from django.db import models
from django.conf import settings


class OnlineExamPromotionCode(models.Model):

    FLAG_PCTA = 'PCTA'
    FLAG_PCTP = 'PCTP'
    FLAG_CHOICES = (
        (FLAG_PCTA, 'PCTA'),
        (FLAG_PCTP, 'PCTP')
    )

    CODE_TYPE_PERSONAL = 0
    CODE_TYPE_GROUP = 1
    CODE_TYPE_CHOICES = (
        (CODE_TYPE_PERSONAL, '个人'),
        (CODE_TYPE_GROUP, '团体')
    )

    code = models.CharField(max_length=32, unique=True, primary_key=True)
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    flag = models.CharField(
        max_length=32, default=FLAG_PCTA, choices=FLAG_CHOICES)
    code_type = models.SmallIntegerField(
        default=CODE_TYPE_PERSONAL, choices=CODE_TYPE_CHOICES)
    remain_times = models.IntegerField(
        default=0, help_text='Only meaningful when code_type is group')
    used = models.BooleanField(default=False)
    used_by = models.ForeignKey(
        settings.AUTH_USER_MODEL, related_name='exam_promotionn_code_used',
        on_delete=models.CASCADE, null=True, blank=True)
    used_time = models.DateTimeField(blank=True, null=True)
    registration = models.ForeignKey(
        'university.OnlineExamRegistrate', on_delete=models.PROTECT, null=True, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    comment = models.CharField(max_length=128, blank=True, null=True)

    class Meta:
        db_table = 'online_exam_promotion_code'