refactoring

Resolve #7779

packages/backend/src/remote/activitypub/audience.ts

@@ -0,0 +1,92 @@
+import { ApObject, getApIds } from './type';
+import Resolver from './resolver';
+import { resolvePerson } from './models/person';
+import { unique, concat } from '@/prelude/array';
+import * as promiseLimit from 'promise-limit';
+import { User, IRemoteUser } from '@/models/entities/user';
+
+type Visibility = 'public' | 'home' | 'followers' | 'specified';
+
+type AudienceInfo = {
+	visibility: Visibility,
+	mentionedUsers: User[],
+	visibleUsers: User[],
+};
+
+export async function parseAudience(actor: IRemoteUser, to?: ApObject, cc?: ApObject, resolver?: Resolver): Promise<AudienceInfo> {
+	const toGroups = groupingAudience(getApIds(to), actor);
+	const ccGroups = groupingAudience(getApIds(cc), actor);
+
+	const others = unique(concat([toGroups.other, ccGroups.other]));
+
+	const limit = promiseLimit<User | null>(2);
+	const mentionedUsers = (await Promise.all(
+		others.map(id => limit(() => resolvePerson(id, resolver).catch(() => null)))
+	)).filter((x): x is User => x != null);
+
+	if (toGroups.public.length > 0) {
+		return {
+			visibility: 'public',
+			mentionedUsers,
+			visibleUsers: []
+		};
+	}
+
+	if (ccGroups.public.length > 0) {
+		return {
+			visibility: 'home',
+			mentionedUsers,
+			visibleUsers: []
+		};
+	}
+
+	if (toGroups.followers.length > 0) {
+		return {
+			visibility: 'followers',
+			mentionedUsers,
+			visibleUsers: []
+		};
+	}
+
+	return {
+		visibility: 'specified',
+		mentionedUsers,
+		visibleUsers: mentionedUsers
+	};
+}
+
+function groupingAudience(ids: string[], actor: IRemoteUser) {
+	const groups = {
+		public: [] as string[],
+		followers: [] as string[],
+		other: [] as string[],
+	};
+
+	for (const id of ids) {
+		if (isPublic(id)) {
+			groups.public.push(id);
+		} else if (isFollowers(id, actor)) {
+			groups.followers.push(id);
+		} else {
+			groups.other.push(id);
+		}
+	}
+
+	groups.other = unique(groups.other);
+
+	return groups;
+}
+
+function isPublic(id: string) {
+	return [
+		'https://www.w3.org/ns/activitystreams#Public',
+		'as#Public',
+		'Public',
+	].includes(id);
+}
+
+function isFollowers(id: string, actor: IRemoteUser) {
+	return (
+		id === (actor.followersUri || `${actor.uri}/followers`)
+	);
+}