feat: 添加用户关注功能

- 新增 Follow 表和 User.bio 字段 (Prisma schema)
- 创建 follow 模块 (action-service-repository)
- 新增 FollowButton/FollowStats/UserList 组件
- 用户页面显示 bio、粉丝/关注数、关注按钮
- 新增 /users/[username]/followers 和 following 页面
- 添加 en-US/zh-CN i18n 翻译

⚠️ 需要运行: prisma migrate dev --name add_follow_and_bio

messages/en-US.json

@@ -354,6 +354,7 @@
     "displayName": "Display Name",
     "notSet": "Not Set",
     "memberSince": "Member Since",
+    "joined": "Joined",
     "logout": "Logout",
     "folders": {
       "title": "Folders",
@@ -364,5 +365,14 @@
       "actions": "Actions",
       "view": "View"
     }
+  },
+  "follow": {
+    "follow": "Follow",
+    "following": "Following",
+    "followers": "Followers",
+    "followersOf": "{username}'s Followers",
+    "followingOf": "{username}'s Following",
+    "noFollowers": "No followers yet",
+    "noFollowing": "Not following anyone yet"
   }
 }

messages/zh-CN.json

@@ -354,6 +354,7 @@
     "displayName": "显示名称",
     "notSet": "未设置",
     "memberSince": "注册时间",
+    "joined": "加入于",
     "logout": "登出",
     "folders": {
       "title": "文件夹",
@@ -364,5 +365,14 @@
       "actions": "操作",
       "view": "查看"
     }
+  },
+  "follow": {
+    "follow": "关注",
+    "following": "已关注",
+    "followers": "粉丝",
+    "followersOf": "{username} 的粉丝",
+    "followingOf": "{username} 的关注",
+    "noFollowers": "还没有粉丝",
+    "noFollowing": "还没有关注任何人"
   }
 }

prisma/schema.prisma

@@ -17,12 +17,15 @@ model User {
   updatedAt            DateTime             @updatedAt
   displayUsername      String?
   username             String               @unique
+  bio                  String?
   accounts             Account[]
   dictionaryLookUps    DictionaryLookUp[]
   folders              Folder[]
   folderFavorites      FolderFavorite[]
   sessions             Session[]
   translationHistories TranslationHistory[]
+  followers            Follow[]             @relation("UserFollowers")
+  following            Follow[]             @relation("UserFollowing")
 
   @@map("user")
 }
@@ -198,3 +201,18 @@ model TranslationHistory {
   @@index([translatedText, sourceLanguage, targetLanguage])
   @@map("translation_history")
 }
+
+model Follow {
+  id          String   @id @default(cuid())
+  followerId  String   @map("follower_id")
+  followingId String   @map("following_id")
+  createdAt   DateTime @default(now()) @map("created_at")
+
+  follower  User @relation("UserFollowers", fields: [followerId], references: [id], onDelete: Cascade)
+  following User @relation("UserFollowing", fields: [followingId], references: [id], onDelete: Cascade)
+
+  @@unique([followerId, followingId])
+  @@index([followerId])
+  @@index([followingId])
+  @@map("follows")
+}

src/app/(auth)/users/[username]/followers/page.tsx

@@ -0,0 +1,44 @@
+import { notFound } from "next/navigation";
+import { getTranslations } from "next-intl/server";
+import { PageLayout } from "@/components/ui/PageLayout";
+import { UserList } from "@/components/follow/UserList";
+import { actionGetUserProfileByUsername } from "@/modules/auth/auth-action";
+import { actionGetFollowers } from "@/modules/follow/follow-action";
+
+interface FollowersPageProps {
+  params: Promise<{ username: string }>;
+}
+
+export default async function FollowersPage({ params }: FollowersPageProps) {
+  const { username } = await params;
+  const t = await getTranslations("follow");
+
+  const userResult = await actionGetUserProfileByUsername({ username });
+
+  if (!userResult.success || !userResult.data) {
+    notFound();
+  }
+
+  const user = userResult.data;
+
+  const followersResult = await actionGetFollowers({
+    userId: user.id,
+    page: 1,
+    limit: 50,
+  });
+
+  const followers = followersResult.success && followersResult.data
+    ? followersResult.data.followers.map((f) => f.user)
+    : [];
+
+  return (
+    <PageLayout>
+      <div className="bg-white rounded-lg shadow-md p-6">
+        <h1 className="text-2xl font-bold text-gray-800 mb-6">
+          {t("followersOf", { username: user.displayUsername || user.username || "User" })}
+        </h1>
+        <UserList users={followers} emptyMessage={t("noFollowers")} />
+      </div>
+    </PageLayout>
+  );
+}

src/app/(auth)/users/[username]/following/page.tsx

@@ -0,0 +1,44 @@
+import { notFound } from "next/navigation";
+import { getTranslations } from "next-intl/server";
+import { PageLayout } from "@/components/ui/PageLayout";
+import { UserList } from "@/components/follow/UserList";
+import { actionGetUserProfileByUsername } from "@/modules/auth/auth-action";
+import { actionGetFollowing } from "@/modules/follow/follow-action";
+
+interface FollowingPageProps {
+  params: Promise<{ username: string }>;
+}
+
+export default async function FollowingPage({ params }: FollowingPageProps) {
+  const { username } = await params;
+  const t = await getTranslations("follow");
+
+  const userResult = await actionGetUserProfileByUsername({ username });
+
+  if (!userResult.success || !userResult.data) {
+    notFound();
+  }
+
+  const user = userResult.data;
+
+  const followingResult = await actionGetFollowing({
+    userId: user.id,
+    page: 1,
+    limit: 50,
+  });
+
+  const following = followingResult.success && followingResult.data
+    ? followingResult.data.following.map((f) => f.user)
+    : [];
+
+  return (
+    <PageLayout>
+      <div className="bg-white rounded-lg shadow-md p-6">
+        <h1 className="text-2xl font-bold text-gray-800 mb-6">
+          {t("followingOf", { username: user.displayUsername || user.username || "User" })}
+        </h1>
+        <UserList users={following} emptyMessage={t("noFollowing")} />
+      </div>
+    </PageLayout>
+  );
+}

src/app/(auth)/users/[username]/page.tsx

@@ -1,14 +1,15 @@
 import Image from "next/image";
 import Link from "next/link";
 import { PageLayout } from "@/components/ui/PageLayout";
-import { LightButton, LinkButton } from "@/design-system/base/button";
+import { LinkButton } from "@/design-system/base/button";
 import { actionGetUserProfileByUsername } from "@/modules/auth/auth-action";
 import { repoGetFoldersWithTotalPairsByUserId } from "@/modules/folder/folder-repository";
+import { actionGetFollowStatus } from "@/modules/follow/follow-action";
 import { notFound } from "next/navigation";
 import { getTranslations } from "next-intl/server";
 import { auth } from "@/auth";
 import { headers } from "next/headers";
-// import { LogoutButton } from "./LogoutButton";
+import { FollowStats } from "@/components/follow/FollowStats";
 
 interface UserPageProps {
     params: Promise<{ username: string; }>;
@@ -18,10 +19,8 @@ export default async function UserPage({ params }: UserPageProps) {
     const { username } = await params;
     const t = await getTranslations("user_profile");
 
-    // Get current session
     const session = await auth.api.getSession({ headers: await headers() });
 
-    // Get user profile
     const result = await actionGetUserProfileByUsername({ username });
 
     if (!result.success || !result.data) {
@@ -30,24 +29,27 @@ export default async function UserPage({ params }: UserPageProps) {
 
     const user = result.data;
 
-    // Get user's folders
+    const [folders, followStatus] = await Promise.all([
-    const folders = await repoGetFoldersWithTotalPairsByUserId(user.id);
+        repoGetFoldersWithTotalPairsByUserId(user.id),
+        actionGetFollowStatus({ targetUserId: user.id }),
+    ]);
 
-    // Check if viewing own profile
     const isOwnProfile = session?.user?.username === username || session?.user?.email === username;
 
+    const followersCount = followStatus.success && followStatus.data ? followStatus.data.followersCount : 0;
+    const followingCount = followStatus.success && followStatus.data ? followStatus.data.followingCount : 0;
+    const isFollowing = followStatus.success && followStatus.data ? followStatus.data.isFollowing : false;
+
     return (
         <PageLayout>
-            {/* Header */}
             <div className="bg-white rounded-lg shadow-md p-6 mb-6">
                 <div className="flex items-center justify-between mb-4">
                     <div></div>
                     {isOwnProfile && <LinkButton href="/logout">{t("logout")}</LinkButton>}
                 </div>
-                    <div className="flex items-center space-x-6">
+                <div className="flex flex-col sm:flex-row items-start sm:items-center space-y-4 sm:space-y-0 sm:space-x-6">
-                        {/* Avatar */}
                     {user.image ? (
-                            <div className="relative w-24 h-24 rounded-full border-4 border-primary-500 overflow-hidden">
+                        <div className="relative w-24 h-24 rounded-full border-4 border-primary-500 overflow-hidden flex-shrink-0">
                             <Image
                                 src={user.image}
                                 alt={user.displayUsername || user.username || user.email}
@@ -57,14 +59,13 @@ export default async function UserPage({ params }: UserPageProps) {
                             />
                         </div>
                     ) : (
-                            <div className="w-24 h-24 rounded-full bg-primary-500 border-4 border-primary-500 flex items-center justify-center">
+                        <div className="w-24 h-24 rounded-full bg-primary-500 border-4 border-primary-500 flex items-center justify-center flex-shrink-0">
                             <span className="text-3xl font-bold text-white">
                                 {(user.displayUsername || user.username || user.email)[0].toUpperCase()}
                             </span>
                         </div>
                     )}
 
-                        {/* User Info */}
                     <div className="flex-1">
                         <h1 className="text-3xl font-bold text-gray-800 mb-2">
                             {user.displayUsername || user.username || t("anonymous")}
@@ -74,27 +75,39 @@ export default async function UserPage({ params }: UserPageProps) {
                                 @{user.username}
                             </p>
                         )}
-                            <p className="text-gray-600 text-sm mb-1">
+                        {user.bio && (
-                                {user.email}
+                            <p className="text-gray-700 mt-2 mb-2">
+                                {user.bio}
                             </p>
-                            <div className="flex items-center space-x-4 text-sm">
+                        )}
+                        <div className="flex flex-wrap items-center gap-4 text-sm mt-3">
                             <span className="text-gray-500">
-                                    Joined: {new Date(user.createdAt).toLocaleDateString()}
+                                {t("joined")}: {new Date(user.createdAt).toLocaleDateString()}
                             </span>
                             {user.emailVerified && (
                                 <span className="flex items-center text-green-600">
                                     <svg className="w-4 h-4 mr-1" fill="currentColor" viewBox="0 0 20 20">
                                         <path fillRule="evenodd" d="M10 18a8 8 0 100-16 8 8 0 000 16zm3.707-9.293a1 1 0 00-1.414-1.414L9 10.586 7.293 12.293a1 1 0 101.414 1.414l2 2a1 1 0 001.414 0l4-4z" clipRule="evenodd" />
                                     </svg>
-                                        Verified
+                                    {t("verified")}
                                 </span>
                             )}
                         </div>
+                        <div className="mt-3">
+                            <FollowStats
+                                userId={user.id}
+                                initialFollowersCount={followersCount}
+                                initialFollowingCount={followingCount}
+                                initialIsFollowing={isFollowing}
+                                currentUserId={session?.user?.id}
+                                isOwnProfile={isOwnProfile}
+                                username={user.username || user.id}
+                            />
+                        </div>
                     </div>
                 </div>
             </div>
 
-                {/* Account Info */}
             <div className="bg-white rounded-lg shadow-md p-6 mb-6">
                 <h2 className="text-xl font-semibold text-gray-800 mb-4">{t("accountInfo")}</h2>
                 <dl className="grid grid-cols-1 gap-4 sm:grid-cols-2">
@@ -123,7 +136,6 @@ export default async function UserPage({ params }: UserPageProps) {
                 </dl>
             </div>
 
-                {/* Folders Section */}
             <div className="bg-white rounded-lg shadow-md p-6">
                 <h2 className="text-xl font-semibold text-gray-800 mb-4">{t("folders.title")}</h2>
                 {folders.length === 0 ? (

src/components/follow/FollowButton.tsx

@@ -0,0 +1,47 @@
+"use client";
+
+import { useState, useTransition } from "react";
+import { PrimaryButton, LightButton } from "@/design-system/base/button";
+import { actionToggleFollow } from "@/modules/follow/follow-action";
+import { toast } from "sonner";
+
+interface FollowButtonProps {
+  targetUserId: string;
+  initialIsFollowing: boolean;
+  onFollowChange?: (isFollowing: boolean, followersCount: number) => void;
+}
+
+export function FollowButton({
+  targetUserId,
+  initialIsFollowing,
+  onFollowChange,
+}: FollowButtonProps) {
+  const [isFollowing, setIsFollowing] = useState(initialIsFollowing);
+  const [isPending, startTransition] = useTransition();
+
+  const handleToggleFollow = () => {
+    startTransition(async () => {
+      const result = await actionToggleFollow({ targetUserId });
+      if (result.success && result.data) {
+        setIsFollowing(result.data.isFollowing);
+        onFollowChange?.(result.data.isFollowing, result.data.followersCount);
+      } else {
+        toast.error(result.message || "Failed to update follow status");
+      }
+    });
+  };
+
+  if (isFollowing) {
+    return (
+      <LightButton onClick={handleToggleFollow} disabled={isPending}>
+        {isPending ? "..." : "Following"}
+      </LightButton>
+    );
+  }
+
+  return (
+    <PrimaryButton onClick={handleToggleFollow} disabled={isPending}>
+      {isPending ? "..." : "Follow"}
+    </PrimaryButton>
+  );
+}

src/components/follow/FollowStats.tsx

@@ -0,0 +1,54 @@
+"use client";
+
+import { useState } from "react";
+import { FollowButton } from "./FollowButton";
+
+interface FollowStatsProps {
+  userId: string;
+  initialFollowersCount: number;
+  initialFollowingCount: number;
+  initialIsFollowing: boolean;
+  currentUserId?: string;
+  isOwnProfile: boolean;
+  username: string;
+}
+
+export function FollowStats({
+  userId,
+  initialFollowersCount,
+  initialFollowingCount,
+  initialIsFollowing,
+  currentUserId,
+  isOwnProfile,
+  username,
+}: FollowStatsProps) {
+  const [followersCount, setFollowersCount] = useState(initialFollowersCount);
+
+  const handleFollowChange = (isFollowing: boolean, count: number) => {
+    setFollowersCount(count);
+  };
+
+  return (
+    <div className="flex items-center gap-4">
+      <a
+        href={`/users/${username}/followers`}
+        className="text-sm text-gray-600 hover:text-primary-500 transition-colors"
+      >
+        <span className="font-semibold text-gray-900">{followersCount}</span> followers
+      </a>
+      <a
+        href={`/users/${username}/following`}
+        className="text-sm text-gray-600 hover:text-primary-500 transition-colors"
+      >
+        <span className="font-semibold text-gray-900">{initialFollowingCount}</span> following
+      </a>
+      {currentUserId && !isOwnProfile && (
+        <FollowButton
+          targetUserId={userId}
+          initialIsFollowing={initialIsFollowing}
+          onFollowChange={handleFollowChange}
+        />
+      )}
+    </div>
+  );
+}

src/components/follow/UserList.tsx

@@ -0,0 +1,68 @@
+import Image from "next/image";
+import Link from "next/link";
+
+interface UserItem {
+  id: string;
+  username: string | null;
+  displayUsername: string | null;
+  image: string | null;
+  bio: string | null;
+}
+
+interface UserListProps {
+  users: UserItem[];
+  emptyMessage: string;
+}
+
+export function UserList({ users, emptyMessage }: UserListProps) {
+  if (users.length === 0) {
+    return (
+      <div className="text-center py-12 text-gray-500">
+        {emptyMessage}
+      </div>
+    );
+  }
+
+  return (
+    <div className="space-y-4">
+      {users.map((user) => (
+        <Link
+          key={user.id}
+          href={`/users/${user.username || user.id}`}
+          className="flex items-center gap-4 p-4 bg-white rounded-lg shadow-sm hover:shadow-md transition-shadow"
+        >
+          {user.image ? (
+            <div className="relative w-12 h-12 rounded-full overflow-hidden flex-shrink-0">
+              <Image
+                src={user.image}
+                alt={user.displayUsername || user.username || "User"}
+                fill
+                className="object-cover"
+                unoptimized
+              />
+            </div>
+          ) : (
+            <div className="w-12 h-12 rounded-full bg-primary-500 flex items-center justify-center flex-shrink-0">
+              <span className="text-lg font-bold text-white">
+                {(user.displayUsername || user.username || "U")[0].toUpperCase()}
+              </span>
+            </div>
+          )}
+          <div className="flex-1 min-w-0">
+            <div className="font-semibold text-gray-900 truncate">
+              {user.displayUsername || user.username || "Anonymous"}
+            </div>
+            {user.username && (
+              <div className="text-sm text-gray-500">@{user.username}</div>
+            )}
+            {user.bio && (
+              <div className="text-sm text-gray-600 truncate mt-1">
+                {user.bio}
+              </div>
+            )}
+          </div>
+        </Link>
+      ))}
+    </div>
+  );
+}

src/modules/auth/auth-action-dto.ts

@@ -56,6 +56,7 @@ export type ActionOutputUserProfile = {
         username: string | null;
         displayUsername: string | null;
         image: string | null;
+        bio: string | null;
         createdAt: Date;
         updatedAt: Date;
     };

src/modules/auth/auth-repository-dto.ts

@@ -8,6 +8,7 @@ export type RepoOutputUserProfile = {
     username: string | null;
     displayUsername: string | null;
     image: string | null;
+    bio: string | null;
     createdAt: Date;
     updatedAt: Date;
 } | null;

src/modules/auth/auth-repository.ts

@@ -6,9 +6,6 @@ import {
     RepoOutputUserProfile
 } from "./auth-repository-dto";
 
-/**
- * Find user by username
- */
 export async function repoFindUserByUsername(dto: RepoInputFindUserByUsername): Promise<RepoOutputUserProfile> {
     const user = await prisma.user.findUnique({
         where: { username: dto.username },
@@ -19,6 +16,7 @@ export async function repoFindUserByUsername(dto: RepoInputFindUserByUsername):
             username: true,
             displayUsername: true,
             image: true,
+            bio: true,
             createdAt: true,
             updatedAt: true,
         }
@@ -27,9 +25,6 @@ export async function repoFindUserByUsername(dto: RepoInputFindUserByUsername):
     return user;
 }
 
-/**
- * Find user by ID
- */
 export async function repoFindUserById(dto: RepoInputFindUserById): Promise<RepoOutputUserProfile> {
     const user = await prisma.user.findUnique({
         where: { id: dto.id },
@@ -40,6 +35,7 @@ export async function repoFindUserById(dto: RepoInputFindUserById): Promise<Repo
             username: true,
             displayUsername: true,
             image: true,
+            bio: true,
             createdAt: true,
             updatedAt: true,
         }
@@ -48,9 +44,6 @@ export async function repoFindUserById(dto: RepoInputFindUserById): Promise<Repo
     return user;
 }
 
-/**
- * Find user by email
- */
 export async function repoFindUserByEmail(dto: RepoInputFindUserByEmail): Promise<RepoOutputUserProfile> {
     const user = await prisma.user.findUnique({
         where: { email: dto.email },
@@ -61,6 +54,7 @@ export async function repoFindUserByEmail(dto: RepoInputFindUserByEmail): Promis
             username: true,
             displayUsername: true,
             image: true,
+            bio: true,
             createdAt: true,
             updatedAt: true,
         }

src/modules/auth/auth-service-dto.ts

@@ -34,6 +34,7 @@ export type ServiceOutputUserProfile = {
     username: string | null;
     displayUsername: string | null;
     image: string | null;
+    bio: string | null;
     createdAt: Date;
     updatedAt: Date;
 } | null;

src/modules/follow/follow-action-dto.ts

@@ -0,0 +1,33 @@
+import { z } from "zod";
+
+const schemaActionInputToggleFollow = z.object({
+  targetUserId: z.string().min(1),
+});
+
+const schemaActionInputGetFollowers = z.object({
+  userId: z.string().min(1),
+  page: z.number().int().min(1).optional().default(1),
+  limit: z.number().int().min(1).max(100).optional().default(20),
+});
+
+const schemaActionInputGetFollowing = z.object({
+  userId: z.string().min(1),
+  page: z.number().int().min(1).optional().default(1),
+  limit: z.number().int().min(1).max(100).optional().default(20),
+});
+
+const schemaActionInputGetFollowStatus = z.object({
+  targetUserId: z.string().min(1),
+});
+
+export type ActionInputToggleFollow = z.infer<typeof schemaActionInputToggleFollow>;
+export type ActionInputGetFollowers = z.infer<typeof schemaActionInputGetFollowers>;
+export type ActionInputGetFollowing = z.infer<typeof schemaActionInputGetFollowing>;
+export type ActionInputGetFollowStatus = z.infer<typeof schemaActionInputGetFollowStatus>;
+
+export {
+  schemaActionInputGetFollowers,
+  schemaActionInputGetFollowing,
+  schemaActionInputGetFollowStatus,
+  schemaActionInputToggleFollow,
+};

src/modules/follow/follow-action.ts

@@ -0,0 +1,84 @@
+"use server";
+
+import { auth } from "@/auth";
+import { headers } from "next/headers";
+import { validate } from "@/utils/validate";
+import { serviceGetFollowers, serviceGetFollowing, serviceGetFollowStatus, serviceToggleFollow } from "./follow-service";
+import {
+  schemaActionInputGetFollowers,
+  schemaActionInputGetFollowing,
+  schemaActionInputGetFollowStatus,
+  schemaActionInputToggleFollow,
+} from "./follow-action-dto";
+import { createLogger } from "@/lib/logger";
+
+const log = createLogger("follow-action");
+
+export async function actionToggleFollow(input: unknown) {
+  const session = await auth.api.getSession({ headers: await headers() });
+  if (!session?.user?.id) {
+    return { success: false, message: "Unauthorized" };
+  }
+
+  try {
+    const dto = validate(input, schemaActionInputToggleFollow);
+    const result = await serviceToggleFollow({
+      currentUserId: session.user.id,
+      targetUserId: dto.targetUserId,
+    });
+    return { success: true, data: result };
+  } catch (error) {
+    const message = error instanceof Error ? error.message : "Failed to toggle follow";
+    log.error("Failed to toggle follow", { error });
+    return { success: false, message };
+  }
+}
+
+export async function actionGetFollowStatus(input: unknown) {
+  const session = await auth.api.getSession({ headers: await headers() });
+
+  try {
+    const dto = validate(input, schemaActionInputGetFollowStatus);
+    const result = await serviceGetFollowStatus({
+      currentUserId: session?.user?.id || "",
+      targetUserId: dto.targetUserId,
+    });
+    return { success: true, data: result };
+  } catch (error) {
+    const message = error instanceof Error ? error.message : "Failed to get follow status";
+    log.error("Failed to get follow status", { error });
+    return { success: false, message };
+  }
+}
+
+export async function actionGetFollowers(input: unknown) {
+  try {
+    const dto = validate(input, schemaActionInputGetFollowers);
+    const result = await serviceGetFollowers({
+      userId: dto.userId,
+      page: dto.page,
+      limit: dto.limit,
+    });
+    return { success: true, data: result };
+  } catch (error) {
+    const message = error instanceof Error ? error.message : "Failed to get followers";
+    log.error("Failed to get followers", { error });
+    return { success: false, message };
+  }
+}
+
+export async function actionGetFollowing(input: unknown) {
+  try {
+    const dto = validate(input, schemaActionInputGetFollowing);
+    const result = await serviceGetFollowing({
+      userId: dto.userId,
+      page: dto.page,
+      limit: dto.limit,
+    });
+    return { success: true, data: result };
+  } catch (error) {
+    const message = error instanceof Error ? error.message : "Failed to get following";
+    log.error("Failed to get following", { error });
+    return { success: false, message };
+  }
+}

src/modules/follow/follow-repository-dto.ts

@@ -0,0 +1,51 @@
+export type RepoInputCreateFollow = {
+  followerId: string;
+  followingId: string;
+};
+
+export type RepoInputDeleteFollow = {
+  followerId: string;
+  followingId: string;
+};
+
+export type RepoInputCheckFollow = {
+  followerId: string;
+  followingId: string;
+};
+
+export type RepoInputGetFollowers = {
+  userId: string;
+  page?: number;
+  limit?: number;
+};
+
+export type RepoInputGetFollowing = {
+  userId: string;
+  page?: number;
+  limit?: number;
+};
+
+export type RepoOutputFollowUser = {
+  id: string;
+  followerId: string;
+  followingId: string;
+  createdAt: Date;
+};
+
+export type RepoOutputFollowWithUser = {
+  id: string;
+  followerId: string;
+  followingId: string;
+  createdAt: Date;
+  user: {
+    id: string;
+    username: string | null;
+    displayUsername: string | null;
+    image: string | null;
+    bio: string | null;
+  };
+};
+
+export type RepoOutputFollowerCount = number;
+export type RepoOutputFollowingCount = number;
+export type RepoOutputIsFollowing = boolean;

src/modules/follow/follow-repository.ts

@@ -0,0 +1,142 @@
+import { prisma } from "@/lib/db";
+import { createLogger } from "@/lib/logger";
+import type {
+  RepoInputCheckFollow,
+  RepoInputCreateFollow,
+  RepoInputDeleteFollow,
+  RepoInputGetFollowers,
+  RepoInputGetFollowing,
+  RepoOutputFollowerCount,
+  RepoOutputFollowUser,
+  RepoOutputFollowWithUser,
+  RepoOutputFollowingCount,
+  RepoOutputIsFollowing,
+} from "./follow-repository-dto";
+
+const log = createLogger("follow-repository");
+
+export async function repoCreateFollow(
+  dto: RepoInputCreateFollow
+): Promise<RepoOutputFollowUser> {
+  log.debug("Creating follow", { followerId: dto.followerId, followingId: dto.followingId });
+
+  const follow = await prisma.follow.create({
+    data: {
+      followerId: dto.followerId,
+      followingId: dto.followingId,
+    },
+  });
+
+  log.info("Follow created", { followId: follow.id });
+  return follow;
+}
+
+export async function repoDeleteFollow(
+  dto: RepoInputDeleteFollow
+): Promise<void> {
+  log.debug("Deleting follow", { followerId: dto.followerId, followingId: dto.followingId });
+
+  await prisma.follow.delete({
+    where: {
+      followerId_followingId: {
+        followerId: dto.followerId,
+        followingId: dto.followingId,
+      },
+    },
+  });
+
+  log.info("Follow deleted");
+}
+
+export async function repoCheckFollow(
+  dto: RepoInputCheckFollow
+): Promise<RepoOutputIsFollowing> {
+  const follow = await prisma.follow.findUnique({
+    where: {
+      followerId_followingId: {
+        followerId: dto.followerId,
+        followingId: dto.followingId,
+      },
+    },
+  });
+
+  return !!follow;
+}
+
+export async function repoGetFollowersCount(userId: string): Promise<RepoOutputFollowerCount> {
+  return prisma.follow.count({
+    where: { followingId: userId },
+  });
+}
+
+export async function repoGetFollowingCount(userId: string): Promise<RepoOutputFollowingCount> {
+  return prisma.follow.count({
+    where: { followerId: userId },
+  });
+}
+
+export async function repoGetFollowers(
+  dto: RepoInputGetFollowers
+): Promise<RepoOutputFollowWithUser[]> {
+  const { userId, page = 1, limit = 20 } = dto;
+  const skip = (page - 1) * limit;
+
+  const follows = await prisma.follow.findMany({
+    where: { followingId: userId },
+    include: {
+      follower: {
+        select: {
+          id: true,
+          username: true,
+          displayUsername: true,
+          image: true,
+          bio: true,
+        },
+      },
+    },
+    orderBy: { createdAt: "desc" },
+    skip,
+    take: limit,
+  });
+
+  return follows.map((f) => ({
+    id: f.id,
+    followerId: f.followerId,
+    followingId: f.followingId,
+    createdAt: f.createdAt,
+    user: f.follower,
+  }));
+}
+
+export async function repoGetFollowing(
+  dto: RepoInputGetFollowing
+): Promise<RepoOutputFollowWithUser[]> {
+  const { userId, page = 1, limit = 20 } = dto;
+  const skip = (page - 1) * limit;
+
+  const follows = await prisma.follow.findMany({
+    where: { followerId: userId },
+    include: {
+      following: {
+        select: {
+          id: true,
+          username: true,
+          displayUsername: true,
+          image: true,
+          bio: true,
+        },
+      },
+    },
+    orderBy: { createdAt: "desc" },
+    skip,
+    take: limit,
+  });
+
+  return follows.map((f) => ({
+    id: f.id,
+    followerId: f.followerId,
+    followingId: f.followingId,
+    createdAt: f.createdAt,
+    user: f.following,
+  }));
+}

src/modules/follow/follow-service-dto.ts

@@ -0,0 +1,51 @@
+export type ServiceInputToggleFollow = {
+  currentUserId: string;
+  targetUserId: string;
+};
+
+export type ServiceInputGetFollowers = {
+  userId: string;
+  page?: number;
+  limit?: number;
+};
+
+export type ServiceInputGetFollowing = {
+  userId: string;
+  page?: number;
+  limit?: number;
+};
+
+export type ServiceInputCheckFollow = {
+  currentUserId: string;
+  targetUserId: string;
+};
+
+export type ServiceOutputFollowUser = {
+  id: string;
+  followerId: string;
+  followingId: string;
+  createdAt: Date;
+};
+
+export type ServiceOutputFollowWithUser = {
+  id: string;
+  createdAt: Date;
+  user: {
+    id: string;
+    username: string | null;
+    displayUsername: string | null;
+    image: string | null;
+    bio: string | null;
+  };
+};
+
+export type ServiceOutputFollowStatus = {
+  isFollowing: boolean;
+  followersCount: number;
+  followingCount: number;
+};
+
+export type ServiceOutputToggleFollow = {
+  isFollowing: boolean;
+  followersCount: number;
+};

src/modules/follow/follow-service.ts

@@ -0,0 +1,103 @@
+import { createLogger } from "@/lib/logger";
+import {
+  repoCheckFollow,
+  repoCreateFollow,
+  repoDeleteFollow,
+  repoGetFollowers,
+  repoGetFollowersCount,
+  repoGetFollowing,
+  repoGetFollowingCount,
+} from "./follow-repository";
+import type {
+  ServiceInputCheckFollow,
+  ServiceInputGetFollowers,
+  ServiceInputGetFollowing,
+  ServiceInputToggleFollow,
+  ServiceOutputFollowStatus,
+  ServiceOutputFollowWithUser,
+  ServiceOutputToggleFollow,
+} from "./follow-service-dto";
+
+const log = createLogger("follow-service");
+
+export async function serviceToggleFollow(
+  dto: ServiceInputToggleFollow
+): Promise<ServiceOutputToggleFollow> {
+  const { currentUserId, targetUserId } = dto;
+
+  if (currentUserId === targetUserId) {
+    throw new Error("Cannot follow yourself");
+  }
+
+  const isFollowing = await repoCheckFollow({
+    followerId: currentUserId,
+    followingId: targetUserId,
+  });
+
+  if (isFollowing) {
+    await repoDeleteFollow({
+      followerId: currentUserId,
+      followingId: targetUserId,
+    });
+    log.info("Unfollowed user", { currentUserId, targetUserId });
+  } else {
+    await repoCreateFollow({
+      followerId: currentUserId,
+      followingId: targetUserId,
+    });
+    log.info("Followed user", { currentUserId, targetUserId });
+  }
+
+  const followersCount = await repoGetFollowersCount(targetUserId);
+
+  return {
+    isFollowing: !isFollowing,
+    followersCount,
+  };
+}
+
+export async function serviceGetFollowStatus(
+  dto: ServiceInputCheckFollow
+): Promise<ServiceOutputFollowStatus> {
+  const { currentUserId, targetUserId } = dto;
+
+  const [isFollowing, followersCount, followingCount] = await Promise.all([
+    currentUserId
+      ? repoCheckFollow({ followerId: currentUserId, followingId: targetUserId })
+      : false,
+    repoGetFollowersCount(targetUserId),
+    repoGetFollowingCount(targetUserId),
+  ]);
+
+  return {
+    isFollowing,
+    followersCount,
+    followingCount,
+  };
+}
+
+export async function serviceGetFollowers(
+  dto: ServiceInputGetFollowers
+): Promise<{ followers: ServiceOutputFollowWithUser[]; total: number }> {
+  const { userId, page, limit } = dto;
+
+  const [followers, total] = await Promise.all([
+    repoGetFollowers({ userId, page, limit }),
+    repoGetFollowersCount(userId),
+  ]);
+
+  return { followers, total };
+}
+
+export async function serviceGetFollowing(
+  dto: ServiceInputGetFollowing
+): Promise<{ following: ServiceOutputFollowWithUser[]; total: number }> {
+  const { userId, page, limit } = dto;
+
+  const [following, total] = await Promise.all([
+    repoGetFollowing({ userId, page, limit }),
+    repoGetFollowingCount(userId),
+  ]);
+
+  return { following, total };
+}