feat(be): implement getUserByUsername api function

server/api/routers/user.ts

@@ -1,11 +1,66 @@
-import { protectedProcedure, createTRPCRouter } from '../trpc'
+import { z } from 'zod'
+
+import { protectedProcedure, createTRPCRouter } from './../trpc'
 
 export const userRouter = createTRPCRouter({
-  currentUser: protectedProcedure.query(({ ctx }) => {
-    return ctx.db.user.findUnique({
+  currentUser: protectedProcedure.query(async ({ ctx }) => {
+    return await ctx.db.user.findUniqueOrThrow({
       where: {
         externalId: ctx.auth.userId
       }
     })
-  })
+  }),
+
+  getUserbyUsername: protectedProcedure
+    .input(
+      z.object({
+        limit: z.number().min(1).max(100).nullish(),
+        cursor: z.number().nullish(), // <-- "cursor" needs to exist, but can be any type
+        username: z.string()
+      })
+    )
+    .query(async (opts) => {
+      const { ctx, input } = opts
+      const limit = input.limit ?? 15
+      const { cursor } = input
+
+      const posts = await ctx.db.user.findMany({
+        take: limit + 1, // get an extra item at the end which we'll use as next cursor
+        cursor: cursor ? { id: cursor } : undefined,
+        where: {
+          username: input.username
+        },
+        select: {
+          id: true,
+          displayName: true,
+          username: true,
+          imageUrl: true,
+          email: true,
+          posts: {
+            select: {
+              id: true,
+              mediaFiles: {
+                select: {
+                  url: true
+                }
+              }
+            },
+            orderBy: {
+              createdAt: 'desc'
+            }
+          }
+        }
+      })
+
+      let nextCursor: typeof cursor | undefined = undefined
+      if (posts.length > limit) {
+        const nextItem = posts.pop()
+        nextCursor = nextItem!.id
+      }
+
+      return {
+        posts,
+        nextCursor
+      }
+    })
 })