from django.db import transaction

from tasks.activity import create_task_activity
from tasks.models import TaskActivityAction, TaskLinkedObject
from tasks.realtime import send_task_board_update


class TaskLinkNotFound(Exception):
    """Raised when a task link cannot be found in the requested resource kind."""


@transaction.atomic
def link_task_object(
    *,
    task,
    actor,
    kind,
    content_type,
    object_id,
    object_label,
    object_type,
    realtime_type,
):
    link, created = TaskLinkedObject.objects.get_or_create(
        task=task,
        kind=kind,
        content_type=content_type,
        object_id=object_id,
        defaults={"created_by": actor},
    )
    if created:
        create_task_activity(
            task,
            actor,
            TaskActivityAction.LINKED,
            object_kind=kind,
            object_id=object_id,
            metadata={
                "object_label": object_label,
                "object_type": object_type,
            },
        )

    send_task_board_update(
        task.board,
        "linked",
        realtime_type,
        object_id,
        extra={"task_id": task.id, "link_id": link.id},
    )
    return link, created


@transaction.atomic
def unlink_task_object(
    *,
    task,
    actor,
    kind,
    link_id,
    object_type,
    realtime_type,
):
    try:
        link = TaskLinkedObject.objects.get(
            task=task,
            kind=kind,
            id=link_id,
        )
    except TaskLinkedObject.DoesNotExist as exc:
        raise TaskLinkNotFound from exc

    object_id = link.object_id
    persisted_link_id = link.id
    link.delete()
    create_task_activity(
        task,
        actor,
        TaskActivityAction.UNLINKED,
        object_kind=kind,
        object_id=object_id,
        metadata={"object_type": object_type},
    )
    send_task_board_update(
        task.board,
        "unlinked",
        realtime_type,
        object_id,
        extra={"task_id": task.id, "link_id": persisted_link_id},
    )