from dataclasses import dataclass

from commerce.models import Product, ProductBinding, SourceSystem


@dataclass(frozen=True)
class ProductMatch:
    product: Product | None
    method: str | None

    @property
    def matched(self) -> bool:
        return self.product is not None


def _normalized(value: str | None) -> str:
    return (value or "").strip()


def match_product(
    *,
    source: SourceSystem,
    external_id: str | None = None,
    external_sku: str | None = None,
    barcode: str | None = None,
) -> ProductMatch:
    """Resolve a source product using explicit bindings before safe identifiers."""

    external_id = _normalized(external_id)
    external_sku = _normalized(external_sku)
    barcode = _normalized(barcode)

    if external_id:
        binding = (
            ProductBinding.objects.select_related("product")
            .filter(source=source, external_id=external_id)
            .first()
        )
        if binding:
            return ProductMatch(binding.product, "external_id")

    if external_sku:
        bindings = list(
            ProductBinding.objects.select_related("product").filter(
                source=source, external_sku__iexact=external_sku
            )[:2]
        )
        if len(bindings) == 1:
            return ProductMatch(bindings[0].product, "external_sku")

        products = list(Product.objects.filter(sku__iexact=external_sku)[:2])
        if len(products) == 1:
            return ProductMatch(products[0], "canonical_sku")

    if barcode:
        products = list(Product.objects.filter(barcode=barcode)[:2])
        if len(products) == 1:
            return ProductMatch(products[0], "barcode")

    return ProductMatch(None, None)