feat: add domain types and quality ranking

worker/tests/test_quality.py

@@ -0,0 +1,37 @@
+from lyra_worker.quality import quality_class, source_tier, rank_key
+from lyra_worker.types import Candidate, Quality
+
+HIRES = Quality(fmt="FLAC", lossless=True, bit_depth=24, sample_rate=96000)
+CD = Quality(fmt="FLAC", lossless=True, bit_depth=16, sample_rate=44100)
+MP3 = Quality(fmt="MP3", lossless=False, bitrate_kbps=320)
+
+
+def _cand(source, quality):
+    return Candidate(source=source, source_ref="x", matched_artist="A",
+                     matched_album="B", quality=quality, track_count=10)
+
+
+def test_quality_class_tiers():
+    assert quality_class(HIRES) == 3
+    assert quality_class(CD) == 2
+    assert quality_class(MP3) == 1
+
+
+def test_source_tier_order():
+    assert source_tier("qobuz") == 0
+    assert source_tier("soulseek") == 1
+    assert source_tier("youtube") == 2
+
+
+def test_design_ranking_order():
+    # Qobuz hi-res > Qobuz lossless > Soulseek FLAC > Soulseek MP3 > YouTube
+    ordered = [
+        _cand("qobuz", HIRES),
+        _cand("qobuz", CD),
+        _cand("soulseek", CD),
+        _cand("soulseek", MP3),
+        _cand("youtube", MP3),
+    ]
+    ranks = [rank_key(c) for c in ordered]
+    assert ranks == sorted(ranks, reverse=True)
+    assert len(set(ranks)) == 5  # strict total order, no ties