Updated the local state after following an account (#21509)

refs https://linear.app/ghost/issue/AP-523

We want to preempt the Accept activity from our Follows, so we make the
assumption that it's succeeded. What this means is that we have to
update our `following`, `followingCount` as well as the fetched profile
to set the `isFollowing` property. This gives a more fluid user
experience when following accounts and keeps our state up to date.

Accounts where the follow request has to be accepted manually, are a
little trickier as we don't currently have easy access to the "requested
but not accepted state"

apps/admin-x-activitypub/src/api/activitypub.ts

@@ -234,9 +234,10 @@ export class ActivityPubAPI {
         };
     }
 
-    async follow(username: string): Promise<void> {
+    async follow(username: string): Promise<Actor> {
         const url = new URL(`.ghost/activitypub/actions/follow/${username}`, this.apiUrl);
-        await this.fetchJSON(url, 'POST');
+        const json = await this.fetchJSON(url, 'POST');
+        return json as Actor;
     }
 
     async getActor(url: string): Promise<Actor> {

apps/admin-x-activitypub/src/hooks/useActivityPubQueries.ts

@@ -282,13 +282,40 @@ export function useSearchForUser(handle: string, query: string) {
 }
 
 export function useFollow(handle: string, onSuccess: () => void, onError: () => void) {
+    const queryClient = useQueryClient();
     return useMutation({
         async mutationFn(username: string) {
             const siteUrl = await getSiteUrl();
             const api = createActivityPubAPI(handle, siteUrl);
             return api.follow(username);
         },
-        onSuccess,
+        onSuccess(followedActor, fullHandle) {
+            queryClient.setQueryData([`profile:${fullHandle}`], (currentProfile: unknown) => {
+                if (!currentProfile) {
+                    return currentProfile;
+                }
+                return {
+                    ...currentProfile,
+                    isFollowing: true
+                };
+            });
+
+            queryClient.setQueryData(['following:index'], (currentFollowing?: unknown[]) => {
+                if (!currentFollowing) {
+                    return currentFollowing;
+                }
+                return [followedActor].concat(currentFollowing);
+            });
+
+            queryClient.setQueryData(['followingCount:index'], (currentFollowingCount?: number) => {
+                if (!currentFollowingCount) {
+                    return 1;
+                }
+                return currentFollowingCount + 1;
+            });
+
+            onSuccess();
+        },
         onError
     });
 }