"""Person service. Writes require editor rights on the tree; reads run every
person through the privacy engine. Each returned Person gets a transient
``primary_name`` for display (not persisted).
"""

import uuid
from datetime import UTC, datetime

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

from app.models.enums import PersonPrivacy
from app.models.person import Name, Person
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 Forbidden, NotFound
from app.services.privacy import Visibility


def _format_name(name: Name) -> str | None:
    parts = [name.given, name.surname]
    joined = " ".join(p for p in parts if p)
    return joined or name.display_name


def _redact(person: Person) -> None:
    """Minimise a possibly-living person for a non-member view (transient only —
    never committed)."""
    person.primary_name = "Living person"
    person.gender = None
    person.is_living = True


async def _attach_primary_name(session: AsyncSession, person: Person) -> None:
    stmt = (
        select(Name)
        .where(Name.person_id == person.id, Name.deleted_at.is_(None))
        .order_by(Name.is_primary.desc(), Name.sort_order)
    )
    name = (await session.execute(stmt)).scalars().first()
    # Transient display attribute consumed by the PersonRead schema.
    person.primary_name = _format_name(name) if name is not None else None


async def create_person(
    session: AsyncSession,
    *,
    actor: User,
    tree: Tree,
    given: str | None = None,
    surname: str | None = None,
    gender: str | None = None,
    is_living: bool | None = None,
    privacy_setting: PersonPrivacy = PersonPrivacy.inherit,
    notes: str | None = None,
) -> Person:
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")

    person = Person(
        tree_id=tree.id,
        gender=gender,
        is_living=is_living,
        privacy=privacy_setting,
        notes=notes,
    )
    session.add(person)
    await session.flush()  # assign person.id

    if given or surname:
        session.add(
            Name(
                tree_id=tree.id,
                person_id=person.id,
                name_type="birth",
                given=given,
                surname=surname,
                is_primary=True,
            )
        )
    record_audit(
        session,
        action="create",
        entity_type="Person",
        entity_id=person.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
        after={"given": given, "surname": surname},
    )
    await session.commit()
    await session.refresh(person)
    await _attach_primary_name(session, person)
    return person


async def get_person(
    session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree, person_id: uuid.UUID
) -> Person:
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")
    person = (
        await session.execute(
            select(Person).where(
                Person.id == person_id,
                Person.tree_id == tree.id,
                Person.deleted_at.is_(None),
            )
        )
    ).scalar_one_or_none()
    if person is None:
        raise NotFound("person not found")
    # Run the single person through the privacy engine (redaction lands Phase 2).
    vis = await privacy.person_visibility(
        session, user_id=viewer_id, tree=tree, person=person
    )
    if vis == Visibility.hidden:
        raise NotFound("person not found")
    if vis == Visibility.redacted:
        _redact(person)
    else:
        await _attach_primary_name(session, person)
    return person


async def delete_person(
    session: AsyncSession, *, actor: User, tree: Tree, person_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")
    person = (
        await session.execute(
            select(Person).where(
                Person.id == person_id, Person.tree_id == tree.id, Person.deleted_at.is_(None)
            )
        )
    ).scalar_one_or_none()
    if person is None:
        raise NotFound("person not found")
    person.deleted_at = datetime.now(UTC)
    record_audit(
        session,
        action="delete",
        entity_type="Person",
        entity_id=person.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
    )
    await session.commit()


async def restore_person(
    session: AsyncSession, *, actor: User, tree: Tree, person_id: uuid.UUID
) -> Person:
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")
    person = (
        await session.execute(
            select(Person).where(
                Person.id == person_id, Person.tree_id == tree.id, Person.deleted_at.is_not(None)
            )
        )
    ).scalar_one_or_none()
    if person is None:
        raise NotFound("deleted person not found")
    person.deleted_at = None
    record_audit(
        session,
        action="restore",
        entity_type="Person",
        entity_id=person.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
    )
    await session.commit()
    await session.refresh(person)
    await _attach_primary_name(session, person)
    return person


async def list_deleted_persons(
    session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree
) -> list[Person]:
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")
    stmt = (
        select(Person)
        .where(Person.tree_id == tree.id, Person.deleted_at.is_not(None))
        .order_by(Person.deleted_at.desc())
    )
    persons = list((await session.execute(stmt)).scalars().all())
    for person in persons:
        await _attach_primary_name(session, person)
    return persons


async def list_persons(
    session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree
) -> list[Person]:
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")

    stmt = (
        select(Person)
        .where(Person.tree_id == tree.id, Person.deleted_at.is_(None))
        .order_by(Person.created_at)
    )
    persons = list((await session.execute(stmt)).scalars().all())

    visible: list[Person] = []
    for person in persons:
        vis = await privacy.person_visibility(
            session, user_id=viewer_id, tree=tree, person=person
        )
        if vis == Visibility.hidden:
            continue
        if vis == Visibility.redacted:
            _redact(person)
        else:
            await _attach_primary_name(session, person)
        visible.append(person)
    return visible


async def search_persons(
    session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree, query: str, limit: int = 50
) -> list[Person]:
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")
    q = query.strip()
    if not q:
        return []
    like = f"%{q}%"
    score = func.greatest(
        func.similarity(func.coalesce(Name.given, ""), q),
        func.similarity(func.coalesce(Name.surname, ""), q),
    )
    sub = (
        select(Name.person_id.label("pid"), func.max(score).label("score"))
        .where(
            Name.tree_id == tree.id,
            Name.deleted_at.is_(None),
            or_(
                Name.given.op("%")(q),
                Name.surname.op("%")(q),
                Name.given.ilike(like),
                Name.surname.ilike(like),
            ),
        )
        .group_by(Name.person_id)
        .order_by(func.max(score).desc())
        .limit(limit)
        .subquery()
    )
    stmt = (
        select(Person)
        .join(sub, sub.c.pid == Person.id)
        .where(Person.tree_id == tree.id, Person.deleted_at.is_(None))
        .order_by(sub.c.score.desc())
    )
    persons = list((await session.execute(stmt)).scalars().all())
    out: list[Person] = []
    for person in persons:
        vis = await privacy.person_visibility(
            session, user_id=viewer_id, tree=tree, person=person
        )
        if vis == Visibility.hidden:
            continue
        if vis == Visibility.redacted:
            _redact(person)
        else:
            await _attach_primary_name(session, person)
        out.append(person)
    return out