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"""Delete DAGs APIs."""

from __future__ import annotations

import logging
from typing import TYPE_CHECKING

from sqlalchemy import and_, delete, or_, select

from airflow import models
from airflow.exceptions import AirflowException, DagNotFound
from airflow.models import DagModel, TaskFail
from airflow.models.errors import ParseImportError
from airflow.models.serialized_dag import SerializedDagModel
from airflow.utils.db import get_sqla_model_classes
from airflow.utils.session import NEW_SESSION, provide_session
from airflow.utils.state import TaskInstanceState

if TYPE_CHECKING:
    from sqlalchemy.orm import Session

log = logging.getLogger(__name__)


@provide_session
def delete_dag(dag_id: str, keep_records_in_log: bool = True, session: Session = NEW_SESSION) -> int:
    """
    Delete a DAG by a dag_id.

    :param dag_id: the dag_id of the DAG to delete
    :param keep_records_in_log: whether keep records of the given dag_id
        in the Log table in the backend database (for reasons like auditing).
        The default value is True.
    :param session: session used
    :return count of deleted dags
    """
    log.info("Deleting DAG: %s", dag_id)
    running_tis = session.scalar(
        select(models.TaskInstance.state)
        .where(models.TaskInstance.dag_id == dag_id)
        .where(models.TaskInstance.state == TaskInstanceState.RUNNING)
        .limit(1)
    )
    if running_tis:
        raise AirflowException("TaskInstances still running")
    dag = session.scalar(select(DagModel).where(DagModel.dag_id == dag_id).limit(1))
    if dag is None:
        raise DagNotFound(f"Dag id {dag_id} not found")

    # deleting a DAG should also delete all of its subdags
    dags_to_delete_query = session.execute(
        select(DagModel.dag_id).where(
            or_(
                DagModel.dag_id == dag_id,
                and_(DagModel.dag_id.like(f"{dag_id}.%"), DagModel.is_subdag),
            )
        )
    )

    dags_to_delete = [dag_id for (dag_id,) in dags_to_delete_query]

    # Scheduler removes DAGs without files from serialized_dag table every dag_dir_list_interval.
    # There may be a lag, so explicitly removes serialized DAG here.
    if SerializedDagModel.has_dag(dag_id=dag_id, session=session):
        SerializedDagModel.remove_dag(dag_id=dag_id, session=session)

    count = 0

    for model in get_sqla_model_classes():
        if hasattr(model, "dag_id") and (not keep_records_in_log or model.__name__ != "Log"):
            count += session.execute(
                delete(model)
                .where(model.dag_id.in_(dags_to_delete))
                .execution_options(synchronize_session="fetch")
            ).rowcount
    if dag.is_subdag:
        parent_dag_id, task_id = dag_id.rsplit(".", 1)
        for model in TaskFail, models.TaskInstance:
            count += session.execute(
                delete(model).where(model.dag_id == parent_dag_id, model.task_id == task_id)
            ).rowcount

    # Delete entries in Import Errors table for a deleted DAG
    # This handles the case when the dag_id is changed in the file
    session.execute(
        delete(ParseImportError)
        .where(ParseImportError.filename == dag.fileloc)
        .execution_options(synchronize_session="fetch")
    )

    return count
