4wswt4ex2: Add like and unlike for post cards

src/app/api/posts/[id]/like/route.ts

@@ -0,0 +1,30 @@
+import { NextResponse, type NextRequest } from "next/server";
+import { SESSION_COOKIE } from "@/lib/cookie";
+import { setPostLike } from "@/lib/post-like";
+
+// POST   /api/posts/:id/like  -> feed POST   /api/v1/posts/{id}/like
+// DELETE /api/posts/:id/like  -> feed DELETE /api/v1/posts/{id}/like
+// No request body. Returns { isLiked, likesCount }; likesCount is null when the
+// feed response carries no count. 401 { error: "sign_in" } without a session.
+
+export const runtime = "nodejs";
+
+type Ctx = { params: Promise<{ id: string }> };
+
+async function handle(req: NextRequest, ctx: Ctx, liked: boolean) {
+  const sessionId = req.cookies.get(SESSION_COOKIE)?.value;
+  const { id } = await ctx.params;
+  const result = await setPostLike(sessionId, id, liked);
+  if (!result.ok) {
+    return NextResponse.json({ error: result.error }, { status: result.status });
+  }
+  return NextResponse.json({ isLiked: result.isLiked, likesCount: result.likesCount });
+}
+
+export function POST(req: NextRequest, ctx: Ctx) {
+  return handle(req, ctx, true);
+}
+
+export function DELETE(req: NextRequest, ctx: Ctx) {
+  return handle(req, ctx, false);
+}

src/app/globals.css

@@ -35,3 +35,10 @@ button:disabled { opacity: .5; cursor: not-allowed; }
 @keyframes spin { to { transform: rotate(360deg); } }
 .new-posts { position: sticky; top: 68px; z-index: 4; align-self: center; margin: 0; padding: 8px 16px; border-radius: 999px; }
 .sentinel { height: 1px; }
+.like-btn { display: inline-flex; align-items: center; gap: 6px; margin: 0; padding: 4px 8px; background: transparent; color: var(--grey); border-radius: 8px; font-size: 14px; font-weight: 400; }
+.like-btn:hover:not(:disabled) { color: var(--red); background: #fff3f3; }
+.like-btn.liked { color: var(--red); }
+.like-btn:disabled { opacity: 1; cursor: default; }
+.like-btn:disabled:not(.liked) { color: var(--grey); }
+.like-error { color: #a8141b; font-size: 13px; align-self: center; }
+.post-stats { align-items: center; }

src/components/Feed.tsx

@@ -2,6 +2,7 @@
 
 import { useCallback, useEffect, useRef, useState } from "react";
 import { fetchFeedPage, FeedLoadError } from "@/lib/feed-client";
+import { applyLikeOutcome, LikeError, sendLike } from "@/lib/like-client";
 import { mergePosts, toCardPosts, type CardPost } from "@/lib/feed-model";
 import { FeedView, type FeedStatus } from "./FeedView";
 
@@ -14,6 +15,8 @@ export function Feed({ onSignedOut }: { onSignedOut: () => void }) {
   const [loadingMore, setLoadingMore] = useState(false);
   const [loadMoreFailed, setLoadMoreFailed] = useState(false);
   const [pending, setPending] = useState<CardPost[]>([]);
+  const [likeBusy, setLikeBusy] = useState<ReadonlySet<string>>(new Set());
+  const [likeErrors, setLikeErrors] = useState<ReadonlySet<string>>(new Set());
   const sentinel = useRef<HTMLDivElement | null>(null);
   const busy = useRef(false);
   const shown = useRef<Set<string>>(new Set());
@@ -121,6 +124,31 @@ export function Feed({ onSignedOut }: { onSignedOut: () => void }) {
     };
   }, [status, fail]);
 
+  const toggleLike = useCallback(
+    async (post: CardPost) => {
+      if (!post.id) return;
+      const wanted = !post.isLiked;
+      const mark = (set: ReadonlySet<string>, on: boolean) => {
+        const next = new Set(set);
+        if (on) next.add(post.key);
+        else next.delete(post.key);
+        return next;
+      };
+      setLikeBusy((s) => mark(s, true));
+      setLikeErrors((s) => mark(s, false));
+      try {
+        const out = await sendLike(post.id, wanted);
+        setPosts((cur) => cur.map((p) => (p.key === post.key ? applyLikeOutcome(p, wanted, out) : p)));
+      } catch (e) {
+        fail(e instanceof LikeError && e.signedOut ? new FeedLoadError(true) : e);
+        setLikeErrors((s) => mark(s, true));
+      } finally {
+        setLikeBusy((s) => mark(s, false));
+      }
+    },
+    [fail],
+  );
+
   function showNew() {
     setPosts((cur) => mergePosts(cur, pending));
     setPending([]);
@@ -136,6 +164,9 @@ export function Feed({ onSignedOut }: { onSignedOut: () => void }) {
       newCount={pending.length}
       onRetry={() => (status === "error" ? void loadFirst() : void loadMore())}
       onShowNew={showNew}
+      onToggleLike={(p) => void toggleLike(p)}
+      likeBusy={likeBusy}
+      likeErrors={likeErrors}
       sentinelRef={sentinel}
     />
   );

src/components/FeedView.tsx

@@ -12,6 +12,9 @@ export interface FeedViewProps {
   newCount: number;
   onRetry: () => void;
   onShowNew: () => void;
+  onToggleLike?: (post: CardPost) => void;
+  likeBusy?: ReadonlySet<string>;
+  likeErrors?: ReadonlySet<string>;
   sentinelRef?: Ref<HTMLDivElement>;
   now?: number;
 }
@@ -50,7 +53,14 @@ export function FeedView(p: FeedViewProps) {
       {p.posts.length === 0 ? (
         <p className="feed-message">No posts yet.</p>
       ) : (
-        p.posts.map((post) => <PostCard key={post.key} post={post} now={p.now} />)
+        p.posts.map((post) => <PostCard
+            key={post.key}
+            post={post}
+            now={p.now}
+            onToggleLike={p.onToggleLike}
+            likeBusy={p.likeBusy?.has(post.key)}
+            likeError={p.likeErrors?.has(post.key)}
+          />)
       )}
       {p.loadMoreFailed ? (
         <div className="feed-message" role="alert">

src/components/PostCard.tsx

@@ -1,7 +1,25 @@
 import { VideoPlayer } from "@/components/VideoPlayer";
 import { initials, relativeTime, type CardPost } from "@/lib/feed-model";
 
-export function PostCard({ post, now }: { post: CardPost; now?: number }) {
+export interface PostCardProps {
+  post: CardPost;
+  now?: number;
+  onToggleLike?: (post: CardPost) => void;
+  likeBusy?: boolean;
+  likeError?: boolean;
+}
+
+function Heart({ filled }: { filled: boolean }) {
+  return (
+    <svg className="heart-icon" viewBox="0 0 24 24" width="18" height="18" aria-hidden="true"
+      fill={filled ? "currentColor" : "none"} stroke="currentColor" strokeWidth="2"
+      strokeLinejoin="round">
+      <path d="M12 21s-7.5-4.6-9.6-9.3C.9 8.4 2.7 4.5 6.4 4.5c2.1 0 3.6 1.2 4.4 2.5.4.6 1.4.6 1.8 0 .8-1.3 2.3-2.5 4.4-2.5 3.7 0 5.5 3.9 4 7.2C19.5 16.4 12 21 12 21z" />
+    </svg>
+  );
+}
+
+export function PostCard({ post, now, onToggleLike, likeBusy, likeError }: PostCardProps) {
   return (
     <article className="post" data-testid="post-card">
       <header className="post-head">
@@ -32,10 +50,20 @@ export function PostCard({ post, now }: { post: CardPost; now?: number }) {
         ) : null,
       )}
       <footer className="post-stats">
-        <span aria-label={`${post.likesCount} likes`}>
-          <span className="heart" aria-hidden="true">&#9829;</span> {post.likesCount}
-        </span>
+        <button
+          type="button"
+          className={post.isLiked ? "like-btn liked" : "like-btn"}
+          aria-pressed={post.isLiked}
+          aria-label={post.isLiked ? `Unlike, ${post.likesCount} likes` : `Like, ${post.likesCount} likes`}
+          disabled={likeBusy || !post.id || !onToggleLike}
+          onClick={() => onToggleLike?.(post)}
+        >
+          <Heart filled={post.isLiked} /> <span className="like-count">{post.likesCount}</span>
+        </button>
         <span aria-label={`${post.commentsCount} comments`}>{post.commentsCount} comments</span>
+        {likeError ? (
+          <span className="like-error" role="alert">Could not update like.</span>
+        ) : null}
       </footer>
     </article>
   );

src/lib/feed-model.ts

@@ -18,6 +18,8 @@ export interface CardPost {
   time: number;
   text: string;
   likesCount: number;
+  /** Whether the signed-in person has liked the post. */
+  isLiked: boolean;
   commentsCount: number;
   media: CardMedia[];
 }
@@ -99,6 +101,7 @@ export function toCardPost(item: unknown, index = 0): CardPost | null {
     time: Number.isFinite(t) ? t : Number.NEGATIVE_INFINITY,
     text: typeof post.content === "string" ? post.content : "",
     likesCount: num(item.likesCount ?? post.likesCount),
+    isLiked: post.isLiked === true || item.isLiked === true,
     commentsCount: num(item.commentsCount ?? post.commentsCount),
     media: toMedia(post.mediaItems),
   };

src/lib/like-client.ts

@@ -0,0 +1,52 @@
+// Browser-side like / unlike calls and the pure card update they drive.
+
+import type { CardPost } from "./feed-model";
+
+export interface LikeOutcome {
+  isLiked: boolean;
+  likesCount: number | null;
+}
+
+export class LikeError extends Error {
+  constructor(public readonly signedOut: boolean) {
+    super(signedOut ? "sign_in" : "like_failed");
+  }
+}
+
+export async function sendLike(
+  postId: string,
+  liked: boolean,
+  fetchImpl: typeof fetch = fetch,
+): Promise<LikeOutcome> {
+  let res: Response;
+  try {
+    res = await fetchImpl(`/api/posts/${encodeURIComponent(postId)}/like`, {
+      method: liked ? "POST" : "DELETE",
+      credentials: "same-origin",
+    });
+  } catch {
+    throw new LikeError(false);
+  }
+  if (res.status === 401) throw new LikeError(true);
+  if (!res.ok) throw new LikeError(false);
+  try {
+    const b = (await res.json()) as { isLiked?: unknown; likesCount?: unknown };
+    return {
+      isLiked: typeof b.isLiked === "boolean" ? b.isLiked : liked,
+      likesCount:
+        typeof b.likesCount === "number" && Number.isInteger(b.likesCount) && b.likesCount >= 0
+          ? b.likesCount
+          : null,
+    };
+  } catch {
+    throw new LikeError(false);
+  }
+}
+
+/** The card after a successful call: the server count when present, else flip and adjust by one. */
+export function applyLikeOutcome(post: CardPost, wanted: boolean, out: LikeOutcome): CardPost {
+  if (out.likesCount !== null) return { ...post, isLiked: out.isLiked, likesCount: out.likesCount };
+  const changed = post.isLiked !== wanted;
+  const delta = changed ? (wanted ? 1 : -1) : 0;
+  return { ...post, isLiked: wanted, likesCount: Math.max(0, post.likesCount + delta) };
+}

src/lib/post-like.ts

@@ -0,0 +1,76 @@
+import { FEED_BASE_URL } from "./env";
+import { ensureFreshSession, refreshSession } from "./session-refresh";
+
+// Like / unlike proxy. One call to the feed per request, with the person's
+// server-held feed token. Like is idempotent: a like is never retried in a
+// loop. The only repeat is one refresh-and-retry after a 401 token rejection.
+
+export type LikeResult =
+  | { ok: true; isLiked: boolean; likesCount: number | null }
+  | { ok: false; status: 400 | 401 | 502; error: "sign_in" | "bad_post" | "like_failed" };
+
+interface LikeOptions {
+  fetchImpl?: typeof fetch;
+  now?: number;
+}
+
+const POST_ID = /^[A-Za-z0-9_-]{1,128}$/;
+
+function call(token: string, postId: string, liked: boolean, doFetch: typeof fetch) {
+  return doFetch(`${FEED_BASE_URL}/api/v1/posts/${encodeURIComponent(postId)}/like`, {
+    method: liked ? "POST" : "DELETE",
+    headers: { Accept: "application/json", Authorization: `Bearer ${token}` },
+  });
+}
+
+function rec(v: unknown): Record<string, unknown> {
+  return v && typeof v === "object" && !Array.isArray(v) ? (v as Record<string, unknown>) : {};
+}
+
+/** A like count from the response body, only when it is a non-negative integer. */
+function readCount(body: unknown): number | null {
+  const root = rec(body);
+  const data = rec(root.data);
+  for (const v of [data.likesCount, data.likeCount, root.likesCount, root.likeCount]) {
+    if (typeof v === "number" && Number.isInteger(v) && v >= 0) return v;
+  }
+  return null;
+}
+
+export async function setPostLike(
+  sessionId: string | undefined,
+  postId: string,
+  liked: boolean,
+  options: LikeOptions = {},
+): Promise<LikeResult> {
+  const signIn = { ok: false, status: 401, error: "sign_in" } as const;
+  const failed = { ok: false, status: 502, error: "like_failed" } as const;
+  const doFetch = options.fetchImpl ?? fetch;
+
+  let session = await ensureFreshSession(sessionId, options);
+  if (!session || !sessionId) return signIn;
+  if (!POST_ID.test(postId)) return { ok: false, status: 400, error: "bad_post" };
+
+  let res: Response;
+  try {
+    res = await call(session.feedAccessToken, postId, liked, doFetch);
+    if (res.status === 401) {
+      session = await refreshSession(sessionId, options);
+      if (!session) return signIn;
+      res = await call(session.feedAccessToken, postId, liked, doFetch);
+      if (res.status === 401) return signIn;
+    }
+  } catch {
+    return failed;
+  }
+  if (res.status !== 200) return failed;
+
+  let body: unknown = null;
+  try {
+    body = await res.json();
+  } catch {
+    return failed;
+  }
+  if (rec(rec(body).data).success !== true) return failed;
+  return { ok: true, isLiked: liked, likesCount: readCount(body) };
+}

tests/like.test.ts

@@ -0,0 +1,160 @@
+import { describe, expect, it, vi } from "vitest";
+import { createElement } from "react";
+import { renderToStaticMarkup } from "react-dom/server";
+import { NextRequest } from "next/server";
+import { DELETE, POST } from "@/app/api/posts/[id]/like/route";
+import { PostCard } from "@/components/PostCard";
+import { toCardPost, type CardPost } from "@/lib/feed-model";
+import { applyLikeOutcome, LikeError, sendLike } from "@/lib/like-client";
+import { createSession } from "@/lib/session-store";
+
+const ctx = (id: string) => ({ params: Promise.resolve({ id }) });
+const card = (extra: Partial<CardPost> = {}): CardPost => ({
+  ...toCardPost({ type: "post", publishedAt: "2026-10-19T10:00:00Z", likesCount: 3, post: { id: "p1", content: "hi", author: {}, isLiked: false } })!,
+  ...extra,
+});
+
+function session() {
+  return createSession({
+    profileAccessToken: "p", profileAccessTokenExpiresAt: null, profileRefreshToken: "r",
+    feedAccessToken: "T", feedAccessTokenExpiresAt: null,
+    person: { userId: "u", name: "A", email: "a@b.co", pictureUrl: null }, createdAt: Date.now(),
+  });
+}
+
+/** A fake feed that keeps real like state: a second like never raises the count. */
+function fakeFeed(withCount: boolean) {
+  const state = { liked: false, count: 3, calls: [] as string[] };
+  const fn = vi.fn(async (url: string, init?: RequestInit) => {
+    state.calls.push(`${init?.method} ${new URL(String(url), "http://x").pathname}`);
+    if (init?.method === "POST" && !state.liked) { state.liked = true; state.count += 1; }
+    if (init?.method === "DELETE" && state.liked) { state.liked = false; state.count -= 1; }
+    const data: Record<string, unknown> = { success: true };
+    if (withCount) data.likesCount = state.count;
+    return new Response(JSON.stringify({ data }), { status: 200 });
+  });
+  return { state, fn };
+}
+
+async function withFetch<T>(fn: typeof fetch, run: () => Promise<T>) {
+  const orig = globalThis.fetch;
+  globalThis.fetch = fn;
+  try { return await run(); } finally { globalThis.fetch = orig; }
+}
+
+describe("like routes", () => {
+  it("401 sign_in without a session", async () => {
+    for (const h of [POST, DELETE]) {
+      const res = await h(new NextRequest("http://localhost/api/posts/p1/like", { method: "POST" }), ctx("p1"));
+      expect(res.status).toBe(401);
+      expect(await res.json()).toEqual({ error: "sign_in" });
+    }
+  });
+
+  it("like then unlike hit the matching feed routes and return server state", async () => {
+    const sid = session();
+    const feed = fakeFeed(true);
+    const h = { cookie: `mfb_session=${sid}` };
+    await withFetch(feed.fn as unknown as typeof fetch, async () => {
+      const a = await POST(new NextRequest("http://localhost/api/posts/p1/like", { method: "POST", headers: h }), ctx("p1"));
+      expect(await a.json()).toEqual({ isLiked: true, likesCount: 4 });
+      const b = await DELETE(new NextRequest("http://localhost/api/posts/p1/like", { method: "DELETE", headers: h }), ctx("p1"));
+      expect(await b.json()).toEqual({ isLiked: false, likesCount: 3 });
+    });
+    expect(feed.state.calls).toEqual(["POST /api/v1/posts/p1/like", "DELETE /api/v1/posts/p1/like"]);
+  });
+
+  it("a second like does not raise the count and is not retried", async () => {
+    const sid = session();
+    const feed = fakeFeed(true);
+    const h = { cookie: `mfb_session=${sid}` };
+    await withFetch(feed.fn as unknown as typeof fetch, async () => {
+      await POST(new NextRequest("http://localhost/x", { method: "POST", headers: h }), ctx("p1"));
+      const r = await POST(new NextRequest("http://localhost/x", { method: "POST", headers: h }), ctx("p1"));
+      expect(await r.json()).toEqual({ isLiked: true, likesCount: 4 });
+    });
+    expect(feed.fn).toHaveBeenCalledTimes(2);
+  });
+
+  it("returns likesCount null when the feed carries none; failure is 502 like_failed", async () => {
+    const sid = session();
+    const h = { cookie: `mfb_session=${sid}` };
+    await withFetch(fakeFeed(false).fn as unknown as typeof fetch, async () => {
+      const r = await POST(new NextRequest("http://localhost/x", { method: "POST", headers: h }), ctx("p1"));
+      expect(await r.json()).toEqual({ isLiked: true, likesCount: null });
+    });
+    const bad = vi.fn(async () => new Response("{}", { status: 500 })) as unknown as typeof fetch;
+    await withFetch(bad, async () => {
+      const r = await POST(new NextRequest("http://localhost/x", { method: "POST", headers: h }), ctx("p1"));
+      expect(r.status).toBe(502);
+      expect(await r.json()).toEqual({ error: "like_failed" });
+    });
+    const notOk = vi.fn(async () => new Response(JSON.stringify({ data: { success: false } }), { status: 200 })) as unknown as typeof fetch;
+    await withFetch(notOk, async () => {
+      const r = await DELETE(new NextRequest("http://localhost/x", { method: "DELETE", headers: h }), ctx("p1"));
+      expect(r.status).toBe(502);
+    });
+  });
+
+  it("rejects a post id that is not a plain id", async () => {
+    const sid = session();
+    const f = vi.fn();
+    await withFetch(f as unknown as typeof fetch, async () => {
+      const r = await POST(new NextRequest("http://localhost/x", { method: "POST", headers: { cookie: `mfb_session=${sid}` } }), ctx("../admin/x"));
+      expect(r.status).toBe(400);
+    });
+    expect(f).not.toHaveBeenCalled();
+  });
+});
+
+describe("card like state", () => {
+  it("reads isLiked from the post", () => {
+    const c = toCardPost({ type: "post", post: { id: "1", isLiked: true, author: {} } });
+    expect(c?.isLiked).toBe(true);
+  });
+
+  it("like then unlike through the client matches server state", async () => {
+    const feed = fakeFeed(true);
+    const proxy = vi.fn(async (url: string, init?: RequestInit) => {
+      const r = await feed.fn(url, init);
+      const b = (await r.json()) as { data: { likesCount: number } };
+      return new Response(JSON.stringify({ isLiked: init?.method === "POST", likesCount: b.data.likesCount }), { status: 200 });
+    }) as unknown as typeof fetch;
+    let c = card();
+    c = applyLikeOutcome(c, true, await sendLike("p1", true, proxy));
+    expect([c.isLiked, c.likesCount]).toEqual([true, 4]);
+    c = applyLikeOutcome(c, false, await sendLike("p1", false, proxy));
+    expect([c.isLiked, c.likesCount]).toEqual([false, 3]);
+  });
+
+  it("without a server count, flips and adjusts by one; a repeat does not double count", () => {
+    let c = card();
+    c = applyLikeOutcome(c, true, { isLiked: true, likesCount: null });
+    expect([c.isLiked, c.likesCount]).toEqual([true, 4]);
+    c = applyLikeOutcome(c, true, { isLiked: true, likesCount: null });
+    expect(c.likesCount).toBe(4);
+    c = applyLikeOutcome(c, false, { isLiked: false, likesCount: null });
+    expect([c.isLiked, c.likesCount]).toEqual([false, 3]);
+  });
+
+  it("a failed call throws and the previous card is untouched", async () => {
+    const before = card();
+    const f = vi.fn(async () => new Response("{}", { status: 502 })) as unknown as typeof fetch;
+    await expect(sendLike("p1", true, f)).rejects.toBeInstanceOf(LikeError);
+    expect(before.isLiked).toBe(false);
+    expect(before.likesCount).toBe(3);
+    const signedOut = vi.fn(async () => new Response("{}", { status: 401 })) as unknown as typeof fetch;
+    await expect(sendLike("p1", true, signedOut)).rejects.toMatchObject({ signedOut: true });
+  });
+
+  it("renders outlined vs filled heart, pressed state, and the action error", () => {
+    const off = renderToStaticMarkup(createElement(PostCard, { post: card(), onToggleLike: () => {} }));
+    expect(off).toContain('aria-pressed="false"');
+    expect(off).toContain('fill="none"');
+    expect(off).not.toContain("Could not update like.");
+    const on = renderToStaticMarkup(createElement(PostCard, { post: card({ isLiked: true }), onToggleLike: () => {}, likeError: true }));
+    expect(on).toContain('aria-pressed="true"');
+    expect(on).toContain('fill="currentColor"');
+    expect(on).toContain("Could not update like.");
+  });
+});