"""Managed thumbnail cache records.

One row per ``cache_key`` (pixel hash + size + algorithm version, or the source
byte hash for undecodable inputs). The row records whether generation succeeded or
failed and why, so a broken original is not retried on every request. Because the
key contains the normalized pixel hash, an EXIF-only change reuses the thumbnail
and a genuine pixel change invalidates it automatically.
"""

from __future__ import annotations

from datetime import datetime

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

from photo_pipeline.db import Base


class Thumbnail(Base):
    __tablename__ = "thumbnails"

    cache_key: Mapped[str] = mapped_column(String, primary_key=True)
    asset_id: Mapped[str] = mapped_column(ForeignKey("assets.id"), nullable=False)
    size: Mapped[int] = mapped_column(Integer, nullable=False)
    state: Mapped[str] = mapped_column(String, nullable=False)  # ready | error
    error_code: Mapped[str | None] = mapped_column(String)
    path: Mapped[str | None] = mapped_column(String)
    width: Mapped[int | None] = mapped_column(Integer)
    height: Mapped[int | None] = mapped_column(Integer)
    format: Mapped[str | None] = mapped_column(String)
    # Durable comparison evidence for an archived asset: never evicted by the LRU
    # quota, because the original may be on a medium that is no longer reachable.
    protected: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, server_default=func.now()
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, server_default=func.now(), onupdate=func.now()
    )