from __future__ import annotations

from datetime import datetime

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

from app.core.database import Base
from app.utils.ids import prefixed_id


class UsageOperation(Base):
    """One privacy-safe, idempotent reservation for an expensive operation."""

    __tablename__ = "usage_operations"
    __table_args__ = (
        UniqueConstraint(
            "user_id",
            "operation",
            "idempotency_key",
            name="uq_usage_operations_user_operation_key",
        ),
        Index(
            "ix_usage_operations_user_period_operation",
            "user_id",
            "period_key",
            "operation",
        ),
    )

    id: Mapped[str] = mapped_column(
        String(40), primary_key=True, default=lambda: prefixed_id("usage")
    )
    user_id: Mapped[str] = mapped_column(
        String(40), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
    )
    operation: Mapped[str] = mapped_column(String(48), nullable=False)
    period_key: Mapped[str] = mapped_column(String(16), nullable=False)
    idempotency_key: Mapped[str] = mapped_column(String(180), nullable=False)
    status: Mapped[str] = mapped_column(String(20), nullable=False, default="reserved")
    units: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
    request_id: Mapped[str | None] = mapped_column(String(100), nullable=True)
    resource_id: Mapped[str | None] = mapped_column(String(80), nullable=True)
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), nullable=False
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False
    )
    completed_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)