"""Durable LLM usage/cost events."""

from __future__ import annotations

from datetime import datetime, timezone
from uuid import uuid4

from sqlalchemy import DateTime, Float, ForeignKey, Index, Integer, String, func, text
from sqlalchemy.orm import Mapped, mapped_column

from ..db import Base


def _utc_now() -> datetime:
    return datetime.now(timezone.utc)


class UsageEvent(Base):
    """One LLM usage record. Never stores prompt content or secrets."""

    __tablename__ = "usage_events"
    __table_args__ = (
        Index("ix_usage_org_created", "organization_id", "created_at"),
        Index("ix_usage_org_user", "organization_id", "user_id"),
    )

    id: Mapped[str] = mapped_column(
        String(64), primary_key=True, default=lambda: f"usage_{uuid4().hex}"
    )
    organization_id: Mapped[str] = mapped_column(
        ForeignKey("organizations.id", ondelete="CASCADE"), nullable=False, index=True
    )
    user_id: Mapped[str | None] = mapped_column(
        ForeignKey("users.id", ondelete="SET NULL"), nullable=True, index=True
    )
    operation: Mapped[str] = mapped_column(String(160), nullable=False)
    model: Mapped[str | None] = mapped_column(String(120), nullable=True)
    input_tokens: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default=text("0"))
    output_tokens: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default=text("0"))
    estimated_cost: Mapped[float] = mapped_column(
        Float, nullable=False, default=0.0, server_default=text("0")
    )
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, default=_utc_now, server_default=func.now()
    )