"""artist_membership_suggestion — "this creator and that membership are the same".

Milestone 388, step E4.

## What was NOT needed here

E4's first job was to check what is actually missing, and the answer was: not
the schema, and not the flows. `Source.artist_id` is a plain FK, so many
sources per artist is already the data model; `POST /api/sources` already takes
an `artist_id`; the add-source dialog already has an artist autocomplete that
attaches to an EXISTING artist; and `SourceService.reassign` already moves a
source between artists WITH post and image re-attribution. A sweep for
one-source-per-artist assumptions found only `func.count()` calls, which are
the opposite of assuming one.

So no parallel association table was built for a relationship the schema
already expresses (rule 28). What was missing is the SUGGESTION — FC proposing
the link from the roster instead of waiting to be told.

## Confirm-only, and what "accept" actually does

Accepting adds a SOURCE for the membership's platform under the artist that
already has the other channel. It does NOT merge two artists. That distinction
is the whole safety margin: adding a source is trivially undone, whereas a
wrong artist merge silently mixes two creators' work and corrupts tagging,
series and provenance downstream — with nothing left to tell them apart by.

Dismissed rows are kept, not deleted, for the same reason as every other review
queue here: the row is what remembers the rejection, and re-proposing a
rejected pair on every scan is what makes a queue get ignored.
"""

from datetime import datetime

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

from .base import Base


class ArtistMembershipSuggestion(Base):
    __tablename__ = "artist_membership_suggestion"
    __table_args__ = (
        UniqueConstraint(
            "platform_membership_id", "artist_id",
            name="uq_artist_membership_suggestion_pair",
        ),
    )

    id: Mapped[int] = mapped_column(Integer, primary_key=True)
    platform_membership_id: Mapped[int] = mapped_column(
        ForeignKey("platform_membership.id", ondelete="CASCADE"),
        nullable=False, index=True,
    )
    artist_id: Mapped[int] = mapped_column(
        ForeignKey("artist.id", ondelete="CASCADE"), nullable=False, index=True
    )

    score: Mapped[float] = mapped_column(Float, nullable=False)
    # Per-signal strengths as scored. Without it, "why was this suggested" is
    # unanswerable the moment a weight or the threshold moves.
    signals: Mapped[dict | None] = mapped_column(JSON, nullable=True)
    # pending | linked | dismissed. Plain String, no CHECK — same call as
    # series_suggestion.status and post_association.status.
    status: Mapped[str] = mapped_column(
        String(16), nullable=False, server_default="pending", index=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(),
    )