"""Canonical serializer + INV-12 round-trip lock (SD-0002 §6.5.5, §6.8)."""
import csv
import io

from app.domains.products import serialize
from app.domains.products.diff import CatalogImage, CatalogProduct, CatalogVariant


def _product(**kw) -> CatalogProduct:
    """A minimal no-option catalog product (one all-NULL variant)."""
    base = dict(
        id=1, handle="moon-mug", title="Moon Mug",
        option_names=(None, None, None),
        fields={
            "title": "Moon Mug", "description_html": None, "vendor": "Acme",
            "product_type": "standalone", "google_product_category": None,
            "tags": [], "status": "active", "published": True,
        },
        variants=[CatalogVariant(
            id=1, options=(None, None, None), position=1,
            fields={"sku": "WG-MUG", "barcode": None, "price": None, "cost": None,
                    "weight": None, "weight_unit": None, "volume": None,
                    "volume_unit": None, "tax_id_1": None, "tax_id_2": None,
                    "inventory_tracker": None, "inventory_qty": None,
                    "variant_image": None})],
        images=[],
    )
    base.update(kw)
    return CatalogProduct(**base)


def _rows(products) -> list[dict]:
    text = "".join(serialize.catalog_to_csv(products))
    return list(csv.DictReader(io.StringIO(text)))


def test_header_is_full_canonical_set():
    text = "".join(serialize.catalog_to_csv([_product()]))
    header = next(csv.reader(io.StringIO(text)))
    # Handle + Title first; every known column present exactly once.
    assert header[0] == "Handle"
    assert "Title" in header and "Variant SKU" in header and "Image Src" in header
    assert len(header) == len(set(header))


def test_single_no_option_product_one_row():
    rows = _rows([_product()])
    assert len(rows) == 1
    assert rows[0]["Handle"] == "moon-mug"
    assert rows[0]["Title"] == "Moon Mug"
    assert rows[0]["Variant SKU"] == "WG-MUG"
    # A no-option product emits no option values.
    assert rows[0]["Option1 Value"] == ""