from django.db.models import Q


DEFECT_OK = 10
DEFECT_OK_B = 20
DEFECT_NOTOK = 30

DEFECT_GRADE_CHOICES = (
    (DEFECT_OK, "合格"),
    (DEFECT_OK_B, "合格B类"),
    (DEFECT_NOTOK, "不合格"),
)
DEFECT_GRADE_NAMES = dict(DEFECT_GRADE_CHOICES)


def effective_defect_grade(instance, notok_sign_field=None):
    """Return the inventory grade without coupling it to inventory state."""
    defect = getattr(instance, "defect", None)
    if defect is not None:
        return defect.okcate
    if notok_sign_field and getattr(instance, notok_sign_field, None):
        return DEFECT_NOTOK
    return DEFECT_OK


def effective_defect_grade_q(value, notok_sign_field=None):
    """Build an index-friendly query matching ``effective_defect_grade``."""
    explicit_grade = Q(defect__okcate=value)
    without_defect = Q(defect__isnull=True)

    if not notok_sign_field:
        return explicit_grade | without_defect if value == DEFECT_OK else explicit_grade

    has_legacy_sign = (
        Q(**{f"{notok_sign_field}__isnull": False})
        & ~Q(**{notok_sign_field: ""})
    )
    if value == DEFECT_OK:
        return explicit_grade | (without_defect & ~has_legacy_sign)
    if value == DEFECT_NOTOK:
        return explicit_grade | (without_defect & has_legacy_sign)
    return explicit_grade