feat: add SourceAdapter contract and fake adapters

worker/tests/test_adapters.py

@@ -0,0 +1,43 @@
+from lyra_worker.adapters.fakes import FakeQobuz, FakeSoulseek, FakeYouTube, FailingAdapter
+from lyra_worker.types import MBTarget
+
+TARGET = MBTarget(artist="Radiohead", album="In Rainbows", track_count=10)
+ALL_FAKES = [FakeQobuz(), FakeSoulseek(), FakeYouTube(), FailingAdapter()]
+
+
+def _noop(_pct: float) -> None:
+    pass
+
+
+def test_adapters_expose_name_and_tier():
+    assert FakeQobuz().name == "qobuz" and FakeQobuz().tier == 0
+    assert FakeSoulseek().name == "soulseek" and FakeSoulseek().tier == 1
+    assert FakeYouTube().name == "youtube" and FakeYouTube().tier == 2
+
+
+def test_search_returns_wellformed_candidates():
+    for adapter in ALL_FAKES:
+        for c in adapter.search(TARGET):
+            assert c.source == adapter.name
+            assert c.matched_artist and c.matched_album
+            assert c.track_count > 0
+            assert c.source_ref
+
+
+def test_matches_false_yields_no_candidates():
+    assert FakeQobuz(matches=False).search(TARGET) == []
+
+
+def test_successful_download_reports_progress_and_ok():
+    seen = []
+    result = FakeQobuz().download(FakeQobuz().search(TARGET)[0], "/tmp/x", seen.append)
+    assert result.ok is True
+    assert result.track_count > 0
+    assert seen and seen[-1] == 1.0  # progress reaches 100%
+
+
+def test_failing_adapter_download_fails():
+    fa = FailingAdapter()
+    result = fa.download(fa.search(TARGET)[0], "/tmp/x", _noop)
+    assert result.ok is False
+    assert result.error