feat: implement user follow system

src/prisma/seed/create/createNewUserFollows.ts

@@ -0,0 +1,54 @@
+// eslint-disable-next-line import/no-extraneous-dependencies
+import { faker } from '@faker-js/faker';
+import type { User } from '@prisma/client';
+
+import DBClient from '../../DBClient';
+
+interface CreateNewUserFollowsArgs {
+  joinData: { users: User[] };
+}
+
+interface UserFollowData {
+  followerId: string;
+  followingId: string;
+  followedAt: Date;
+}
+
+const createNewUserFollows = async ({
+  joinData: { users },
+}: CreateNewUserFollowsArgs) => {
+  const userFollows: UserFollowData[] = [];
+
+  users.forEach((user) => {
+    // Get 20 random users to follow.
+    const randomUsers = users
+      .filter((randomUser) => randomUser.id !== user.id)
+      .sort(() => Math.random() - Math.random())
+      .slice(0, 20);
+
+    // Get the user to follow the random users, and the random users to follow the user.
+    const data = randomUsers.flatMap((randomUser) => [
+      {
+        followerId: user.id,
+        followingId: randomUser.id,
+        followedAt: faker.date.between({ from: user.createdAt, to: new Date() }),
+      },
+      {
+        followerId: randomUser.id,
+        followingId: user.id,
+        followedAt: faker.date.between({ from: randomUser.createdAt, to: new Date() }),
+      },
+    ]);
+
+    userFollows.push(...data);
+  });
+
+  await DBClient.instance.userFollow.createMany({
+    data: userFollows,
+    skipDuplicates: true,
+  });
+
+  return DBClient.instance.userFollow.findMany();
+};
+
+export default createNewUserFollows;