feat: add methods to fetch post categories

config/collections/index.js

@@ -0,0 +1,32 @@
+const path = require("path");
+const { dir } = require("../constants.js");
+
+const getAllPosts = (collection) => {
+  const posts = collection.getFilteredByGlob(
+    path.join(dir.input, "content/posts/**/*.md"),
+  );
+  return posts.reverse();
+};
+
+const getAllPostCategories = (collection) => {
+  const posts = getAllPosts(collection);
+
+  const allCategories = posts.flatMap((post) => post.data.categories);
+
+  const categories = allCategories.reduce((acc, category) => {
+    if (acc[category]) {
+      acc[category]++;
+    } else {
+      acc[category] = 1;
+    }
+
+    return acc;
+  }, {});
+
+  return categories;
+};
+
+module.exports = {
+  getAllPosts,
+  getAllPostCategories,
+};