diff --git a/packages/hydrooj/package.json b/packages/hydrooj/package.json
index 2938e6ce1..e260acf27 100644
--- a/packages/hydrooj/package.json
+++ b/packages/hydrooj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "2.13.4",
+    "version": "2.13.5",
     "bin": "bin/hydrooj.js",
     "main": "dist/loader.js",
     "typings": "dist/loader.d.ts",
diff --git a/packages/hydrooj/src/handler/home.ts b/packages/hydrooj/src/handler/home.ts
index d165dcf88..3cd48a476 100644
--- a/packages/hydrooj/src/handler/home.ts
+++ b/packages/hydrooj/src/handler/home.ts
@@ -159,7 +159,7 @@ class HomeSecurityHandler extends Handler {
         if (udoc) throw new UserAlreadyExistError(email);
         const [code] = await token.add(
             token.TYPE_CHANGEMAIL,
-            await system.get('changemail_token_expire_seconds'),
+            await system.get('changemail_token_expire_seconds') as number,
             { uid: this.user._id, email },
         );
         const m = await this.renderHTML('user_changemail_mail.html', {
diff --git a/packages/hydrooj/src/handler/training.ts b/packages/hydrooj/src/handler/training.ts
index a18c01560..5cf626250 100644
--- a/packages/hydrooj/src/handler/training.ts
+++ b/packages/hydrooj/src/handler/training.ts
@@ -13,10 +13,10 @@ import {
 } from '../service/server';
 import { Tdoc } from '../interface';
 
-async function _parseDagJson(domainId, dag) {
+async function _parseDagJson(domainId: string, _dag: string): Promise<Tdoc['dag']> {
     const parsed = [];
     try {
-        dag = JSON.parse(dag);
+        const dag = JSON.parse(_dag);
         assert(dag instanceof Array, 'dag must be an array');
         const ids = new Set(dag.map((s) => s._id));
         assert(dag.length === ids.size, '_id must be unique');
@@ -177,16 +177,6 @@ class TrainingCreateHandler extends Handler {
         const pids = training.getPids(dag);
         assert(pids.length, new ValidationError('dag'));
         const pdocs = await problem.getMulti(domainId, { docId: { $in: pids } }).sort('_id', 1).toArray();
-        const existPids = pdocs.map((pdoc) => pdoc.docId);
-        const existPnames = pdocs.map((pdoc) => pdoc.pid);
-        if (pids.length !== existPids.length) {
-            for (const pid of pids) {
-                assert(
-                    existPids.includes(pid) || existPnames.includes(pid),
-                    new ProblemNotFoundError(pid),
-                );
-            }
-        }
         for (const pdoc of pdocs) {
             if (pdoc.hidden) this.checkPerm(PERM.PERM_VIEW_PROBLEM_HIDDEN);
         }
@@ -242,11 +232,10 @@ class TrainingEditHandler extends Handler {
             ],
         }).sort('_id', 1).toArray();
         const existPids = pdocs.map((pdoc) => pdoc.docId);
-        const existPnames = pdocs.map((pdoc) => pdoc.pid);
         if (pids.length !== existPids.length) {
             for (const pid in pids) {
                 assert(
-                    existPids.includes(pid) || existPnames.includes(pid),
+                    existPids.includes(parseInt(pid, 10)),
                     new ProblemNotFoundError(pid),
                 );
             }
diff --git a/packages/hydrooj/src/handler/user.ts b/packages/hydrooj/src/handler/user.ts
index bcb6b2fe2..2545975b8 100644
--- a/packages/hydrooj/src/handler/user.ts
+++ b/packages/hydrooj/src/handler/user.ts
@@ -62,7 +62,7 @@ class UserRegisterHandler extends Handler {
         this.limitRate('send_mail', 3600, 30);
         const t = await token.add(
             token.TYPE_REGISTRATION,
-            await system.get('registration_token_expire_seconds'),
+            await system.get('registration_token_expire_seconds') as number,
             { mail },
         );
         if (await system.get('smtp.user')) {
@@ -118,7 +118,7 @@ class UserLostPassHandler extends Handler {
         if (!udoc) throw new UserNotFoundError(mail);
         const [tid] = await token.add(
             token.TYPE_LOSTPASS,
-            await system.get('lostpass_token_expire_seconds'),
+            await system.get('lostpass_token_expire_seconds') as number,
             { uid: udoc._id },
         );
         const m = await this.renderHTML('user_lostpass_mail', { url: `lostpass/${tid}`, uname: udoc.uname });
diff --git a/packages/hydrooj/src/interface.ts b/packages/hydrooj/src/interface.ts
index 64af21769..c34110df1 100644
--- a/packages/hydrooj/src/interface.ts
+++ b/packages/hydrooj/src/interface.ts
@@ -3,6 +3,15 @@ import { ObjectID, GridFSBucket } from 'mongodb';
 import fs from 'fs';
 import { Dictionary, NumericDictionary } from 'lodash';
 
+export type NumberKeys<O> = {
+    [K in keyof O]: number extends O[K] ? K : never
+}[keyof O]
+
+export interface System {
+    _id: string,
+    value: string | number,
+}
+
 export interface Setting {
     family: string,
     key: string,
@@ -175,7 +184,7 @@ export interface PretestConfig {
 }
 
 export interface ContestInfo {
-    type: number,
+    type: 30 | 60,
     tid: ObjectID,
 }
 
@@ -293,6 +302,8 @@ export interface Ddoc {
     ip: string,
     pin: boolean,
     highlight: boolean,
+    updateAt: Date,
+    nReply: number,
 }
 
 // Discussion reply
@@ -379,6 +390,29 @@ export interface JudgeResultBody {
 
 export type PathComponent = [string, string, Dictionary<any>?, boolean?];
 
+export interface Collections {
+    'blacklist': Bdoc,
+    'contest': Tdoc,
+    'domain': DomainDoc,
+    'domain.user': any,
+    'record': Rdoc,
+    'document': any,
+    'problem': Pdoc,
+    'user': Udoc,
+    'check': any,
+    'message': Mdoc,
+    'token': TokenDoc,
+    'file': Ufdoc,
+    'status': any,
+    'oauth': any,
+    'system': System,
+    'task': any,
+    'opcount': any,
+    'fs.chunks': any,
+    'fs.files': any,
+    'document.status': any,
+}
+
 export interface Model {
     blacklist: typeof import('./model/blacklist'),
     builtin: typeof import('./model/builtin'),
diff --git a/packages/hydrooj/src/lib/mail.ts b/packages/hydrooj/src/lib/mail.ts
index 7d5827106..76c9a2677 100644
--- a/packages/hydrooj/src/lib/mail.ts
+++ b/packages/hydrooj/src/lib/mail.ts
@@ -12,7 +12,7 @@ export async function sendMail(to: string, subject: string, text: string, html:
             system.get('smtp.user'),
             system.get('smtp.pass'),
             system.get('smtp.from'),
-        ]);
+        ]) as unknown as [string, number, boolean, string, string, string];
         const transporter = nodemailer.createTransport({
             host, port, secure, auth: { user, pass },
         });
diff --git a/packages/hydrooj/src/model/contest.ts b/packages/hydrooj/src/model/contest.ts
index fe255bad7..01b04d144 100644
--- a/packages/hydrooj/src/model/contest.ts
+++ b/packages/hydrooj/src/model/contest.ts
@@ -1,4 +1,4 @@
-import { ObjectID } from 'mongodb';
+import { ObjectID, FilterQuery } from 'mongodb';
 import * as user from './user';
 import * as problem from './problem';
 import * as document from './document';
@@ -13,6 +13,8 @@ import {
 import * as misc from '../lib/misc';
 import ranked from '../lib/rank';
 
+type Type = 30 | 60;
+
 const acm: ContestRule = {
     TEXT: 'ACM/ICPC',
     check: () => { },
@@ -356,7 +358,7 @@ function _getStatusJournal(tsdoc) {
 export function add(
     domainId: string, title: string, content: string, owner: number,
     rule: string, beginAt = new Date(), endAt = new Date(), pids = [],
-    rated = false, data = {}, type = document.TYPE_CONTEST,
+    rated = false, data: Partial<Tdoc> = {}, type: Type = document.TYPE_CONTEST,
 ) {
     if (!this.RULES[rule]) throw new ValidationError('rule');
     if (beginAt >= endAt) throw new ValidationError('beginAt', 'endAt');
@@ -371,7 +373,7 @@ export function add(
 
 export async function edit(
     domainId: string, tid: ObjectID,
-    $set: any, type = document.TYPE_CONTEST,
+    $set: any, type: Type = document.TYPE_CONTEST,
 ) {
     if ($set.rule) {
         if (!this.RULES[$set.rule]) throw new ValidationError('rule');
@@ -383,7 +385,7 @@ export async function edit(
 }
 
 export async function get(
-    domainId: string, tid: ObjectID, type = document.TYPE_CONTEST,
+    domainId: string, tid: ObjectID, type: Type | -1 = document.TYPE_CONTEST,
 ) {
     let tdoc: Tdoc;
     if (type === -1) {
@@ -396,7 +398,7 @@ export async function get(
 
 export async function updateStatus(
     domainId: string, tid: ObjectID, uid: number, rid: ObjectID, pid: number,
-    accept = false, score = 0, type = document.TYPE_CONTEST,
+    accept = false, score = 0, type: 30 | 60 = document.TYPE_CONTEST,
 ) {
     const tdoc = await get(domainId, tid, type);
     const tsdoc = await document.revPushStatus(domainId, type, tid, uid, 'journal', {
@@ -427,7 +429,7 @@ export async function getListStatus(
 
 export async function attend(
     domainId: string, tid: ObjectID, uid: number,
-    type = document.TYPE_CONTEST,
+    type: Type = document.TYPE_CONTEST,
 ) {
     try {
         await document.cappedIncStatus(domainId, type, tid, uid, 'attend', 1, 0, 1);
@@ -491,7 +493,7 @@ export const ContestHandlerMixin = (c) => class extends c {
 
     async getScoreboard(
         domainId: string, tid: ObjectID,
-        isExport = false, docType = document.TYPE_CONTEST,
+        isExport = false, docType: 30 | 60 = document.TYPE_CONTEST,
     ): Promise<[Tdoc, ScoreboardNode[][], Udict]> {
         const tdoc = await get(domainId, tid, docType);
         if (!this.canShowScoreboard(tdoc)) throw new ContestScoreboardHiddenError(tid);
@@ -522,16 +524,18 @@ export function setStatus(domainId: string, tid: ObjectID, uid: number, $set: an
     return document.setStatus(domainId, document.TYPE_CONTEST, tid, uid, $set);
 }
 
-export function count(domainId: string, query: any, type = document.TYPE_CONTEST) {
+export function count(domainId: string, query: any, type: Type = document.TYPE_CONTEST) {
     return document.count(domainId, type, query);
 }
 
-export function getMulti(domainId: string, query = {}, type = document.TYPE_CONTEST) {
-    return document.getMulti(domainId, type, query);
+export function getMulti<K extends Type & keyof document.DocumentType>(
+    domainId: string, query: FilterQuery<document.DocumentType[K]> = {}, type?: K,
+) {
+    return document.getMulti(domainId, type || document.TYPE_CONTEST, query);
 }
 
 export async function getAndListStatus(
-    domainId: string, tid: ObjectID, docType = document.TYPE_CONTEST,
+    domainId: string, tid: ObjectID, docType: Type | -1 = document.TYPE_CONTEST,
 ): Promise<[Tdoc, any[]]> {
     // TODO(iceboy): projection, pagination.
     const tdoc = await get(domainId, tid, docType);
@@ -540,7 +544,7 @@ export async function getAndListStatus(
     return [tdoc, tsdocs];
 }
 
-export async function recalcStatus(domainId: string, tid: ObjectID, type = document.TYPE_CONTEST) {
+export async function recalcStatus(domainId: string, tid: ObjectID, type: Type = document.TYPE_CONTEST) {
     const [tdoc, tsdocs] = await Promise.all([
         document.get(domainId, type, tid),
         document.getMultiStatus(domainId, type, { docId: tid }).toArray(),
diff --git a/packages/hydrooj/src/model/document.ts b/packages/hydrooj/src/model/document.ts
index c9a155280..bcc113e9c 100644
--- a/packages/hydrooj/src/model/document.ts
+++ b/packages/hydrooj/src/model/document.ts
@@ -1,7 +1,10 @@
 import assert from 'assert';
-import { ObjectID } from 'mongodb';
+import { ObjectID, Cursor, FilterQuery } from 'mongodb';
 import * as db from '../service/db';
 import * as bus from '../service/bus';
+import {
+    Pdoc, Ddoc, Ufdoc, Drdoc, Tdoc, TrainingDoc, NumberKeys,
+} from '../interface';
 
 type DocID = ObjectID | string | number;
 
@@ -19,15 +22,28 @@ export const TYPE_TRAINING = 40;
 export const TYPE_FILE = 50;
 export const TYPE_HOMEWORK = 60;
 
-export async function add<T extends DocID>(
+export interface DocumentType {
+    [TYPE_PROBLEM]: Pdoc,
+    [TYPE_PROBLEM_SOLUTION]: any,
+    [TYPE_PROBLEM_LIST]: any,
+    [TYPE_DISCUSSION_NODE]: any,
+    [TYPE_DISCUSSION]: Ddoc,
+    [TYPE_DISCUSSION_REPLY]: Drdoc,
+    [TYPE_CONTEST]: Tdoc,
+    [TYPE_TRAINING]: TrainingDoc,
+    [TYPE_FILE]: Ufdoc,
+    [TYPE_HOMEWORK]: Tdoc,
+}
+
+export async function add<T extends DocID, K extends keyof DocumentType>(
     domainId: string, content: string, owner: number,
-    docType: number, docId: T,
+    docType: K, docId: DocumentType[K]['docId'],
     parentType?: number | null, parentId?: DocID,
     args?: any,
 ): Promise<T>
-export async function add(
+export async function add<K extends keyof DocumentType>(
     domainId: string, content: string, owner: number,
-    docType: number, docId: null,
+    docType: K, docId: null,
     parentType?: number, parentId?: DocID,
     args?: any,
 ): Promise<ObjectID>
@@ -57,11 +73,13 @@ export async function add(
     return docId || res.insertedId;
 }
 
-export function get(domainId: string, docType: number, docId: DocID) {
+export function get<K extends keyof DocumentType>(domainId: string, docType: K, docId: DocumentType[K]['docId']) {
     return coll.findOne({ domainId, docType, docId });
 }
 
-export async function set(domainId: string, docType: number, docId: DocID, $set: any) {
+export async function set<K extends keyof DocumentType>(
+    domainId: string, docType: K, docId: DocumentType[K]['docId'], $set: Partial<DocumentType[K]>,
+): Promise<DocumentType[K]> {
     await bus.parallel('document/set', domainId, docType, docId, $set);
     const res = await coll.findOneAndUpdate(
         { domainId, docType, docId },
@@ -71,28 +89,36 @@ export async function set(domainId: string, docType: number, docId: DocID, $set:
     return res.value;
 }
 
-export function deleteOne(domainId: string, docType: number, docId: DocID) {
+export function deleteOne<K extends keyof DocumentType>(
+    domainId: string, docType: K, docId: DocumentType[K]['docId'],
+) {
     return Promise.all([
         collStatus.deleteMany({ domainId, docType, docId }),
         coll.deleteOne({ domainId, docType, docId }),
     ]);
 }
 
-export function deleteMulti(domainId: string, docType: number, args: any = {}) {
-    return coll.deleteMany({ ...args, domainId, docType });
+export function deleteMulti<K extends keyof DocumentType>(
+    domainId: string, docType: K, query?: FilterQuery<DocumentType[K]>,
+) {
+    return coll.deleteMany({ ...query, domainId, docType });
 }
 
-export function deleteMultiStatus(domainId: string, docType: number, args: any = {}) {
-    return collStatus.deleteMany({ ...args, domainId, docType });
+export function deleteMultiStatus<K extends keyof DocumentType>(
+    domainId: string, docType: K, query?: FilterQuery<DocumentType[K]>,
+) {
+    return collStatus.deleteMany({ ...query, domainId, docType });
 }
 
-export function getMulti(domainId: string, docType: number, args: any = {}) {
-    return coll.find({ ...args, docType, domainId });
+export function getMulti<K extends keyof DocumentType>(
+    domainId: string, docType: K, query?: FilterQuery<DocumentType[K]>,
+): Cursor<DocumentType[K]> {
+    return coll.find({ ...query, docType, domainId });
 }
 
-export async function inc(
-    domainId: string, docType: number, docId: DocID,
-    key: string, value: number,
+export async function inc<K extends keyof DocumentType>(
+    domainId: string, docType: K, docId: DocumentType[K]['docId'],
+    key: NumberKeys<DocumentType[K]>, value: number,
 ) {
     const res = await coll.findOneAndUpdate(
         { domainId, docType, docId },
@@ -102,9 +128,11 @@ export async function inc(
     return res.value;
 }
 
-export async function incAndSet(
-    domainId: string, docType: number, docId: DocID,
-    key: string, value: number, args: any,
+type Q = NumberKeys<DocumentType[10]>
+
+export async function incAndSet<K extends keyof DocumentType>(
+    domainId: string, docType: K, docId: DocumentType[K]['docId'],
+    key: NumberKeys<DocumentType[K]>, value: number, args: Partial<DocumentType[K]>,
 ) {
     const res = await coll.findOneAndUpdate(
         { domainId, docType, docId },
@@ -114,13 +142,15 @@ export async function incAndSet(
     return res.value;
 }
 
-export function count(domainId: string, docType: number, query: any) {
+export function count<K extends keyof DocumentType>(
+    domainId: string, docType: K, query?: FilterQuery<DocumentType[K]>,
+) {
     return coll.find({ ...query, docType, domainId }).count();
 }
 
-export async function push(
-    domainId: string, docType: number, docId: DocID,
-    key: string, content: string, owner: number, args: any = {},
+export async function push<K extends keyof DocumentType, T extends keyof DocumentType[K]>(
+    domainId: string, docType: K, docId: DocumentType[K]['docId'],
+    key: keyof DocumentType[K], content: string, owner: number, args: DocumentType[K][T][0] = {},
 ) {
     const _id = new ObjectID();
     const doc = await coll.findOneAndUpdate(
@@ -137,10 +167,10 @@ export async function push(
     return [doc.value, _id];
 }
 
-export async function pull(
-    domainId: string, docType: number, docId: DocID,
+export async function pull<K extends keyof DocumentType>(
+    domainId: string, docType: K, docId: DocumentType[K]['docId'],
     setKey: string, contents: string[],
-) {
+): Promise<DocumentType[K]> {
     const res = await coll.findOneAndUpdate(
         { domainId, docType, docId },
         { $pull: { [setKey]: { $in: contents } } },
diff --git a/packages/hydrooj/src/model/domain.ts b/packages/hydrooj/src/model/domain.ts
index 6f14b53d9..559b3a023 100644
--- a/packages/hydrooj/src/model/domain.ts
+++ b/packages/hydrooj/src/model/domain.ts
@@ -1,10 +1,9 @@
 import { Dictionary } from 'lodash';
-import { Collection } from 'mongodb';
 import { BUILTIN_ROLES, PRIV } from './builtin';
 import { DomainDoc } from '../interface';
 import * as db from '../service/db';
 
-const coll: Collection<DomainDoc> = db.collection('domain');
+const coll = db.collection('domain');
 const collUser = db.collection('domain.user');
 
 export const JOIN_METHOD_NONE = 0;
diff --git a/packages/hydrooj/src/model/problem.ts b/packages/hydrooj/src/model/problem.ts
index 571000d8d..de51ed9b4 100644
--- a/packages/hydrooj/src/model/problem.ts
+++ b/packages/hydrooj/src/model/problem.ts
@@ -6,7 +6,7 @@ import * as file from './file';
 import * as document from './document';
 import * as domain from './domain';
 import {
-    Pdoc, Pdict, ProblemDataSource, ProblemStatusDoc,
+    Pdoc, Pdict, ProblemDataSource, ProblemStatusDoc, NumberKeys,
 } from '../interface';
 import { ProblemNotFoundError } from '../error';
 import * as testdataConfig from '../lib/testdataConfig';
@@ -63,7 +63,7 @@ export async function get(
     if (typeof pid !== 'number') {
         if (Number.isSafeInteger(parseInt(pid, 10))) pid = parseInt(pid, 10);
     }
-    const pdoc = Number.isInteger(pid)
+    const pdoc = typeof pid === 'number'
         ? await document.get(domainId, document.TYPE_PROBLEM, pid)
         : (await document.getMulti(domainId, document.TYPE_PROBLEM, { pid }).toArray())[0];
     if (!pdoc) return null;
@@ -85,7 +85,7 @@ export function edit(domainId: string, _id: number, $set: Partial<Pdoc>): Promis
     return document.set(domainId, document.TYPE_PROBLEM, _id, $set);
 }
 
-export function inc(domainId: string, _id: number, field: string, n: number): Promise<Pdoc> {
+export function inc(domainId: string, _id: number, field: NumberKeys<Pdoc>, n: number): Promise<Pdoc> {
     return document.inc(domainId, document.TYPE_PROBLEM, _id, field, n);
 }
 
diff --git a/packages/hydrooj/src/model/system.ts b/packages/hydrooj/src/model/system.ts
index 14a47af16..3330de20f 100644
--- a/packages/hydrooj/src/model/system.ts
+++ b/packages/hydrooj/src/model/system.ts
@@ -2,11 +2,11 @@ import Lru from 'lru-cache';
 import * as db from '../service/db';
 
 const coll = db.collection('system');
-const cache = new Lru({
+const cache = new Lru<string, string | number>({
     maxAge: 5000,
 });
 
-export async function get(_id: string) {
+export async function get(_id: string): Promise<string | number> {
     const res = cache.get(_id);
     if (res !== undefined) return res;
     const doc = await coll.findOne({ _id });
@@ -51,11 +51,13 @@ export async function set(_id: string, value: any) {
 export async function inc(_id: string) {
     const res = await coll.findOneAndUpdate(
         { _id },
+        // FIXME NumberKeys<>
+        // @ts-ignore
         { $inc: { value: 1 } },
         { upsert: true, returnOriginal: false },
     );
     cache.set(_id, res.value.value);
-    return res.value.value;
+    return res.value.value as number;
 }
 
 global.Hydro.model.system = {
diff --git a/packages/hydrooj/src/model/training.ts b/packages/hydrooj/src/model/training.ts
index c01244576..0462f82d8 100644
--- a/packages/hydrooj/src/model/training.ts
+++ b/packages/hydrooj/src/model/training.ts
@@ -27,7 +27,7 @@ export async function enroll(domainId: string, tid: ObjectID, uid: number) {
     } catch (e) {
         throw new TrainingAlreadyEnrollError(tid, uid);
     }
-    return await document.inc(domainId, document.TYPE_TRAINING, tid, 'enroll', 1);
+    return await document.inc(domainId, document.TYPE_TRAINING, tid, 'attend', 1);
 }
 
 export function setStatus(domainId: string, tid: ObjectID, uid: number, $set: any) {
@@ -42,7 +42,7 @@ export function add(
         dag,
         title,
         description,
-        enroll: 0,
+        attend: 0,
     });
 }
 
diff --git a/packages/hydrooj/src/script/rating.ts b/packages/hydrooj/src/script/rating.ts
index d24b238f6..503ee5d83 100644
--- a/packages/hydrooj/src/script/rating.ts
+++ b/packages/hydrooj/src/script/rating.ts
@@ -128,7 +128,7 @@ async function runInDomain(domainId: string, isSub: boolean, report: Function) {
     for (const dudoc of dudocs) {
         deltaudict[dudoc.uid] = dudoc.rpdelta || 0;
     }
-    const contests = await contest.getMulti(domainId, { rated: true }, -1).sort('endAt', -1).toArray();
+    const contests = await contest.getMulti(domainId, { rated: true }).sort('endAt', -1).toArray();
     await report({ message: `Found ${contests.length} contests in ${domainId}` });
     for (const i in contests) {
         const tdoc = contests[i];
diff --git a/packages/hydrooj/src/service/db.ts b/packages/hydrooj/src/service/db.ts
index 4bb0ac593..d763b58a3 100644
--- a/packages/hydrooj/src/service/db.ts
+++ b/packages/hydrooj/src/service/db.ts
@@ -1,6 +1,7 @@
-import mongodb from 'mongodb';
+import mongodb, { Collection } from 'mongodb';
 import * as bus from './bus';
 import options from '../options';
+import { Collections } from '../interface';
 
 const opts = options();
 
@@ -25,7 +26,7 @@ mongodb.MongoClient.connect(mongourl, { useNewUrlParser: true, useUnifiedTopolog
             });
     });
 
-export function collection(c: string) {
+export function collection<K extends keyof Collections>(c: K): Collection<Collections[K]> {
     if (opts.prefix) return db.collection(`${opts.prefix}.${c}`);
     return db.collection(c);
 }
diff --git a/packages/hydrooj/src/service/server.ts b/packages/hydrooj/src/service/server.ts
index 4b866d513..699034f8f 100644
--- a/packages/hydrooj/src/service/server.ts
+++ b/packages/hydrooj/src/service/server.ts
@@ -203,7 +203,7 @@ export function requireCsrfToken(target: any, funcName: string, obj: any) {
 }
 
 export async function prepare() {
-    app.keys = await system.get('session.keys');
+    app.keys = await system.get('session.keys') as unknown as string[];
     if (argv.public) {
         app.use(cache(argv.public, {
             maxAge: 0,
@@ -402,7 +402,7 @@ export class Handler {
     }
 
     async init({ domainId }) {
-        const xff = await system.get('server.xff');
+        const xff = await system.get('server.xff') as string;
         if (xff) this.request.ip = this.request.headers[xff.toLowerCase()];
         [this.domain] = await Promise.all([
             domain.get(domainId),
@@ -498,8 +498,8 @@ export class Handler {
 
     async saveCookie() {
         const expireSeconds = this.session.save
-            ? await system.get('session.expire_seconds')
-            : await system.get('session.unsaved_expire_seconds');
+            ? await system.get('session.expire_seconds') as number
+            : await system.get('session.unsaved_expire_seconds') as number;
         if (this.session._id) {
             await token.update(
                 this.session._id,
@@ -525,7 +525,7 @@ export class Handler {
             );
         }
         const cookie: SetOption = {
-            secure: await system.get('session.secure'),
+            secure: !!await system.get('session.secure'),
             httpOnly: false,
         };
         if (this.session.save) {
diff --git a/packages/migrate-vijos/package.json b/packages/migrate-vijos/package.json
index c5111fc12..f6237bba7 100644
--- a/packages/migrate-vijos/package.json
+++ b/packages/migrate-vijos/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@hydrooj/migrate-vijos",
-    "version": "1.3.7",
+    "version": "1.3.8",
     "main": "package.json",
     "repository": "git@github.com:hydro-dev/Hydro.git",
     "author": "undefined <masnn0@outlook.com>",
@@ -14,7 +14,7 @@
         "@types/mongodb": "^3.5.27"
     },
     "peerDependencies": {
-        "hydrooj": "^2.13.0"
+        "hydrooj": "^2.13.5"
     },
     "dependencies": {
         "js-yaml": "^3.14.0",
diff --git a/packages/migrate-vijos/script.ts b/packages/migrate-vijos/script.ts
index 7ce962f24..a17faa95d 100644
--- a/packages/migrate-vijos/script.ts
+++ b/packages/migrate-vijos/script.ts
@@ -1,6 +1,6 @@
 /* eslint-disable no-await-in-loop */
 import {
-    Rdoc, TestCase, Mdoc, Drrdoc,
+    Rdoc, TestCase, Mdoc, Drrdoc, TrainingNode,
 } from 'hydrooj';
 import fs from 'fs';
 import os from 'os';
@@ -126,12 +126,12 @@ const tasks = {
         },
         attend: 'attend',
         desc: 'description',
-        enroll: 'enroll',
+        enroll: 'attend',
         rated: 'rated',
         dag: {
             field: 'dag',
             processer: (dag) => {
-                const r = [];
+                const r: TrainingNode[] = [];
                 for (const t of dag) {
                     r.push({
                         _id: t._id,