feat(be): implement follow, unfollow and check functionality

server/api/root.ts

@@ -1,11 +1,13 @@
 import { createTRPCRouter } from './trpc'
 import { userRouter } from './routers/user'
 import { postRouter } from './routers/post'
+import { followRouter } from './routers/follow'
 import { hashtagRouter } from './routers/hashtag'
 
 export const appRouter = createTRPCRouter({
   user: userRouter,
   post: postRouter,
+  follow: followRouter,
   hashtag: hashtagRouter
 })
 

server/api/routers/follow.ts

@@ -0,0 +1,96 @@
+import { z } from 'zod'
+import { TRPCError } from '@trpc/server'
+
+import { protectedProcedure, createTRPCRouter } from './../trpc'
+
+const UserRelation = z.object({
+  targetId: z.number(),
+  authorId: z.number()
+})
+
+export const followRouter = createTRPCRouter({
+  follow: protectedProcedure.input(UserRelation).query(async ({ ctx, input }) => {
+    if (input.authorId === input.targetId) {
+      throw new TRPCError({
+        code: 'BAD_REQUEST',
+        message: 'You cannot follow yourself.'
+      })
+    }
+
+    const targetUserFound = await ctx.db.user.findUnique({
+      where: { id: input.targetId }
+    })
+
+    if (!targetUserFound) {
+      throw new TRPCError({
+        code: 'NOT_FOUND',
+        message: 'Target user not found.'
+      })
+    }
+
+    return await ctx.db.follow.create({
+      data: {
+        follower: {
+          connect: {
+            id: input.targetId
+          }
+        },
+        following: {
+          connect: {
+            id: input.authorId
+          }
+        }
+      },
+      include: {
+        follower: true,
+        following: true
+      }
+    })
+  }),
+
+  unfollow: protectedProcedure.input(UserRelation).query(async ({ ctx, input }) => {
+    if (input.authorId === input.targetId) {
+      throw new TRPCError({
+        code: 'BAD_REQUEST',
+        message: 'You cannot follow yourself.'
+      })
+    }
+
+    const targetUserFound = await ctx.db.user.findUnique({
+      where: { id: input.targetId }
+    })
+
+    if (!targetUserFound) {
+      throw new TRPCError({
+        code: 'NOT_FOUND',
+        message: 'Target user not found.'
+      })
+    }
+
+    return await ctx.db.follow.delete({
+      where: {
+        followerId_followingId: {
+          followerId: input.targetId,
+          followingId: input.authorId
+        }
+      },
+      include: {
+        follower: true,
+        following: true
+      }
+    })
+  }),
+
+  checkUserFollowed: protectedProcedure.input(UserRelation).query(({ ctx, input }) => {
+    const followRelationship = ctx.db.follow.findUnique({
+      where: {
+        followerId_followingId: {
+          followerId: input.targetId,
+          followingId: input.authorId
+        }
+      }
+    })
+
+    return !!followRelationship
+  })
+})