from datetime import datetime, timedelta
from keyword import iskeyword

# Django
from django import get_version
from django.core.exceptions import ValidationError
from django.db import models
from django.template.defaultfilters import truncatechars
from django.urls import reverse
from django.utils import timezone
from django.utils.timezone import is_aware
from django.utils.html import format_html
from django.utils.translation import gettext_lazy as _
from django.utils.functional import cached_property

# External
from picklefield import PickledObjectField
from picklefield.fields import dbsafe_decode

# Local
from django_q.conf import croniter, Conf
from django_q.signing import SignedPackage
from django_q.utils import localtime, add_months, add_years

from .utils import get_func_repr


class Task(models.Model):
    id = models.CharField(max_length=32, primary_key=True, editable=False)
    name = models.CharField(max_length=100, editable=False)
    func = models.CharField(max_length=256)
    hook = models.CharField(max_length=256, null=True)
    args = PickledObjectField(null=True, protocol=-1)
    kwargs = PickledObjectField(null=True, protocol=-1)
    result = PickledObjectField(null=True, protocol=-1)
    group = models.CharField(max_length=100, editable=False, null=True)
    cluster = models.CharField(max_length=100, default=None, null=True, blank=True)
    started = models.DateTimeField(editable=False)
    stopped = models.DateTimeField(editable=False)
    success = models.BooleanField(default=True, editable=False)
    attempt_count = models.IntegerField(default=0)

    @staticmethod
    def get_result(task_id):
        if len(task_id) == 32 and Task.objects.filter(id=task_id).exists():
            return Task.objects.get(id=task_id).result
        elif Task.objects.filter(name=task_id).exists():
            return Task.objects.get(name=task_id).result

    @staticmethod
    def get_result_group(group_id, failures=False):
        if failures:
            values = Task.objects.filter(group=group_id).values_list(
                "result", flat=True
            )
        else:
            values = (
                Task.objects.filter(group=group_id)
                .exclude(success=False)
                .values_list("result", flat=True)
            )
        return decode_results(values)

    def group_result(self, failures=False):
        if self.group:
            return self.get_result_group(self.group, failures)

    @staticmethod
    def get_group_count(group_id, failures=False):
        if failures:
            return Failure.objects.filter(group=group_id).count()
        return Task.objects.filter(group=group_id).count()

    def group_count(self, failures=False):
        if self.group:
            return self.get_group_count(self.group, failures)

    @staticmethod
    def delete_group(group_id, objects=False):
        group = Task.objects.filter(group=group_id)
        if objects:
            return group.delete()
        return group.update(group=None)

    def group_delete(self, tasks=False):
        if self.group:
            return self.delete_group(self.group, tasks)

    @staticmethod
    def get_task(task_id):
        if len(task_id) == 32 and Task.objects.filter(id=task_id).exists():
            return Task.objects.get(id=task_id)
        elif Task.objects.filter(name=task_id).exists():
            return Task.objects.get(name=task_id)

    @staticmethod
    def get_task_group(group_id, failures=True):
        if failures:
            return Task.objects.filter(group=group_id)
        return Task.objects.filter(group=group_id).exclude(success=False)

    def time_taken(self):
        return (self.stopped - self.started).total_seconds()

    @property
    def short_result(self):
        return truncatechars(self.result, 100)

    def __str__(self):
        return f"{self.name or self.id}"

    class Meta:
        app_label = "django_q"
        ordering = ["-stopped"]


class SuccessManager(models.Manager):
    def get_queryset(self):
        return super(SuccessManager, self).get_queryset().filter(success=True)


class Success(Task):
    objects = SuccessManager()

    class Meta:
        app_label = "django_q"
        verbose_name = _("Successful task")
        verbose_name_plural = _("Successful tasks")
        ordering = ["-stopped"]
        proxy = True


class FailureManager(models.Manager):
    def get_queryset(self):
        return super(FailureManager, self).get_queryset().filter(success=False)


class Failure(Task):
    objects = FailureManager()

    class Meta:
        app_label = "django_q"
        verbose_name = _("Failed task")
        verbose_name_plural = _("Failed tasks")
        ordering = ["-stopped"]
        proxy = True


# Optional Cron validator
def validate_cron(value):
    if not croniter:
        raise ImportError(_("Please install croniter to enable cron expressions"))
    try:
        croniter.expand(value)
    except ValueError as e:
        raise ValidationError(e)


def validate_kwarg(value):
    return value.isidentifier() and not iskeyword(value)


class Schedule(models.Model):
    name = models.CharField(max_length=100, null=True, blank=True)
    func = models.CharField(max_length=256, help_text="e.g. module.tasks.function")
    hook = models.CharField(
        max_length=256,
        null=True,
        blank=True,
        help_text="e.g. module.tasks.result_function",
    )
    args = models.TextField(null=True, blank=True, help_text=_("e.g. 1, 2, 'John'"))
    kwargs = models.TextField(
        null=True, blank=True, help_text=_("e.g. x=1, y=2, name='John'")
    )
    ONCE = "O"
    MINUTES = "I"
    HOURLY = "H"
    DAILY = "D"
    WEEKLY = "W"
    BIWEEKLY = "BW"
    MONTHLY = "M"
    BIMONTHLY = "BM"
    QUARTERLY = "Q"
    YEARLY = "Y"
    CRON = "C"
    TYPE = (
        (ONCE, _("Once")),
        (MINUTES, _("Minutes")),
        (HOURLY, _("Hourly")),
        (DAILY, _("Daily")),
        (WEEKLY, _("Weekly")),
        (BIWEEKLY, _("Biweekly")),
        (MONTHLY, _("Monthly")),
        (BIMONTHLY, _("Bimonthly")),
        (QUARTERLY, _("Quarterly")),
        (YEARLY, _("Yearly")),
        (CRON, _("Cron")),
    )
    schedule_type = models.CharField(
        max_length=2, choices=TYPE, default=TYPE[0][0], verbose_name=_("Schedule Type")
    )
    minutes = models.PositiveSmallIntegerField(
        null=True, blank=True, help_text=_("Number of minutes for the Minutes type")
    )
    repeats = models.IntegerField(
        default=-1, verbose_name=_("Repeats"), help_text=_("n = n times, -1 = forever")
    )
    next_run = models.DateTimeField(
        verbose_name=_("Next Run"), default=timezone.now, null=True
    )
    cron = models.CharField(
        max_length=100,
        null=True,
        blank=True,
        validators=[validate_cron],
        help_text=_("Cron expression"),
    )
    task = models.CharField(max_length=100, null=True, editable=False)
    cluster = models.CharField(
        max_length=100, default=None, null=True, blank=True,
        help_text=_("Name of the target cluster")
    )
    intended_date_kwarg = models.CharField(
        max_length=100,
        null=True,
        blank=True,
        validators=[validate_kwarg],
        help_text=_("Name of kwarg to pass intended schedule date"),
    )

    def calculate_next_run(self, next_run=None):
        # next run is always in UTC
        next_run = next_run or self.next_run

        if self.schedule_type == self.CRON:
            if not croniter:
                raise ImportError(
                    _("Please install croniter to enable cron expressions")
                )
            return croniter(self.cron, localtime()).get_next(datetime)

        if self.schedule_type == self.MINUTES:
            add = timedelta(minutes=(self.minutes or 1))
        elif self.schedule_type == self.HOURLY:
            add = timedelta(hours=1)
        elif self.schedule_type == self.DAILY:
            add = timedelta(days=1)
        elif self.schedule_type == self.WEEKLY:
            add = timedelta(weeks=1)
        elif self.schedule_type == self.BIWEEKLY:
            add = timedelta(weeks=2)
        elif self.schedule_type == self.MONTHLY:
            add = timedelta(days=(add_months(next_run, 1) - next_run).days)
        elif self.schedule_type == self.BIMONTHLY:
            add = timedelta(days=(add_months(next_run, 2) - next_run).days)
        elif self.schedule_type == self.QUARTERLY:
            add = timedelta(days=(add_months(next_run, 3) - next_run).days)
        elif self.schedule_type == self.YEARLY:
            add = timedelta(days=(add_years(next_run, 1) - next_run).days)

        # add normal timedelta, we will correct this later based on timezone
        next_run += add

        # DST differencers don't matter with minutes, hourly or yearly, so skip those
        if self.schedule_type not in [self.MINUTES, self.HOURLY, self.YEARLY]:
            # Get localtimes and then remove the tzinfo, so we can get the actual difference
            current_next_run = localtime(next_run - add).replace(tzinfo=None)
            new_next_run = localtime(next_run).replace(tzinfo=None)

            # get the difference between them, this should be (-)1 or (-)0.5 hour
            # based on DST active or not
            extra_diff = (new_next_run - current_next_run) - add

            # subtract difference
            next_run -= extra_diff

        return next_run

    def success(self):
        if self.task and Task.objects.filter(id=self.task):
            return Task.objects.get(id=self.task).success

    def last_run(self):
        if self.task and Task.objects.filter(id=self.task):
            task = Task.objects.get(id=self.task)
            if task.success:
                url = reverse("admin:django_q_success_change", args=(task.id,))
            else:
                url = reverse("admin:django_q_failure_change", args=(task.id,))
            return format_html(f'<a href="{url}">[{task.name}]</a>')
        return None

    def __str__(self):
        return self.func

    success.boolean = True
    success.short_description = _("success")
    last_run.allow_tags = True
    last_run.short_description = _("last_run")

    class Meta:
        app_label = "django_q"
        verbose_name = _("Scheduled task")
        verbose_name_plural = _("Scheduled tasks")
        ordering = ["next_run"]


class OrmQ(models.Model):
    key = models.CharField(max_length=100, help_text=_("Name of the target cluster"))
    payload = models.TextField()
    lock = models.DateTimeField(null=True, help_text=_("Prevent any cluster from pulling until"))

    @cached_property
    def task(self):
        try:
            return SignedPackage.loads(self.payload)
        except Exception as e:
            return {"id": "*" + e.__class__.__name__}

    def func(self):
        return get_func_repr(self.task.get("func"))

    def task_id(self):
        return self.task.get("id")

    def name(self):
        return self.task.get("name")

    def group(self):
        return self.task.get("group")

    def args(self):
        return self.task.get("args")

    def kwargs(self):
        return self.task.get("kwargs")

    def q_options(self):
        exclude = {"id", "name", "group", "func", "args", "kwargs"}
        return {k: v for k, v in self.task.items() if k not in exclude}

    class Meta:
        app_label = "django_q"
        verbose_name = _("Queued task")
        verbose_name_plural = _("Queued tasks")


# Backwards compatibility for Django 1.7
def decode_results(values):
    if get_version().split(".")[1] == "7":
        # decode values in 1.7
        return [dbsafe_decode(v) for v in values]
    return values