from django.db import models
from django.conf import settings
from products.models import Product
from django.contrib.auth import get_user_model
from django.db.models.signals import m2m_changed, pre_save
from django.dispatch import receiver


User = get_user_model()

class CartManager(models.Manager):
    def new_or_get(self, request):
        cart_id = request.session.get("cart_id", None)
        qs = self.get_queryset().filter(id=cart_id)
        if qs.count() == 1:

            new_obj = False
            cart_obj = qs.first()
            if request.user.is_authenticated() and cart_obj.user is None:
                cart_obj.user = request.user
                cart_obj.save()
        else:
            cart_obj = Cart.objects.new(user=request.user)
            new_obj = True
            request.session["cart_id"] = cart_obj.id
        return cart_obj, new_obj

    def new(self, user=None, products=None):
        if user is not None:
            if user.is_authenticated():
                return self.model.objects.create(user=user)
        return self.model.objects.create(user=None)


class Cart(models.Model):
    user = models.ForeignKey(User, null=True, blank=True)
    products = models.ManyToManyField(Product, null=True, blank=True)
    total = models.DecimalField(default=0.00, max_digits=100, decimal_places=2)
    subtotal = models.DecimalField(default=0.00, max_digits=100, decimal_places=2)
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)

    objects = CartManager()

    def __str__(self):
        return str(self.id)


@receiver(m2m_changed, sender=Cart.products.through)
def cart_change(sender, instance, action, **kwargs):
    if action in ("post_add", "post_remove", "post_clear"):

        print('change')
        prs = instance.products.all()
        t = 0
        for i in prs:
            t += i.price
        if instance.subtotal != t:

            instance.subtotal = t
            instance.save()
    # cart_obj.save()

@receiver(pre_save, sender=Cart)
def cart_save(sender, instance, **kwargs):
    instance.total = float(instance.subtotal) * float(0.95) # 5% discount