refactoring

Resolve #7779

packages/backend/src/server/api/common/inject-promo.ts

@@ -0,0 +1,34 @@
+import rndstr from 'rndstr';
+import { Note } from '@/models/entities/note';
+import { User } from '@/models/entities/user';
+import { PromoReads, PromoNotes, Notes, Users } from '@/models/index';
+
+export async function injectPromo(timeline: Note[], user?: User | null) {
+	if (timeline.length < 5) return;
+
+	// TODO: readやexpireフィルタはクエリ側でやる
+
+	const reads = user ? await PromoReads.find({
+		userId: user.id
+	}) : [];
+
+	let promos = await PromoNotes.find();
+
+	promos = promos.filter(n => n.expiresAt.getTime() > Date.now());
+	promos = promos.filter(n => !reads.map(r => r.noteId).includes(n.noteId));
+
+	if (promos.length === 0) return;
+
+	// Pick random promo
+	const promo = promos[Math.floor(Math.random() * promos.length)];
+
+	const note = await Notes.findOneOrFail(promo.noteId);
+
+	// Join
+	note.user = await Users.findOneOrFail(note.userId);
+
+	(note as any)._prId_ = rndstr('a-z0-9', 8);
+
+	// Inject promo
+	timeline.splice(3, 0, note);
+}