"""Tree service. Creating a tree also creates the owner's TreeMembership (the
authorization basis) and an audit entry. Reads go through the privacy engine.
"""

import uuid
from datetime import UTC, datetime

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

from app.integrations.objectstore.base import ObjectStore
from app.models.enums import MembershipRole, TreeVisibility
from app.models.media import Media
from app.models.tree import Tree, TreeMembership
from app.models.user import User
from app.repositories.base import BaseRepository
from app.services import privacy
from app.services.audit import record_audit
from app.services.exceptions import Conflict, Forbidden, NotFound


async def create_tree(
    session: AsyncSession,
    *,
    owner: User,
    name: str,
    description: str | None = None,
    visibility: TreeVisibility = TreeVisibility.private,
) -> Tree:
    tree = Tree(owner_id=owner.id, name=name, description=description, visibility=visibility)
    session.add(tree)
    await session.flush()  # assign tree.id
    session.add(TreeMembership(tree_id=tree.id, user_id=owner.id, role=MembershipRole.owner))
    record_audit(
        session,
        action="create",
        entity_type="Tree",
        entity_id=tree.id,
        tree_id=tree.id,
        actor_user_id=owner.id,
        after={"name": name, "visibility": visibility.value},
    )
    await session.commit()
    await session.refresh(tree)
    return tree


async def list_trees_for_user(session: AsyncSession, *, user: User) -> list[Tree]:
    stmt = (
        select(Tree)
        .join(TreeMembership, TreeMembership.tree_id == Tree.id)
        .where(TreeMembership.user_id == user.id, Tree.deleted_at.is_(None))
        .order_by(Tree.created_at)
    )
    return list((await session.execute(stmt)).scalars().all())


async def get_tree(session: AsyncSession, *, viewer_id: uuid.UUID, tree_id: uuid.UUID) -> Tree:
    tree = await BaseRepository(session, Tree).get(tree_id)
    if tree is None:
        raise NotFound("tree not found")
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")
    return tree


async def update_tree(
    session: AsyncSession, *, actor: User, tree_id: uuid.UUID, changes: dict
) -> Tree:
    tree = await BaseRepository(session, Tree).get(tree_id)
    if tree is None:
        raise NotFound("tree not found")
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")
    for key in {"name", "description", "visibility", "home_person_id"} & changes.keys():
        setattr(tree, key, changes[key])
    record_audit(
        session,
        action="update",
        entity_type="Tree",
        entity_id=tree.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
        after=changes,
    )
    await session.commit()
    await session.refresh(tree)
    return tree


async def _owned_tree(session: AsyncSession, *, actor: User, tree_id: uuid.UUID) -> Tree:
    """Load a tree (including soft-deleted) and require the actor be its owner."""
    tree = await BaseRepository(session, Tree).get(tree_id, include_deleted=True)
    if tree is None:
        raise NotFound("tree not found")
    role = await privacy.get_membership_role(session, actor.id, tree.id)
    if role is not MembershipRole.owner:
        raise Forbidden("only the owner can delete or restore a tree")
    return tree


async def delete_tree(session: AsyncSession, *, actor: User, tree_id: uuid.UUID) -> None:
    tree = await _owned_tree(session, actor=actor, tree_id=tree_id)
    if tree.deleted_at is None:
        tree.deleted_at = datetime.now(UTC)
        record_audit(
            session,
            action="delete",
            entity_type="Tree",
            entity_id=tree.id,
            tree_id=tree.id,
            actor_user_id=actor.id,
        )
        await session.commit()


async def restore_tree(session: AsyncSession, *, actor: User, tree_id: uuid.UUID) -> Tree:
    tree = await _owned_tree(session, actor=actor, tree_id=tree_id)
    if tree.deleted_at is not None:
        tree.deleted_at = None
        record_audit(
            session,
            action="restore",
            entity_type="Tree",
            entity_id=tree.id,
            tree_id=tree.id,
            actor_user_id=actor.id,
        )
        await session.commit()
    return tree


async def purge_tree(
    session: AsyncSession,
    store: ObjectStore,
    *,
    actor: User,
    tree_id: uuid.UUID,
    confirm_name: str,
) -> None:
    """Permanently delete a soft-deleted tree and ALL its data — irreversible.
    Owner-only. The tree must already be in the trash (soft-deleted) and the
    caller must retype its name. Tree-owned rows are removed by the `tree_id`
    ON DELETE CASCADE; we delete the media objects from storage first (the DB
    cascade drops the rows but not the bytes). Audit entries survive with their
    `tree_id` nulled (ON DELETE SET NULL), so the purge stays in the log."""
    tree = await _owned_tree(session, actor=actor, tree_id=tree_id)
    if tree.deleted_at is None:
        raise Conflict("delete the tree first, then purge it from the trash")
    if confirm_name.strip() != (tree.name or "").strip():
        raise Forbidden("tree name confirmation does not match")

    keys = list(
        (
            await session.execute(select(Media.storage_key).where(Media.tree_id == tree.id))
        ).scalars().all()
    )
    for key in keys:
        try:
            await store.delete_object(key=key)
        except Exception:  # noqa: BLE001 — best-effort; a missing object must not block the purge
            pass

    record_audit(
        session,
        action="purge",
        entity_type="Tree",
        entity_id=tree.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
        before={"name": tree.name},
    )
    await session.execute(delete(Tree).where(Tree.id == tree.id))
    await session.commit()


async def list_deleted_trees_for_user(session: AsyncSession, *, user: User) -> list[Tree]:
    stmt = (
        select(Tree)
        .join(TreeMembership, TreeMembership.tree_id == Tree.id)
        .where(TreeMembership.user_id == user.id, Tree.deleted_at.is_not(None))
        .order_by(Tree.deleted_at.desc())
    )
    return list((await session.execute(stmt)).scalars().all())