"""Citation service. A citation links one Source to exactly one fact (person,
event, name, or relationship) within a tree — the provenance spine."""

import uuid
from datetime import UTC, datetime

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.enums import CitationConfidence
from app.models.event import Event
from app.models.person import Name, Person
from app.models.relationship import Relationship
from app.models.source import Citation, Source
from app.models.tree import Tree
from app.models.user import User
from app.services import privacy
from app.services.audit import record_audit
from app.services.exceptions import Conflict, Forbidden, NotFound

# Citation target column -> model, for tenant/existence validation.
_TARGET_MODELS = {
    "person_id": Person,
    "event_id": Event,
    "name_id": Name,
    "relationship_id": Relationship,
}


async def _in_tree(session: AsyncSession, model: type, id_: uuid.UUID, tree_id: uuid.UUID) -> bool:
    row = (
        await session.execute(
            select(model.id).where(
                model.id == id_, model.tree_id == tree_id, model.deleted_at.is_(None)
            )
        )
    ).scalar_one_or_none()
    return row is not None


async def create_citation(
    session: AsyncSession,
    *,
    actor: User,
    tree: Tree,
    source_id: uuid.UUID,
    person_id: uuid.UUID | None = None,
    event_id: uuid.UUID | None = None,
    name_id: uuid.UUID | None = None,
    relationship_id: uuid.UUID | None = None,
    page: str | None = None,
    detail: str | None = None,
    confidence: CitationConfidence | None = None,
) -> Citation:
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")

    targets = {
        "person_id": person_id,
        "event_id": event_id,
        "name_id": name_id,
        "relationship_id": relationship_id,
    }
    set_targets = {k: v for k, v in targets.items() if v is not None}
    if len(set_targets) != 1:
        raise Conflict("a citation must reference exactly one fact")

    if not await _in_tree(session, Source, source_id, tree.id):
        raise NotFound("source not found in this tree")
    (target_col, target_id), = set_targets.items()
    if not await _in_tree(session, _TARGET_MODELS[target_col], target_id, tree.id):
        raise NotFound("cited fact not found in this tree")

    citation = Citation(
        tree_id=tree.id,
        source_id=source_id,
        person_id=person_id,
        event_id=event_id,
        name_id=name_id,
        relationship_id=relationship_id,
        page=page,
        detail=detail,
        confidence=confidence,
    )
    session.add(citation)
    await session.flush()
    record_audit(
        session,
        action="create",
        entity_type="Citation",
        entity_id=citation.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
        after={"source_id": str(source_id), target_col: str(target_id)},
    )
    await session.commit()
    await session.refresh(citation)
    return citation


async def list_citations(
    session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree
) -> list[Citation]:
    """All citations in the tree — the UI maps them to facts to show 'sourced'
    indicators in a single round-trip."""
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")
    stmt = (
        select(Citation)
        .where(Citation.tree_id == tree.id, Citation.deleted_at.is_(None))
        .order_by(Citation.created_at)
    )
    return list((await session.execute(stmt)).scalars().all())


async def delete_citation(
    session: AsyncSession, *, actor: User, tree: Tree, citation_id: uuid.UUID
) -> None:
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")
    citation = (
        await session.execute(
            select(Citation).where(
                Citation.id == citation_id,
                Citation.tree_id == tree.id,
                Citation.deleted_at.is_(None),
            )
        )
    ).scalar_one_or_none()
    if citation is None:
        raise NotFound("citation not found")
    citation.deleted_at = datetime.now(UTC)
    record_audit(
        session,
        action="delete",
        entity_type="Citation",
        entity_id=citation.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
    )
    await session.commit()