from django.db import models

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


class LearningMentor(models.Model):
    mentor = models.OneToOneField(User, on_delete=models.CASCADE)
    course = models.ForeignKey("course.Course", on_delete=models.CASCADE)

    participants = models.ManyToManyField(
        CourseSessionUser,
        related_name="participants",
        blank=True,
    )

    class Meta:
        unique_together = [["mentor", "course"]]

    def __str__(self):
        return f"{self.mentor} ({self.course.title})"

    @property
    def course_sessions(self):
        return self.participants.values_list("course_session", flat=True).distinct()