"""SeriesPage — ordered image membership for a series-kind Tag.

A series IS a Tag with kind='series'; series_page gives it a SINGLE flat,
series-global ordered run of pages (FC-6.x divider reframe). An image belongs to
at most one series (UNIQUE image_id). Reading order is `page_number` alone — a
series-wide ordering key (not unique), rewritten 1..N wholesale on reorder so a
reorder can't transiently collide on an index.

Chapters are cosmetic DIVIDERS anchored to a page (see SeriesChapter); they do
NOT own pages, so there is no chapter_id here — a page's chapter is derived at
read time as the nearest preceding divider. stated_page carries the printed page
number parsed from the source post, nullable when unknown.
"""

from datetime import datetime

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

from .base import Base


class SeriesPage(Base):
    __tablename__ = "series_page"

    __table_args__ = (
        # alembic 0005 named this `uq_series_page_image`; a bare `unique=True`
        # on the column renders `uq_series_page_image_id` under the naming
        # convention, which is a different object from the one the database
        # has (#3275).
        UniqueConstraint("image_id", name="uq_series_page_image"),
    )

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    series_tag_id: Mapped[int] = mapped_column(
        ForeignKey("tag.id", ondelete="CASCADE"), nullable=False, index=True
    )
    # UNIQUE lives in __table_args__ above, under the name 0005 gave it.
    image_id: Mapped[int] = mapped_column(
        ForeignKey("image_record.id", ondelete="CASCADE"),
        nullable=False,
    )
    # 'placed' = in the series-global run (page_number set); 'pending' = staged
    # from a post awaiting the operator's sort (page_number NULL). (#789 P2)
    status: Mapped[str] = mapped_column(
        String(16), nullable=False, server_default="placed"
    )
    page_number: Mapped[int | None] = mapped_column(Integer, nullable=True)
    stated_page: Mapped[int | None] = mapped_column(Integer, nullable=True)
    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(),
    )