"""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()


# ── Topic CRUD ──────────────────────────────────────────────────────────

from fabledassistant.models.rulebook import RulebookTopic


async def _assert_rulebook_owned(session, rulebook_id: int, user_id: int) -> None:
    """Raise ValueError if rulebook doesn't exist or isn't owned by user.
    Centralizes ownership check used by all topic/rule operations.
    """
    result = await session.execute(
        select(Rulebook).where(
            Rulebook.id == rulebook_id,
            Rulebook.owner_user_id == user_id,
        )
    )
    if result.scalar_one_or_none() is None:
        raise ValueError(f"rulebook {rulebook_id} not found")


async def create_topic(
    rulebook_id: int, user_id: int, title: str,
    description: str = "", order_index: int = 0,
) -> RulebookTopic:
    async with async_session() as session:
        await _assert_rulebook_owned(session, rulebook_id, user_id)
        topic = RulebookTopic(
            rulebook_id=rulebook_id,
            title=title,
            description=description or None,
            order_index=order_index,
        )
        session.add(topic)
        await session.commit()
        await session.refresh(topic)
        return topic


async def list_topics(rulebook_id: int, user_id: int) -> list[RulebookTopic]:
    async with async_session() as session:
        await _assert_rulebook_owned(session, rulebook_id, user_id)
        result = await session.execute(
            select(RulebookTopic)
            .where(RulebookTopic.rulebook_id == rulebook_id)
            .order_by(RulebookTopic.order_index, RulebookTopic.title)
        )
        return list(result.scalars().all())


async def get_topic(topic_id: int, user_id: int) -> Optional[RulebookTopic]:
    """Get a topic, scoped via the rulebook owner."""
    async with async_session() as session:
        result = await session.execute(
            select(RulebookTopic)
            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
            .where(
                RulebookTopic.id == topic_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        return result.scalar_one_or_none()


async def update_topic(
    topic_id: int, user_id: int, **fields,
) -> Optional[RulebookTopic]:
    async with async_session() as session:
        result = await session.execute(
            select(RulebookTopic)
            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
            .where(
                RulebookTopic.id == topic_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        topic = result.scalar_one_or_none()
        if topic is None:
            return None
        allowed = {"title", "description", "order_index"}
        for key, value in fields.items():
            if key in allowed and value is not None:
                setattr(topic, key, value)
        await session.commit()
        await session.refresh(topic)
        return topic


async def delete_topic(topic_id: int, user_id: int) -> None:
    async with async_session() as session:
        result = await session.execute(
            select(RulebookTopic)
            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
            .where(
                RulebookTopic.id == topic_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        topic = result.scalar_one_or_none()
        if topic is None:
            return
        await session.delete(topic)
        await session.commit()


# ── Rule CRUD ──────────────────────────────────────────────────────────

from fabledassistant.models.rulebook import Rule


async def _assert_topic_owned(session, topic_id: int, user_id: int) -> None:
    """Raise ValueError if topic doesn't exist or isn't in user's rulebook."""
    result = await session.execute(
        select(RulebookTopic)
        .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
        .where(
            RulebookTopic.id == topic_id,
            Rulebook.owner_user_id == user_id,
        )
    )
    if result.scalar_one_or_none() is None:
        raise ValueError(f"topic {topic_id} not found")


async def create_rule(
    topic_id: int, user_id: int, title: str, statement: str,
    why: str = "", how_to_apply: str = "", order_index: int = 0,
) -> Rule:
    async with async_session() as session:
        await _assert_topic_owned(session, topic_id, user_id)
        rule = Rule(
            topic_id=topic_id,
            title=title,
            statement=statement,
            why=why or None,
            how_to_apply=how_to_apply or None,
            order_index=order_index,
        )
        session.add(rule)
        await session.commit()
        await session.refresh(rule)
        return rule


async def list_rules(
    user_id: int,
    rulebook_id: int | None = None,
    topic_id: int | None = None,
    project_id: int | None = None,
) -> list[Rule]:
    """List rules filtered by any of the three IDs. All filters are ownership-scoped.

    project_id resolves rules through project_rulebook_subscriptions.
    """
    from fabledassistant.models.rulebook import project_rulebook_subscriptions

    async with async_session() as session:
        stmt = (
            select(Rule)
            .join(RulebookTopic, Rule.topic_id == RulebookTopic.id)
            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
            .where(Rulebook.owner_user_id == user_id)
        )
        if topic_id:
            stmt = stmt.where(Rule.topic_id == topic_id)
        if rulebook_id:
            stmt = stmt.where(RulebookTopic.rulebook_id == rulebook_id)
        if project_id:
            stmt = (
                stmt.join(
                    project_rulebook_subscriptions,
                    project_rulebook_subscriptions.c.rulebook_id == Rulebook.id,
                )
                .where(project_rulebook_subscriptions.c.project_id == project_id)
            )
        stmt = stmt.order_by(
            Rulebook.id, RulebookTopic.order_index, Rule.order_index, Rule.title,
        )
        result = await session.execute(stmt)
        return list(result.scalars().all())


async def get_rule(rule_id: int, user_id: int) -> Optional[Rule]:
    async with async_session() as session:
        result = await session.execute(
            select(Rule)
            .join(RulebookTopic, Rule.topic_id == RulebookTopic.id)
            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
            .where(
                Rule.id == rule_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        return result.scalar_one_or_none()


async def update_rule(rule_id: int, user_id: int, **fields) -> Optional[Rule]:
    async with async_session() as session:
        result = await session.execute(
            select(Rule)
            .join(RulebookTopic, Rule.topic_id == RulebookTopic.id)
            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
            .where(
                Rule.id == rule_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        rule = result.scalar_one_or_none()
        if rule is None:
            return None
        allowed = {"title", "statement", "why", "how_to_apply", "order_index"}
        for key, value in fields.items():
            if key in allowed and value is not None:
                setattr(rule, key, value)
        await session.commit()
        await session.refresh(rule)
        return rule


async def delete_rule(rule_id: int, user_id: int) -> None:
    async with async_session() as session:
        result = await session.execute(
            select(Rule)
            .join(RulebookTopic, Rule.topic_id == RulebookTopic.id)
            .join(Rulebook, RulebookTopic.rulebook_id == Rulebook.id)
            .where(
                Rule.id == rule_id,
                Rulebook.owner_user_id == user_id,
            )
        )
        rule = result.scalar_one_or_none()
        if rule is None:
            return
        await session.delete(rule)
        await session.commit()