from django.db import models
from django.conf import settings
from django.utils.translation import gettext_lazy as _


class UserExamRedemption(models.Model):
    class RedeemType(models.IntegerChoices):
        CREDITS = 0, _("Credits")
        VOUCHER = 1, _("Voucher")

    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    exam = models.ForeignKey("labs.Exam", on_delete=models.CASCADE)
    # NULL means "unused redemption" (redeem first, consume when starting an attempt).
    exam_attempt = models.ForeignKey(
        "labs.ExamAttempt",
        on_delete=models.CASCADE,
        null=True,
        blank=True,
    )
    redeem_type = models.IntegerField(choices=RedeemType.choices, default=RedeemType.CREDITS)
    redeem_detail = models.JSONField(default=dict)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        db_table = "user_exam_redemptions"
        unique_together = ("user", "exam_attempt")
        indexes = [
            models.Index(
                fields=["user", "exam", "exam_attempt"],
                name="idx_uer_user_exam_attempt",
            ),
        ]