"""Event model for audit logging."""

import uuid
from datetime import datetime, timezone
from typing import TYPE_CHECKING, Any

from sqlalchemy import DateTime, ForeignKey, String
from sqlalchemy.dialects.postgresql import JSONB
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.models.base import Base, UUIDMixin

if TYPE_CHECKING:
    from app.models.task import Task
    from app.models.tenant import Tenant


def utc_now() -> datetime:
    """Return current UTC datetime."""
    return datetime.now(timezone.utc)


class Event(UUIDMixin, Base):
    """
    Event model for audit logging and activity tracking.

    Events are immutable records of system activity.
    Only has created_at (no updated_at since events are immutable).
    """

    __tablename__ = "events"

    tenant_id: Mapped[uuid.UUID] = mapped_column(
        ForeignKey("tenants.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )
    task_id: Mapped[uuid.UUID | None] = mapped_column(
        ForeignKey("tasks.id", ondelete="SET NULL"),
        nullable=True,
        index=True,
    )
    event_type: Mapped[str] = mapped_column(
        String(100),
        nullable=False,
        index=True,
    )
    payload: Mapped[dict[str, Any]] = mapped_column(
        JSONB,
        nullable=False,
        default=dict,
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        default=utc_now,
        nullable=False,
        index=True,
    )

    # Relationships
    tenant: Mapped["Tenant"] = relationship(
        back_populates="events",
    )
    task: Mapped["Task | None"] = relationship(
        back_populates="events",
    )

    def __repr__(self) -> str:
        return f"<Event(id={self.id}, type={self.event_type})>"