core&ui: enhanced category selector

packages/hydrooj/src/handler/compat.ts

@@ -0,0 +1,11 @@
+import { Handler, Route } from '../service/server';
+
+class ProblemCategoryCompatHandler extends Handler {
+    async get({ category }) {
+        this.response.redirect = this.url('problem_main', { query: { q: `category:${category}` } });
+    }
+}
+
+global.Hydro.handler.compat = () => {
+    Route('problem_category_compat', '/p/category/:category', ProblemCategoryCompatHandler);
+};