#  Copyright 2021 Collate
#  Licensed under the Apache License, Version 2.0 (the "License");
#  you may not use this file except in compliance with the License.
#  You may obtain a copy of the License at
#  http://www.apache.org/licenses/LICENSE-2.0
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS,
#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#  See the License for the specific language governing permissions and
#  limitations under the License.

import importlib
import os
import re
import sys
import traceback
from multiprocessing import Process
from typing import Optional

from airflow import settings
from airflow.jobs.scheduler_job import SchedulerJob
from airflow.models import DagBag
from flask import request
from openmetadata_managed_apis.utils.logger import api_logger

logger = api_logger()


class MissingArgException(Exception):
    """
    Raised when we cannot properly validate the incoming data
    """


def import_path(path):
    module_name = os.path.basename(path).replace("-", "_")
    spec = importlib.util.spec_from_loader(
        module_name, importlib.machinery.SourceFileLoader(module_name, path)
    )
    module = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(module)
    sys.modules[module_name] = module
    return module


def clean_dag_id(raw_dag_id: Optional[str]) -> Optional[str]:
    """
    Given a string we want to use as a dag_id, we should
    give it a cleanup as Airflow does not support anything
    that is not alphanumeric for the name
    """
    return re.sub("[^0-9a-zA-Z-_]+", "_", raw_dag_id) if raw_dag_id else None


def get_request_arg(req, arg, raise_missing: bool = True) -> Optional[str]:
    """
    Pick up the `arg` from the flask `req`.
    E.g., GET api/v1/endpoint?key=value

    If raise_missing, throw an exception if the argument is
    not present in the request
    """
    request_argument = req.args.get(arg) or req.form.get(arg)

    if not request_argument and raise_missing:
        raise MissingArgException(f"Missing {arg} from request {req} argument")

    return request_argument


def get_arg_dag_id() -> Optional[str]:
    """
    Try to fetch the dag_id from the args
    and clean it
    """
    raw_dag_id = get_request_arg(request, "dag_id")

    return clean_dag_id(raw_dag_id)


def get_request_dag_id() -> Optional[str]:
    """
    Try to fetch the dag_id from the JSON request
    and clean it
    """
    raw_dag_id = request.get_json().get("dag_id")

    if not raw_dag_id:
        raise MissingArgException("Missing dag_id from request JSON")

    return clean_dag_id(raw_dag_id)


def get_dagbag():
    """
    Load the dagbag from Airflow settings
    """
    dagbag = DagBag(dag_folder=settings.DAGS_FOLDER, read_dags_from_db=True)
    dagbag.collect_dags()
    dagbag.collect_dags_from_db()
    return dagbag


class ScanDagsTask(Process):
    def run(self):
        scheduler_job = SchedulerJob(num_times_parse_dags=1)
        scheduler_job.heartrate = 0
        scheduler_job.run()
        try:
            scheduler_job.kill()
        except Exception as exc:
            logger.debug(traceback.format_exc())
            logger.info(f"Rescan Complete: Killed Job: {exc}")


def scan_dags_job_background():
    """
    Runs the scheduler scan in another thread
    to not block the API call
    """
    process = ScanDagsTask()
    process.start()