feat: odesli_resolve — resolve any song link to metadata via song.link

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

musicfetch

@@ -95,6 +95,21 @@ class Hit:
         return self.title or self.album or self.artist
 
 
+@dataclass
+class Resolved:
+    title: str = ""
+    artist: str = ""
+    thumb: str = ""
+    youtube_url: str = ""
+
+
+class OdesliError(Exception):
+    """Raised when an Odesli link can't be resolved to usable metadata."""
+
+
+ODESLI_URL = "https://api.song.link/v1-alpha.1/links"
+
+
 # ---------------------------------------------------------------------------
 # Helpers
 # ---------------------------------------------------------------------------
@@ -762,6 +777,32 @@ def _entry_to_hit(entry: dict) -> Hit:
                         "extractor": source})
 
 
+def odesli_resolve(url: str) -> Optional[Resolved]:
+    """Resolve any streaming link to {title, artist, thumb, youtube_url} via the
+    Odesli (song.link) public API. Returns None on any failure (network, non-200,
+    malformed body, missing title+artist) so callers can fall back loudly."""
+    try:
+        resp = requests.get(ODESLI_URL,
+                            params={"url": url, "userCountry": "US"},
+                            timeout=8)
+        if resp.status_code != 200:
+            dbg(f"odesli {resp.status_code} for {url}")
+            return None
+        data = resp.json()
+        entity = data["entitiesByUniqueId"][data["entityUniqueId"]]
+        title = entity.get("title", "")
+        artist = entity.get("artistName", "")
+        if not title and not artist:
+            return None
+        platforms = data.get("linksByPlatform", {})
+        yt = (platforms.get("youtubeMusic") or platforms.get("youtube") or {}).get("url", "")
+        return Resolved(title=title, artist=artist,
+                        thumb=entity.get("thumbnailUrl", ""), youtube_url=yt)
+    except (RequestException, ValueError, KeyError, TypeError) as e:
+        dbg(f"odesli resolve failed for {url}: {e}")
+        return None
+
+
 def probe_url(url: str) -> tuple[str, str, list[Hit]]:
     """Classify a URL via yt-dlp. Returns (kind, title, hits) where kind is
     'playlist' (hits populated) or 'track' (hits empty; caller downloads the URL).

tests/test_odesli.py

@@ -0,0 +1,68 @@
+import server.mf  # noqa: F401 — loads musicfetch, registers musicfetch_core
+import musicfetch_core as mf
+
+
+class _FakeResp:
+    def __init__(self, status, payload):
+        self.status_code = status
+        self._payload = payload
+
+    def json(self):
+        return self._payload
+
+
+FULL = {
+    "entityUniqueId": "SPOTIFY_SONG::abc",
+    "entitiesByUniqueId": {
+        "SPOTIFY_SONG::abc": {
+            "title": "Bloom",
+            "artistName": "ODESZA",
+            "thumbnailUrl": "https://img/cover.jpg",
+        }
+    },
+    "linksByPlatform": {
+        "youtubeMusic": {"url": "https://music.youtube.com/watch?v=YYY"},
+        "youtube": {"url": "https://youtube.com/watch?v=YYY"},
+    },
+}
+
+
+def test_odesli_resolve_full(monkeypatch):
+    monkeypatch.setattr(mf.requests, "get", lambda *a, **k: _FakeResp(200, FULL))
+    r = mf.odesli_resolve("https://open.spotify.com/track/abc")
+    assert r.title == "Bloom"
+    assert r.artist == "ODESZA"
+    assert r.thumb == "https://img/cover.jpg"
+    assert r.youtube_url == "https://music.youtube.com/watch?v=YYY"
+
+
+def test_odesli_resolve_prefers_ytmusic_then_youtube(monkeypatch):
+    payload = {**FULL, "linksByPlatform": {"youtube": {"url": "https://youtube.com/watch?v=ZZZ"}}}
+    monkeypatch.setattr(mf.requests, "get", lambda *a, **k: _FakeResp(200, payload))
+    r = mf.odesli_resolve("https://open.spotify.com/track/abc")
+    assert r.youtube_url == "https://youtube.com/watch?v=ZZZ"
+
+
+def test_odesli_resolve_no_youtube_link(monkeypatch):
+    payload = {**FULL, "linksByPlatform": {}}
+    monkeypatch.setattr(mf.requests, "get", lambda *a, **k: _FakeResp(200, payload))
+    r = mf.odesli_resolve("https://open.spotify.com/track/abc")
+    assert r.youtube_url == ""
+    assert r.title == "Bloom"
+
+
+def test_odesli_resolve_non_200_returns_none(monkeypatch):
+    monkeypatch.setattr(mf.requests, "get", lambda *a, **k: _FakeResp(429, {}))
+    assert mf.odesli_resolve("https://open.spotify.com/track/abc") is None
+
+
+def test_odesli_resolve_malformed_returns_none(monkeypatch):
+    monkeypatch.setattr(mf.requests, "get", lambda *a, **k: _FakeResp(200, {"nope": 1}))
+    assert mf.odesli_resolve("https://open.spotify.com/track/abc") is None
+
+
+def test_odesli_resolve_network_error_returns_none(monkeypatch):
+    def boom(*a, **k):
+        raise mf.RequestException("down")
+    monkeypatch.setattr(mf.requests, "get", boom)
+    assert mf.odesli_resolve("https://open.spotify.com/track/abc") is None