"""Base model and common mixins."""
from datetime import datetime
from sqlalchemy import Column, Integer, DateTime, String
from app.database import Base


class TimestampMixin:
    """Adds created_at and updated_at columns."""
    created_at = Column(DateTime, default=datetime.utcnow, nullable=False)
    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)


class TenantMixin:
    """Adds tenant_id column for multi-tenant isolation.

    Every domain model inherits this to guarantee row-level tenant isolation.
    Queries must always filter by tenant_id.
    """
    tenant_id = Column(Integer, nullable=False, index=True)