fix: pick best targeted momo offer per pchome item

tests/test_external_market_offer_service.py

@@ -361,6 +361,74 @@ def test_sync_targeted_momo_candidates_skips_total_price_identity_review(monkeyp
     assert count == 0
 
 
+def test_sync_targeted_momo_candidates_keeps_best_unit_quantity_match(monkeypatch):
+    from services import external_market_offer_service as service
+
+    monkeypatch.setattr(service, "mark_pchome_growth_cache_stale", lambda: None)
+
+    engine = create_engine("sqlite:///:memory:")
+    _seed_external_offer_sync_tables(engine)
+
+    payload = service.sync_targeted_momo_candidates_to_external_offers(engine, [
+        {
+            "product_id": "MOMO-SINGLE",
+            "name": "雪之上 全效合一水凝霜 80g/瓶",
+            "price": 1380,
+            "target_pchome_product_id": "PCH-YUKINOUE",
+            "target_pchome_name": "雪之上 全效合一水凝霜 80g 3入組",
+            "target_pchome_price": 2960,
+            "target_match_score": 0.74,
+            "auto_compare_type": "unit_price",
+            "target_price_basis": "unit_price",
+            "target_match_reasons": ["count_conflict", "unit_comparable"],
+            "target_comparison_mode": "unit_comparable",
+            "target_unit_price_comparison": {
+                "comparable": True,
+                "unit_label": "g",
+                "momo_total_quantity": 80,
+                "competitor_total_quantity": 240,
+                "momo_unit_price": 17.25,
+                "competitor_unit_price": 12.33,
+                "unit_gap_pct": 39.86,
+            },
+        },
+        {
+            "product_id": "MOMO-THREE",
+            "name": "雪之上 全效合一水凝霜 80g X 3入瓶裝",
+            "price": 2680,
+            "target_pchome_product_id": "PCH-YUKINOUE",
+            "target_pchome_name": "雪之上 全效合一水凝霜 80g 3入組",
+            "target_pchome_price": 2960,
+            "target_match_score": 0.74,
+            "auto_compare_type": "unit_price",
+            "target_price_basis": "unit_price",
+            "target_match_reasons": ["unit_comparable"],
+            "target_comparison_mode": "unit_comparable",
+            "target_unit_price_comparison": {
+                "comparable": True,
+                "unit_label": "g",
+                "momo_total_quantity": 240,
+                "competitor_total_quantity": 240,
+                "momo_unit_price": 11.17,
+                "competitor_unit_price": 12.33,
+                "unit_gap_pct": -9.46,
+            },
+        },
+    ])
+
+    assert payload["success"] is True
+    assert payload["candidate_count"] == 2
+    assert payload["written_count"] == 1
+    with engine.connect() as conn:
+        row = conn.execute(text("""
+            SELECT source_product_id, raw_payload_json
+            FROM external_offers
+        """)).mappings().one()
+    raw_payload = __import__("json").loads(row["raw_payload_json"])
+    assert row["source_product_id"] == "MOMO-THREE"
+    assert raw_payload["unit_price_comparison"]["momo_total_quantity"] == 240
+
+
 def test_external_source_readiness_uses_legacy_momo_reference_cache():
     from services.external_market_offer_service import build_external_source_readiness