feat(preview): /discover/artist/[mbid] preview page (disco + tracks + own-state)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/discover/artist/[mbid]/page.tsx

@@ -0,0 +1,20 @@
+import { PreviewClient } from "./preview-client";
+
+export default async function PreviewPage({
+  params,
+  searchParams,
+}: {
+  params: Promise<{ mbid: string }>;
+  searchParams: Promise<{ name?: string }>;
+}) {
+  const { mbid } = await params;
+  const { name } = await searchParams;
+  return (
+    <main>
+      <p>
+        <a href="/discover">← Discover</a> · <a href="/artists">Artists</a>
+      </p>
+      <PreviewClient mbid={mbid} initialName={name ?? ""} />
+    </main>
+  );
+}

web/src/app/discover/artist/[mbid]/preview-client.tsx

@@ -0,0 +1,156 @@
+"use client";
+
+import { useCallback, useEffect, useState } from "react";
+
+type Release = {
+  rgMbid: string;
+  album: string;
+  primaryType: string | null;
+  secondaryTypes: string[];
+  firstReleaseDate: string | null;
+  monitored: boolean;
+  have: boolean;
+};
+type Preview = { artistName: string; followed: boolean; releases: Release[] };
+type Track = { position: number; title: string; lengthMs: number | null };
+
+function fmt(ms: number | null): string {
+  if (ms == null) return "";
+  const s = Math.round(ms / 1000);
+  return `${Math.floor(s / 60)}:${String(s % 60).padStart(2, "0")}`;
+}
+
+export function PreviewClient({ mbid, initialName }: { mbid: string; initialName: string }) {
+  const [data, setData] = useState<Preview | null>(null);
+  const [showAll, setShowAll] = useState(false);
+  const [followed, setFollowed] = useState(false);
+  const [tracks, setTracks] = useState<Record<string, Track[] | "loading" | "error">>({});
+  const [error, setError] = useState(false);
+
+  const load = useCallback(async () => {
+    setError(false);
+    const qs = new URLSearchParams();
+    if (initialName) qs.set("name", initialName);
+    if (showAll) qs.set("all", "true");
+    const res = await fetch(`/api/discover/preview/${mbid}?${qs.toString()}`);
+    if (!res.ok) {
+      setError(true);
+      return;
+    }
+    const d: Preview = await res.json();
+    setData(d);
+    setFollowed(d.followed);
+  }, [mbid, initialName, showAll]);
+
+  useEffect(() => {
+    load();
+  }, [load]);
+
+  // Scroll to the album an album-suggestion deep-linked to (#rg-<rgMbid>) once data is in.
+  useEffect(() => {
+    if (!data) return;
+    const hash = window.location.hash;
+    if (!hash) return;
+    document.getElementById(hash.slice(1))?.scrollIntoView();
+  }, [data]);
+
+  async function follow() {
+    const name = data?.artistName || initialName;
+    const res = await fetch("/api/artists", {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ mbid, name }),
+    });
+    if (res.ok || res.status === 409) setFollowed(true);
+  }
+
+  async function want(r: Release) {
+    await fetch("/api/discover/want", {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({
+        rgMbid: r.rgMbid,
+        artistMbid: mbid,
+        artistName: data?.artistName || initialName,
+        album: r.album,
+        primaryType: r.primaryType,
+        secondaryTypes: r.secondaryTypes,
+        firstReleaseDate: r.firstReleaseDate,
+      }),
+    });
+    setData((d) =>
+      d ? { ...d, releases: d.releases.map((x) => (x.rgMbid === r.rgMbid ? { ...x, monitored: true } : x)) } : d,
+    );
+  }
+
+  async function toggleTracks(rgMbid: string) {
+    if (tracks[rgMbid]) {
+      setTracks((t) => {
+        const n = { ...t };
+        delete n[rgMbid];
+        return n;
+      });
+      return;
+    }
+    setTracks((t) => ({ ...t, [rgMbid]: "loading" }));
+    const res = await fetch(`/api/mb/release-groups/${rgMbid}/tracks`);
+    if (!res.ok) {
+      setTracks((t) => ({ ...t, [rgMbid]: "error" }));
+      return;
+    }
+    const { tracks: ts } = await res.json();
+    setTracks((t) => ({ ...t, [rgMbid]: ts }));
+  }
+
+  if (error)
+    return (
+      <p>
+        Couldn’t load this artist. <button onClick={load}>Retry</button>
+      </p>
+    );
+  if (!data) return <p>Loading…</p>;
+
+  return (
+    <div>
+      <h1>{data.artistName || "Artist"}</h1>
+      <p>
+        {followed ? <span>Following</span> : <button onClick={follow}>Follow</button>}
+        {" · "}
+        <a href={`https://musicbrainz.org/artist/${mbid}`} target="_blank" rel="noreferrer">
+          MusicBrainz ↗
+        </a>
+      </p>
+      <label>
+        <input type="checkbox" checked={showAll} onChange={(e) => setShowAll(e.target.checked)} /> Show all release
+        types
+      </label>
+      <ul>
+        {data.releases.map((r) => (
+          <li key={r.rgMbid} id={`rg-${r.rgMbid}`}>
+            <strong>{r.album}</strong>{" "}
+            <small>
+              {r.primaryType}
+              {r.firstReleaseDate ? ` · ${r.firstReleaseDate.slice(0, 4)}` : ""}
+            </small>{" "}
+            {r.have ? <em>In library</em> : r.monitored ? <em>Monitored</em> : null}{" "}
+            <button onClick={() => want(r)} disabled={r.have || r.monitored}>
+              Want
+            </button>{" "}
+            <button onClick={() => toggleTracks(r.rgMbid)}>{tracks[r.rgMbid] ? "Hide tracks" : "Tracks"}</button>
+            {tracks[r.rgMbid] === "loading" && <p>Loading tracks…</p>}
+            {tracks[r.rgMbid] === "error" && <p>Couldn’t load tracks.</p>}
+            {Array.isArray(tracks[r.rgMbid]) && (
+              <ol>
+                {(tracks[r.rgMbid] as Track[]).map((t) => (
+                  <li key={t.position}>
+                    {t.title} {t.lengthMs != null && <small>({fmt(t.lengthMs)})</small>}
+                  </li>
+                ))}
+              </ol>
+            )}
+          </li>
+        ))}
+      </ul>
+    </div>
+  );
+}