# Suspense Boundaries & Streaming Implementation Plan

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** Stream the feed page immediately while sidebar widgets load independently, and fix the N+1 top-friends profile fetch by having the backend return full user objects in one query.

**Architecture:** The `TopFriendRepository::list_for_user` already JOINs users — the backend just discards the user data and returns only usernames. We fix the handler to return `Vec<UserResponse>`. Frontend: `TopFriends` becomes self-contained (fetches its own data via cookies, no props from page), wrapped in `<Suspense>`. `app/page.tsx` drops all sidebar awaits, reducing critical-path work to two parallel calls.

**Tech Stack:** Rust/Axum (backend), Next.js 15 App Router, React 19 Suspense, Tailwind CSS, shadcn/ui

---

## Key Facts

- `TopFriendRepository::list_for_user` already returns `Vec<(TopFriend, User)>` — the JOIN with the users table is done. The handler just discards the `User` data.
- `to_user_response(u: &User) -> UserResponse` lives in `crates/presentation/src/handlers/auth.rs` as `pub fn` — import it where needed.
- Auth token in frontend server components: `(await cookies()).get("auth_token")?.value ?? null` via `next/headers`.
- Baseline test suite: `cargo test` (148 tests) in the backend; `npx tsc --noEmit` in `thoughts-frontend/`.

---

## File Map

| File | Change |
|---|---|
| `crates/api-types/src/responses.rs` | Add `TopFriendsResponse { top_friends: Vec<UserResponse> }` |
| `crates/presentation/src/handlers/social.rs` | Return `TopFriendsResponse` instead of `{ topFriends: usernames }` |
| `thoughts-frontend/lib/api.ts` | Update `getTopFriends` schema to `z.array(UserSchema)` |
| `thoughts-frontend/components/loading-skeleton.tsx` | Add `TagsSkeleton`, `CountSkeleton` |
| `thoughts-frontend/components/top-friends.tsx` | Self-contained: fetches own data, no `usernames` prop |
| `thoughts-frontend/app/page.tsx` | Strip `getFriends`/`getTopFriends`/`shouldDisplayTopFriends`; add Suspense |
| `thoughts-frontend/app/loading.tsx` | New — feed page skeleton |
| `thoughts-frontend/app/tags/[tagName]/loading.tsx` | New |
| `thoughts-frontend/app/search/loading.tsx` | New |
| `thoughts-frontend/app/thoughts/[thoughtId]/loading.tsx` | New |

---

## Task 1: Add `TopFriendsResponse` to api-types

**Files:**
- Modify: `crates/api-types/src/responses.rs`

- [ ] **Step 1: Add the response struct**

In `crates/api-types/src/responses.rs`, after the `NotificationResponse` block, add:

```rust
#[derive(Serialize, utoipa::ToSchema)]
#[serde(rename_all = "camelCase")]
pub struct TopFriendsResponse {
    pub top_friends: Vec<UserResponse>,
}
```

- [ ] **Step 2: Verify it compiles**

```bash
cargo build -p api-types
```

Expected: Compiles with no errors.

- [ ] **Step 3: Commit**

```bash
git add crates/api-types/src/responses.rs
git commit -m "feat(api-types): TopFriendsResponse with Vec<UserResponse>"
```

---

## Task 2: Update `get_top_friends_handler` to return full user objects

**Files:**
- Modify: `crates/presentation/src/handlers/social.rs`

- [ ] **Step 1: Read the current handler**

Current code (around line 159–167 in `social.rs`):

```rust
pub async fn get_top_friends_handler(
    Deps(d): Deps<SocialDeps>,
    Path(username): Path<String>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let user = get_user_by_username(&*d.users, &username).await?;
    let friends = get_top_friends(&*d.top_friends, &user.id).await?;
    let usernames: Vec<&str> = friends.iter().map(|(_, u)| u.username.as_str()).collect();
    Ok(Json(serde_json::json!({ "topFriends": usernames })))
}
```

`friends` is already `Vec<(TopFriend, User)>` — the user data is there.

- [ ] **Step 2: Add import and update the handler**

Add to the imports at the top of `social.rs`:
```rust
use api_types::responses::TopFriendsResponse;
use crate::handlers::auth::to_user_response;
```

Replace the handler body:

```rust
#[utoipa::path(get, path = "/users/{username}/top-friends",
    params(("username" = String, Path, description = "Username")),
    responses((status = 200, description = "Top friends list", body = TopFriendsResponse)))]
pub async fn get_top_friends_handler(
    Deps(d): Deps<SocialDeps>,
    Path(username): Path<String>,
) -> Result<Json<TopFriendsResponse>, ApiError> {
    let user = get_user_by_username(&*d.users, &username).await?;
    let friends = get_top_friends(&*d.top_friends, &user.id).await?;
    let top_friends = friends.iter().map(|(_, u)| to_user_response(u)).collect();
    Ok(Json(TopFriendsResponse { top_friends }))
}
```

- [ ] **Step 3: Run backend tests**

```bash
cargo test
```

Expected: 148 tests pass (same as before — no test exercises the response shape directly).

- [ ] **Step 4: Smoke-test the endpoint manually (optional)**

```bash
curl -s -H "Authorization: Bearer <your_token>" http://localhost:3001/users/me/top-friends | python3 -m json.tool
```

Expected: `{ "topFriends": [ { "id": "...", "username": "...", "avatarUrl": "...", ... } ] }`

- [ ] **Step 5: Commit**

```bash
git add crates/presentation/src/handlers/social.rs
git commit -m "fix(api): top-friends endpoint returns full UserResponse — eliminates frontend N+1"
```

---

## Task 3: Update frontend `getTopFriends` Zod schema

**Files:**
- Modify: `thoughts-frontend/lib/api.ts`

- [ ] **Step 1: Find and update `getTopFriends`**

In `lib/api.ts`, find `getTopFriends` (around line 232). Current:

```ts
export const getTopFriends = (username: string, token: string | null) =>
  apiFetch(
    `/users/${username}/top-friends`,
    { next: { tags: [`profile:${username}`] } },
    z.object({ topFriends: z.array(z.string()) }),
    token
  );
```

Replace with:

```ts
export const getTopFriends = (username: string, token: string | null) =>
  apiFetch(
    `/users/${username}/top-friends`,
    { next: { tags: [`profile:${username}`] } },
    z.object({ topFriends: z.array(UserSchema) }),
    token
  );
```

`UserSchema` is already defined in the same file — no new import needed.

- [ ] **Step 2: Type-check**

```bash
cd thoughts-frontend && npx tsc --noEmit
```

Expected: 0 errors. (TypeScript will flag call sites that use `getTopFriends` and expect `string[]` — these are fixed in Task 4.)

If errors: note them, they'll be resolved in Task 4.

- [ ] **Step 3: Commit**

```bash
git add thoughts-frontend/lib/api.ts
git commit -m "fix(frontend): getTopFriends schema returns UserSchema[] not string[]"
```

---

## Task 4: Add `TagsSkeleton` and `CountSkeleton` to loading-skeleton.tsx

**Files:**
- Modify: `thoughts-frontend/components/loading-skeleton.tsx`

- [ ] **Step 1: Add the two new exports**

In `thoughts-frontend/components/loading-skeleton.tsx`, append after the existing exports:

```tsx
export function TagsSkeleton() {
  return (
    <Card>
      <CardContent className="pt-4 space-y-2">
        <Skeleton className="h-4 w-24 mb-3" />
        {[...Array(5)].map((_, i) => (
          <Skeleton key={i} className="h-6 w-full rounded-full" />
        ))}
      </CardContent>
    </Card>
  )
}

export function CountSkeleton() {
  return (
    <Card>
      <CardContent className="pt-4 pb-4">
        <Skeleton className="h-6 w-32" />
      </CardContent>
    </Card>
  )
}
```

`Card`, `CardContent`, and `Skeleton` are already imported in the file.

- [ ] **Step 2: Type-check**

```bash
cd thoughts-frontend && npx tsc --noEmit
```

Expected: 0 errors.

- [ ] **Step 3: Commit**

```bash
git add thoughts-frontend/components/loading-skeleton.tsx
git commit -m "feat(frontend): TagsSkeleton and CountSkeleton for sidebar Suspense fallbacks"
```

---

## Task 5: Rewrite `TopFriends` to be self-contained

**Files:**
- Modify: `thoughts-frontend/components/top-friends.tsx`

- [ ] **Step 1: Replace the component**

Replace the entire file with:

```tsx
import Link from "next/link";
import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
import { UserAvatar } from "./user-avatar";
import { getTopFriends } from "@/lib/api";
import { cookies } from "next/headers";

interface TopFriendsProps {
  username: string;
}

export async function TopFriends({ username }: TopFriendsProps) {
  const token = (await cookies()).get("auth_token")?.value ?? null;
  const data = await getTopFriends(username, token).catch(() => ({ topFriends: [] }));
  const friends = data.topFriends;

  if (friends.length === 0) return null;

  return (
    <Card id="top-friends" className="p-4">
      <CardHeader id="top-friends__header" className="p-0 pb-2">
        <CardTitle id="top-friends__title" className="text-lg text-shadow-md">
          Top Friends
        </CardTitle>
      </CardHeader>
      <CardContent id="top-friends__content" className="p-0">
        {friends.map((friend) => (
          <Link
            id={`top-friends__link-${friend.id}`}
            href={`/users/${friend.username}`}
            key={friend.id}
            className="flex items-center gap-3 py-2 px-2 -mx-2 rounded-lg hover:bg-accent/50 transition-colors"
          >
            <UserAvatar src={friend.avatarUrl} alt={friend.username} />
            <span
              id={`top-friends__name-${friend.id}`}
              className="text-xs truncate w-full font-medium text-shadow-sm"
            >
              {friend.displayName || friend.username}
            </span>
          </Link>
        ))}
      </CardContent>
    </Card>
  );
}
```

Changes from old component:
- Props: was `{ mode, usernames: string[] }`, now `{ username: string }` — fetches its own data
- No more N+1 `getUserProfile` calls — renders `data.topFriends` (already `User[]`) directly
- `mode` prop removed — always shows "Top Friends" title (the "friends fallback" mode is dropped)
- Returns `null` if no top friends (sidebar just hides the widget)

- [ ] **Step 2: Type-check**

```bash
cd thoughts-frontend && npx tsc --noEmit
```

Expected: Errors at `app/page.tsx` call sites (still pass old props) — will be fixed in Task 6.

- [ ] **Step 3: Commit (even with type errors from call sites)**

```bash
git add thoughts-frontend/components/top-friends.tsx
git commit -m "refactor(frontend): TopFriends self-contained — fetches own data, no N+1"
```

---

## Task 6: Update `app/page.tsx` — strip blocking awaits + add Suspense

**Files:**
- Modify: `thoughts-frontend/app/page.tsx`

- [ ] **Step 1: Update imports**

Replace the current import block at the top of `app/page.tsx`:

```ts
import type { Metadata } from "next";
import { cookies } from "next/headers";
import { getFeed, getMe, Me } from "@/lib/api";
import { ThoughtForm } from "@/components/thought-form";
import { EmptyState } from "@/components/empty-state";
import { Button } from "@/components/ui/button";
import Link from "next/link";
import { PopularTags } from "@/components/popular-tags";
import { ThoughtThread } from "@/components/thought-thread";
import { buildThoughtThreads } from "@/lib/utils";
import { TopFriends } from "@/components/top-friends";
import { UsersCount } from "@/components/users-count";
import { PaginationNav } from "@/components/pagination-nav";
import { redirect } from "next/navigation";
import { Suspense } from "react";
import { ProfileSkeleton, TagsSkeleton, CountSkeleton } from "@/components/loading-skeleton";
```

(Removed: `getFriends`, `getTopFriends`, `User`)

- [ ] **Step 2: Replace `FeedPage` function**

```tsx
async function FeedPage({
  token,
  searchParams,
}: {
  token: string;
  searchParams: { page?: string };
}) {
  const page = parseInt(searchParams.page ?? "1", 10);

  const [feedData, me] = await Promise.all([
    getFeed(token, page).catch(() => null),
    getMe(token).catch(() => null) as Promise<Me | null>,
  ]);

  if (!feedData || !me) {
    redirect("/login");
  }

  const { items: allThoughts, totalPages } = feedData!;
  const thoughtThreads = buildThoughtThreads(allThoughts);

  const sidebar = (
    <>
      <Suspense fallback={<ProfileSkeleton />}>
        <TopFriends username={me.username} />
      </Suspense>
      <Suspense fallback={<TagsSkeleton />}>
        <PopularTags />
      </Suspense>
      <Suspense fallback={<CountSkeleton />}>
        <UsersCount />
      </Suspense>
    </>
  );

  return (
    <div className="container mx-auto max-w-6xl p-4 sm:p-6">
      <div className="grid grid-cols-1 lg:grid-cols-4 gap-8">
        <aside className="hidden lg:block lg:col-span-1">
          <div className="sticky top-20 space-y-6 glass-effect glossy-effect bottom rounded-md p-4">
            <h2 className="text-lg font-semibold">Filters &amp; Sorting</h2>
            <p className="text-sm text-muted-foreground">Coming soon...</p>
          </div>
        </aside>

        <main className="col-span-1 lg:col-span-2 space-y-6">
          <header className="mb-6">
            <h1 className="text-3xl font-bold text-shadow-sm">Your Feed</h1>
          </header>
          <ThoughtForm />

          <div className="block lg:hidden space-y-6">
            {sidebar}
          </div>

          <div className="space-y-6">
            {thoughtThreads.map((thought) => (
              <ThoughtThread
                key={thought.id}
                thought={thought}
                currentUser={me}
              />
            ))}
            {thoughtThreads.length === 0 && (
              <EmptyState message="Your feed is empty. Follow some users to see their thoughts!" />
            )}
          </div>
          <PaginationNav
            page={page}
            totalPages={totalPages}
            buildHref={(p) => `/?page=${p}`}
          />
        </main>

        <aside className="hidden lg:block lg:col-span-1">
          <div className="sticky top-20 space-y-6">
            {sidebar}
          </div>
        </aside>
      </div>
    </div>
  );
}
```

- [ ] **Step 3: Type-check**

```bash
cd thoughts-frontend && npx tsc --noEmit
```

Expected: 0 errors.

- [ ] **Step 4: Commit**

```bash
git add thoughts-frontend/app/page.tsx
git commit -m "perf(frontend): stream sidebar via Suspense — feed renders immediately, sidebar loads async"
```

---

## Task 7: Add `loading.tsx` files for pages missing them

**Files:**
- Create: `thoughts-frontend/app/loading.tsx`
- Create: `thoughts-frontend/app/tags/[tagName]/loading.tsx`
- Create: `thoughts-frontend/app/search/loading.tsx`
- Create: `thoughts-frontend/app/thoughts/[thoughtId]/loading.tsx`

- [ ] **Step 1: Create `thoughts-frontend/app/loading.tsx`**

This matches the feed page layout (3-column grid with feed column visible):

```tsx
import { ThoughtSkeleton } from "@/components/loading-skeleton";

export default function FeedLoading() {
  return (
    <div className="container mx-auto max-w-6xl p-4 sm:p-6">
      <div className="grid grid-cols-1 lg:grid-cols-4 gap-8">
        <aside className="hidden lg:block lg:col-span-1" />
        <main className="col-span-1 lg:col-span-2 space-y-6">
          <div className="h-10 w-32 bg-muted rounded animate-pulse mb-6" />
          <div className="space-y-4">
            <ThoughtSkeleton />
            <ThoughtSkeleton />
            <ThoughtSkeleton />
          </div>
        </main>
        <aside className="hidden lg:block lg:col-span-1" />
      </div>
    </div>
  );
}
```

- [ ] **Step 2: Create `thoughts-frontend/app/tags/[tagName]/loading.tsx`**

```tsx
import { ThoughtSkeleton } from "@/components/loading-skeleton";

export default function TagLoading() {
  return (
    <div className="container mx-auto max-w-2xl p-4 sm:p-6 space-y-4">
      <div className="h-8 w-40 bg-muted rounded animate-pulse" />
      <ThoughtSkeleton />
      <ThoughtSkeleton />
      <ThoughtSkeleton />
    </div>
  );
}
```

- [ ] **Step 3: Create `thoughts-frontend/app/search/loading.tsx`**

```tsx
import { ThoughtSkeleton } from "@/components/loading-skeleton";

export default function SearchLoading() {
  return (
    <div className="container mx-auto max-w-2xl p-4 sm:p-6 space-y-4">
      <div className="h-8 w-48 bg-muted rounded animate-pulse" />
      <ThoughtSkeleton />
      <ThoughtSkeleton />
      <ThoughtSkeleton />
    </div>
  );
}
```

- [ ] **Step 4: Create `thoughts-frontend/app/thoughts/[thoughtId]/loading.tsx`**

```tsx
import { ThoughtSkeleton } from "@/components/loading-skeleton";

export default function ThoughtLoading() {
  return (
    <div className="container mx-auto max-w-2xl p-4 sm:p-6 space-y-4">
      <ThoughtSkeleton />
      <div className="pl-6 border-l-2 border-primary border-dashed space-y-4">
        <ThoughtSkeleton />
        <ThoughtSkeleton />
      </div>
    </div>
  );
}
```

- [ ] **Step 5: Type-check**

```bash
cd thoughts-frontend && npx tsc --noEmit
```

Expected: 0 errors.

- [ ] **Step 6: Commit**

```bash
git add thoughts-frontend/app/loading.tsx \
        thoughts-frontend/app/tags \
        thoughts-frontend/app/search/loading.tsx \
        thoughts-frontend/app/thoughts
git commit -m "feat(frontend): loading.tsx skeletons for feed, tags, search, and thread pages"
```

---

## Final Verification

- [ ] `cargo test` — 148 tests pass
- [ ] `cd thoughts-frontend && npx tsc --noEmit` — 0 errors
- [ ] `grep -r "usernames" thoughts-frontend/components/top-friends.tsx` — 0 results (old prop gone)
- [ ] `grep -r "getFriends\|getTopFriends\|shouldDisplayTopFriends" thoughts-frontend/app/page.tsx` — 0 results
- [ ] `grep -r "Suspense" thoughts-frontend/app/page.tsx` — 3+ results (one per sidebar widget)