import uuid
from datetime import datetime, timezone
from typing import Optional
from sqlalchemy import DateTime
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, declared_attr

class Base(DeclarativeBase):
    """Base class for all SQLAlchemy 2.0 models."""
    pass

class UUIDMixin:
    """Mixin to automatically add UUID v4 primary keys to a model."""
    @declared_attr
    def id(cls) -> Mapped[uuid.UUID]:
        return mapped_column(
            UUID(as_uuid=True),
            primary_key=True,
            default=uuid.uuid4,
            index=True
        )

class TimestampMixin:
    """Mixin to add created_at and updated_at datetime timestamps to a model."""
    @declared_attr
    def created_at(cls) -> Mapped[datetime]:
        return mapped_column(
            DateTime(timezone=True),
            default=lambda: datetime.now(timezone.utc),
            nullable=False
        )

    @declared_attr
    def updated_at(cls) -> Mapped[datetime]:
        return mapped_column(
            DateTime(timezone=True),
            default=lambda: datetime.now(timezone.utc),
            onupdate=lambda: datetime.now(timezone.utc),
            nullable=False
        )

class SoftDeleteMixin:
    """Mixin to add soft-delete capabilities to database models."""
    @declared_attr
    def deleted_at(cls) -> Mapped[Optional[datetime]]:
        return mapped_column(DateTime(timezone=True), nullable=True, default=None)

    @property
    def is_deleted(self) -> bool:
        return self.deleted_at is not None