"""Version model — annotation state snapshots for history/recovery."""

import uuid
from datetime import datetime, timezone

from sqlalchemy import ForeignKey, Index, Text
from sqlalchemy.orm import Mapped, mapped_column, relationship

from app.db import Base


def _uuid() -> str:
    return str(uuid.uuid4())


def _now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


class Version(Base):
    """
    A snapshot of a document's annotation state at a point in time.

    Versions serve as a safety net for accidental annotation loss.
    `kind` is either 'manual' (user-created) or 'auto' (system-created
    at safety boundaries like document close or before destructive ops).
    """

    __tablename__ = "versions"

    id: Mapped[str] = mapped_column(Text, primary_key=True, default=_uuid)
    document_id: Mapped[str] = mapped_column(
        Text, ForeignKey("documents.id", ondelete="CASCADE"), nullable=False
    )
    label: Mapped[str | None] = mapped_column(Text, nullable=True, default=None)
    data: Mapped[str] = mapped_column(Text, nullable=False)  # JSON snapshot
    kind: Mapped[str] = mapped_column(Text, nullable=False)  # 'manual' | 'auto'
    created_at: Mapped[str] = mapped_column(Text, default=_now_iso)

    # Relationships
    document: Mapped["Document"] = relationship("Document", back_populates="versions")

    __table_args__ = (
        Index("ix_versions_document_created", "document_id", "created_at"),
    )