from django.db.models import Q

from .models import MainProduct, ProjectAccess, ProjectAccessPolicy, SubProduct


def _mode(user):
    try:
        return user.project_access_policy.mode
    except ProjectAccessPolicy.DoesNotExist:
        return ProjectAccessPolicy.OWN


def accessible_projects(user, model, *, edit=False):
    """Return projects visible/editable by a user; explicit overrides win."""
    if model not in (MainProduct, SubProduct):
        raise ValueError("Expected a main project or sub-project model")
    if not user.is_authenticated or not user.is_active:
        return model.objects.none()
    if user.is_superuser:
        return model.objects.all()

    field = "main_product" if model is MainProduct else "sub_product"
    overrides = ProjectAccess.objects.filter(user=user, **{f"{field}__isnull": False})
    allowed_levels = (ProjectAccess.EDIT,) if edit else (ProjectAccess.VIEW, ProjectAccess.EDIT)
    permitted = overrides.filter(level__in=allowed_levels)
    excluded = overrides.exclude(level__in=allowed_levels)

    mode = _mode(user)
    base = Q(created_by=user) if mode != ProjectAccessPolicy.NONE else Q(pk__in=[])
    if mode == ProjectAccessPolicy.ALL_EDIT or (mode == ProjectAccessPolicy.ALL_VIEW and not edit):
        base = Q(pk__isnull=False)
    return model.objects.filter(base | Q(pk__in=permitted.values_list(f"{field}_id", flat=True))).exclude(
        pk__in=excluded.values_list(f"{field}_id", flat=True)
    ).distinct()


def can_access_project(user, project, *, edit=False):
    if project is None:
        return False
    return accessible_projects(user, type(project), edit=edit).filter(pk=project.pk).exists()


def can_create_project(user):
    return user.is_authenticated and user.is_active and (
        user.is_superuser or _mode(user) != ProjectAccessPolicy.NONE
    )


def project_for_related(obj):
    if isinstance(obj, (MainProduct, SubProduct)):
        return obj
    if getattr(obj, "sub_product_id", None):
        return obj.sub_product
    if getattr(obj, "main_product_id", None):
        return obj.main_product
    if getattr(obj, "article_id", None):
        return project_for_related(obj.article)
    return None