refactor(backend): `core/activitypub` (#11247)

* eslint: `explicit-function-return-type`

* eslint: `no-unnecessary-condition`

* eslint: `eslint-disable-next-line`

* eslint: `no-unused-vars`

* eslint: `comma-dangle`

* eslint: `import/order`

* cleanup: unnecessary non-null assertion

* cleanup: `IActivity`に`actor`は常に存在するようなので

* cleanup: unnecessary `as`

* cleanup: unnecessary `Promise.resolve`

* cleanup

* refactor: `String.prototype.match()`である必要がない部分をよりシンプルな書き方に変更

* refactor: よりよい型定義

* refactor: よりよい型定義

- `LdSignature`の`normalize`メソッドでの使われ方から、
	- `data`引数の型定義を`any`から`JsonLdDocument`へ修正
	- `getLoader`メソッドの返り値の型定義の一部を`any`から`RemoteDocument`へ修正
		- `contextUrl`が不正な値（`null`）となっていたことが判明したため`undefined`へ修正
		- `document`の型と合わせるために`CONTEXTS`の型定義の一部を`unknown`から`JsonLd`へ修正
			- とりあえず`satisfies`を使用
		- `document`の型と合わせるために`fetchDocument`メソッドの返り値の型定義の一部を`unknown`から`JsonLd`へ修正
			- どうしようもなく`as`を使用

* refactor: 型ガードを使うことでnon-null assertionをやめた

* refactor: non-null assertionをやめた

`.filter()`で行っている型ガードなどの文脈から、より適しているだろうと思われる書き方に変更した。

* refactor: 型ガードを使うことで`as`をやめた

* refactor: `as`をやめた

* refactor: よりよい型定義

- `id`は`null`とのunionになっていたが、`null`を渡している場面はなかった
	- またおそらくこのメソッドは`IOrderedCollection`を返すため、そちらに合わせて`null`とのunionをやめた
		- `IOrderedCollection`とはまだ型に相違がある
- `totalItems`をコメントや使われ方を元に`number`へ推論

* refactor: `for-of` -> `Array.prototype.map`

* refactor: `delete`演算子を使わない形に

13 files changed, 163 insertions, 159 deletions

diff --git a/packages/backend/src/core/activitypub/ApAudienceService.ts b/packages/backend/src/core/activitypub/ApAudienceService.ts
index 0eab7fa335..a4ab5eae20 100644
--- a/packages/backend/src/core/activitypub/ApAudienceService.ts
+++ b/packages/backend/src/core/activitypub/ApAudienceService.ts
@@ -16,6 +16,8 @@ type AudienceInfo = {
 	visibleUsers: User[],
 };
 
+type GroupedAudience = Record<'public' | 'followers' | 'other', string[]>;
+
 @Injectable()
 export class ApAudienceService {
 	constructor(
@@ -67,11 +69,11 @@ export class ApAudienceService {
 	}
 
 	@bindThis
-	private groupingAudience(ids: string[], actor: RemoteUser) {
-		const groups = {
-			public: [] as string[],
-			followers: [] as string[],
-			other: [] as string[],
+	private groupingAudience(ids: string[], actor: RemoteUser): GroupedAudience {
+		const groups: GroupedAudience = {
+			public: [],
+			followers: [],
+			other: [],
 		};
 
 		for (const id of ids) {
@@ -90,7 +92,7 @@ export class ApAudienceService {
 	}
 
 	@bindThis
-	private isPublic(id: string) {
+	private isPublic(id: string): boolean {
 		return [
 			'https://www.w3.org/ns/activitystreams#Public',
 			'as#Public',
@@ -99,9 +101,7 @@ export class ApAudienceService {
 	}
 
 	@bindThis
-	private isFollowers(id: string, actor: RemoteUser) {
-		return (
-			id === (actor.followersUri ?? `${actor.uri}/followers`)
-		);
+	private isFollowers(id: string, actor: RemoteUser): boolean {
+		return id === (actor.followersUri ?? `${actor.uri}/followers`);
 	}
 }
diff --git a/packages/backend/src/core/activitypub/ApDbResolverService.ts b/packages/backend/src/core/activitypub/ApDbResolverService.ts
index 20283a163c..d5a530c903 100644
--- a/packages/backend/src/core/activitypub/ApDbResolverService.ts
+++ b/packages/backend/src/core/activitypub/ApDbResolverService.ts
@@ -99,13 +99,15 @@ export class ApDbResolverService implements OnApplicationShutdown {
 		if (parsed.local) {
 			if (parsed.type !== 'users') return null;
 
-			return await this.cacheService.userByIdCache.fetchMaybe(parsed.id, () => this.usersRepository.findOneBy({
-				id: parsed.id,
-			}).then(x => x ?? undefined)) as LocalUser | undefined ?? null;
+			return await this.cacheService.userByIdCache.fetchMaybe(
+				parsed.id,
+				() => this.usersRepository.findOneBy({ id: parsed.id }).then(x => x ?? undefined),
+			) as LocalUser | undefined ?? null;
 		} else {
-			return await this.cacheService.uriPersonCache.fetch(parsed.uri, () => this.usersRepository.findOneBy({
-				uri: parsed.uri,
-			})) as RemoteUser | null;
+			return await this.cacheService.uriPersonCache.fetch(
+				parsed.uri,
+				() => this.usersRepository.findOneBy({ uri: parsed.uri }),
+			) as RemoteUser | null;
 		}
 	}
 
@@ -145,9 +147,11 @@ export class ApDbResolverService implements OnApplicationShutdown {
 	} | null> {
 		const user = await this.apPersonService.resolvePerson(uri) as RemoteUser;
 
-		if (user == null) return null;
-
-		const key = await this.publicKeyByUserIdCache.fetch(user.id, () => this.userPublickeysRepository.findOneBy({ userId: user.id }), v => v != null);
+		const key = await this.publicKeyByUserIdCache.fetch(
+			user.id,
+			() => this.userPublickeysRepository.findOneBy({ userId: user.id }),
+			v => v != null,
+		);
 
 		return {
 			user,
diff --git a/packages/backend/src/core/activitypub/ApDeliverManagerService.ts b/packages/backend/src/core/activitypub/ApDeliverManagerService.ts
index 82c2c9f71f..ae1e42bf53 100644
--- a/packages/backend/src/core/activitypub/ApDeliverManagerService.ts
+++ b/packages/backend/src/core/activitypub/ApDeliverManagerService.ts
@@ -52,7 +52,7 @@ export class ApDeliverManagerService {
 	 * @param activity Activity
 	 */
 	@bindThis
-	public async deliverToFollowers(actor: { id: LocalUser['id']; host: null; }, activity: IActivity) {
+	public async deliverToFollowers(actor: { id: LocalUser['id']; host: null; }, activity: IActivity): Promise<void> {
 		const manager = new DeliverManager(
 			this.userEntityService,
 			this.followingsRepository,
@@ -71,7 +71,7 @@ export class ApDeliverManagerService {
 	 * @param to Target user
 	 */
 	@bindThis
-	public async deliverToUser(actor: { id: LocalUser['id']; host: null; }, activity: IActivity, to: RemoteUser) {
+	public async deliverToUser(actor: { id: LocalUser['id']; host: null; }, activity: IActivity, to: RemoteUser): Promise<void> {
 		const manager = new DeliverManager(
 			this.userEntityService,
 			this.followingsRepository,
@@ -84,7 +84,7 @@ export class ApDeliverManagerService {
 	}
 
 	@bindThis
-	public createDeliverManager(actor: { id: User['id']; host: null; }, activity: IActivity | null) {
+	public createDeliverManager(actor: { id: User['id']; host: null; }, activity: IActivity | null): DeliverManager {
 		return new DeliverManager(
 			this.userEntityService,
 			this.followingsRepository,
@@ -118,6 +118,7 @@ class DeliverManager {
 		activity: IActivity | null,
 	) {
 		// 型で弾いてはいるが一応ローカルユーザーかチェック
+		// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
 		if (actor.host != null) throw new Error('actor.host must be null');
 
 		// パフォーマンス向上のためキューに突っ込むのはidのみに絞る
@@ -131,10 +132,10 @@ class DeliverManager {
 	 * Add recipe for followers deliver
 	 */
 	@bindThis
-	public addFollowersRecipe() {
-		const deliver = {
+	public addFollowersRecipe(): void {
+		const deliver: IFollowersRecipe = {
 			type: 'Followers',
-		} as IFollowersRecipe;
+		};
 
 		this.addRecipe(deliver);
 	}
@@ -144,11 +145,11 @@ class DeliverManager {
 	 * @param to To
 	 */
 	@bindThis
-	public addDirectRecipe(to: RemoteUser) {
-		const recipe = {
+	public addDirectRecipe(to: RemoteUser): void {
+		const recipe: IDirectRecipe = {
 			type: 'Direct',
 			to,
-		} as IDirectRecipe;
+		};
 
 		this.addRecipe(recipe);
 	}
@@ -158,7 +159,7 @@ class DeliverManager {
 	 * @param recipe Recipe
 	 */
 	@bindThis
-	public addRecipe(recipe: IRecipe) {
+	public addRecipe(recipe: IRecipe): void {
 		this.recipes.push(recipe);
 	}
 
@@ -166,17 +167,13 @@ class DeliverManager {
 	 * Execute delivers
 	 */
 	@bindThis
-	public async execute() {
+	public async execute(): Promise<void> {
 		// The value flags whether it is shared or not.
 		// key: inbox URL, value: whether it is sharedInbox
 		const inboxes = new Map<string, boolean>();
 
-		/*
-		build inbox list
-
-		Process follower recipes first to avoid duplication when processing
-		direct recipes later.
-		*/
+		// build inbox list
+		// Process follower recipes first to avoid duplication when processing direct recipes later.
 		if (this.recipes.some(r => isFollowers(r))) {
 			// followers deliver
 			// TODO: SELECT DISTINCT ON ("followerSharedInbox") "followerSharedInbox" みたいな問い合わせにすればよりパフォーマンス向上できそう
@@ -190,26 +187,24 @@ class DeliverManager {
 					followerSharedInbox: true,
 					followerInbox: true,
 				},
-			}) as {
-				followerSharedInbox: string | null;
-				followerInbox: string;
-			}[];
+			});
 
 			for (const following of followers) {
 				const inbox = following.followerSharedInbox ?? following.followerInbox;
+				if (inbox === null) throw new Error('inbox is null');
 				inboxes.set(inbox, following.followerSharedInbox != null);
 			}
 		}
 
-		this.recipes.filter((recipe): recipe is IDirectRecipe =>
-			// followers recipes have already been processed
-			isDirect(recipe)
+		for (const recipe of this.recipes.filter(isDirect)) {
 			// check that shared inbox has not been added yet
-			&& !(recipe.to.sharedInbox && inboxes.has(recipe.to.sharedInbox))
+			if (recipe.to.sharedInbox !== null && inboxes.has(recipe.to.sharedInbox)) continue;
+
 			// check that they actually have an inbox
-			&& recipe.to.inbox != null,
-		)
-			.forEach(recipe => inboxes.set(recipe.to.inbox!, false));
+			if (recipe.to.inbox === null) continue;
+
+			inboxes.set(recipe.to.inbox, false);
+		}
 
 		// deliver
 		this.queueService.deliverMany(this.actor, this.activity, inboxes);
diff --git a/packages/backend/src/core/activitypub/ApInboxService.ts b/packages/backend/src/core/activitypub/ApInboxService.ts
index b0428763c9..8d5f4883e4 100644
--- a/packages/backend/src/core/activitypub/ApInboxService.ts
+++ b/packages/backend/src/core/activitypub/ApInboxService.ts
@@ -21,10 +21,10 @@ import { CacheService } from '@/core/CacheService.js';
 import { NoteEntityService } from '@/core/entities/NoteEntityService.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
 import { QueueService } from '@/core/QueueService.js';
-import type { UsersRepository, NotesRepository, FollowingsRepository, AbuseUserReportsRepository, FollowRequestsRepository, } from '@/models/index.js';
+import type { UsersRepository, NotesRepository, FollowingsRepository, AbuseUserReportsRepository, FollowRequestsRepository } from '@/models/index.js';
 import { bindThis } from '@/decorators.js';
 import type { RemoteUser } from '@/models/entities/User.js';
-import { getApHrefNullable, getApId, getApIds, getApType, getOneApHrefNullable, isAccept, isActor, isAdd, isAnnounce, isBlock, isCollection, isCollectionOrOrderedCollection, isCreate, isDelete, isFlag, isFollow, isLike, isMove, isPost, isReject, isRemove, isTombstone, isUndo, isUpdate, validActor, validPost } from './type.js';
+import { getApHrefNullable, getApId, getApIds, getApType, isAccept, isActor, isAdd, isAnnounce, isBlock, isCollection, isCollectionOrOrderedCollection, isCreate, isDelete, isFlag, isFollow, isLike, isMove, isPost, isReject, isRemove, isTombstone, isUndo, isUpdate, validActor, validPost } from './type.js';
 import { ApNoteService } from './models/ApNoteService.js';
 import { ApLoggerService } from './ApLoggerService.js';
 import { ApDbResolverService } from './ApDbResolverService.js';
@@ -86,7 +86,7 @@ export class ApInboxService {
 	}
 
 	@bindThis
-	public async performActivity(actor: RemoteUser, activity: IObject) {
+	public async performActivity(actor: RemoteUser, activity: IObject): Promise<void> {
 		if (isCollectionOrOrderedCollection(activity)) {
 			const resolver = this.apResolverService.createResolver();
 			for (const item of toArray(isCollection(activity) ? activity.items : activity.orderedItems)) {
@@ -107,7 +107,7 @@ export class ApInboxService {
 		if (actor.uri) {
 			if (actor.lastFetchedAt == null || Date.now() - actor.lastFetchedAt.getTime() > 1000 * 60 * 60 * 24) {
 				setImmediate(() => {
-					this.apPersonService.updatePerson(actor.uri!);
+					this.apPersonService.updatePerson(actor.uri);
 				});
 			}
 		}
@@ -229,7 +229,7 @@ export class ApInboxService {
 
 	@bindThis
 	private async add(actor: RemoteUser, activity: IAdd): Promise<void> {
-		if ('actor' in activity && actor.uri !== activity.actor) {
+		if (actor.uri !== activity.actor) {
 			throw new Error('invalid actor');
 		}
 
@@ -273,7 +273,7 @@ export class ApInboxService {
 		const unlock = await this.appLockService.getApLock(uri);
 
 		try {
-		// 既に同じURIを持つものが登録されていないかチェック
+			// 既に同じURIを持つものが登録されていないかチェック
 			const exist = await this.apNoteService.fetchNote(uri);
 			if (exist) {
 				return;
@@ -292,7 +292,7 @@ export class ApInboxService {
 						return;
 					}
 
-					this.logger.warn(`Error in announce target ${targetUri} - ${err.statusCode ?? err}`);
+					this.logger.warn(`Error in announce target ${targetUri} - ${err.statusCode}`);
 				}
 				throw err;
 			}
@@ -409,7 +409,7 @@ export class ApInboxService {
 
 	@bindThis
 	private async delete(actor: RemoteUser, activity: IDelete): Promise<string> {
-		if ('actor' in activity && actor.uri !== activity.actor) {
+		if (actor.uri !== activity.actor) {
 			throw new Error('invalid actor');
 		}
 
@@ -420,7 +420,7 @@ export class ApInboxService {
 			// typeが不明だけど、どうせ消えてるのでremote resolveしない
 			formerType = undefined;
 		} else {
-			const object = activity.object as IObject;
+			const object = activity.object;
 			if (isTombstone(object)) {
 				formerType = toSingle(object.formerType);
 			} else {
@@ -503,7 +503,10 @@ export class ApInboxService {
 		// 対象ユーザーは一番最初のユーザー として あとはコメントとして格納する
 		const uris = getApIds(activity.object);
 
-		const userIds = uris.filter(uri => uri.startsWith(this.config.url + '/users/')).map(uri => uri.split('/').pop()!);
+		const userIds = uris
+			.filter(uri => uri.startsWith(this.config.url + '/users/'))
+			.map(uri => uri.split('/').at(-1))
+			.filter((userId): userId is string => userId !== undefined);
 		const users = await this.usersRepository.findBy({
 			id: In(userIds),
 		});
@@ -566,7 +569,7 @@ export class ApInboxService {
 
 	@bindThis
 	private async remove(actor: RemoteUser, activity: IRemove): Promise<void> {
-		if ('actor' in activity && actor.uri !== activity.actor) {
+		if (actor.uri !== activity.actor) {
 			throw new Error('invalid actor');
 		}
 
@@ -586,7 +589,7 @@ export class ApInboxService {
 
 	@bindThis
 	private async undo(actor: RemoteUser, activity: IUndo): Promise<string> {
-		if ('actor' in activity && actor.uri !== activity.actor) {
+		if (actor.uri !== activity.actor) {
 			throw new Error('invalid actor');
 		}
 
@@ -719,7 +722,7 @@ export class ApInboxService {
 
 	@bindThis
 	private async update(actor: RemoteUser, activity: IUpdate): Promise<string> {
-		if ('actor' in activity && actor.uri !== activity.actor) {
+		if (actor.uri !== activity.actor) {
 			return 'skip: invalid actor';
 		}
 
@@ -733,7 +736,7 @@ export class ApInboxService {
 		});
 
 		if (isActor(object)) {
-			await this.apPersonService.updatePerson(actor.uri!, resolver, object);
+			await this.apPersonService.updatePerson(actor.uri, resolver, object);
 			return 'ok: Person updated';
 		} else if (getApType(object) === 'Question') {
 			await this.apQuestionService.updateQuestion(object, resolver).catch(err => console.error(err));
diff --git a/packages/backend/src/core/activitypub/ApMfmService.ts b/packages/backend/src/core/activitypub/ApMfmService.ts
index 411cf17d19..d7269eca92 100644
--- a/packages/backend/src/core/activitypub/ApMfmService.ts
+++ b/packages/backend/src/core/activitypub/ApMfmService.ts
@@ -4,9 +4,9 @@ import { DI } from '@/di-symbols.js';
 import type { Config } from '@/config.js';
 import { MfmService } from '@/core/MfmService.js';
 import type { Note } from '@/models/entities/Note.js';
+import { bindThis } from '@/decorators.js';
 import { extractApHashtagObjects } from './models/tag.js';
 import type { IObject } from './type.js';
-import { bindThis } from '@/decorators.js';
 
 @Injectable()
 export class ApMfmService {
@@ -19,14 +19,13 @@ export class ApMfmService {
 	}
 
 	@bindThis
-	public htmlToMfm(html: string, tag?: IObject | IObject[]) {
-		const hashtagNames = extractApHashtagObjects(tag).map(x => x.name).filter((x): x is string => x != null);
-
+	public htmlToMfm(html: string, tag?: IObject | IObject[]): string {
+		const hashtagNames = extractApHashtagObjects(tag).map(x => x.name);
 		return this.mfmService.fromHtml(html, hashtagNames);
 	}
 
 	@bindThis
-	public getNoteHtml(note: Note) {
+	public getNoteHtml(note: Note): string | null {
 		if (!note.text) return '';
 		return this.mfmService.toHtml(mfm.parse(note.text), JSON.parse(note.mentionedRemoteUsers));
 	}
diff --git a/packages/backend/src/core/activitypub/ApRendererService.ts b/packages/backend/src/core/activitypub/ApRendererService.ts
index 96ac5c61f1..95e3a936d2 100644
--- a/packages/backend/src/core/activitypub/ApRendererService.ts
+++ b/packages/backend/src/core/activitypub/ApRendererService.ts
@@ -1,6 +1,6 @@
 import { createPublicKey } from 'node:crypto';
 import { Inject, Injectable } from '@nestjs/common';
-import { In, IsNull } from 'typeorm';
+import { In } from 'typeorm';
 import { v4 as uuid } from 'uuid';
 import * as mfm from 'mfm-js';
 import { DI } from '@/di-symbols.js';
@@ -26,7 +26,6 @@ import { isNotNull } from '@/misc/is-not-null.js';
 import { LdSignatureService } from './LdSignatureService.js';
 import { ApMfmService } from './ApMfmService.js';
 import type { IAccept, IActivity, IAdd, IAnnounce, IApDocument, IApEmoji, IApHashtag, IApImage, IApMention, IBlock, ICreate, IDelete, IFlag, IFollow, IKey, ILike, IMove, IObject, IPost, IQuestion, IReject, IRemove, ITombstone, IUndo, IUpdate } from './type.js';
-import type { IIdentifier } from './models/identifier.js';
 
 @Injectable()
 export class ApRendererService {
@@ -63,7 +62,7 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderAccept(object: any, user: { id: User['id']; host: null }): IAccept {
+	public renderAccept(object: string | IObject, user: { id: User['id']; host: null }): IAccept {
 		return {
 			type: 'Accept',
 			actor: this.userEntityService.genLocalUserUri(user.id),
@@ -72,7 +71,7 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderAdd(user: LocalUser, target: any, object: any): IAdd {
+	public renderAdd(user: LocalUser, target: string | IObject | undefined, object: string | IObject): IAdd {
 		return {
 			type: 'Add',
 			actor: this.userEntityService.genLocalUserUri(user.id),
@@ -82,7 +81,7 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderAnnounce(object: any, note: Note): IAnnounce {
+	public renderAnnounce(object: string | IObject, note: Note): IAnnounce {
 		const attributedTo = this.userEntityService.genLocalUserUri(note.userId);
 
 		let to: string[] = [];
@@ -133,13 +132,13 @@ export class ApRendererService {
 
 	@bindThis
 	public renderCreate(object: IObject, note: Note): ICreate {
-		const activity = {
+		const activity: ICreate = {
 			id: `${this.config.url}/notes/${note.id}/activity`,
 			actor: this.userEntityService.genLocalUserUri(note.userId),
 			type: 'Create',
 			published: note.createdAt.toISOString(),
 			object,
-		} as ICreate;
+		};
 
 		if (object.to) activity.to = object.to;
 		if (object.cc) activity.cc = object.cc;
@@ -209,7 +208,7 @@ export class ApRendererService {
 	 * @param id Follower|Followee ID
 	 */
 	@bindThis
-	public async renderFollowUser(id: User['id']) {
+	public async renderFollowUser(id: User['id']): Promise<string> {
 		const user = await this.usersRepository.findOneByOrFail({ id: id }) as PartialLocalUser | PartialRemoteUser;
 		return this.userEntityService.getUserUri(user);
 	}
@@ -223,8 +222,8 @@ export class ApRendererService {
 		return {
 			id: requestId ?? `${this.config.url}/follows/${follower.id}/${followee.id}`,
 			type: 'Follow',
-			actor: this.userEntityService.getUserUri(follower)!,
-			object: this.userEntityService.getUserUri(followee)!,
+			actor: this.userEntityService.getUserUri(follower),
+			object: this.userEntityService.getUserUri(followee),
 		};
 	}
 
@@ -264,14 +263,14 @@ export class ApRendererService {
 	public async renderLike(noteReaction: NoteReaction, note: { uri: string | null }): Promise<ILike> {
 		const reaction = noteReaction.reaction;
 
-		const object = {
+		const object: ILike = {
 			type: 'Like',
 			id: `${this.config.url}/likes/${noteReaction.id}`,
 			actor: `${this.config.url}/users/${noteReaction.userId}`,
 			object: note.uri ? note.uri : `${this.config.url}/notes/${noteReaction.noteId}`,
 			content: reaction,
 			_misskey_reaction: reaction,
-		} as ILike;
+		};
 
 		if (reaction.startsWith(':')) {
 			const name = reaction.replaceAll(':', '');
@@ -287,7 +286,7 @@ export class ApRendererService {
 	public renderMention(mention: PartialLocalUser | PartialRemoteUser): IApMention {
 		return {
 			type: 'Mention',
-			href: this.userEntityService.getUserUri(mention)!,
+			href: this.userEntityService.getUserUri(mention),
 			name: this.userEntityService.isRemoteUser(mention) ? `@${mention.username}@${mention.host}` : `@${(mention as LocalUser).username}`,
 		};
 	}
@@ -297,8 +296,8 @@ export class ApRendererService {
 		src: PartialLocalUser | PartialRemoteUser,
 		dst: PartialLocalUser | PartialRemoteUser,
 	): IMove {
-		const actor = this.userEntityService.getUserUri(src)!;
-		const target = this.userEntityService.getUserUri(dst)!;
+		const actor = this.userEntityService.getUserUri(src);
+		const target = this.userEntityService.getUserUri(dst);
 		return {
 			id: `${this.config.url}/moves/${src.id}/${dst.id}`,
 			actor,
@@ -310,10 +309,10 @@ export class ApRendererService {
 
 	@bindThis
 	public async renderNote(note: Note, dive = true): Promise<IPost> {
-		const getPromisedFiles = async (ids: string[]) => {
-			if (!ids || ids.length === 0) return [];
+		const getPromisedFiles = async (ids: string[]): Promise<DriveFile[]> => {
+			if (ids.length === 0) return [];
 			const items = await this.driveFilesRepository.findBy({ id: In(ids) });
-			return ids.map(id => items.find(item => item.id === id)).filter(item => item != null) as DriveFile[];
+			return ids.map(id => items.find(item => item.id === id)).filter((item): item is DriveFile => item != null);
 		};
 
 		let inReplyTo;
@@ -375,7 +374,7 @@ export class ApRendererService {
 			id: In(note.mentions),
 		}) : [];
 
-		const hashtagTags = (note.tags ?? []).map(tag => this.renderHashtag(tag));
+		const hashtagTags = note.tags.map(tag => this.renderHashtag(tag));
 		const mentionTags = mentionedUsers.map(u => this.renderMention(u as LocalUser | RemoteUser));
 
 		const files = await getPromisedFiles(note.fileIds);
@@ -451,37 +450,26 @@ export class ApRendererService {
 	@bindThis
 	public async renderPerson(user: LocalUser) {
 		const id = this.userEntityService.genLocalUserUri(user.id);
-		const isSystem = !!user.username.match(/\./);
+		const isSystem = user.username.includes('.');
 
 		const [avatar, banner, profile] = await Promise.all([
-			user.avatarId ? this.driveFilesRepository.findOneBy({ id: user.avatarId }) : Promise.resolve(undefined),
-			user.bannerId ? this.driveFilesRepository.findOneBy({ id: user.bannerId }) : Promise.resolve(undefined),
+			user.avatarId ? this.driveFilesRepository.findOneBy({ id: user.avatarId }) : undefined,
+			user.bannerId ? this.driveFilesRepository.findOneBy({ id: user.bannerId }) : undefined,
 			this.userProfilesRepository.findOneByOrFail({ userId: user.id }),
 		]);
 
-		const attachment: {
+		const attachment = profile.fields.map(field => ({
 			type: 'PropertyValue',
-			name: string,
-			value: string,
-			identifier?: IIdentifier,
-		}[] = [];
-
-		if (profile.fields) {
-			for (const field of profile.fields) {
-				attachment.push({
-					type: 'PropertyValue',
-					name: field.name,
-					value: (field.value != null && field.value.match(/^https?:/))
-						? `<a href="${new URL(field.value).href}" rel="me nofollow noopener" target="_blank">${new URL(field.value).href}</a>`
-						: field.value,
-				});
-			}
-		}
+			name: field.name,
+			value: /^https?:/.test(field.value)
+				? `<a href="${new URL(field.value).href}" rel="me nofollow noopener" target="_blank">${new URL(field.value).href}</a>`
+				: field.value,
+		}));
 
 		const emojis = await this.getEmojis(user.emojis);
 		const apemojis = emojis.filter(emoji => !emoji.localOnly).map(emoji => this.renderEmoji(emoji));
 
-		const hashtagTags = (user.tags ?? []).map(tag => this.renderHashtag(tag));
+		const hashtagTags = user.tags.map(tag => this.renderHashtag(tag));
 
 		const tag = [
 			...apemojis,
@@ -490,7 +478,7 @@ export class ApRendererService {
 
 		const keypair = await this.userKeypairService.getUserKeypair(user.id);
 
-		const person = {
+		const person: any = {
 			type: isSystem ? 'Application' : user.isBot ? 'Service' : 'Person',
 			id,
 			inbox: `${id}/inbox`,
@@ -508,11 +496,11 @@ export class ApRendererService {
 			image: banner ? this.renderImage(banner) : null,
 			tag,
 			manuallyApprovesFollowers: user.isLocked,
-			discoverable: !!user.isExplorable,
+			discoverable: user.isExplorable,
 			publicKey: this.renderKey(user, keypair, '#main-key'),
 			isCat: user.isCat,
 			attachment: attachment.length ? attachment : undefined,
-		} as any;
+		};
 
 		if (user.movedToUri) {
 			person.movedTo = user.movedToUri;
@@ -552,7 +540,7 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderReject(object: any, user: { id: User['id'] }): IReject {
+	public renderReject(object: string | IObject, user: { id: User['id'] }): IReject {
 		return {
 			type: 'Reject',
 			actor: this.userEntityService.genLocalUserUri(user.id),
@@ -561,7 +549,7 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderRemove(user: { id: User['id'] }, target: any, object: any): IRemove {
+	public renderRemove(user: { id: User['id'] }, target: string | IObject | undefined, object: string | IObject): IRemove {
 		return {
 			type: 'Remove',
 			actor: this.userEntityService.genLocalUserUri(user.id),
@@ -579,8 +567,8 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderUndo(object: any, user: { id: User['id'] }): IUndo {
-		const id = typeof object.id === 'string' && object.id.startsWith(this.config.url) ? `${object.id}/undo` : undefined;
+	public renderUndo(object: string | IObject, user: { id: User['id'] }): IUndo {
+		const id = typeof object !== 'string' && typeof object.id === 'string' && object.id.startsWith(this.config.url) ? `${object.id}/undo` : undefined;
 
 		return {
 			type: 'Undo',
@@ -592,7 +580,7 @@ export class ApRendererService {
 	}
 
 	@bindThis
-	public renderUpdate(object: any, user: { id: User['id'] }): IUpdate {
+	public renderUpdate(object: string | IObject, user: { id: User['id'] }): IUpdate {
 		return {
 			id: `${this.config.url}/users/${user.id}#updates/${new Date().getTime()}`,
 			actor: this.userEntityService.genLocalUserUri(user.id),
@@ -658,7 +646,7 @@ export class ApRendererService {
 					vcard: 'http://www.w3.org/2006/vcard/ns#',
 				},
 			],
-		}, x as T & { id: string; });
+		}, x as T & { id: string });
 	}
 
 	@bindThis
@@ -683,13 +671,13 @@ export class ApRendererService {
 	 */
 	@bindThis
 	public renderOrderedCollectionPage(id: string, totalItems: any, orderedItems: any, partOf: string, prev?: string, next?: string) {
-		const page = {
+		const page: any = {
 			id,
 			partOf,
 			type: 'OrderedCollectionPage',
 			totalItems,
 			orderedItems,
-		} as any;
+		};
 
 		if (prev) page.prev = prev;
 		if (next) page.next = next;
@@ -706,7 +694,7 @@ export class ApRendererService {
 	 * @param orderedItems attached objects (optional)
 	 */
 	@bindThis
-	public renderOrderedCollection(id: string | null, totalItems: any, first?: string, last?: string, orderedItems?: IObject[]) {
+	public renderOrderedCollection(id: string, totalItems: number, first?: string, last?: string, orderedItems?: IObject[]) {
 		const page: any = {
 			id,
 			type: 'OrderedCollection',
@@ -722,7 +710,7 @@ export class ApRendererService {
 
 	@bindThis
 	private async getEmojis(names: string[]): Promise<Emoji[]> {
-		if (names == null || names.length === 0) return [];
+		if (names.length === 0) return [];
 
 		const allEmojis = await this.customEmojiService.localEmojisCache.fetch();
 		const emojis = names.map(name => allEmojis.get(name)).filter(isNotNull);
diff --git a/packages/backend/src/core/activitypub/ApRequestService.ts b/packages/backend/src/core/activitypub/ApRequestService.ts
index 5005612ab8..44676cac20 100644
--- a/packages/backend/src/core/activitypub/ApRequestService.ts
+++ b/packages/backend/src/core/activitypub/ApRequestService.ts
@@ -140,7 +140,7 @@ export class ApRequestService {
 	}
 
 	@bindThis
-	public async signedPost(user: { id: User['id'] }, url: string, object: any) {
+	public async signedPost(user: { id: User['id'] }, url: string, object: unknown): Promise<void> {
 		const body = JSON.stringify(object);
 
 		const keypair = await this.userKeypairService.getUserKeypair(user.id);
@@ -169,7 +169,7 @@ export class ApRequestService {
 	 * @param url URL to fetch
 	 */
 	@bindThis
-	public async signedGet(url: string, user: { id: User['id'] }) {
+	public async signedGet(url: string, user: { id: User['id'] }): Promise<unknown> {
 		const keypair = await this.userKeypairService.getUserKeypair(user.id);
 
 		const req = ApRequestCreator.createSignedGet({
diff --git a/packages/backend/src/core/activitypub/ApResolverService.ts b/packages/backend/src/core/activitypub/ApResolverService.ts
index d3e0345c9c..aa4720c56e 100644
--- a/packages/backend/src/core/activitypub/ApResolverService.ts
+++ b/packages/backend/src/core/activitypub/ApResolverService.ts
@@ -61,10 +61,6 @@ export class Resolver {
 
 	@bindThis
 	public async resolve(value: string | IObject): Promise<IObject> {
-		if (value == null) {
-			throw new Error('resolvee is null (or undefined)');
-		}
-
 		if (typeof value !== 'string') {
 			return value;
 		}
@@ -104,11 +100,11 @@ export class Resolver {
 			? await this.apRequestService.signedGet(value, this.user) as IObject
 			: await this.httpRequestService.getJson(value, 'application/activity+json, application/ld+json')) as IObject;
 
-		if (object == null || (
+		if (
 			Array.isArray(object['@context']) ?
 				!(object['@context'] as unknown[]).includes('https://www.w3.org/ns/activitystreams') :
 				object['@context'] !== 'https://www.w3.org/ns/activitystreams'
-		)) {
+		) {
 			throw new Error('invalid response');
 		}
 
diff --git a/packages/backend/src/core/activitypub/LdSignatureService.ts b/packages/backend/src/core/activitypub/LdSignatureService.ts
index 20fe2a0a77..af7e243229 100644
--- a/packages/backend/src/core/activitypub/LdSignatureService.ts
+++ b/packages/backend/src/core/activitypub/LdSignatureService.ts
@@ -3,6 +3,8 @@ import { Injectable } from '@nestjs/common';
 import { HttpRequestService } from '@/core/HttpRequestService.js';
 import { bindThis } from '@/decorators.js';
 import { CONTEXTS } from './misc/contexts.js';
+import type { JsonLdDocument } from 'jsonld';
+import type { JsonLd, RemoteDocument } from 'jsonld/jsonld-spec.js';
 
 // RsaSignature2017 based from https://github.com/transmute-industries/RsaSignature2017
 
@@ -18,22 +20,21 @@ class LdSignature {
 
 	@bindThis
 	public async signRsaSignature2017(data: any, privateKey: string, creator: string, domain?: string, created?: Date): Promise<any> {
-		const options = {
-			type: 'RsaSignature2017',
-			creator,
-			domain,
-			nonce: crypto.randomBytes(16).toString('hex'),
-			created: (created ?? new Date()).toISOString(),
-		} as {
+		const options: {
 			type: string;
 			creator: string;
 			domain?: string;
 			nonce: string;
 			created: string;
+		} = {
+			type: 'RsaSignature2017',
+			creator,
+			nonce: crypto.randomBytes(16).toString('hex'),
+			created: (created ?? new Date()).toISOString(),
 		};
 
-		if (!domain) {
-			delete options.domain;
+		if (domain) {
+			options.domain = domain;
 		}
 
 		const toBeSigned = await this.createVerifyData(data, options);
@@ -62,7 +63,7 @@ class LdSignature {
 	}
 
 	@bindThis
-	public async createVerifyData(data: any, options: any) {
+	public async createVerifyData(data: any, options: any): Promise<string> {
 		const transformedOptions = {
 			...options,
 			'@context': 'https://w3id.org/identity/v1',
@@ -82,7 +83,7 @@ class LdSignature {
 	}
 
 	@bindThis
-	public async normalize(data: any) {
+	public async normalize(data: JsonLdDocument): Promise<string> {
 		const customLoader = this.getLoader();
 		// XXX: Importing jsonld dynamically since Jest frequently fails to import it statically
 		// https://github.com/misskey-dev/misskey/pull/9894#discussion_r1103753595
@@ -93,14 +94,14 @@ class LdSignature {
 
 	@bindThis
 	private getLoader() {
-		return async (url: string): Promise<any> => {
-			if (!url.match('^https?\:\/\/')) throw new Error(`Invalid URL ${url}`);
+		return async (url: string): Promise<RemoteDocument> => {
+			if (!/^https?:\/\//.test(url)) throw new Error(`Invalid URL ${url}`);
 
 			if (this.preLoad) {
 				if (url in CONTEXTS) {
 					if (this.debug) console.debug(`HIT: ${url}`);
 					return {
-						contextUrl: null,
+						contextUrl: undefined,
 						document: CONTEXTS[url],
 						documentUrl: url,
 					};
@@ -110,7 +111,7 @@ class LdSignature {
 			if (this.debug) console.debug(`MISS: ${url}`);
 			const document = await this.fetchDocument(url);
 			return {
-				contextUrl: null,
+				contextUrl: undefined,
 				document: document,
 				documentUrl: url,
 			};
@@ -118,13 +119,17 @@ class LdSignature {
 	}
 
 	@bindThis
-	private async fetchDocument(url: string) {
-		const json = await this.httpRequestService.send(url, {
-			headers: {
-				Accept: 'application/ld+json, application/json',
+	private async fetchDocument(url: string): Promise<JsonLd> {
+		const json = await this.httpRequestService.send(
+			url,
+			{
+				headers: {
+					Accept: 'application/ld+json, application/json',
+				},
+				timeout: this.loderTimeout,
 			},
-			timeout: this.loderTimeout,
-		}, { throwErrorWhenResponseNotOk: false }).then(res => {
+			{ throwErrorWhenResponseNotOk: false },
+		).then(res => {
 			if (!res.ok) {
 				throw new Error(`${res.status} ${res.statusText}`);
 			} else {
@@ -132,7 +137,7 @@ class LdSignature {
 			}
 		});
 
-		return json;
+		return json as JsonLd;
 	}
 
 	@bindThis
diff --git a/packages/backend/src/core/activitypub/misc/contexts.ts b/packages/backend/src/core/activitypub/misc/contexts.ts
index aee0d3629c..2bcd3811b2 100644
--- a/packages/backend/src/core/activitypub/misc/contexts.ts
+++ b/packages/backend/src/core/activitypub/misc/contexts.ts
@@ -1,3 +1,5 @@
+import type { JsonLd } from 'jsonld/jsonld-spec.js';
+
 /* eslint:disable:quotemark indent */
 const id_v1 = {
 	'@context': {
@@ -86,7 +88,7 @@ const id_v1 = {
 		'accessControl': { '@id': 'perm:accessControl', '@type': '@id' },
 		'writePermission': { '@id': 'perm:writePermission', '@type': '@id' },
 	},
-};
+} satisfies JsonLd;
 
 const security_v1 = {
 	'@context': {
@@ -137,7 +139,7 @@ const security_v1 = {
 		'signatureAlgorithm': 'sec:signingAlgorithm',
 		'signatureValue': 'sec:signatureValue',
 	},
-};
+} satisfies JsonLd;
 
 const activitystreams = {
 	'@context': {
@@ -517,9 +519,9 @@ const activitystreams = {
 			'@type': '@id',
 		},
 	},
-};
+} satisfies JsonLd;
 
-export const CONTEXTS: Record<string, unknown> = {
+export const CONTEXTS: Record<string, JsonLd> = {
 	'https://w3id.org/identity/v1': id_v1,
 	'https://w3id.org/security/v1': security_v1,
 	'https://www.w3.org/ns/activitystreams': activitystreams,
diff --git a/packages/backend/src/core/activitypub/models/ApNoteService.ts b/packages/backend/src/core/activitypub/models/ApNoteService.ts
index d3359ef900..46ed976a6b 100644
--- a/packages/backend/src/core/activitypub/models/ApNoteService.ts
+++ b/packages/backend/src/core/activitypub/models/ApNoteService.ts
@@ -200,7 +200,7 @@ export class ApNoteService {
 				| { status: 'ok'; res: Note }
 				| { status: 'permerror' | 'temperror' }
 			> => {
-				if (!uri.match(/^https?:/)) return { status: 'permerror' };
+				if (!/^https?:/.test(uri)) return { status: 'permerror' };
 				try {
 					const res = await this.resolveNote(uri);
 					if (res == null) return { status: 'permerror' };
diff --git a/packages/backend/src/core/activitypub/type.ts b/packages/backend/src/core/activitypub/type.ts
index 625135da6c..4bb0fa61ec 100644
--- a/packages/backend/src/core/activitypub/type.ts
+++ b/packages/backend/src/core/activitypub/type.ts
@@ -194,7 +194,6 @@ export interface IApPropertyValue extends IObject {
 }
 
 export const isPropertyValue = (object: IObject): object is IApPropertyValue =>
-	object &&
 	getApType(object) === 'PropertyValue' &&
 	typeof object.name === 'string' &&
 	'value' in object &&
diff --git a/packages/backend/src/server/ActivityPubServerService.ts b/packages/backend/src/server/ActivityPubServerService.ts
index f53351d999..f751709345 100644
--- a/packages/backend/src/server/ActivityPubServerService.ts
+++ b/packages/backend/src/server/ActivityPubServerService.ts
@@ -189,7 +189,11 @@ export class ActivityPubServerService {
 			return (this.apRendererService.addContext(rendered));
 		} else {
 			// index page
-			const rendered = this.apRendererService.renderOrderedCollection(partOf, user.followersCount, `${partOf}?page=true`);
+			const rendered = this.apRendererService.renderOrderedCollection(
+				partOf,
+				user.followersCount,
+				`${partOf}?page=true`,
+			);
 			reply.header('Cache-Control', 'public, max-age=180');
 			this.setResponseType(request, reply);
 			return (this.apRendererService.addContext(rendered));
@@ -277,7 +281,11 @@ export class ActivityPubServerService {
 			return (this.apRendererService.addContext(rendered));
 		} else {
 			// index page
-			const rendered = this.apRendererService.renderOrderedCollection(partOf, user.followingCount, `${partOf}?page=true`);
+			const rendered = this.apRendererService.renderOrderedCollection(
+				partOf,
+				user.followingCount,
+				`${partOf}?page=true`,
+			);
 			reply.header('Cache-Control', 'public, max-age=180');
 			this.setResponseType(request, reply);
 			return (this.apRendererService.addContext(rendered));
@@ -310,7 +318,10 @@ export class ActivityPubServerService {
 
 		const rendered = this.apRendererService.renderOrderedCollection(
 			`${this.config.url}/users/${userId}/collections/featured`,
-			renderedNotes.length, undefined, undefined, renderedNotes,
+			renderedNotes.length,
+			undefined,
+			undefined,
+			renderedNotes,
 		);
 
 		reply.header('Cache-Control', 'public, max-age=180');
@@ -395,7 +406,9 @@ export class ActivityPubServerService {
 			return (this.apRendererService.addContext(rendered));
 		} else {
 			// index page
-			const rendered = this.apRendererService.renderOrderedCollection(partOf, user.notesCount,
+			const rendered = this.apRendererService.renderOrderedCollection(
+				partOf,
+				user.notesCount,
 				`${partOf}?page=true`,
 				`${partOf}?page=true&since_id=000000000000000000000000`,
 			);