Emoji reactions on songs

React to a friend's current song or any of their recent plays: tap an
emoji to add yours (or take it back), "☺+" for the quick six, and a full
picker with search and categories (Unicode emoji up to 13.1, generated
into the shared package so web and mobile match). One reaction per person
per play; a new one replaces the old. Chips show counts and, on hover/
long label, who reacted; yours is highlighted. Listeners and followers get
the update live. Not on your own plays, not across a block (blocking also
clears reactions between the two people).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MzFywujuH9TiuXbr9vjoX8

apps/api/test/reactions.test.ts

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+import { describe, expect, it } from 'vitest';
+import { applyPollResult } from '../src/services/nowPlaying';
+import { bearer, createUser, follow, useTestApp } from './helpers';
+
+const app = useTestApp();
+const song = (title: string) => ({ track: { title, artist: 'Massive Attack' }, isPlaying: true, progressMs: null });
+
+async function setup() {
+  const alice = await createUser(app(), 'alice');
+  const bob = await createUser(app(), 'bob');
+  const carol = await createUser(app(), 'carol');
+  await follow(app(), bob.token, 'alice');
+  await applyPollResult(alice.user.id, 'lastfm', song('Teardrop'));
+  const feed = (await app().inject({ url: '/feed', headers: bearer(bob.token) })).json();
+  return { alice, bob, carol, listenId: feed[0].listenId as string };
+}
+const react = (token: string, listenId: string, emoji: string) =>
+  app().inject({ method: 'PUT', url: `/listens/${listenId}/reaction`, headers: bearer(token), payload: { emoji } });
+
+describe('reactions', () => {
+  it('shows up on the feed and profile, grouped by emoji', async () => {
+    const { alice, bob, carol, listenId } = await setup();
+    expect(listenId).toBeTruthy();
+    await react(bob.token, listenId, '🔥');
+    const res = await react(carol.token, listenId, '🔥');
+    expect(res.json()).toEqual([{ emoji: '🔥', count: 2, users: [expect.objectContaining({ username: 'carol' }), expect.objectContaining({ username: 'bob' })] }]);
+
+    const profile = (await app().inject({ url: '/users/alice', headers: bearer(alice.token) })).json();
+    expect(profile.nowPlaying.reactions[0]).toMatchObject({ emoji: '🔥', count: 2 });
+  });
+
+  it('one per person: a new emoji replaces the old one, and it can be removed', async () => {
+    const { bob, listenId } = await setup();
+    await react(bob.token, listenId, '🔥');
+    expect((await react(bob.token, listenId, '😂')).json()).toEqual([expect.objectContaining({ emoji: '😂', count: 1 })]);
+    const removed = await app().inject({ method: 'DELETE', url: `/listens/${listenId}/reaction`, headers: bearer(bob.token) });
+    expect(removed.json()).toEqual([]);
+  });
+
+  it('follows the play into recently played', async () => {
+    const { alice, bob, listenId } = await setup();
+    await react(bob.token, listenId, '❤️');
+    await applyPollResult(alice.user.id, 'lastfm', song('Angel'));
+    const profile = (await app().inject({ url: '/users/alice', headers: bearer(bob.token) })).json();
+    expect(profile.nowPlaying.reactions).toEqual([]);
+    expect(profile.recent[0]).toMatchObject({ listenId, reactions: [expect.objectContaining({ emoji: '❤️' })] });
+  });
+
+  it('rejects anything but one emoji, your own plays, and blocked people', async () => {
+    const { alice, bob, listenId } = await setup();
+    expect((await react(bob.token, listenId, 'lol')).statusCode).toBe(400);
+    expect((await react(bob.token, listenId, '🔥🔥')).statusCode).toBe(400);
+    expect((await react(alice.token, listenId, '🔥')).statusCode).toBe(400);
+
+    await react(bob.token, listenId, '🔥');
+    await app().inject({ method: 'POST', url: '/users/bob/block', headers: bearer(alice.token), payload: {} });
+    expect((await react(bob.token, listenId, '😂')).statusCode).toBe(404);
+    const profile = (await app().inject({ url: '/users/alice', headers: bearer(alice.token) })).json();
+    expect(profile.nowPlaying.reactions).toEqual([]); // their earlier reaction went with the block
+  });
+});