"""Rulebook / topic / rule service layer — single source of truth used by
both routes/rulebooks.py and mcp/tools/rulebooks.py.

Ownership enforcement: every function takes user_id and scopes through
rulebooks.owner_user_id. Functions return models or model.to_dict() output
depending on the caller's needs (mirroring services/events.py pattern).
"""
from __future__ import annotations

import logging
from typing import Optional

from sqlalchemy import select

from fabledassistant.models import async_session
from fabledassistant.models.rulebook import Rulebook

logger = logging.getLogger(__name__)


# ── Rulebook CRUD ────────────────────────────────────────────────────────

async def create_rulebook(
    user_id: int, title: str, description: str = "",
) -> Rulebook:
    """Create a new rulebook owned by user_id. Returns the persisted model."""
    async with async_session() as session:
        rb = Rulebook(
            owner_user_id=user_id, title=title, description=description or None,
        )
        session.add(rb)
        await session.commit()
        await session.refresh(rb)
        return rb


async def list_rulebooks(user_id: int) -> list[Rulebook]:
    """List rulebooks owned by user_id, ordered by title."""
    async with async_session() as session:
        result = await session.execute(
            select(Rulebook)
            .where(Rulebook.owner_user_id == user_id)
            .order_by(Rulebook.title)
        )
        return list(result.scalars().all())


async def get_rulebook(rulebook_id: int, user_id: int) -> Optional[Rulebook]:
    """Get a rulebook by id, scoped to user_id. None if not owned or not found."""
    async with async_session() as session:
        result = await session.execute(
            select(Rulebook).where(
                Rulebook.id == rulebook_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        return result.scalar_one_or_none()


async def update_rulebook(
    rulebook_id: int, user_id: int, **fields,
) -> Optional[Rulebook]:
    """Partial update. Returns updated rulebook or None if not found."""
    async with async_session() as session:
        result = await session.execute(
            select(Rulebook).where(
                Rulebook.id == rulebook_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        rb = result.scalar_one_or_none()
        if rb is None:
            return None
        allowed = {"title", "description"}
        for key, value in fields.items():
            if key in allowed and value is not None:
                setattr(rb, key, value)
        await session.commit()
        await session.refresh(rb)
        return rb


async def delete_rulebook(rulebook_id: int, user_id: int) -> None:
    """Delete a rulebook. Cascade-deletes topics, rules, subscriptions."""
    async with async_session() as session:
        result = await session.execute(
            select(Rulebook).where(
                Rulebook.id == rulebook_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        rb = result.scalar_one_or_none()
        if rb is None:
            return
        await session.delete(rb)
        await session.commit()


async def find_rulebook_by_title(
    user_id: int, title: str,
) -> Optional[Rulebook]:
    """Used by the port script for the dupe-guard. None if not found."""
    async with async_session() as session:
        result = await session.execute(
            select(Rulebook).where(
                Rulebook.owner_user_id == user_id,
                Rulebook.title == title,
            )
        )
        return result.scalar_one_or_none()