Share songs, with link previews

- "Share ↗" on every song (web and mobile): the phone's share sheet, or
  copy the link on desktop. Links go to a new song page, /t/<id>?from=you,
  with big artwork and open-in buttons for every service.
- Server-rendered previews (Open Graph / Twitter cards) for song pages and
  profiles: title, who shared it or what they're playing, and the album
  art, avatar or logo. The web server fetches from the API over the
  compose network (INTERNAL_API_URL).

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

apps/mobile/src/components/TrackCard.tsx

@@ -1,6 +1,8 @@
 import { Image } from 'expo-image';
-import { Linking, Pressable, StyleSheet, Text, View } from 'react-native';
+import { Linking, Pressable, Share, StyleSheet, Text, View } from 'react-native';
-import { SERVICE_LABELS, STREAMING_SERVICES, openUrl, type StreamingService, type TrackDTO } from '@musicshare/shared';
+import { SERVICE_LABELS, STREAMING_SERVICES, openUrl, shareText, trackUrl, type StreamingService, type TrackDTO } from '@musicshare/shared';
+import { WEB_URL } from '@/lib/config';
+import { useSession } from '@/lib/session';
 import { showError } from '@/lib/errors';
 import { colors, fonts, radius, space } from '@/lib/theme';
 import { Button } from './ui';
@@ -11,7 +13,15 @@ import { Button } from './ui';
  */
 const open = (url: string) => Linking.openURL(url).catch((e) => showError(e, "Couldn't open link"));
 
+/** The phone's share sheet, with a link to the song's page (which opens it in any service). */
+function shareTrack(track: TrackDTO, from: string | undefined) {
+  const url = trackUrl(WEB_URL, track.id, from);
+  // Android shows only `message`; iOS shows `url` as a rich link next to it.
+  Share.share({ message: `${shareText(track)} ${url}`, url, title: shareText(track) }).catch((e) => showError(e, "Couldn't share"));
+}
+
 export function TrackCard({ track, preferred }: { track: TrackDTO; preferred: StreamingService | null | undefined }) {
+  const { me } = useSession();
   const primary = preferred ? openUrl(track, preferred) : null;
   const others = STREAMING_SERVICES.filter((s) => s !== preferred);
 
@@ -50,6 +60,9 @@ export function TrackCard({ track, preferred }: { track: TrackDTO; preferred: St
               </Pressable>
             );
           })}
+          <Pressable onPress={() => shareTrack(track, me?.username)} hitSlop={6} accessibilityRole="button" accessibilityLabel="Share this song">
+            <Text style={[styles.service, styles.share]}>Share ↗</Text>
+          </Pressable>
         </View>
       </View>
     </View>
@@ -72,6 +85,7 @@ const styles = StyleSheet.create({
   title: { color: colors.text, fontFamily: fonts.display, fontSize: 18, letterSpacing: -0.2 },
   artist: { color: colors.text, opacity: 0.85, fontSize: 14 },
   muted: { color: colors.muted },
+  share: { backgroundColor: 'rgba(123,47,247,0.28)', borderColor: 'rgba(123,47,247,0.5)' },
   primary: { alignSelf: 'flex-start', marginTop: space.sm },
   services: { flexDirection: 'row', flexWrap: 'wrap', gap: space.xs + 2, marginTop: space.sm + 2 },
   service: {

apps/web/src/app/globals.css

@@ -99,6 +99,9 @@ input:focus, textarea:focus, select:focus {
 .legal { line-height: 1.6; }
 .legal h2 { margin-top: 1.5rem; }
 .legal ul { padding-left: 1.2rem; display: flex; flex-direction: column; gap: 0.45rem; }
+.share-link { font: inherit; cursor: pointer; color: var(--text); }
+.song-page { display: flex; flex-direction: column; gap: 1.25rem; align-items: stretch; }
+.song-art { width: 100%; max-width: 360px; aspect-ratio: 1; object-fit: cover; border-radius: 1.1rem; align-self: center; box-shadow: 0 30px 60px -30px rgba(0, 0, 0, 0.8); }
 .avatar-picker { display: flex; gap: 1rem; align-items: center; }
 .avatar-picker-actions { display: flex; flex-direction: column; gap: 0.4rem; }
 .grow { flex: 1; min-width: 0; }

apps/web/src/app/layout.tsx

@@ -8,7 +8,11 @@ import './globals.css';
 const inter = Inter({ subsets: ['latin'], variable: '--font-inter', display: 'swap' });
 const spaceGrotesk = Space_Grotesk({ subsets: ['latin'], variable: '--font-space-grotesk', display: 'swap' });
 
+// Previews need absolute image URLs. In production the API lives at <site>/api, so its origin is the site's.
+const siteUrl = process.env.SITE_URL ?? new URL(process.env.NEXT_PUBLIC_API_URL ?? 'http://localhost:3737').origin;
+
 export const metadata: Metadata = {
+  metadataBase: new URL(siteUrl),
   title: 'musicshare',
   description: "See what your friends are listening to, and play it on your own service.",
   applicationName: 'musicshare',

apps/web/src/app/t/[id]/TrackClient.tsx

@@ -0,0 +1,38 @@
+'use client';
+
+import Link from 'next/link';
+import useSWR from 'swr';
+import type { TrackDTO } from '@musicshare/shared';
+import { TrackCard } from '@/components/TrackCard';
+import { fetcher, useMe } from '@/lib/api';
+
+/** A shared song: big artwork and "open in" buttons for every service. */
+export function TrackClient({ id, from }: { id: string; from: string | null }) {
+  const { me } = useMe();
+  const { data: track, error } = useSWR<TrackDTO>(`/tracks/${id}`, fetcher);
+
+  if (error) return <p className="muted">This song couldn&apos;t be found.</p>;
+  if (!track) return null;
+  return (
+    <div className="stack">
+      {from && (
+        <p className="muted">
+          <Link href={`/u/${from}`}>@{from}</Link> shared a song with you
+        </p>
+      )}
+      <section className="card song-page">
+        {track.artworkUrl && <img className="song-art" src={track.artworkUrl} alt="" />}
+        <TrackCard track={track} preferred={me?.preferredService} hideArtwork />
+      </section>
+      {!me && (
+        <section className="card">
+          <h2>See what your friends are playing</h2>
+          <p className="muted">musicshare shows you what friends are listening to right now, and opens it in your app.</p>
+          <Link href="/register" className="btn btn-primary">
+            Join musicshare
+          </Link>
+        </section>
+      )}
+    </div>
+  );
+}

apps/web/src/app/t/[id]/page.tsx

@@ -0,0 +1,28 @@
+import type { Metadata } from 'next';
+import type { TrackDTO } from '@musicshare/shared';
+import { serverGet } from '@/lib/server';
+import { TrackClient } from './TrackClient';
+
+type Props = { params: Promise<{ id: string }>; searchParams: Promise<{ from?: string }> };
+
+export async function generateMetadata({ params, searchParams }: Props): Promise<Metadata> {
+  const [{ id }, { from }] = await Promise.all([params, searchParams]);
+  const track = await serverGet<TrackDTO>(`/tracks/${encodeURIComponent(id)}`);
+  if (!track) return { title: 'musicshare' };
+  const title = `${track.title} · ${track.artist}`;
+  const description = from
+    ? `@${from} shared this on musicshare. Play it on Spotify, Apple Music, YouTube Music and more.`
+    : `Play it on Spotify, Apple Music, YouTube Music and more.`;
+  const images = [track.artworkUrl ? { url: track.artworkUrl, width: 1000, height: 1000 } : { url: '/icon-512.png', width: 512, height: 512 }];
+  return {
+    title: `${title} · musicshare`,
+    description,
+    openGraph: { title, description, type: 'music.song', images },
+    twitter: { card: 'summary', title, description, images: [track.artworkUrl ?? '/icon-512.png'] },
+  };
+}
+
+export default async function TrackPage({ params, searchParams }: Props) {
+  const [{ id }, { from }] = await Promise.all([params, searchParams]);
+  return <TrackClient id={id} from={from ?? null} />;
+}

apps/web/src/app/u/[username]/ProfileClient.tsx

@@ -0,0 +1,144 @@
+'use client';
+
+import { motion } from 'motion/react';
+import Link from 'next/link';
+import { useParams } from 'next/navigation';
+import { useState } from 'react';
+import useSWR from 'swr';
+import { profileUrl, type ProfileDTO } from '@musicshare/shared';
+import { Avatar } from '@/components/Avatar';
+import { NowPlayingCard } from '@/components/NowPlayingCard';
+import { ProfileMenu } from '@/components/ProfileMenu';
+import { QrCode } from '@/components/QrCode';
+import { RecentPlays } from '@/components/RecentPlays';
+import { TrackCard } from '@/components/TrackCard';
+import { api, fetcher, useMe } from '@/lib/api';
+import { useRealtime } from '@/lib/useRealtime';
+
+export function ProfileClient() {
+  const { username } = useParams<{ username: string }>();
+  const { me } = useMe();
+  const { data: profile, error, mutate } = useSWR<ProfileDTO>(`/users/${username}`, fetcher);
+  const [busy, setBusy] = useState(false);
+  const [showQr, setShowQr] = useState(false);
+
+  // Live updates arrive for people you follow (and yourself)
+  useRealtime(Boolean(me), (msg) => {
+    if (msg.type === 'now_playing' && profile && msg.data.user.id === profile.user.id) {
+      // A new track moves the previous one into "Recently played", so refetch; otherwise patch in place.
+      const newTrack = msg.data.track.id !== profile.nowPlaying?.track.id;
+      mutate({ ...profile, nowPlaying: msg.data }, { revalidate: newTrack });
+    }
+  });
+
+  if (error) return <p className="muted">User not found.</p>;
+  if (!profile) return null;
+
+  const togglePin = async () => {
+    setBusy(true);
+    try {
+      await api(`/users/${username}/pin`, { method: profile.isPinned ? 'DELETE' : 'PUT', body: profile.isPinned ? undefined : {} });
+      await mutate();
+    } catch (err) {
+      alert((err as Error).message);
+    }
+    setBusy(false);
+  };
+
+  const toggleFollow = async () => {
+    setBusy(true);
+    await api(`/users/${username}/follow`, { method: profile.isFollowing ? 'DELETE' : 'POST', body: {} });
+    await mutate();
+    setBusy(false);
+  };
+
+  const { user } = profile;
+  const preferred = me?.preferredService;
+
+  return (
+    <div className="stack">
+      <motion.section
+        className="profile-header"
+        initial={{ opacity: 0, y: 16 }}
+        animate={{ opacity: 1, y: 0 }}
+        transition={{ duration: 0.5, ease: [0.22, 1, 0.36, 1] }}
+      >
+        <Avatar user={user} size={96} live={Boolean(profile.nowPlaying?.isPlaying)} />
+        <div>
+          <h1>{user.displayName ?? user.username}</h1>
+          <div className="muted">
+            @{user.username}
+            {profile.followsYou && !profile.isSelf && <span className="chip-small">Follows you</span>}
+          </div>
+        </div>
+        <div className="stats">
+          <Link href={`/u/${user.username}/followers`}>
+            <strong>{profile.followerCount}</strong> {profile.followerCount === 1 ? 'follower' : 'followers'}
+          </Link>
+          <Link href={`/u/${user.username}/following`}>
+            <strong>{profile.followingCount}</strong> following
+          </Link>
+        </div>
+        {user.bio && <p className="bio">{user.bio}</p>}
+        {profile.isSelf ? (
+          <div className="row">
+            <button className="btn" onClick={() => setShowQr((v) => !v)}>
+              {showQr ? 'Hide QR code' : 'Show QR code'}
+            </button>
+            <Link href="/settings" className="btn">
+              Edit profile
+            </Link>
+          </div>
+        ) : me ? (
+          <div className="row">
+            {profile.isFollowing && (
+              <button className="btn" onClick={togglePin} disabled={busy}>
+                {profile.isPinned ? '★ Pinned' : '☆ Pin'}
+              </button>
+            )}
+            {!profile.isBlocked && (
+              <button className={`btn ${profile.isFollowing ? '' : 'btn-primary'}`} onClick={toggleFollow} disabled={busy}>
+                {profile.isFollowing ? 'Following' : profile.followsYou ? 'Follow back' : 'Follow'}
+              </button>
+            )}
+            <ProfileMenu profile={profile} onChanged={() => mutate()} />
+          </div>
+        ) : (
+          <Link href="/register" className="btn btn-primary">
+            Sign up to follow
+          </Link>
+        )}
+      </motion.section>
+
+      {profile.isBlocked && (
+        <p className="card muted">
+          You blocked @{user.username}. They can&apos;t see your profile or what you play, and you won&apos;t see theirs. Unblock
+          them from the ⋯ menu.
+        </p>
+      )}
+
+      {profile.isSelf && showQr && (
+        <section className="card qr-card">
+          <QrCode value={profileUrl(window.location.origin, user.username)} size={220} />
+          <p className="muted">Friends scan this in the musicshare app (or their camera) to open your profile.</p>
+        </section>
+      )}
+
+      {profile.featured && (
+        <section className="card featured">
+          <h2>Featured song</h2>
+          <TrackCard track={profile.featured.track} preferred={preferred} />
+          {profile.featured.comment && <blockquote>{profile.featured.comment}</blockquote>}
+        </section>
+      )}
+
+      {profile.nowPlaying ? (
+        <NowPlayingCard np={profile.nowPlaying} preferred={preferred} showUser={false} />
+      ) : (
+        <p className="muted">Nothing playing right now.</p>
+      )}
+
+      <RecentPlays plays={profile.recent} preferred={preferred} attribution={profile.attribution} />
+    </div>
+  );
+}

apps/web/src/app/u/[username]/page.tsx

@@ -1,144 +1,29 @@
-'use client';
+import type { Metadata } from 'next';
+import type { ProfileDTO } from '@musicshare/shared';
+import { serverGet } from '@/lib/server';
+import { ProfileClient } from './ProfileClient';
 
-import { motion } from 'motion/react';
+type Props = { params: Promise<{ username: string }> };
-import Link from 'next/link';
+
-import { useParams } from 'next/navigation';
+/** Link previews (iMessage, Discord, WhatsApp…): who it is, and what they're playing. */
-import { useState } from 'react';
+export async function generateMetadata({ params }: Props): Promise<Metadata> {
-import useSWR from 'swr';
+  const { username } = await params;
-import { profileUrl, type ProfileDTO } from '@musicshare/shared';
+  const profile = await serverGet<ProfileDTO>(`/users/${encodeURIComponent(username)}`);
-import { Avatar } from '@/components/Avatar';
+  if (!profile) return { title: 'musicshare' };
-import { NowPlayingCard } from '@/components/NowPlayingCard';
+  const name = profile.user.displayName ?? profile.user.username;
-import { ProfileMenu } from '@/components/ProfileMenu';
+  const np = profile.nowPlaying;
-import { QrCode } from '@/components/QrCode';
+  const description = np?.isPlaying
-import { RecentPlays } from '@/components/RecentPlays';
+    ? `Listening to ${np.track.title} by ${np.track.artist}`
-import { TrackCard } from '@/components/TrackCard';
+    : (profile.user.bio ?? `See what ${name} is listening to on musicshare.`);
-import { api, fetcher, useMe } from '@/lib/api';
+  const image = (np?.isPlaying && np.track.artworkUrl) || profile.user.avatarUrl || '/icon-512.png';
-import { useRealtime } from '@/lib/useRealtime';
+  return {
+    title: `${name} (@${profile.user.username}) · musicshare`,
+    description,
+    openGraph: { title: `${name} on musicshare`, description, type: 'profile', images: [{ url: image }] },
+    twitter: { card: 'summary', title: `${name} on musicshare`, description, images: [image] },
+  };
+}
 
 export default function ProfilePage() {
-  const { username } = useParams<{ username: string }>();
+  return <ProfileClient />;
-  const { me } = useMe();
-  const { data: profile, error, mutate } = useSWR<ProfileDTO>(`/users/${username}`, fetcher);
-  const [busy, setBusy] = useState(false);
-  const [showQr, setShowQr] = useState(false);
-
-  // Live updates arrive for people you follow (and yourself)
-  useRealtime(Boolean(me), (msg) => {
-    if (msg.type === 'now_playing' && profile && msg.data.user.id === profile.user.id) {
-      // A new track moves the previous one into "Recently played", so refetch; otherwise patch in place.
-      const newTrack = msg.data.track.id !== profile.nowPlaying?.track.id;
-      mutate({ ...profile, nowPlaying: msg.data }, { revalidate: newTrack });
-    }
-  });
-
-  if (error) return <p className="muted">User not found.</p>;
-  if (!profile) return null;
-
-  const togglePin = async () => {
-    setBusy(true);
-    try {
-      await api(`/users/${username}/pin`, { method: profile.isPinned ? 'DELETE' : 'PUT', body: profile.isPinned ? undefined : {} });
-      await mutate();
-    } catch (err) {
-      alert((err as Error).message);
-    }
-    setBusy(false);
-  };
-
-  const toggleFollow = async () => {
-    setBusy(true);
-    await api(`/users/${username}/follow`, { method: profile.isFollowing ? 'DELETE' : 'POST', body: {} });
-    await mutate();
-    setBusy(false);
-  };
-
-  const { user } = profile;
-  const preferred = me?.preferredService;
-
-  return (
-    <div className="stack">
-      <motion.section
-        className="profile-header"
-        initial={{ opacity: 0, y: 16 }}
-        animate={{ opacity: 1, y: 0 }}
-        transition={{ duration: 0.5, ease: [0.22, 1, 0.36, 1] }}
-      >
-        <Avatar user={user} size={96} live={Boolean(profile.nowPlaying?.isPlaying)} />
-        <div>
-          <h1>{user.displayName ?? user.username}</h1>
-          <div className="muted">
-            @{user.username}
-            {profile.followsYou && !profile.isSelf && <span className="chip-small">Follows you</span>}
-          </div>
-        </div>
-        <div className="stats">
-          <Link href={`/u/${user.username}/followers`}>
-            <strong>{profile.followerCount}</strong> {profile.followerCount === 1 ? 'follower' : 'followers'}
-          </Link>
-          <Link href={`/u/${user.username}/following`}>
-            <strong>{profile.followingCount}</strong> following
-          </Link>
-        </div>
-        {user.bio && <p className="bio">{user.bio}</p>}
-        {profile.isSelf ? (
-          <div className="row">
-            <button className="btn" onClick={() => setShowQr((v) => !v)}>
-              {showQr ? 'Hide QR code' : 'Show QR code'}
-            </button>
-            <Link href="/settings" className="btn">
-              Edit profile
-            </Link>
-          </div>
-        ) : me ? (
-          <div className="row">
-            {profile.isFollowing && (
-              <button className="btn" onClick={togglePin} disabled={busy}>
-                {profile.isPinned ? '★ Pinned' : '☆ Pin'}
-              </button>
-            )}
-            {!profile.isBlocked && (
-              <button className={`btn ${profile.isFollowing ? '' : 'btn-primary'}`} onClick={toggleFollow} disabled={busy}>
-                {profile.isFollowing ? 'Following' : profile.followsYou ? 'Follow back' : 'Follow'}
-              </button>
-            )}
-            <ProfileMenu profile={profile} onChanged={() => mutate()} />
-          </div>
-        ) : (
-          <Link href="/register" className="btn btn-primary">
-            Sign up to follow
-          </Link>
-        )}
-      </motion.section>
-
-      {profile.isBlocked && (
-        <p className="card muted">
-          You blocked @{user.username}. They can&apos;t see your profile or what you play, and you won&apos;t see theirs. Unblock
-          them from the ⋯ menu.
-        </p>
-      )}
-
-      {profile.isSelf && showQr && (
-        <section className="card qr-card">
-          <QrCode value={profileUrl(window.location.origin, user.username)} size={220} />
-          <p className="muted">Friends scan this in the musicshare app (or their camera) to open your profile.</p>
-        </section>
-      )}
-
-      {profile.featured && (
-        <section className="card featured">
-          <h2>Featured song</h2>
-          <TrackCard track={profile.featured.track} preferred={preferred} />
-          {profile.featured.comment && <blockquote>{profile.featured.comment}</blockquote>}
-        </section>
-      )}
-
-      {profile.nowPlaying ? (
-        <NowPlayingCard np={profile.nowPlaying} preferred={preferred} showUser={false} />
-      ) : (
-        <p className="muted">Nothing playing right now.</p>
-      )}
-
-      <RecentPlays plays={profile.recent} preferred={preferred} attribution={profile.attribution} />
-    </div>
-  );
 }

apps/web/src/components/ShareButton.tsx

@@ -0,0 +1,32 @@
+'use client';
+
+import { useState } from 'react';
+import { shareText, trackUrl, type TrackDTO } from '@musicshare/shared';
+import { useMe } from '@/lib/api';
+
+/** Share a song: the phone's share sheet where there is one, otherwise copy the link. */
+export function ShareButton({ track }: { track: TrackDTO }) {
+  const { me } = useMe();
+  const [copied, setCopied] = useState(false);
+
+  const share = async () => {
+    const url = trackUrl(window.location.origin, track.id, me?.username);
+    if (navigator.share) {
+      try {
+        await navigator.share({ title: shareText(track), text: shareText(track), url });
+        return;
+      } catch (err) {
+        if ((err as Error).name === 'AbortError') return; // they closed the sheet
+      }
+    }
+    await navigator.clipboard.writeText(url);
+    setCopied(true);
+    setTimeout(() => setCopied(false), 2000);
+  };
+
+  return (
+    <button type="button" className="service-link share-link" onClick={share} title="Share this song">
+      {copied ? 'Link copied ✓' : 'Share ↗'}
+    </button>
+  );
+}

apps/web/src/components/TrackCard.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { STREAMING_SERVICES, SERVICE_LABELS, openUrl, type StreamingService, type TrackDTO } from '@musicshare/shared';
+import { ShareButton } from './ShareButton';
 
 /**
  * Artwork + title, with a primary button for the viewer's preferred service
@@ -11,17 +12,20 @@ export function TrackCard({
   track,
   preferred,
   compact,
+  hideArtwork,
 }: {
   track: TrackDTO;
   preferred: StreamingService | null | undefined;
   compact?: boolean;
+  /** When the page already shows the artwork big. */
+  hideArtwork?: boolean;
 }) {
   const others = STREAMING_SERVICES.filter((s) => s !== preferred);
   const primary = preferred ? openUrl(track, preferred) : null;
 
   return (
     <div className={`track ${compact ? 'track-compact' : ''}`}>
-      {track.artworkUrl ? (
+      {hideArtwork ? null : track.artworkUrl ? (
         <img className="artwork" src={track.artworkUrl} alt="" />
       ) : (
         <div className="artwork artwork-empty">♪</div>
@@ -53,6 +57,7 @@ export function TrackCard({
               </a>
             );
           })}
+          <ShareButton track={track} />
         </div>
       </div>
     </div>

apps/web/src/lib/server.ts

@@ -0,0 +1,16 @@
+import 'server-only';
+
+/**
+ * For server-rendered link previews. Inside Docker the web server reaches the API
+ * by service name (INTERNAL_API_URL); elsewhere it uses the public URL.
+ */
+const INTERNAL_API = process.env.INTERNAL_API_URL ?? process.env.NEXT_PUBLIC_API_URL ?? 'http://localhost:4000';
+
+export async function serverGet<T>(path: string): Promise<T | null> {
+  try {
+    const res = await fetch(INTERNAL_API + path, { next: { revalidate: 60 }, signal: AbortSignal.timeout(3000) });
+    return res.ok ? ((await res.json()) as T) : null;
+  } catch {
+    return null; // previews are best-effort; the page itself still loads
+  }
+}

docker-compose.yml

@@ -93,6 +93,9 @@ services:
         # Optional donation link shown on the website, e.g. DONATION_URL=https://ko-fi.com/you
         NEXT_PUBLIC_DONATION_URL: ${DONATION_URL:-}
     image: musicshare-web:local
+    environment:
+      # Server-side rendering (link previews) talks to the API inside the compose network.
+      INTERNAL_API_URL: http://api:4000
     ports:
       - "${WEB_PORT:-3737}:3737"
     init: true

packages/shared/src/links.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { parseProfileLink, profileUrl } from './links';
+import { parseProfileLink, profileUrl, trackUrl } from './links';
 
 describe('profileUrl', () => {
   it('builds a website profile link, tolerating a trailing slash', () => {
@@ -34,3 +34,10 @@ describe('parseProfileLink', () => {
     expect(parseProfileLink(text)).toBeNull();
   });
 });
+
+describe('trackUrl', () => {
+  it('links to the song page, optionally saying who shared it', () => {
+    expect(trackUrl('https://m.test/', 'abc')).toBe('https://m.test/t/abc');
+    expect(trackUrl('https://m.test', 'abc', 'alice')).toBe('https://m.test/t/abc?from=alice');
+  });
+});

packages/shared/src/links.ts

@@ -29,6 +29,15 @@ export function parseProfileLink(text: string): string | null {
   return match ? valid(decodeURIComponent(match[1]!)) : null;
 }
 
+/** Shareable song page on the website, e.g. https://musicshare.app/t/<id>?from=alice */
+export function trackUrl(webBase: string, trackId: string, from?: string | null): string {
+  const url = `${webBase.replace(/\/+$/, '')}/t/${encodeURIComponent(trackId)}`;
+  return from ? `${url}?from=${encodeURIComponent(from)}` : url;
+}
+
+/** What goes in the share sheet next to the link. */
+export const shareText = (track: { title: string; artist: string }) => `${track.title} by ${track.artist}`;
+
 function valid(name: string): string | null {
   const username = name.toLowerCase();
   return USERNAME.test(username) ? username : null;