# -*- coding: utf-8 -*-
from django.contrib.auth.models import AnonymousUser
from django.db import models, transaction
from django.db.models.aggregates import Count
from polymorphic.manager import PolymorphicManager

from shop.order_signals import processing


#==============================================================================
# Product
#==============================================================================

class ProductStatisticsManager(PolymorphicManager):
    """
    A Manager for all the non-object manipulation needs, mostly statistics and
    other "data-mining" toys.
    """

    def top_selling_products(self, quantity):
        """
        This method "mines" the previously passed orders, and gets a list of
        products (of a size equal to the quantity parameter), ordered by how
        many times they have been purchased.
        """
        # Importing here is fugly, but it saves us from circular imports...
        from shop.models.ordermodel import OrderItem
        # Get an aggregate of product references and their respective counts
        top_products_data = OrderItem.objects.values(
                'product').annotate(
                    product_count=Count('product')
                ).order_by('product_count'
            )[:quantity]

        # The top_products_data result should be in the form:
        # [{'product_reference': '<product_id>', 'product_count': <count>}, ..]

        top_products_list = []  # The actual list of products
        for values in top_products_data:
            prod = values.get('product')
            # We could eventually return the count easily here, if needed.
            top_products_list.append(prod)

        return top_products_list


class ProductManager(PolymorphicManager):
    """
    A more classic manager for Product filtering and manipulation.
    """
    def active(self):
        return self.filter(active=True)


#==============================================================================
# Order
#==============================================================================

class OrderManager(models.Manager):

    def get_latest_for_user(self, user):
        """
        Returns the last Order (from a time perspective) a given user has
        placed.
        """
        if user and not isinstance(user, AnonymousUser):
            return self.filter(user=user).order_by('-modified')[0]
        else:
            return None

    def get_unconfirmed_for_cart(self, cart):
        return self.filter(cart_pk=cart.pk, status__lt=self.model.CONFIRMED)

    def remove_old_orders(self, cart):
        """
        Removes all old unconfirmed order objects.
        """
        old_orders = self.get_unconfirmed_for_cart(cart)
        old_orders.delete()

    def create_order_object(self, cart, request):
        """
        Create an empty order object and fill it with the given cart data.
        """
        order = self.model()
        order.cart_pk = cart.pk
        order.user = cart.user
        order.status = self.model.PROCESSING  # Processing
        order.order_subtotal = cart.subtotal_price
        order.order_total = cart.total_price
        return order

    @transaction.commit_on_success
    def create_from_cart(self, cart, request):
        """
        This creates a new Order object (and all the rest) from a passed Cart
        object.

        Specifically, it creates an Order with corresponding OrderItems and
        eventually corresponding ExtraPriceFields

        This will only actually commit the transaction once the function exits
        to minimize useless database access.

        The `state` parameter is further passed to process_cart_item,
        process_cart, and post_process_cart, so it can be used as a way to
        store per-request arbitrary information.

        Emits the ``processing`` signal.
        """
        # must be imported here!
        from shop.models.ordermodel import (
            ExtraOrderItemPriceField,
            ExtraOrderPriceField,
            OrderItem,
        )
        from shop.models.cartmodel import CartItem

        # First, let's remove old orders
        self.remove_old_orders(cart)

        # Create an empty order object
        order = self.create_order_object(cart, request)
        order.save()

        # Let's serialize all the extra price arguments in DB
        for field in cart.extra_price_fields:
            eoi = ExtraOrderPriceField()
            eoi.order = order
            eoi.label = unicode(field[0])
            eoi.value = field[1]
            if len(field) == 3:
                eoi.data = field[2]
            eoi.save()

        # There, now move on to the order items.
        cart_items = CartItem.objects.filter(cart=cart)
        for item in cart_items:
            item.update(request)
            order_item = OrderItem()
            order_item.order = order
            order_item.product_reference = item.product.get_product_reference()
            order_item.product_name = item.product.get_name()
            order_item.product = item.product
            order_item.unit_price = item.product.get_price()
            order_item.quantity = item.quantity
            order_item.line_total = item.line_total
            order_item.line_subtotal = item.line_subtotal
            order_item.save()
            # For each order item, we save the extra_price_fields to DB
            for field in item.extra_price_fields:
                eoi = ExtraOrderItemPriceField()
                eoi.order_item = order_item
                # Force unicode, in case it has àö...
                eoi.label = unicode(field[0])
                eoi.value = field[1]
                if len(field) == 3:
                    eoi.data = field[2]
                eoi.save()

        processing.send(self.model, order=order, cart=cart)
        return order
