"""Artist overview + paged images.

Images are linked to an artist through the provenance chain
Source(artist_id) -> ImageProvenance(source_id) -> ImageRecord. DISTINCT
guards against an image having several provenance rows for one artist.
Dates come from Post.post_date via ImageProvenance.post_id.
"""

from dataclasses import dataclass

from sqlalchemy import and_, func, or_, select
from sqlalchemy.ext.asyncio import AsyncSession

from ..models import (
    Artist,
    ImageProvenance,
    ImageRecord,
    Post,
    Source,
    Tag,
)
from ..models.tag import image_tag
from .gallery_service import decode_cursor, encode_cursor, thumbnail_url


@dataclass(frozen=True)
class ArtistImagesPage:
    images: list[dict]
    next_cursor: str | None


class ArtistService:
    def __init__(self, session: AsyncSession):
        self.session = session

    async def _artist_by_slug(self, slug: str) -> Artist | None:
        return (
            await self.session.execute(
                select(Artist).where(Artist.slug == slug)
            )
        ).scalar_one_or_none()

    async def overview(self, slug: str) -> dict | None:
        artist = await self._artist_by_slug(slug)
        if artist is None:
            return None
        aid = artist.id

        img_join = (
            select(ImageRecord.id)
            .join(ImageProvenance, ImageProvenance.image_record_id == ImageRecord.id)
            .join(Source, Source.id == ImageProvenance.source_id)
            .where(Source.artist_id == aid)
        )
        image_count = (
            await self.session.execute(
                select(func.count(func.distinct(ImageRecord.id)))
                .select_from(ImageRecord)
                .join(ImageProvenance, ImageProvenance.image_record_id == ImageRecord.id)
                .join(Source, Source.id == ImageProvenance.source_id)
                .where(Source.artist_id == aid)
            )
        ).scalar_one()

        date_row = (
            await self.session.execute(
                select(func.min(Post.post_date), func.max(Post.post_date))
                .select_from(Post)
                .join(ImageProvenance, ImageProvenance.post_id == Post.id)
                .join(Source, Source.id == ImageProvenance.source_id)
                .where(Source.artist_id == aid)
            )
        ).first()
        dmin, dmax = date_row if date_row else (None, None)

        cooccurring = (
            await self.session.execute(
                select(
                    Tag.id, Tag.name, Tag.kind,
                    func.count(image_tag.c.image_record_id).label("cnt"),
                )
                .select_from(Tag)
                .join(image_tag, image_tag.c.tag_id == Tag.id)
                .where(image_tag.c.image_record_id.in_(img_join))
                .group_by(Tag.id, Tag.name, Tag.kind)
                .order_by(func.count(image_tag.c.image_record_id).desc())
                .limit(20)
            )
        ).all()

        sources = (
            await self.session.execute(
                select(
                    Source.id, Source.platform, Source.url,
                    func.count(func.distinct(ImageProvenance.image_record_id)).label("cnt"),
                )
                .select_from(Source)
                .outerjoin(ImageProvenance, ImageProvenance.source_id == Source.id)
                .where(Source.artist_id == aid)
                .group_by(Source.id, Source.platform, Source.url)
                .order_by(Source.id)
            )
        ).all()

        month = func.date_trunc("month", Post.post_date).label("m")
        activity = (
            await self.session.execute(
                select(month, func.count(func.distinct(ImageProvenance.image_record_id)))
                .select_from(Post)
                .join(ImageProvenance, ImageProvenance.post_id == Post.id)
                .join(Source, Source.id == ImageProvenance.source_id)
                .where(and_(Source.artist_id == aid, Post.post_date.isnot(None)))
                .group_by(month)
                .order_by(month)
            )
        ).all()

        return {
            "id": artist.id,
            "name": artist.name,
            "slug": artist.slug,
            "image_count": int(image_count),
            "date_range": {
                "min": dmin.isoformat() if dmin else None,
                "max": dmax.isoformat() if dmax else None,
            },
            "cooccurring_tags": [
                {
                    "id": tid,
                    "name": name,
                    "kind": kind.value if hasattr(kind, "value") else kind,
                    "count": int(cnt),
                }
                for tid, name, kind, cnt in cooccurring
            ],
            "sources": [
                {
                    "id": sid,
                    "platform": platform,
                    "url": url,
                    "image_count": int(cnt),
                }
                for sid, platform, url, cnt in sources
            ],
            "activity": [
                {"month": m.isoformat(), "count": int(cnt)}
                for m, cnt in activity
            ],
        }

    async def images(
        self, slug: str, cursor: str | None, limit: int = 60
    ) -> ArtistImagesPage | None:
        if limit < 1 or limit > 200:
            raise ValueError("limit must be between 1 and 200")
        artist = await self._artist_by_slug(slug)
        if artist is None:
            return None

        # Dedupe via IN-subquery rather than JOIN + DISTINCT: an image can
        # have several provenance rows for one artist, and SELECT DISTINCT
        # over ImageRecord fails in Postgres because its json columns have
        # no equality operator.
        stmt = select(ImageRecord).where(
            ImageRecord.id.in_(
                select(ImageProvenance.image_record_id)
                .join(Source, Source.id == ImageProvenance.source_id)
                .where(Source.artist_id == artist.id)
            )
        )
        if cursor:
            cur_ts, cur_id = decode_cursor(cursor)
            stmt = stmt.where(
                or_(
                    ImageRecord.created_at < cur_ts,
                    and_(ImageRecord.created_at == cur_ts, ImageRecord.id < cur_id),
                )
            )
        stmt = stmt.order_by(
            ImageRecord.created_at.desc(), ImageRecord.id.desc()
        ).limit(limit + 1)
        rows = (await self.session.execute(stmt)).scalars().all()

        next_cursor = None
        if len(rows) > limit:
            last = rows[limit - 1]
            next_cursor = encode_cursor(last.created_at, last.id)
            rows = rows[:limit]

        return ArtistImagesPage(
            images=[
                {
                    "id": r.id,
                    "sha256": r.sha256,
                    "mime": r.mime,
                    "width": r.width,
                    "height": r.height,
                    "thumbnail_url": thumbnail_url(r.sha256, r.mime),
                }
                for r in rows
            ],
            next_cursor=next_cursor,
        )