import datetime

from django.core.exceptions import ObjectDoesNotExist

from django.core.exceptions import ValidationError

from django.db.models import Max, Sum

from django.utils import timezone

from registrasion import models as rego

from conditions import ConditionController

from product import ProductController

class CartController(object):

    def __init__(self, cart):

        self.cart = cart

    @staticmethod

    def for_user(user):

        ''' Returns the user's current cart, or creates a new cart

        if there isn't one ready yet. '''

        try:

            existing = rego.Cart.objects.get(user=user, active=True)

        except ObjectDoesNotExist:

            existing = rego.Cart.objects.create(

                user=user,

                time_last_updated=timezone.now(),

                reservation_duration=datetime.timedelta(),

                 )

            existing.save()

        return CartController(existing)

    def extend_reservation(self):

        ''' Updates the cart's time last updated value, which is used to

        determine whether the cart has reserved the items and discounts it

        holds. '''

        reservations = [datetime.timedelta()]

        # If we have vouchers, we're entitled to an hour at minimum.

        if len(self.cart.vouchers.all()) >= 1:

            reservations.append(rego.Voucher.RESERVATION_DURATION)

        # Else, it's the maximum of the included products

        items = rego.ProductItem.objects.filter(cart=self.cart)

        agg = items.aggregate(Max("product__reservation_duration"))

        product_max = agg["product__reservation_duration__max"]

        if product_max is not None:

            reservations.append(product_max)

        self.cart.time_last_updated = timezone.now()

        self.cart.reservation_duration = max(reservations)

        try:

            product_item = rego.ProductItem.objects.get(

                cart=self.cart,

                product=product)

        except ObjectDoesNotExist:

            product_item = rego.ProductItem.objects.create(

                cart=self.cart,

                product=product,

            )

        product_item.save()

    def apply_voucher(self, voucher):

        ''' Applies the given voucher to this cart. '''

        # TODO: is it valid for a cart to re-add a voucher that they have?

        # Is voucher exhausted?

        active_carts = rego.Cart.reserved_carts()

        carts_with_voucher = active_carts.filter(vouchers=voucher)

        if len(carts_with_voucher) >= voucher.limit:

            raise ValidationError("This voucher is no longer available")

        # If successful...

        self.cart.vouchers.add(voucher)

    def validate_cart(self):

        ''' Determines whether the status of the current cart is valid;

        this is normally called before generating or paying an invoice '''

        is_reserved = self.cart in rego.Cart.reserved_carts()

        # TODO: validate vouchers

        items = rego.ProductItem.objects.filter(cart=self.cart)

        for item in items:

            # NOTE: per-user limits are tested at add time

            # and are unliklely to change

            prod = ProductController(item.product)

            # If the cart is not reserved, we need to see if we can re-reserve

            quantity = 0 if is_reserved else item.quantity

            if not prod.can_add_with_enabling_conditions(

                    self.cart.user, quantity):

                raise ValidationError("Products are no longer available")

        # Validate the discounts

        discount_items = rego.DiscountItem.objects.filter(cart=self.cart)

        seen_discounts = set()

        for discount_item in discount_items:

            discount = discount_item.discount

            if discount in seen_discounts:

                continue

            seen_discounts.add(discount)

            real_discount = rego.DiscountBase.objects.get_subclass(

                pk=discount.pk)

            cond = ConditionController.for_condition(real_discount)

            quantity = 0 if is_reserved else discount_item.quantity

            if not cond.is_met(self.cart.user, quantity):

                raise ValidationError("Discounts are no longer available")

    def recalculate_discounts(self):

        ''' Calculates all of the discounts available for this product.

        NB should be transactional, and it's terribly inefficient.

        '''

        # Delete the existing entries.

        rego.DiscountItem.objects.filter(cart=self.cart).delete()

        for item in self.cart.productitem_set.all():

            self._add_discount(item.product, item.quantity)

    def _add_discount(self, product, quantity):

        ''' Calculates the best available discounts for this product.

        NB this will be super-inefficient in aggregate because discounts will

        be re-tested for each product. We should work on that.'''

        prod = ProductController(product)

        discounts = prod.available_discounts(self.cart.user)

        discounts.sort(key=lambda discount: discount.value)

        for discount in reversed(discounts):

            if quantity == 0:

                break

            # Get the count of past uses of this discount condition

            # as this affects the total amount we're allowed to use now.

            past_uses = rego.DiscountItem.objects.filter(

                cart__active=False,

                discount=discount.discount,

                product=product,

            )

            agg = past_uses.aggregate(Sum("quantity"))

            past_uses = agg["quantity__sum"]

            if past_uses is None:

                past_uses = 0

            if past_uses == discount.condition.quantity:

                continue

            # Get a provisional instance for this DiscountItem

            # with the quantity set to as much as we have in the cart

            discount_item = rego.DiscountItem.objects.create(

                product=product,

                cart=self.cart,

                discount=discount.discount,

                quantity=quantity,

            )

            # Truncate the quantity for this DiscountItem if we exceed quantity

            ours = discount_item.quantity

            allowed = discount.condition.quantity - past_uses

            if ours > allowed:

                discount_item.quantity = allowed

                # Update the remaining quantity.

                quantity = ours - allowed

            else:

                quantity = 0

import datetime

import pytz

from decimal import Decimal

from django.contrib.auth.models import User

from django.core.exceptions import ValidationError

from django.test import TestCase

from registrasion import models as rego

from registrasion.controllers.cart import CartController

from patch_datetime import SetTimeMixin

UTC = pytz.timezone('UTC')

class RegistrationCartTestCase(SetTimeMixin, TestCase):

    def setUp(self):

        super(RegistrationCartTestCase, self).setUp()

    @classmethod

    def setUpTestData(cls):

        cls.USER_1 = User.objects.create_user(

            username='testuser',

            email='test@example.com',

            password='top_secret')

        cls.USER_2 = User.objects.create_user(

            username='testuser2',

            email='test2@example.com',

            password='top_secret')

        cls.CAT_1 = rego.Category.objects.create(

            name="Category 1",

            description="This is a test category",

            order=10,

            render_type=rego.Category.RENDER_TYPE_RADIO,

        )

        cls.CAT_1.save()

        cls.CAT_2 = rego.Category.objects.create(

            name="Category 2",

            description="This is a test category",

            order=10,

            render_type=rego.Category.RENDER_TYPE_RADIO,

        )

        cls.CAT_2.save()

        cls.RESERVATION = datetime.timedelta(hours=1)

        cls.PROD_1 = rego.Product.objects.create(

            name="Product 1",

            description="This is a test product. It costs $10. "

                        "A user may have 10 of them.",

            category=cls.CAT_1,

            price=Decimal("10.00"),

            reservation_duration=cls.RESERVATION,

            limit_per_user=10,

            order=10,

        )

        cls.PROD_1.save()

        cls.PROD_2 = rego.Product.objects.create(

            name="Product 2",

            description="This is a test product. It costs $10. "

                        "A user may have 10 of them.",

            category=cls.CAT_1,

            price=Decimal("10.00"),

            limit_per_user=10,

            order=10,

        )

        cls.PROD_2.save()

        cls.PROD_3 = rego.Product.objects.create(

            name="Product 3",

            description="This is a test product. It costs $10. "

                        "A user may have 10 of them.",

            category=cls.CAT_2,

            price=Decimal("10.00"),

            limit_per_user=10,

            order=10,

        )

        cls.PROD_2.save()

    @classmethod

    def make_ceiling(cls, name, limit=None, start_time=None, end_time=None):

        limit_ceiling = rego.TimeOrStockLimitEnablingCondition.objects.create(

            description=name,

            mandatory=True,

            limit=limit,

            start_time=start_time,

            end_time=end_time

        )

        limit_ceiling.save()

        limit_ceiling.products.add(cls.PROD_1, cls.PROD_2)

        limit_ceiling.save()

    @classmethod

    def make_category_ceiling(

            cls, name, limit=None, start_time=None, end_time=None):

        limit_ceiling = rego.TimeOrStockLimitEnablingCondition.objects.create(

            description=name,

            mandatory=True,

            limit=limit,

            start_time=start_time,

            end_time=end_time

        )

        limit_ceiling.save()

        limit_ceiling.categories.add(cls.CAT_1)

        limit_ceiling.save()

    @classmethod

    def make_discount_ceiling(

            cls, name, limit=None, start_time=None, end_time=None):

        limit_ceiling = rego.TimeOrStockLimitDiscount.objects.create(

            description=name,

            start_time=start_time,

            end_time=end_time,

            limit=limit,

        )

        limit_ceiling.save()

        rego.DiscountForProduct.objects.create(

            discount=limit_ceiling,

            product=cls.PROD_1,

            percentage=100,

            quantity=10,

        ).save()

class BasicCartTests(RegistrationCartTestCase):

    def test_get_cart(self):

        current_cart = CartController.for_user(self.USER_1)

        current_cart.cart.active = False

        current_cart.cart.save()

        old_cart = current_cart

        current_cart = CartController.for_user(self.USER_1)

        self.assertNotEqual(old_cart.cart, current_cart.cart)

        current_cart2 = CartController.for_user(self.USER_1)

        self.assertEqual(current_cart.cart, current_cart2.cart)

    def test_add_to_cart_collapses_product_items(self):

        current_cart = CartController.for_user(self.USER_1)

        # Add a product twice

        current_cart.add_to_cart(self.PROD_1, 1)

        current_cart.add_to_cart(self.PROD_1, 1)

        # Count of products for a given user should be collapsed.

        items = rego.ProductItem.objects.filter(

            cart=current_cart.cart,

            product=self.PROD_1)

        self.assertEqual(1, len(items))

        item = items[0]

        self.assertEquals(2, item.quantity)

    def test_add_to_cart_per_user_limit(self):

        current_cart = CartController.for_user(self.USER_1)

        # User should be able to add 1 of PROD_1 to the current cart.

        current_cart.add_to_cart(self.PROD_1, 1)

        # User should be able to add 1 of PROD_1 to the current cart.

        current_cart.add_to_cart(self.PROD_1, 1)

        # User should not be able to add 10 of PROD_1 to the current cart now,

        # because they have a limit of 10.

        with self.assertRaises(ValidationError):

            current_cart.add_to_cart(self.PROD_1, 10)

        current_cart.cart.active = False

        current_cart.cart.save()

        current_cart = CartController.for_user(self.USER_1)

        # User should not be able to add 10 of PROD_1 to the current cart now,

        # even though it's a new cart.

        with self.assertRaises(ValidationError):

            current_cart.add_to_cart(self.PROD_1, 10)

        # Second user should not be affected by first user's limits

        second_user_cart = CartController.for_user(self.USER_2)

        second_user_cart.add_to_cart(self.PROD_1, 10)