
+
+  return {
+    years: Array.from(yearsSet).sort((a, b) => Number(b) - Number(a)),
+    tags: Array.from(tagsSet).sort(),
+  };
+}