feat: allow passing viewer FID to user API

Adds a `viewer` parameter to `getUserByFid` and updates the return type to be more accurate

BREAKING CHANGE: The return type of `getUserByFid` no longer contains the `viewerContext` field
unless the `viewer` parameter is passed.

README.md

@@ -220,7 +220,11 @@ export async function GET(request: Request, { params }: Props) {
   const fid = parseInt(params.fid)
   if (!fid) return new Response('fid is invalid', { status: 400 })
 
-  const user = await neynarClient.getUserByFid(fid)
+  // You can pass an optional viewer FID to get back the mutual following status as well, for example to display on another user's profile page
+  // const { searchParams } = new URL(request.url)
+  // const viewer = searchParams.get('viewer')
+
+  const user = await neynarClient.getUserByFid(fid /*, viewer */)
   return NextResponse.json(signer)
 }
 ```

src/server/NeynarClient.ts

@@ -1,6 +1,13 @@
 import { Hash } from 'viem'
 import { mnemonicToAccount } from 'viem/accounts'
-import { Cast, GeneratedSigner, PendingSigner, Signer, User } from './types'
+import {
+  Cast,
+  GeneratedSigner,
+  PendingSigner,
+  Signer,
+  User,
+  UserWithViewerContext,
+} from './types'
 
 type Pagination = {
   cursor?: string
@@ -45,13 +52,14 @@ export default class NeynarClient {
     })
   }
 
-  async getUserByFid(fid: number) {
+  getUserByFid(fid: number, viewer?: null): Promise<User>
+  getUserByFid(fid: number, viewer: number): Promise<UserWithViewerContext>
+  async getUserByFid(fid: number, viewer?: number | null) {
     const params = new URLSearchParams({ fid: fid.toString() })
-    const response = await this.get<{ result: { user: User } }>(
-      'user',
-      params,
-      1,
-    )
+    if (viewer) params.set('viewerFid', viewer.toString())
+    const response = await this.get<{
+      result: { user: User | UserWithViewerContext }
+    }>('user', params, 1)
     return response.result.user
   }
 

src/server/types/User.ts

@@ -17,9 +17,10 @@ export type User = {
   followingCount: number
   verifications: Hash[]
   activeStatus: 'active' | 'inactive'
+}
 
-  // Only returned if you pass `viewerFid`
-  viewerContext?: {
+export type UserWithViewerContext = User & {
+  viewerContext: {
     following: boolean
     followedBy: boolean
   }