# Copyright (c) 2015 Ansible, Inc.
# All Rights Reserved.

import re
import logging
import datetime
import dateutil.rrule
from dateutil.tz import gettz, datetime_exists

# Django
from django.db import models
from django.db.models.query import QuerySet
from django.utils.timezone import now
from django.utils.translation import ugettext_lazy as _

# AWX
from awx.api.versioning import reverse
from awx.main.models.base import * # noqa
from awx.main.models.jobs import LaunchTimeConfig
from awx.main.utils import ignore_inventory_computed_fields
from awx.main.consumers import emit_channel_notification

import pytz


logger = logging.getLogger('awx.main.models.schedule')

__all__ = ['Schedule']


class ScheduleFilterMethods(object):

    def enabled(self, enabled=True):
        return self.filter(enabled=enabled)

    def before(self, dt):
        return self.filter(next_run__lt=dt)

    def after(self, dt):
        return self.filter(next_run__gt=dt)

    def between(self, begin, end):
        return self.after(begin).before(end)


class ScheduleQuerySet(ScheduleFilterMethods, QuerySet):
    pass


class ScheduleManager(ScheduleFilterMethods, models.Manager):

    use_for_related_objects = True

    def get_queryset(self):
        return ScheduleQuerySet(self.model, using=self._db)


class Schedule(CommonModel, LaunchTimeConfig):

    TZID_REGEX = re.compile(
        "^(DTSTART;TZID=(?P<tzid>[^:]+)(?P<stamp>\:[0-9]+T[0-9]+))(?P<rrule> .*)$"
    )

    class Meta:
        app_label = 'main'
        ordering = ['-next_run']

    objects = ScheduleManager()

    unified_job_template = models.ForeignKey(
        'UnifiedJobTemplate',
        related_name='schedules',
        on_delete=models.CASCADE,
    )
    enabled = models.BooleanField(
        default=True,
        help_text=_("Enables processing of this schedule.")
    )
    dtstart = models.DateTimeField(
        null=True,
        default=None,
        editable=False,
        help_text=_("The first occurrence of the schedule occurs on or after this time.")
    )
    dtend = models.DateTimeField(
        null=True,
        default=None,
        editable=False,
        help_text=_("The last occurrence of the schedule occurs before this time, aftewards the schedule expires.")
    )
    rrule = models.CharField(
        max_length=255,
        help_text=_("A value representing the schedules iCal recurrence rule.")
    )
    next_run = models.DateTimeField(
        null=True,
        default=None,
        editable=False,
        help_text=_("The next time that the scheduled action will run.")
    )

    @classmethod
    def rrulestr(cls, rrule, **kwargs):
        """
        Apply our own custom rrule parsing logic to support TZID=

        python-dateutil doesn't _natively_ support `DTSTART;TZID=`; this
        function parses out the TZID= component and uses it to produce the
        `tzinfos` keyword argument to `dateutil.rrule.rrulestr()`. In this
        way, we translate:

        DTSTART;TZID=America/New_York:20180601T120000 RRULE:FREQ=DAILY;INTERVAL=1

        ...into...

        DTSTART:20180601T120000TZID RRULE:FREQ=DAILY;INTERVAL=1

        ...and we pass a hint about the local timezone to dateutil's parser:
        `dateutil.rrule.rrulestr(rrule, {
            'tzinfos': {
                'TZID': dateutil.tz.gettz('America/New_York')
              }
         })`

        it's likely that we can remove the custom code that performs this
        parsing if TZID= gains support in upstream dateutil:
        https://github.com/dateutil/dateutil/pull/619
        """
        kwargs['forceset'] = True
        kwargs['tzinfos'] = {x: dateutil.tz.tzutc() for x in dateutil.parser.parserinfo().UTCZONE}
        match = cls.TZID_REGEX.match(rrule)
        if match is not None:
            rrule = cls.TZID_REGEX.sub("DTSTART\g<stamp>TZI\g<rrule>", rrule)
            timezone = gettz(match.group('tzid'))
            kwargs['tzinfos']['TZI'] = timezone
        x = dateutil.rrule.rrulestr(rrule, **kwargs)

        for r in x._rrule:
            if r._dtstart and r._until:
                if all((
                    r._dtstart.tzinfo != dateutil.tz.tzlocal(),
                    r._until.tzinfo != dateutil.tz.tzutc(),
                )):
                    # According to RFC5545 Section 3.3.10:
                    # https://tools.ietf.org/html/rfc5545#section-3.3.10
                    #
                    # > If the "DTSTART" property is specified as a date with UTC
                    # > time or a date with local time and time zone reference,
                    # > then the UNTIL rule part MUST be specified as a date with
                    # > UTC time.
                    raise ValueError('RRULE UNTIL values must be specified in UTC')

        try:
            first_event = x[0]
            if first_event < now() - datetime.timedelta(days=365 * 5):
                # For older DTSTART values, if there are more than 1000 recurrences...
                if len(x[:1001]) > 1000:
                    raise ValueError('RRULE values that yield more than 1000 events are not allowed.')
        except IndexError:
            pass
        return x

    def __unicode__(self):
        return u'%s_t%s_%s_%s' % (self.name, self.unified_job_template.id, self.id, self.next_run)

    def get_absolute_url(self, request=None):
        return reverse('api:schedule_detail', kwargs={'pk': self.pk}, request=request)

    def get_job_kwargs(self):
        config_data = self.prompts_dict()
        job_kwargs, rejected, errors = self.unified_job_template._accept_or_ignore_job_kwargs(**config_data)
        if errors:
            logger.info('Errors creating scheduled job: {}'.format(errors))
        job_kwargs['_eager_fields'] = {'launch_type': 'scheduled', 'schedule': self}
        return job_kwargs

    def update_computed_fields(self):
        future_rs = Schedule.rrulestr(self.rrule)
        next_run_actual = future_rs.after(now())

        if next_run_actual is not None:
            if not datetime_exists(next_run_actual):
                # skip imaginary dates, like 2:30 on DST boundaries
                next_run_actual = future_rs.after(next_run_actual)
            next_run_actual = next_run_actual.astimezone(pytz.utc)

        self.next_run = next_run_actual
        try:
            self.dtstart = future_rs[0].astimezone(pytz.utc)
        except IndexError:
            self.dtstart = None
        self.dtend = None
        if 'until' in self.rrule.lower() or 'count' in self.rrule.lower():
            try:
                self.dtend = future_rs[-1].astimezone(pytz.utc)
            except IndexError:
                self.dtend = None
        emit_channel_notification('schedules-changed', dict(id=self.id, group_name='schedules'))
        with ignore_inventory_computed_fields():
            self.unified_job_template.update_computed_fields()

    def save(self, *args, **kwargs):
        self.update_computed_fields()
        super(Schedule, self).save(*args, **kwargs)