"""FC-3a: CRUD over Source rows, with platform/url/config validation and
is_subscription auto-flip on first add / last delete.
"""

from dataclasses import dataclass

from sqlalchemy import func, select
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.asyncio import AsyncSession

from ..models import Artist, ImportSettings, Source
from .platforms import known_platform_keys
from .scheduler_service import compute_next_check_at

# Re-exported for back-compat with FC-3a; the registry in
# services/platforms.py is the single source of truth.
KNOWN_PLATFORMS = known_platform_keys()


# --- Errors -----------------------------------------------------------------

class SourceServiceError(Exception):
    """Base."""


class ArtistNotFoundError(SourceServiceError):
    pass


class UnknownPlatformError(SourceServiceError):
    def __init__(self, platform: str):
        super().__init__(f"unknown platform: {platform!r}")
        self.platform = platform


class InvalidConfigError(SourceServiceError):
    pass


class EmptyUrlError(SourceServiceError):
    pass


class DuplicateSourceError(SourceServiceError):
    def __init__(self, existing_id: int):
        super().__init__(f"duplicate source (existing id={existing_id})")
        self.existing_id = existing_id


@dataclass(frozen=True)
class SourceRecord:
    id: int
    artist_id: int
    artist_name: str
    artist_slug: str
    platform: str
    url: str
    enabled: bool
    config_overrides: dict | None
    last_checked_at: str | None
    last_error: str | None
    check_interval_override: int | None
    consecutive_failures: int
    next_check_at: str | None

    def to_dict(self) -> dict:
        return {
            "id": self.id,
            "artist_id": self.artist_id,
            "artist_name": self.artist_name,
            "artist_slug": self.artist_slug,
            "platform": self.platform,
            "url": self.url,
            "enabled": self.enabled,
            "config_overrides": self.config_overrides,
            "last_checked_at": self.last_checked_at,
            "last_error": self.last_error,
            "check_interval_override": self.check_interval_override,
            "consecutive_failures": self.consecutive_failures,
            "next_check_at": self.next_check_at,
        }


# --- Service ----------------------------------------------------------------

_EDITABLE = {"enabled", "url", "config_overrides", "check_interval_override", "platform"}


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

    async def _artist_or_raise(self, artist_id: int) -> Artist:
        row = (await self.session.execute(
            select(Artist).where(Artist.id == artist_id)
        )).scalar_one_or_none()
        if row is None:
            raise ArtistNotFoundError(f"artist id={artist_id} not found")
        return row

    @staticmethod
    def _validate_platform(platform: str) -> str:
        if platform not in KNOWN_PLATFORMS:
            raise UnknownPlatformError(platform)
        return platform

    @staticmethod
    def _validate_url(url: str) -> str:
        cleaned = (url or "").strip()
        if not cleaned:
            raise EmptyUrlError("url must not be empty")
        return cleaned

    @staticmethod
    def _validate_config(config: object) -> dict | None:
        if config is None:
            return None
        if not isinstance(config, dict):
            raise InvalidConfigError("config_overrides must be a JSON object")
        return config

    async def _load_settings(self) -> ImportSettings:
        return await ImportSettings.load(self.session)

    def _build_record(
        self, source: Source, artist: Artist, settings: ImportSettings,
    ) -> SourceRecord:
        nxt = compute_next_check_at(source, artist, settings)
        return SourceRecord(
            id=source.id,
            artist_id=source.artist_id,
            artist_name=artist.name,
            artist_slug=artist.slug,
            platform=source.platform,
            url=source.url,
            enabled=source.enabled,
            config_overrides=source.config_overrides,
            last_checked_at=source.last_checked_at.isoformat() if source.last_checked_at else None,
            last_error=source.last_error,
            check_interval_override=source.check_interval_override,
            consecutive_failures=source.consecutive_failures or 0,
            next_check_at=nxt.isoformat() if nxt else None,
        )

    async def _row_to_record(self, source: Source) -> SourceRecord:
        artist = (await self.session.execute(
            select(Artist).where(Artist.id == source.artist_id)
        )).scalar_one()
        settings = await self._load_settings()
        return self._build_record(source, artist, settings)

    async def list(
        self, artist_id: int | None = None, failing: bool = False,
        include_synthetic: bool = False,
    ) -> list[SourceRecord]:
        stmt = select(Source, Artist).join(Artist, Artist.id == Source.artist_id)
        if artist_id is not None:
            stmt = stmt.where(Source.artist_id == artist_id)
        if not include_synthetic:
            # Pre-alembic-0030 sidecar synthetic anchors
            # have url='sidecar:<platform>:<slug>' and exist only to give
            # imported Posts a NOT-NULL Source FK. They aren't pollable
            # feeds; the Subscriptions UI used to render them as phantom
            # subscriptions. Hide by default.
            stmt = stmt.where(~Source.url.like("sidecar:%"))
        if failing:
            # Worst-first so the rollup card surfaces the loudest failures.
            stmt = stmt.where(Source.consecutive_failures > 0).order_by(
                Source.consecutive_failures.desc(), Artist.name.asc(),
            )
        else:
            stmt = stmt.order_by(Artist.name.asc(), Source.id.asc())
        rows = (await self.session.execute(stmt)).all()
        settings = await self._load_settings()
        return [self._build_record(s, a, settings) for s, a in rows]

    async def get(self, source_id: int) -> SourceRecord | None:
        source = (await self.session.execute(
            select(Source).where(Source.id == source_id)
        )).scalar_one_or_none()
        if source is None:
            return None
        return await self._row_to_record(source)

    async def create(
        self,
        *,
        artist_id: int,
        platform: str,
        url: str,
        enabled: bool = True,
        config_overrides: dict | None = None,
        check_interval_override: int | None = None,
    ) -> SourceRecord:
        await self._artist_or_raise(artist_id)
        platform = self._validate_platform(platform)
        url = self._validate_url(url)
        config_overrides = self._validate_config(config_overrides)

        prior_count = (await self.session.execute(
            select(func.count(Source.id)).where(Source.artist_id == artist_id)
        )).scalar_one()

        source = Source(
            artist_id=artist_id, platform=platform, url=url,
            enabled=enabled, config_overrides=config_overrides,
            check_interval_override=check_interval_override,
        )
        self.session.add(source)
        try:
            await self.session.flush()
        except IntegrityError as exc:
            await self.session.rollback()
            existing = (await self.session.execute(
                select(Source.id).where(
                    Source.artist_id == artist_id,
                    Source.platform == platform,
                    Source.url == url,
                )
            )).scalar_one()
            raise DuplicateSourceError(existing_id=existing) from exc

        if prior_count == 0:
            await self.session.execute(
                Artist.__table__.update()
                .where(Artist.id == artist_id)
                .values(is_subscription=True)
            )
        await self.session.commit()
        return await self._row_to_record(source)

    async def update(self, source_id: int, **fields) -> SourceRecord:
        source = (await self.session.execute(
            select(Source).where(Source.id == source_id)
        )).scalar_one_or_none()
        if source is None:
            raise LookupError(f"source id={source_id} not found")

        for key in list(fields.keys()):
            if key not in _EDITABLE:
                fields.pop(key)
        if "platform" in fields:
            fields["platform"] = self._validate_platform(fields["platform"])
        if "url" in fields:
            fields["url"] = self._validate_url(fields["url"])
        if "config_overrides" in fields:
            fields["config_overrides"] = self._validate_config(fields["config_overrides"])

        for key, value in fields.items():
            setattr(source, key, value)
        try:
            await self.session.flush()
        except IntegrityError as exc:
            await self.session.rollback()
            existing = (await self.session.execute(
                select(Source.id).where(
                    Source.artist_id == source.artist_id,
                    Source.platform == source.platform,
                    Source.url == source.url,
                    Source.id != source.id,
                )
            )).scalar_one()
            raise DuplicateSourceError(existing_id=existing) from exc
        await self.session.commit()
        return await self._row_to_record(source)

    async def delete(self, source_id: int) -> None:
        source = (await self.session.execute(
            select(Source).where(Source.id == source_id)
        )).scalar_one_or_none()
        if source is None:
            raise LookupError(f"source id={source_id} not found")
        artist_id = source.artist_id
        await self.session.delete(source)
        await self.session.flush()

        remaining = (await self.session.execute(
            select(func.count(Source.id)).where(Source.artist_id == artist_id)
        )).scalar_one()
        if remaining == 0:
            await self.session.execute(
                Artist.__table__.update()
                .where(Artist.id == artist_id)
                .values(is_subscription=False)
            )
        await self.session.commit()