"""Stable asset identity and path history.

A file path is mutable metadata, never identity: ``assets.id`` is a generated
UUID that never changes across moves, renames, or archival. ``asset_paths``
records every path an asset has occupied. ``state_version`` supports optimistic
concurrency; ``created_at``/``updated_at`` are the audit timestamps.

Later-stage columns (canonical link, safety score, archive location) are added by
the migrations of the stories that own them, not speculatively here.
"""

from __future__ import annotations

from datetime import datetime

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

from photo_pipeline.db import Base


class Asset(Base):
    __tablename__ = "assets"

    id: Mapped[str] = mapped_column(String, primary_key=True)
    original_path: Mapped[str] = mapped_column(String, nullable=False)
    current_path: Mapped[str | None] = mapped_column(String, unique=True)

    current_sha256: Mapped[str | None] = mapped_column(String)
    pixel_sha256: Mapped[str | None] = mapped_column(String)
    phash: Mapped[str | None] = mapped_column(String)
    hash_version: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
    phash_version: Mapped[int | None] = mapped_column(Integer)
    byte_size: Mapped[int | None] = mapped_column(Integer)

    discovered_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
    missing_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    availability_state: Mapped[str] = mapped_column(String, nullable=False, default="active")
    # Duplicate canonical link: NULL when the asset is itself canonical or undecided.
    canonical_asset_id: Mapped[str | None] = mapped_column(ForeignKey("assets.id"))

    state_version: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
    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()
    )


class AssetPath(Base):
    __tablename__ = "asset_paths"

    asset_id: Mapped[str] = mapped_column(
        ForeignKey("assets.id"), primary_key=True
    )
    path: Mapped[str] = mapped_column(String, primary_key=True)
    valid_from: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), primary_key=True
    )
    valid_until: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
    reason: Mapped[str | None] = mapped_column(String)