core: support search by difficulty

packages/hydrooj/package.json

@@ -49,6 +49,7 @@
         "require-resolve-hook": "^1.1.0",
         "saslprep": "^1.0.3",
         "schemastery": "^3.11.1",
+        "search-query-parser": "^1.6.0",
         "semver": "^7.5.4",
         "serialize-javascript": "^6.0.1",
         "superagent": "^8.0.9",

packages/hydrooj/src/handler/problem.ts

@@ -5,6 +5,7 @@ import {
 } from 'lodash';
 import { Filter, ObjectId } from 'mongodb';
 import { nanoid } from 'nanoid';
+import parser from 'search-query-parser';
 import { sortFiles, streamToBuffer } from '@hydrooj/utils/lib/utils';
 import {
     BadRequestError, ContestNotAttendedError, ContestNotEndedError, ContestNotFoundError, ContestNotLiveError,
@@ -144,10 +145,17 @@ export class ProblemMainHandler extends Handler {
         let sort: string[];
         let fail = false;
         let pcountRelation = 'eq';
-        const category = flattenDeep(q.split(' ')
-            .filter((i) => i.startsWith('category:'))
-            .map((i) => i.split('category:')[1]?.split(',')));
-        const text = q.split(' ').filter((i) => !i.startsWith('category:')).join(' ');
+        const parsed = parser.parse(q, {
+            keywords: ['category', 'difficulty'],
+            offsets: false,
+            alwaysArray: true,
+            tokenize: true,
+        });
+        const category = parsed.category || [];
+        const text = (parsed.text || []).join(' ');
+        if (parsed.difficulty?.every((i) => Number.isSafeInteger(+i))) {
+            query.difficulty = { $in: parsed.difficulty.map(Number) };
+        }
         if (category.length) query.$and = category.map((tag) => ({ tag }));
         if (text) category.push(text);
         if (category.length) this.UiContext.extraTitleContent = category.join(',');
@@ -214,7 +222,6 @@ export class ProblemMainHandler extends Handler {
                 pcountRelation,
                 pdocs,
                 psdict,
-                category: category.join(','),
                 qs: q,
             };
         }

packages/ui-default/templates/problem_main.html

@@ -2,9 +2,6 @@
 {% import "components/problem.html" as problem with context %}
 {% extends "layout/basic.html" %}
 {% block content %}
-  {{ set(UiContext, {
-      currentCategory: category
-  }) }}
   <div class="row">
     <div class="medium-9 columns">
       <div class="section display-mode">