from django.contrib.auth.models import User
from django.core.validators import RegexValidator
from django.db import models


class UserPreference(models.Model):
    """A user's preference, stored as generic text to be processed by client"""
    KEY_REGEX = r"[-_a-zA-Z0-9]+"
    user = models.ForeignKey(User, db_index=True, related_name="preferences")
    key = models.CharField(max_length=255, db_index=True, validators=[RegexValidator(KEY_REGEX)])
    value = models.TextField()

    class Meta:  # pylint: disable=missing-docstring
        unique_together = ("user", "key")

    @classmethod
    def set_preference(cls, user, preference_key, preference_value):
        """
        Sets the user preference for a given key
        """
        user_pref, _ = cls.objects.get_or_create(user=user, key=preference_key)
        user_pref.value = preference_value
        user_pref.save()

    @classmethod
    def get_preference(cls, user, preference_key, default=None):
        """
        Gets the user preference value for a given key

        Returns the given default if there isn't a preference for the given key
        """

        try:
            user_pref = cls.objects.get(user=user, key=preference_key)
            return user_pref.value
        except cls.DoesNotExist:
            return default


class UserCourseTag(models.Model):
    """
    Per-course user tags, to be used by various things that want to store tags about
    the user.  Added initially to store assignment to experimental groups.
    """
    user = models.ForeignKey(User, db_index=True, related_name="+")
    key = models.CharField(max_length=255, db_index=True)
    course_id = models.CharField(max_length=255, db_index=True)
    value = models.TextField()

    class Meta:  # pylint: disable=missing-docstring
        unique_together = ("user", "course_id", "key")
