from datetime import datetime, timezone
from sqlalchemy import Integer, Float, DateTime, ForeignKey, Index
from sqlalchemy.orm import Mapped, mapped_column, relationship

from backend.models.base import Base


class MetricSnapshot(Base):
    __tablename__ = "metric_snapshots"
    __table_args__ = (
        Index("ix_metric_snapshots_post_snapshot", "post_id", "snapshot_at"),
    )

    id: Mapped[int] = mapped_column(primary_key=True)
    post_id: Mapped[int] = mapped_column(ForeignKey("posts.id"), nullable=False)
    score: Mapped[int] = mapped_column(Integer, nullable=False)
    num_comments: Mapped[int] = mapped_column(Integer, nullable=False)
    upvote_ratio: Mapped[float | None] = mapped_column(Float)
    snapshot_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
    )

    post: Mapped["Post"] = relationship(back_populates="metric_snapshots")  # noqa: F821