feat(products): serialize multi-variant + interleaved images (§6.5.1 row grammar)

backend/app/domains/products/serialize.py

@@ -71,7 +71,9 @@ def _drain(buf: io.StringIO) -> str:
 
 
 def _product_rows(product: CatalogProduct) -> list[dict[str, str]]:
-    """The product's CSV rows (§6.5.1 grammar). Task 1: first variant only."""
+    """The product's CSV rows (§6.5.1 grammar): product fields + option names on
+    the first row; one variant per row; images interleaved; image-only rows when
+    a product has more images than variants."""
     base = {"Handle": product.handle, "Title": product.title}
     for field, col in _PRODUCT_FIELD_TO_COL.items():
         if field in product.fields:
@@ -79,10 +81,25 @@ def _product_rows(product: CatalogProduct) -> list[dict[str, str]]:
     for slot, name in enumerate(product.option_names, start=1):
         if name:
             base[f"Option{slot} Name"] = name
-    variant = product.variants[0]
+
-    row = dict(base)
+    count = max(len(product.variants), len(product.images))
-    _write_variant(row, product, variant)
+    rows: list[dict[str, str]] = []
-    return [row]
+    for i in range(count):
+        # Row 0 carries the product-level fields; later rows carry only Handle.
+        row = dict(base) if i == 0 else {"Handle": product.handle}
+        if i < len(product.variants):
+            _write_variant(row, product, product.variants[i])
+        if i < len(product.images):
+            _write_image(row, product.images[i])
+        rows.append(row)
+    return rows
+
+
+def _write_image(row: dict[str, str], image) -> None:
+    row["Image Src"] = image.source_url
+    row["Image Position"] = str(image.position)
+    if image.alt_text is not None:
+        row["Image Alt Text"] = image.alt_text
 
 
 def _write_variant(row: dict[str, str], product: CatalogProduct, variant) -> None:

backend/tests/test_products_serialize.py

@@ -51,3 +51,54 @@ def test_single_no_option_product_one_row():
     assert rows[0]["Variant SKU"] == "WG-MUG"
     # A no-option product emits no option values.
     assert rows[0]["Option1 Value"] == ""
+
+
+def _star_tee() -> CatalogProduct:
+    """A 3-variant, 2-image product (the sample.csv shape)."""
+    return CatalogProduct(
+        id=2, handle="star-tee", title="Star Tee",
+        option_names=("Size", "Color", None),
+        fields={"title": "Star Tee", "description_html": None, "vendor": "Acme",
+                "product_type": "standalone", "google_product_category": None,
+                "tags": ["apparel", "tees"], "status": "active", "published": True},
+        variants=[
+            CatalogVariant(id=10, options=("S", "Indigo", None), position=1,
+                           fields={"sku": "WG-TEE-S", "variant_image": None}),
+            CatalogVariant(id=11, options=("M", "Indigo", None), position=2,
+                           fields={"sku": "WG-TEE-M", "variant_image": None}),
+            CatalogVariant(id=12, options=("L", "Indigo", None), position=3,
+                           fields={"sku": "WG-TEE-L", "variant_image": None}),
+        ],
+        images=[
+            CatalogImage(id=1, source_url="https://x/a.jpg", position=1, alt_text="front"),
+            CatalogImage(id=2, source_url="https://x/b.jpg", position=2, alt_text="back"),
+        ],
+    )
+
+
+def test_multivariant_with_images_interleaves():
+    rows = _rows([_star_tee()])
+    assert len(rows) == 3  # max(3 variants, 2 images)
+    # Product-level fields only on the first row.
+    assert rows[0]["Title"] == "Star Tee" and rows[1]["Title"] == ""
+    assert rows[0]["Tags"] == "apparel, tees" and rows[1]["Tags"] == ""
+    # Option names on row 0; option values on every variant row.
+    assert rows[0]["Option1 Name"] == "Size" and rows[1]["Option1 Name"] == ""
+    assert [r["Option1 Value"] for r in rows] == ["S", "M", "L"]
+    assert [r["Variant SKU"] for r in rows] == ["WG-TEE-S", "WG-TEE-M", "WG-TEE-L"]
+    # Two images on the first two rows; third row has no image.
+    assert [r["Image Src"] for r in rows] == ["https://x/a.jpg", "https://x/b.jpg", ""]
+    assert [r["Image Position"] for r in rows] == ["1", "2", ""]
+
+
+def test_more_images_than_variants_emits_image_only_rows():
+    p = _product(images=[
+        CatalogImage(id=1, source_url="https://x/a.jpg", position=1, alt_text=None),
+        CatalogImage(id=2, source_url="https://x/b.jpg", position=2, alt_text=None),
+        CatalogImage(id=3, source_url="https://x/c.jpg", position=3, alt_text=None),
+    ])
+    rows = _rows([p])
+    assert len(rows) == 3  # 1 variant, 3 images
+    assert rows[0]["Variant SKU"] == "WG-MUG"
+    assert rows[1]["Variant SKU"] == "" and rows[1]["Handle"] == "moon-mug"
+    assert [r["Image Src"] for r in rows] == ["https://x/a.jpg", "https://x/b.jpg", "https://x/c.jpg"]