initial commit

app/api/categories/route.ts

@@ -0,0 +1,35 @@
+import { HttpError } from "@/lib/errors";
+import { readJson, route } from "@/lib/http";
+import { categoryCounts, mutatePosts, readPosts } from "@/lib/store";
+import { SLUG_RE } from "@/lib/validate";
+
+export const dynamic = "force-dynamic";
+
+export const GET = route(async () => {
+  const { posts, revision } = await readPosts();
+  return Response.json({ categories: categoryCounts(posts), revision });
+});
+
+/**
+ * Body: { from, to, revision? }. Moves every post in `from` to `to`; if `to`
+ * is already in use this is a merge. Categories are derived from posts, so a
+ * category disappears once no post uses it.
+ */
+export const PATCH = route(async (req) => {
+  const { from, to, revision: expected } = await readJson<{ from?: string; to?: string; revision?: string }>(req);
+  const target = to?.trim() ?? "";
+  if (!from) throw new HttpError(400, "from is required");
+  if (!SLUG_RE.test(target)) throw new HttpError(400, "category must be lowercase kebab-case");
+
+  const { result, revision } = await mutatePosts(expected, (posts) => {
+    let changed = 0;
+    for (const post of posts) {
+      if (post.category !== from) continue;
+      post.category = target;
+      changed++;
+    }
+    if (!changed) throw new HttpError(404, `no posts in category "${from}"`);
+    return changed;
+  });
+  return Response.json({ changed: result, revision });
+});