from django.db import models
from django.contrib.auth.models import User
from django.db.models.signals import post_save
from django.dispatch import receiver

class Profile(models.Model):
    ROLE_CHOICES = (
        ('ADMIN', 'Admin'),
        ('DONOR', 'Donor'),
        ('RECEIVER', 'Receiver/Hospital'),
    )
    BLOOD_GROUPS = (
        ('A+', 'A+'), ('A-', 'A-'),
        ('B+', 'B+'), ('B-', 'B-'),
        ('AB+', 'AB+'), ('AB-', 'AB-'),
        ('O+', 'O+'), ('O-', 'O-'),
    )
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    role = models.CharField(max_length=20, choices=ROLE_CHOICES, default='DONOR')
    blood_group = models.CharField(max_length=5, choices=BLOOD_GROUPS, blank=True, null=True)
    location = models.CharField(max_length=255, blank=True, null=True)
    contact = models.CharField(max_length=15, blank=True, null=True)

    def __str__(self):
        return f"{self.user.username} - {self.role}"

class BloodStock(models.Model):
    BLOOD_GROUPS = (
        ('A+', 'A+'), ('A-', 'A-'),
        ('B+', 'B+'), ('B-', 'B-'),
        ('AB+', 'AB+'), ('AB-', 'AB-'),
        ('O+', 'O+'), ('O-', 'O-'),
    )
    blood_group = models.CharField(max_length=5, choices=BLOOD_GROUPS, unique=True)
    units = models.PositiveIntegerField(default=0)

    def __str__(self):
        return f"{self.blood_group}: {self.units} Units"

class BloodRequest(models.Model):
    STATUS_CHOICES = (
        ('PENDING', 'Pending'),
        ('APPROVED', 'Approved'),
        ('REJECTED', 'Rejected'),
    )
    BLOOD_GROUPS = (
        ('A+', 'A+'), ('A-', 'A-'),
        ('B+', 'B+'), ('B-', 'B-'),
        ('AB+', 'AB+'), ('AB-', 'AB-'),
        ('O+', 'O+'), ('O-', 'O-'),
    )
    requester = models.ForeignKey(User, on_delete=models.CASCADE)
    blood_group = models.CharField(max_length=5, choices=BLOOD_GROUPS)
    units = models.PositiveIntegerField()
    status = models.CharField(max_length=20, choices=STATUS_CHOICES, default='PENDING')
    request_date = models.DateTimeField(auto_now_add=True)
    reason = models.TextField(blank=True, null=True)

    def __str__(self):
        return f"{self.requester.username} requested {self.units} units of {self.blood_group}"

class Donation(models.Model):
    STATUS_CHOICES = (
        ('PENDING', 'Pending'),
        ('APPROVED', 'Approved'),
        ('REJECTED', 'Rejected'),
    )
    donor = models.ForeignKey(User, on_delete=models.CASCADE)
    blood_group = models.CharField(max_length=5)
    units = models.PositiveIntegerField()
    status = models.CharField(max_length=20, choices=STATUS_CHOICES, default='PENDING')
    donation_date = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return f"{self.donor.username} donated {self.units} units"


# Signals to automatically create profile
@receiver(post_save, sender=User)
def create_user_profile(sender, instance, created, **kwargs):
    if created:
        Profile.objects.create(user=instance)

@receiver(post_save, sender=User)
def save_user_profile(sender, instance, **kwargs):
    instance.profile.save()