"""Media service. Bytes go to the ObjectStore; a metadata row goes to the DB.
Writes require editor rights; reads go through the privacy engine."""

import hashlib
import uuid
from datetime import UTC, datetime

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

from app.integrations.objectstore.base import ObjectStore
from app.models.media import Media
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


async def upload_media(
    session: AsyncSession,
    store: ObjectStore,
    *,
    actor: User,
    tree: Tree,
    data: bytes,
    filename: str,
    content_type: str,
    title: str | None = None,
    person_id: uuid.UUID | None = None,
    event_id: uuid.UUID | None = None,
    source_id: uuid.UUID | None = None,
) -> Media:
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")

    media_id = uuid.uuid4()
    key = f"{tree.id}/{media_id}/{filename}"
    await store.ensure_bucket()
    await store.put_object(key=key, data=data, content_type=content_type)

    media = Media(
        id=media_id,
        tree_id=tree.id,
        uploader_id=actor.id,
        storage_key=key,
        original_filename=filename,
        content_type=content_type,
        byte_size=len(data),
        checksum_sha256=hashlib.sha256(data).hexdigest(),
        title=title,
        person_id=person_id,
        event_id=event_id,
        source_id=source_id,
    )
    session.add(media)
    await session.flush()
    record_audit(
        session,
        action="create",
        entity_type="Media",
        entity_id=media.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
        after={"filename": filename, "bytes": len(data)},
    )
    await session.commit()
    await session.refresh(media)
    return media


async def list_media(session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree) -> list[Media]:
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")
    stmt = (
        select(Media)
        .where(Media.tree_id == tree.id, Media.deleted_at.is_(None))
        .order_by(Media.created_at.desc())
    )
    return list((await session.execute(stmt)).scalars().all())


async def delete_media(
    session: AsyncSession, *, actor: User, tree: Tree, media_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")
    media = (
        await session.execute(
            select(Media).where(
                Media.id == media_id, Media.tree_id == tree.id, Media.deleted_at.is_(None)
            )
        )
    ).scalar_one_or_none()
    if media is None:
        raise NotFound("media not found")
    # Soft delete the row; the object is removed by the worker's purge job.
    media.deleted_at = datetime.now(UTC)
    record_audit(
        session,
        action="delete",
        entity_type="Media",
        entity_id=media.id,
        tree_id=tree.id,
        actor_user_id=actor.id,
    )
    await session.commit()