from __future__ import unicode_literals

import logging

from django.http import HttpResponseBadRequest, HttpResponseRedirect
from django.core.urlresolvers import reverse
from django.utils.translation import ugettext_lazy as _
from requests.exceptions import ConnectionError, Timeout
from opaque_keys.edx.keys import CourseKey
from oscar.apps.basket.views import *  # pylint: disable=wildcard-import, unused-wildcard-import
from slumber.exceptions import SlumberBaseException

from ecommerce.core.constants import ENROLLMENT_CODE_PRODUCT_CLASS_NAME, SEAT_PRODUCT_CLASS_NAME
from ecommerce.core.url_utils import get_lms_url
from ecommerce.coupons.views import get_voucher_and_products_from_code
from ecommerce.courses.utils import get_certificate_type_display_value, get_course_info_from_lms, mode_for_seat
from ecommerce.extensions.analytics.utils import prepare_analytics_data
from ecommerce.extensions.basket.utils import prepare_basket, get_basket_switch_data
from ecommerce.extensions.offer.utils import format_benefit_value
from ecommerce.extensions.partner.shortcuts import get_partner_for_site

Benefit = get_model('offer', 'Benefit')
logger = logging.getLogger(__name__)
StockRecord = get_model('partner', 'StockRecord')


class BasketSingleItemView(View):
    """
    View that adds a single product to a user's basket.
    An additional coupon code can be supplied so the offer is applied to the basket.
    """
    def get(self, request):
        partner = get_partner_for_site(request)

        sku = request.GET.get('sku', None)
        code = request.GET.get('code', None)

        if not sku:
            return HttpResponseBadRequest(_('No SKU provided.'))

        if code:
            voucher, __ = get_voucher_and_products_from_code(code=code)
        else:
            voucher = None

        try:
            product = StockRecord.objects.get(partner=partner, partner_sku=sku).product
        except StockRecord.DoesNotExist:
            return HttpResponseBadRequest(_('SKU [{sku}] does not exist.').format(sku=sku))

        # If the product isn't available then there's no reason to continue with the basket addition
        purchase_info = request.strategy.fetch_for_product(product)
        if not purchase_info.availability.is_available_to_buy:
            msg = _('Product [{product}] not available to buy.').format(product=product.title)
            return HttpResponseBadRequest(msg)

        # If the product is not an Enrollment Code, we check to see if the user is already
        # enrolled to prevent double-enrollment and/or accidental coupon usage
        if product.get_product_class().name != ENROLLMENT_CODE_PRODUCT_CLASS_NAME:
            try:
                if request.user.is_user_already_enrolled(request, product):
                    logger.warning(
                        'User [%s] attempted to repurchase the [%s] seat of course [%s]',
                        request.user.username,
                        mode_for_seat(product),
                        product.attr.course_key
                    )
                    msg = _('You are already enrolled in {course}.').format(course=product.course.name)
                    return HttpResponseBadRequest(msg)
            except (ConnectionError, SlumberBaseException, Timeout):
                msg = _('An error occurred while retrieving enrollment details. Please try again.')
                return HttpResponseBadRequest(msg)

        # At this point we're either adding an Enrollment Code product to the basket,
        # or the user is adding a Seat product for which they are not already enrolled
        prepare_basket(request, product, voucher)
        return HttpResponseRedirect(reverse('basket:summary'), status=303)


class BasketSummaryView(BasketView):
    """
    Display basket contents and checkout/payment options.
    """
    def _determine_seat_type(self, product):
        """
        Return the seat type based on the product class
        """
        seat_type = None
        if product.get_product_class().name == SEAT_PRODUCT_CLASS_NAME:
            seat_type = get_certificate_type_display_value(product.attr.certificate_type)
        elif product.get_product_class().name == ENROLLMENT_CODE_PRODUCT_CLASS_NAME:
            seat_type = get_certificate_type_display_value(product.attr.seat_type)
        return seat_type

    def get_context_data(self, **kwargs):
        context = super(BasketSummaryView, self).get_context_data(**kwargs)
        formset = context.get('formset', [])
        lines = context.get('line_list', [])
        lines_data = []
        is_verification_required = is_bulk_purchase = False
        switch_link_text = partner_sku = ''

        for line in lines:
            course_key = CourseKey.from_string(line.product.attr.course_key)
            course_name = None
            image_url = None
            short_description = None
            try:
                course = get_course_info_from_lms(course_key)
                image_url = get_lms_url(course['media']['course_image']['uri'])
                short_description = course['short_description']
                course_name = course['name']
            except (ConnectionError, SlumberBaseException, Timeout):
                logger.exception('Failed to retrieve data from Course API for course [%s].', course_key)

            if self.request.site.siteconfiguration.enable_enrollment_codes:
                # Get variables for the switch link that toggles from enrollment codes and seat.
                switch_link_text, partner_sku = get_basket_switch_data(line.product)
                if line.product.get_product_class().name == ENROLLMENT_CODE_PRODUCT_CLASS_NAME:
                    is_bulk_purchase = True
                    # Iterate on message storage so all messages are marked as read.
                    # This will hide the success messages when a user updates the quantity
                    # for an item in the basket.
                    list(messages.get_messages(self.request))

            if line.has_discount:
                benefit = self.request.basket.applied_offers().values()[0].benefit
                benefit_value = format_benefit_value(benefit)
            else:
                benefit_value = None

            lines_data.append({
                'seat_type': self._determine_seat_type(line.product),
                'course_name': course_name,
                'course_key': course_key,
                'image_url': image_url,
                'course_short_description': short_description,
                'benefit_value': benefit_value,
                'enrollment_code': line.product.get_product_class().name == ENROLLMENT_CODE_PRODUCT_CLASS_NAME,
                'line': line,
            })

            context.update({
                'analytics_data': prepare_analytics_data(
                    self.request.user,
                    self.request.site.siteconfiguration.segment_key,
                    unicode(course_key)
                ),
            })

            # Check product attributes to determine if ID verification is required for this basket
            try:
                is_verification_required = is_verification_required or line.product.attr.id_verification_required
            except AttributeError:
                pass

        context.update({
            'free_basket': context['order_total'].incl_tax == 0,
            'payment_processors': self.request.site.siteconfiguration.get_payment_processors(),
            'homepage_url': get_lms_url(''),
            'formset_lines_data': zip(formset, lines_data),
            'is_verification_required': is_verification_required,
            'min_seat_quantity': 1,
            'is_bulk_purchase': is_bulk_purchase,
            'switch_link_text': switch_link_text,
            'partner_sku': partner_sku,
        })

        return context
