from django.shortcuts import render
from django.db import transaction
from django.contrib.auth import get_user_model
from rest_framework import viewsets, mixins, permissions, status, views
from rest_framework.renderers import TemplateHTMLRenderer
from rest_framework.response import Response
from rest_framework.decorators import action
from rest_framework.reverse import reverse
from rest_framework.decorators import renderer_classes
from vat_validator import validate_vat, vies
from vat_validator.countries import EU_COUNTRY_CODES
from hardcopy import bytestring_to_pdf
from django.core.files.temp import NamedTemporaryFile
from django.http import FileResponse
from django.template.loader import render_to_string
from copy import deepcopy

import json
import logging

from .models import *
from .serializers import *
from datetime import datetime
from vat_validator import sanitize_vat
import uncloud_pay.stripe as uncloud_stripe

logger = logging.getLogger(__name__)

###
# Payments and Payment Methods.

class PaymentViewSet(viewsets.ReadOnlyModelViewSet):
    serializer_class = PaymentSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        return Payment.objects.filter(owner=self.request.user)

class OrderViewSet(viewsets.ReadOnlyModelViewSet):
    serializer_class = OrderSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        return Order.objects.filter(owner=self.request.user)

class PaymentMethodViewSet(viewsets.ModelViewSet):
    permission_classes = [permissions.IsAuthenticated]

    def get_serializer_class(self):
        if self.action == 'create':
            return CreatePaymentMethodSerializer
        elif self.action == 'update':
            return UpdatePaymentMethodSerializer
        elif self.action == 'charge':
            return ChargePaymentMethodSerializer
        else:
            return PaymentMethodSerializer

    def get_queryset(self):
        return PaymentMethod.objects.filter(owner=self.request.user)

    # XXX: Handling of errors is far from great down there.
    @transaction.atomic
    def create(self, request):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)

        # Set newly created method as primary if no other method is.
        if PaymentMethod.get_primary_for(request.user) == None:
            serializer.validated_data['primary'] = True

        if serializer.validated_data['source'] == "stripe":
            # Retrieve Stripe customer ID for user.
            customer_id = uncloud_stripe.get_customer_id_for(request.user)
            if customer_id == None:
                return Response(
                    {'error': 'Could not resolve customer stripe ID.'},
                    status=status.HTTP_500_INTERNAL_SERVER_ERROR)

            try:
                setup_intent = uncloud_stripe.create_setup_intent(customer_id)
            except Exception as e:
                return Response({'error': str(e)},
                    status=status.HTTP_500_INTERNAL_SERVER_ERROR)

            payment_method = PaymentMethod.objects.create(
                    owner=request.user,
                    stripe_setup_intent_id=setup_intent.id,
                    **serializer.validated_data)

            # TODO: find a way to use reverse properly:
            # https://www.django-rest-framework.org/api-guide/reverse/
            path = "payment-method/{}/register-stripe-cc".format(
                    payment_method.uuid)
            stripe_registration_url = reverse('api-root', request=request) + path
            return Response({'please_visit': stripe_registration_url})
        else:
           serializer.save(owner=request.user, **serializer.validated_data)
           return Response(serializer.data)

    @action(detail=True, methods=['post'])
    def charge(self, request, pk=None):
        payment_method = self.get_object()
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        amount = serializer.validated_data['amount']
        try:
            payment = payment_method.charge(amount)
            output_serializer = PaymentSerializer(payment)
            return Response(output_serializer.data)
        except Exception as e:
            return Response({'error': str(e)}, status=status.HTTP_500_INTERNAL_SERVER_ERROR)

    @action(detail=True, methods=['get'], url_path='register-stripe-cc', renderer_classes=[TemplateHTMLRenderer])
    def register_stripe_cc(self, request, pk=None):
        payment_method = self.get_object()

        if payment_method.source != 'stripe':
            return Response(
                    {'error': 'This is not a Stripe-based payment method.'},
                    template_name='error.html.j2')

        if payment_method.active:
            return Response(
                    {'error': 'This payment method is already active'},
                    template_name='error.html.j2')

        try:
            setup_intent = uncloud_stripe.get_setup_intent(
                    payment_method.stripe_setup_intent_id)
        except Exception as e:
            return Response(
                    {'error': str(e)},
                    template_name='error.html.j2')

        # TODO: find a way to use reverse properly:
        # https://www.django-rest-framework.org/api-guide/reverse/
        callback_path= "payment-method/{}/activate-stripe-cc/".format(
                payment_method.uuid)
        callback = reverse('api-root', request=request) + callback_path

        # Render stripe card registration form.
        template_args = {
                'client_secret': setup_intent.client_secret,
                'stripe_pk': uncloud_stripe.public_api_key,
                'callback': callback
                }
        return Response(template_args, template_name='stripe-payment.html.j2')

    @action(detail=True, methods=['post'], url_path='activate-stripe-cc')
    def activate_stripe_cc(self, request, pk=None):
        payment_method = self.get_object()
        try:
            setup_intent = uncloud_stripe.get_setup_intent(
                    payment_method.stripe_setup_intent_id)
        except Exception as e:
            return Response({'error': str(e)}, status=status.HTTP_500_INTERNAL_SERVER_ERROR)

        # Card had been registered, fetching payment method.
        print(setup_intent)
        if setup_intent.payment_method:
            payment_method.stripe_payment_method_id = setup_intent.payment_method
            payment_method.save()

            return Response({
                'uuid': payment_method.uuid,
                'activated': payment_method.active})
        else:
            error = 'Could not fetch payment method from stripe. Please try again.'
            return Response({'error': error})

    @action(detail=True, methods=['post'], url_path='set-as-primary')
    def set_as_primary(self, request, pk=None):
        payment_method = self.get_object()
        payment_method.set_as_primary_for(request.user)

        serializer = self.get_serializer(payment_method)
        return Response(serializer.data)

###
# Bills and Orders.

class BillViewSet(viewsets.ReadOnlyModelViewSet):
    serializer_class = BillSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        return Bill.objects.filter(owner=self.request.user)


    @action(detail=False, methods=['get'])
    def unpaid(self, request):
        serializer = self.get_serializer(
                Bill.get_unpaid_for(self.request.user),
                many=True)
        return Response(serializer.data)

    @action(detail=True, methods=['get'])
    def download(self, *args, **kwargs):
        bill = self.get_object()
        output_file = NamedTemporaryFile()
        bill_html = render_to_string("bill.html.j2", {'bill': bill})

        bytestring_to_pdf(bill_html.encode('utf-8'), output_file)
        response = FileResponse(output_file, content_type="application/pdf")
        response['Content-Disposition'] = 'filename="{}_{}.pdf"'.format(
                bill.reference, bill.uuid
        )

        return response


class OrderViewSet(viewsets.ReadOnlyModelViewSet):
    serializer_class = OrderSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_queryset(self):
        return Order.objects.filter(owner=self.request.user)

class BillingAddressViewSet(mixins.CreateModelMixin,
        mixins.RetrieveModelMixin,
        mixins.UpdateModelMixin,
        mixins.ListModelMixin,
        viewsets.GenericViewSet):
    permission_classes = [permissions.IsAuthenticated]

    def get_serializer_class(self):
        if self.action == 'update':
            return UpdateBillingAddressSerializer
        else:
            return BillingAddressSerializer

    def get_queryset(self):
        return self.request.user.billingaddress_set.all()

    def create(self, request):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)

        # Validate VAT numbers.
        country = serializer.validated_data["country"]

        # We ignore empty VAT numbers.
        if 'vat_number' in serializer.validated_data and serializer.validated_data["vat_number"] != "":
            vat_number = serializer.validated_data["vat_number"]

            if not validate_vat(country, vat_number):
                return Response(
                    {'error': 'Malformed VAT number.'},
                    status=status.HTTP_400_BAD_REQUEST)
            elif country in EU_COUNTRY_CODES:
                # XXX: make a synchroneous call to a third patry API here might not be a good idea..
                try:
                    vies_state = vies.check_vat(country, vat_number)
                    if not vies_state.valid:
                        return Response(
                                {'error': 'European VAT number does not exist in VIES.'},
                                status=status.HTTP_400_BAD_REQUEST)
                except Exception as e:
                    logger.warning(e)
                    return Response(
                            {'error': 'Could not validate EU VAT number against VIES. Try again later..'},
                            status=status.HTTP_500_INTERNAL_SERVER_ERROR)


        serializer.save(owner=request.user)
        return Response(serializer.data)

###
# Admin stuff.

class AdminPaymentViewSet(viewsets.ModelViewSet):
    serializer_class = PaymentSerializer
    permission_classes = [permissions.IsAdminUser]

    def get_queryset(self):
        return Payment.objects.all()

    def create(self, request):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        serializer.save(timestamp=datetime.now())

        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

# Bills are generated from orders and should not be created or updated by hand.
class AdminBillViewSet(BillViewSet):
    serializer_class = BillSerializer
    permission_classes = [permissions.IsAdminUser]

    def get_queryset(self):
        return Bill.objects.all()

    @action(detail=False, methods=['get'])
    def unpaid(self, request):
        unpaid_bills = []
        # XXX: works but we can do better than number of users + 1 SQL requests...
        for user in get_user_model().objects.all():
            unpaid_bills = unpaid_bills + Bill.get_unpaid_for(self.request.user)

        serializer = self.get_serializer(unpaid_bills, many=True)
        return Response(serializer.data)

    @action(detail=False, methods=['post'])
    def generate(self, request):
        users = get_user_model().objects.all()

        generated_bills = []
        for user in users:
            now = timezone.now()
            generated_bills = generated_bills + Bill.generate_for(
                    year=now.year,
                    month=now.month,
                    user=user)

        return Response(
                map(lambda b: b.reference, generated_bills),
                status=status.HTTP_200_OK)

class AdminOrderViewSet(mixins.ListModelMixin,
        mixins.RetrieveModelMixin,
        mixins.CreateModelMixin,
        mixins.UpdateModelMixin,
        viewsets.GenericViewSet):
    serializer_class = OrderSerializer
    permission_classes = [permissions.IsAdminUser]

    def get_serializer(self, *args, **kwargs):
        return self.serializer_class(*args, **kwargs, admin=True)

    def get_queryset(self):
        return Order.objects.all()

    # Updates create a new order and terminate the 'old' one.
    @transaction.atomic
    def update(self, request, *args, **kwargs):
       order = self.get_object()
       partial = kwargs.pop('partial', False)
       serializer = self.get_serializer(order, data=request.data, partial=partial)
       serializer.is_valid(raise_exception=True)

       # Clone existing order for replacement.
       replacing_order = deepcopy(order)

       # Yes, that's how you make a new entry in DB:
       #   https://docs.djangoproject.com/en/3.0/topics/db/queries/#copying-model-instances
       replacing_order.pk = None

       for attr, value in serializer.validated_data.items():
          setattr(replacing_order, attr, value)

       # Save replacing order and terminate 'previous' one.
       replacing_order.save()
       order.replaced_by = replacing_order
       order.save()
       order.terminate()

       return Response(replacing_order)

    @action(detail=True, methods=['post'])
    def terminate(self, request, pk):
        order = self.get_object()
        if order.is_terminated:
            return Response(
                    {'error': 'Order is already terminated.'},
                    status=status.HTTP_500_INTERNAL_SERVER_ERROR)

        else:
            order.terminate()
            return Response({}, status=status.HTTP_200_OK)