from __future__ import unicode_literals

import logging
from datetime import datetime
from decimal import Decimal
from urllib import urlencode

import dateutil.parser
import newrelic.agent
import waffle
from django.http import HttpResponseBadRequest, HttpResponseRedirect
from django.shortcuts import redirect, render
from django.utils.translation import ugettext as _
from opaque_keys.edx.keys import CourseKey
from oscar.apps.basket.views import VoucherAddView as BaseVoucherAddView
from oscar.apps.basket.views import VoucherRemoveView as BaseVoucherRemoveView
from oscar.apps.basket.views import *  # pylint: disable=wildcard-import, unused-wildcard-import
from requests.exceptions import ConnectionError, Timeout
from slumber.exceptions import SlumberBaseException

from ecommerce.core.exceptions import SiteConfigurationError
from ecommerce.core.url_utils import get_lms_course_about_url, get_lms_url
from ecommerce.courses.utils import get_certificate_type_display_value, get_course_info_from_catalog
from ecommerce.enterprise.entitlements import get_enterprise_code_redemption_redirect
from ecommerce.enterprise.utils import CONSENT_FAILED_PARAM, get_enterprise_customer_from_voucher, has_enterprise_offer
from ecommerce.extensions.analytics.utils import (
    prepare_analytics_data,
    track_segment_event,
    translate_basket_line_for_segment
)
from ecommerce.extensions.basket.utils import add_utm_params_to_url, get_basket_switch_data, prepare_basket
from ecommerce.extensions.offer.utils import format_benefit_value, render_email_confirmation_if_required
from ecommerce.extensions.order.exceptions import AlreadyPlacedOrderException
from ecommerce.extensions.partner.shortcuts import get_partner_for_site
from ecommerce.extensions.payment.constants import CLIENT_SIDE_CHECKOUT_FLAG_NAME
from ecommerce.extensions.payment.forms import PaymentForm

Benefit = get_model('offer', 'Benefit')
logger = logging.getLogger(__name__)
Product = get_model('catalogue', 'Product')
StockRecord = get_model('partner', 'StockRecord')
Voucher = get_model('voucher', 'Voucher')


class BasketAddItemsView(View):
    """
    View that adds multiple products 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)

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

        if not skus:
            return HttpResponseBadRequest(_('No SKUs provided.'))

        products = Product.objects.filter(stockrecords__partner=partner, stockrecords__partner_sku__in=skus)
        if not products:
            return HttpResponseBadRequest(_('Products with SKU(s) [{skus}] do not exist.').format(skus=', '.join(skus)))

        logger.info('Starting payment flow for user[%s] for products[%s].', request.user.username, skus)

        voucher = Voucher.objects.get(code=code) if code else None

        if voucher is None:
            # If there is an Enterprise entitlement available for this basket,
            # we redirect to the CouponRedeemView to apply the discount to the
            # basket and handle the data sharing consent requirement.
            code_redemption_redirect = get_enterprise_code_redemption_redirect(
                request,
                products,
                skus,
                'basket:basket-add'
            )
            if code_redemption_redirect:
                return code_redemption_redirect

        # check availability of products
        unavailable_product_ids = []
        for product in products:
            purchase_info = request.strategy.fetch_for_product(product)
            if not purchase_info.availability.is_available_to_buy:
                logger.warning('Product [%s] is not available to buy.', product.title)
                unavailable_product_ids.append(product.id)

        available_products = products.exclude(id__in=unavailable_product_ids)
        if not available_products:
            msg = _('No product is available to buy.')
            return HttpResponseBadRequest(msg)

        try:
            prepare_basket(request, available_products, voucher)
        except AlreadyPlacedOrderException:
            return render(request, 'edx/error.html', {'error': _('You have already purchased these products')})
        url = add_utm_params_to_url(reverse('basket:summary'), self.request.GET.items())
        return HttpResponseRedirect(url, status=303)


class BasketSummaryView(BasketView):
    """
    Display basket contents and checkout/payment options.
    """

    @newrelic.agent.function_trace()
    def _determine_product_type(self, product):
        """
        Return the seat type based on the product class
        """
        seat_type = None
        if product.is_seat_product or product.is_course_entitlement_product:
            seat_type = get_certificate_type_display_value(product.attr.certificate_type)
        elif product.is_enrollment_code_product:
            seat_type = get_certificate_type_display_value(product.attr.seat_type)
        return seat_type

    @newrelic.agent.function_trace()
    def _deserialize_date(self, date_string):
        date = None
        try:
            date = dateutil.parser.parse(date_string)
        except (AttributeError, ValueError):
            pass
        return date

    @newrelic.agent.function_trace()
    def _get_course_data(self, product):
        """
        Return course data.

        Args:
            product (Product): A product that has course_key as attribute (seat or bulk enrollment coupon)
        Returns:
            Dictionary containing course name, course key, course image URL and description.
        """
        if product.is_seat_product:
            course_key = CourseKey.from_string(product.attr.course_key)
        else:
            course_key = None
        course_name = None
        image_url = None
        short_description = None
        course_start = None
        course_end = None
        course = None

        try:
            course = get_course_info_from_catalog(self.request.site, product)
            try:
                image_url = course['image']['src']
            except (KeyError, TypeError):
                image_url = ''
            short_description = course.get('short_description', '')
            course_name = course.get('title', '')

            # The course start/end dates are not currently used
            # in the default basket templates, but we are adding
            # the dates to the template context so that theme
            # template overrides can make use of them.
            course_start = self._deserialize_date(course.get('start'))
            course_end = self._deserialize_date(course.get('end'))
        except (ConnectionError, SlumberBaseException, Timeout):
            logger.exception('Failed to retrieve data from Discovery Service for course [%s].', course_key)

        if self.request.basket.num_items == 1 and product.is_enrollment_code_product:
            course_key = CourseKey.from_string(product.attr.course_key)
            if course and course.get('marketing_url', None):
                course_about_url = course['marketing_url']
            else:
                course_about_url = get_lms_course_about_url(course_key=course_key)
            messages.info(
                self.request,
                _(
                    '{strong_start}Purchasing just for yourself?{strong_end}{paragraph_start}If you are '
                    'purchasing a single code for someone else, please continue with checkout. However, if you are the '
                    'learner {link_start}go back{link_end} to enroll directly.{paragraph_end}'
                ).format(
                    strong_start='<strong>',
                    strong_end='</strong>',
                    paragraph_start='<p>',
                    paragraph_end='</p>',
                    link_start='<a href="{course_about}">'.format(course_about=course_about_url),
                    link_end='</a>'
                ),
                extra_tags='safe'
            )

        return {
            'product_title': course_name,
            'course_key': course_key,
            'image_url': image_url,
            'product_description': short_description,
            'course_start': course_start,
            'course_end': course_end,
        }

    @newrelic.agent.function_trace()
    def _process_basket_lines(self, lines):
        """Processes the basket lines and extracts information for the view's context.
        In addition determines whether:
            * verification message should be displayed
            * voucher form should be displayed
            * switch link (for switching between seat and enrollment code products) should be displayed
        and returns that information for the basket view context to be updated with it.

        Args:
            lines (list): List of basket lines.
        Returns:
            context_updates (dict): Containing information with which the context needs to
                                    be updated with.
            lines_data (list): List of information about the basket lines.
        """
        display_verification_message = False
        lines_data = []
        show_voucher_form = True
        is_enrollment_code_purchase = False
        switch_link_text = partner_sku = order_details_msg = None

        for line in lines:
            if line.product.is_seat_product or line.product.is_course_entitlement_product:
                line_data = self._get_course_data(line.product)
                certificate_type = line.product.attr.certificate_type

                if getattr(line.product.attr, 'id_verification_required', False) and certificate_type != 'credit':
                    display_verification_message = True

                if line.product.is_course_entitlement_product:
                    order_details_msg = _(
                        'After you complete your order you will be able to select course dates from your dashboard.'
                    )
                else:
                    if certificate_type == 'verified':
                        order_details_msg = _(
                            'After you complete your order you will be automatically enrolled '
                            'in the verified track of the course.'
                        )
                    elif certificate_type == 'credit':
                        order_details_msg = _('After you complete your order you will receive credit for your course.')
                    else:
                        order_details_msg = _(
                            'After you complete your order you will be automatically enrolled in the course.'
                        )
            elif line.product.is_enrollment_code_product:
                line_data = self._get_course_data(line.product)
                is_enrollment_code_purchase = True
                show_voucher_form = False
                order_details_msg = _(
                    '{paragraph_start}By purchasing, you and your organization agree to the following terms:'
                    '{paragraph_end} {ul_start} {li_start}Each code is valid for the one course covered and can be '
                    'used only one time.{li_end} '
                    '{li_start}You are responsible for distributing codes to your learners in your organization.'
                    '{li_end} {li_start}Each code will expire in one year from date of purchase or, if earlier, once '
                    'the course is closed.{li_end} {li_start}If a course is not designated as self-paced, you should '
                    'confirm that a course run is available before expiration. {li_end} {li_start}You may not resell '
                    'codes to third parties.{li_end} '
                    '{li_start}All edX for Business Sales are final and not eligible for refunds.{li_end}{ul_end} '
                    '{paragraph_start}You will receive an email at {user_email} with your enrollment code(s). '
                    '{paragraph_end}'
                ).format(
                    paragraph_start='<p>',
                    paragraph_end='</p>',
                    ul_start='<ul>',
                    li_start='<li>',
                    li_end='</li>',
                    ul_end='</ul>',
                    user_email=self.request.user.email
                )
            else:
                line_data = {
                    'product_title': line.product.title,
                    'image_url': None,
                    'product_description': line.product.description
                }

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

            line_data.update({
                'sku': line.product.stockrecords.first().partner_sku,
                'benefit_value': benefit_value,
                'enrollment_code': line.product.is_enrollment_code_product,
                'line': line,
                'seat_type': self._determine_product_type(line.product),
            })
            lines_data.append(line_data)

        context_updates = {
            'display_verification_message': display_verification_message,
            'order_details_msg': order_details_msg,
            'partner_sku': partner_sku,
            'show_voucher_form': show_voucher_form,
            'switch_link_text': switch_link_text,
            'is_enrollment_code_purchase': is_enrollment_code_purchase
        }

        return context_updates, lines_data

    @newrelic.agent.function_trace()
    def _get_payment_processors_data(self, payment_processors):
        """Retrieve information about payment processors for the client side checkout basket.

        Args:
            payment_processors (list): List of all available payment processors.
        Returns:
            A dictionary containing information about the payment processor(s) with which the
            basket view context needs to be updated with.
        """
        site_configuration = self.request.site.siteconfiguration
        payment_processor_class = site_configuration.get_client_side_payment_processor_class()

        if payment_processor_class:
            payment_processor = payment_processor_class(self.request.site)
            current_year = datetime.today().year

            return {
                'client_side_payment_processor': payment_processor,
                'enable_client_side_checkout': True,
                'months': range(1, 13),
                'payment_form': PaymentForm(
                    user=self.request.user,
                    request=self.request,
                    initial={'basket': self.request.basket},
                    label_suffix=''
                ),
                'paypal_enabled': 'paypal' in (p.NAME for p in payment_processors),
                # Assumption is that the credit card duration is 15 years
                'years': range(current_year, current_year + 16),
            }
        else:
            msg = 'Unable to load client-side payment processor [{processor}] for ' \
                  'site configuration [{sc}]'.format(processor=site_configuration.client_side_payment_processor,
                                                     sc=site_configuration.id)
            raise SiteConfigurationError(msg)

    def get(self, request, *args, **kwargs):
        basket = request.basket

        try:
            properties = {
                'cart_id': basket.id,
                'products': [translate_basket_line_for_segment(line) for line in basket.all_lines()],
            }
            track_segment_event(request.site, request.user, 'Cart Viewed', properties)

            properties = {
                'checkout_id': basket.order_number,
                'step': 1
            }
            track_segment_event(request.site, request.user, 'Checkout Step Viewed', properties)
        except Exception:  # pylint: disable=broad-except
            logger.exception('Failed to fire Cart Viewed event for basket [%d]', basket.id)

        if has_enterprise_offer(basket) and basket.total_incl_tax == Decimal(0):
            return redirect('checkout:free-checkout')
        else:
            return super(BasketSummaryView, self).get(request, *args, **kwargs)

    @newrelic.agent.function_trace()
    def get_context_data(self, **kwargs):
        context = super(BasketSummaryView, self).get_context_data(**kwargs)
        formset = context.get('formset', [])
        lines = context.get('line_list', [])
        site_configuration = self.request.site.siteconfiguration

        failed_enterprise_consent_code = self.request.GET.get(CONSENT_FAILED_PARAM)
        if failed_enterprise_consent_code:
            messages.error(
                self.request,
                _("Could not apply the code '{code}'; it requires data sharing consent.").format(
                    code=failed_enterprise_consent_code
                )
            )

        context_updates, lines_data = self._process_basket_lines(lines)
        context.update(context_updates)

        user = self.request.user
        context.update({
            'analytics_data': prepare_analytics_data(
                user,
                site_configuration.segment_key,
            ),
            'enable_client_side_checkout': False,
            'sdn_check': site_configuration.enable_sdn_check
        })

        payment_processors = site_configuration.get_payment_processors()
        if site_configuration.client_side_payment_processor \
                and waffle.flag_is_active(self.request, CLIENT_SIDE_CHECKOUT_FLAG_NAME):
            payment_processors_data = self._get_payment_processors_data(payment_processors)
            context.update(payment_processors_data)

        # Total benefit displayed in price summary.
        # Currently only one voucher per basket is supported.
        try:
            applied_voucher = self.request.basket.vouchers.first()
            total_benefit = (
                format_benefit_value(applied_voucher.offers.first().benefit)
                if applied_voucher else None
            )
        except ValueError:
            total_benefit = None
        num_of_items = self.request.basket.num_items
        context.update({
            'formset_lines_data': zip(formset, lines_data),
            'free_basket': context['order_total'].incl_tax == 0,
            'homepage_url': get_lms_url(''),
            'min_seat_quantity': 1,
            'max_seat_quantity': 100,
            'payment_processors': payment_processors,
            'total_benefit': total_benefit,
            'line_price': (self.request.basket.total_incl_tax_excl_discounts / num_of_items) if num_of_items > 0 else 0
        })
        return context


class VoucherAddView(BaseVoucherAddView):  # pylint: disable=function-redefined
    def apply_voucher_to_basket(self, voucher):
        code = voucher.code
        if voucher.is_expired():
            messages.error(
                self.request,
                _("Coupon code '{code}' has expired.").format(code=code)
            )
            return

        if not voucher.is_active():
            messages.error(
                self.request,
                _("Coupon code '{code}' is not active.").format(code=code))
            return

        is_available, message = voucher.is_available_to_user(self.request.user)

        if not is_available:
            if voucher.usage == Voucher.SINGLE_USE:
                message = _("Coupon code '{code}' has already been redeemed.").format(code=code)
            messages.error(self.request, message)
            return

        # Do not allow coupons for one site to be used on another site
        request_site = self.request.site
        voucher_site = voucher.offers.first().site
        if request_site and voucher_site and request_site != voucher_site:
            messages.error(
                self.request,
                _("Coupon code '{code}' is not valid for this basket.").format(code=code))
            return

        # Do not allow single course run coupons used on bundles.
        BUNDLE = 'bundle_identifier'
        BasketAttribute = get_model('basket', 'BasketAttribute')
        BasketAttributeType = get_model('basket', 'BasketAttributeType')
        bundle_attribute = BasketAttribute.objects.filter(
            basket=self.request.basket,
            attribute_type=BasketAttributeType.objects.get(name=BUNDLE)
        )
        is_bundle_purchase = len(bundle_attribute) > 0
        voucher_program_uuid = voucher.offers.first().condition.program_uuid
        is_voucher_valid_for_bundle = voucher_program_uuid or voucher.usage == Voucher.MULTI_USE
        if is_bundle_purchase and not is_voucher_valid_for_bundle:
            messages.error(
                self.request,
                _("Coupon code '{code}' is not valid for this basket.").format(code=code))
            return

        # Reset any site offers that are applied so that only one offer is active.
        self.request.basket.reset_offer_applications()
        self.request.basket.vouchers.add(voucher)

        # Raise signal
        self.add_signal.send(sender=self, basket=self.request.basket, voucher=voucher)

        # Recalculate discounts to see if the voucher gives any
        Applicator().apply(self.request.basket, self.request.user,
                           self.request)
        discounts_after = self.request.basket.offer_applications

        # Look for discounts from this new voucher
        found_discount = False
        for discount in discounts_after:
            if discount['voucher'] and discount['voucher'] == voucher:
                found_discount = True
                break
        if not found_discount:
            messages.warning(
                self.request,
                _('Your basket does not qualify for a coupon code discount.'))
            self.request.basket.vouchers.remove(voucher)
        else:
            messages.info(
                self.request,
                _("Coupon code '{code}' added to basket.").format(code=code)
            )

    def form_valid(self, form):
        code = form.cleaned_data['code']
        if self.request.basket.is_empty:
            return redirect_to_referrer(self.request, 'basket:summary')
        if self.request.basket.contains_voucher(code):
            messages.error(
                self.request,
                _("You have already added coupon code '{code}' to your basket.").format(code=code)
            )
        else:
            try:
                voucher = self.voucher_model._default_manager.get(code=code)  # pylint: disable=protected-access
            except self.voucher_model.DoesNotExist:
                messages.error(
                    self.request,
                    _("Coupon code '{code}' does not exist.").format(code=code)
                )
            else:
                basket_lines = self.request.basket.all_lines()

                # TODO: for multiline baskets, select the StockRecord for the product associated
                # specifically with the code that was submitted.
                stock_record = basket_lines[0].stockrecord

                offer = voucher.offers.first()
                product = stock_record.product
                email_confirmation_response = render_email_confirmation_if_required(self.request, offer, product)
                if email_confirmation_response:
                    return email_confirmation_response

                if get_enterprise_customer_from_voucher(self.request.site, voucher) is not None:
                    # The below lines only apply if the voucher that was entered is attached
                    # to an EnterpriseCustomer. If that's the case, then rather than following
                    # the standard redemption flow, we kick the user out to the `redeem` flow.
                    # This flow will handle any additional information that needs to be gathered
                    # due to the fact that the voucher is attached to an Enterprise Customer.
                    params = urlencode(
                        {
                            'code': code,
                            'sku': stock_record.partner_sku,
                            'failure_url': self.request.build_absolute_uri(
                                '{path}?{params}'.format(
                                    path=reverse('basket:summary'),
                                    params=urlencode(
                                        {
                                            CONSENT_FAILED_PARAM: code
                                        }
                                    )
                                )
                            ),
                        }
                    )
                    return HttpResponseRedirect(
                        '{path}?{params}'.format(
                            path=reverse('coupons:redeem'),
                            params=params
                        )
                    )
                self.apply_voucher_to_basket(voucher)
        return redirect_to_referrer(self.request, 'basket:summary')


class VoucherRemoveView(BaseVoucherRemoveView):  # pylint: disable=function-redefined
    def post(self, request, *args, **kwargs):
        # TODO Remove this once https://github.com/django-oscar/django-oscar/pull/2241 is merged.
        # This prevents an issue that arises when the user applies a voucher, opens the basket page in
        # another window/tab, and attempts to remove the voucher on both screens. Under this scenario the
        # second attempt to remove the voucher will raise an error.
        kwargs['pk'] = int(kwargs['pk'])
        return super(VoucherRemoveView, self).post(request, *args, **kwargs)
