"""Abstract model mixins for tenant-owned and global+override resources.

Using a mixin keeps the ``tenant`` field and managers consistent across every
app without repeating them. Concrete models still declare their own ``db_table``
and constraints. The mixin is the sanctioned way for another app to depend on
``infrasynth.tenancy`` (see the dependency graph in ``PLAN.md`` §3).
"""

from __future__ import annotations

from typing import Any

from django.db import models

from .context import get_current_tenant
from .managers import AllObjectsManager, GlobalOrTenantManager, TenantManager

__all__ = ["TenantOwnedModel", "GlobalOrTenantModel"]


class TenantOwnedModel(models.Model):
    """Base for every tenant-owned model (``TENANCY.md`` §4).

    Provides a non-null ``tenant`` FK, the fail-closed default ``TenantManager``,
    and the unscoped ``all_objects`` escape hatch. On save, an unset tenant is
    filled from the bound context so writes inside a request/task land in the
    right tenant; a write with neither is rejected by the database.
    """

    tenant = models.ForeignKey(
        "tenancy.Tenant",
        on_delete=models.CASCADE,
        related_name="+",
        editable=False,
    )

    objects = TenantManager()
    all_objects = AllObjectsManager()

    class Meta:
        abstract = True

    def save(self, *args: Any, **kwargs: Any) -> None:
        if self.tenant_id is None:
            tenant = get_current_tenant()
            if tenant is not None:
                self.tenant = tenant
        super().save(*args, **kwargs)


class GlobalOrTenantModel(models.Model):
    """Base for resources that exist globally and can be overridden per tenant.

    ``tenant IS NULL`` is the platform default; a non-null tenant is that
    tenant's override. The default manager only ever exposes the global rows
    plus the current tenant's rows, never another tenant's.
    """

    tenant = models.ForeignKey(
        "tenancy.Tenant",
        on_delete=models.CASCADE,
        null=True,
        blank=True,
        related_name="+",
    )

    objects = GlobalOrTenantManager()
    all_objects = AllObjectsManager()

    class Meta:
        abstract = True