"""ORM model for periodic concurrency (system-pressure) samples.

A background sampler writes one row every few seconds holding the number of
in-flight model runs at that instant. The admin monitor aggregates these into
per-minute / per-hour buckets to draw the 并发量 pressure line chart, even for
time windows before the admin opened the page.
"""

from __future__ import annotations

from datetime import UTC, datetime

from sqlalchemy import Integer
from sqlalchemy.orm import Mapped, mapped_column

from deerflow.persistence.base import Base
from deerflow.persistence.types import BeijingDateTime


class ConcurrencySampleRow(Base):
    """One sampled snapshot of concurrent in-flight model runs."""

    __tablename__ = "concurrency_samples"

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
    # Wall-clock time the sample was taken (Beijing time on disk, tz-aware in Python).
    sampled_at: Mapped[datetime] = mapped_column(
        BeijingDateTime(), index=True, default=lambda: datetime.now(UTC)
    )
    # Number of runs whose status was pending/running at ``sampled_at``.
    active_count: Mapped[int] = mapped_column(Integer, default=0)