import ast
from multiprocessing.process import current_process

from django import core, db
from django.utils import timezone
from django.utils.translation import gettext_lazy as _

from django.apps.registry import apps

try:
    apps.check_apps_ready()
except core.exceptions.AppRegistryNotReady:
    import django

    django.setup()

from django_q.brokers import Broker, get_broker
from django_q.conf import Conf, logger
from django_q.humanhash import humanize
from django_q.models import Schedule
from django_q.tasks import async_task
from django_q.utils import close_old_django_connections, localtime


def scheduler(broker: Broker = None):
    """
    Creates a task from a schedule at the scheduled time and schedules next run
    """
    if not broker:
        broker = get_broker()
    close_old_django_connections()
    try:
        # Only default cluster will handler schedule with default(null) cluster
        Q_default = (
            db.models.Q(cluster__isnull=True)
            if Conf.CLUSTER_NAME == Conf.PREFIX
            else db.models.Q(pk__in=[])
        )

        with db.transaction.atomic(using=db.router.db_for_write(Schedule)):
            for s in (
                Schedule.objects.select_for_update()
                .exclude(repeats=0)
                .filter(next_run__lt=timezone.now())
                .filter(Q_default | db.models.Q(cluster=Conf.CLUSTER_NAME))
            ):
                args = ()
                kwargs = {}
                # get args, kwargs and hook
                if s.kwargs:
                    try:
                        # first try the dict syntax
                        kwargs = ast.literal_eval(s.kwargs)
                    except (SyntaxError, ValueError):
                        # else use the kwargs syntax
                        try:
                            parsed_kwargs = (
                                ast.parse(f"f({s.kwargs})").body[0].value.keywords
                            )
                            kwargs = {
                                kwarg.arg: ast.literal_eval(kwarg.value)
                                for kwarg in parsed_kwargs
                            }
                        except (SyntaxError, ValueError):
                            kwargs = {}
                if s.args:
                    args = ast.literal_eval(s.args)
                    # single value won't eval to tuple, so:
                    if type(args) != tuple:
                        args = (args,)
                q_options = kwargs.get("q_options", {})
                if s.intended_date_kwarg:
                    kwargs[s.intended_date_kwarg] = s.next_run.isoformat()
                if s.hook:
                    q_options["hook"] = s.hook
                # set up the next run time
                if s.schedule_type != s.ONCE:
                    next_run = s.next_run
                    while True:
                        next_run = s.calculate_next_run(next_run)
                        if Conf.CATCH_UP or next_run > localtime():
                            break

                    s.next_run = next_run
                    s.repeats += -1
                # send it to the cluster; any cluster name is allowed in multi-queue scenarios
                # because `broker_name` is confusing, using `cluster` name is recommended and takes precedence
                q_options["cluster"] = s.cluster or q_options.get(
                    "cluster", q_options.pop("broker_name", None)
                )
                if (
                    q_options["cluster"] is None
                    or q_options["cluster"] == Conf.CLUSTER_NAME
                ):
                    q_options["broker"] = broker
                q_options["group"] = q_options.get("group", s.name or s.id)
                kwargs["q_options"] = q_options
                s.task = async_task(s.func, *args, **kwargs)
                # log it
                if not s.task:
                    logger.error(
                        _(
                            "%(process_name)s failed to create a task from schedule "
                            "[%(schedule)s]"
                        )
                        % {
                            "process_name": current_process().name,
                            "schedule": s.name or s.id,
                        }
                    )
                else:
                    logger.info(
                        _(
                            "%(process_name)s created task %(task_name)s from schedule "
                            "[%(schedule)s]"
                        )
                        % {
                            "process_name": current_process().name,
                            "task_name": humanize(s.task),
                            "schedule": s.name or s.id,
                        }
                    )
                # default behavior is to delete a ONCE schedule
                if s.schedule_type == s.ONCE:
                    if s.repeats < 0:
                        s.delete()
                        continue
                    # but not if it has a positive repeats
                    s.repeats = 0
                # save the schedule
                s.save()
    except Exception:
        logger.exception("Could not create task from schedule")