import datetime

from django.db import models
from django.utils import timezone
from django.utils.translation import gettext_lazy as _

from vbv_lernwelt.core.models import User
from vbv_lernwelt.course.models import CourseSession


class Event(models.Model):
    start = models.DateTimeField(null=True, db_index=True)
    end = models.DateTimeField(db_index=True, null=True)
    title = models.CharField(default=_('Termin'), max_length=1024)
    url = models.URLField(null=True, blank=True, max_length=1024)
    course_session = models.ForeignKey(
        'course.CourseSession',
        on_delete=models.CASCADE,
        related_name='events',
        null=True,
        blank=True,
    )

    learning_content_id = models.CharField(blank=True, null=True, max_length=255)

    def Meta(self):
        ordering = ['start', 'end']
        verbose_name = _("Termin")

    def __str__(self):
        return f"Event: {self.title} {self.start} to {self.end}"

    @property
    def unset(self):
        return self.end is None

    @property
    def duration(self):
        if self.start is None:
            return datetime.timedelta(0)
        return self.end - self.start

    @classmethod
    def get_users_next_events_qs(cls, user: User, course_session: CourseSession = None, limit=10):
        """
        Returns a queryset of all events that are relevant for the given user. Ordered nearest start date first.
        If course_session is given, only events for that course_session are returned.
        The user is determined by via a course session user of an course_assignment.

        """
        qs = cls.get_next_events_qs()

        if course_session:
            qs = qs.filter(course_session=course_session, course_session__course_assignment__user=user)
        else:
            qs = qs.filter(course_session__course_assignment__user=user)

        qs = qs.order_by('start')[:limit]

        return qs

    @classmethod
    def get_next_events_qs(cls):
        now = timezone.now()
        qs = cls.objects.filter(end__gte=now)
        return qs