Fix #177 - Allow to change the payment method

src/pretix/presale/templates/pretixpresale/event/order.html

@@ -33,6 +33,12 @@
     {% if order.status == "n" %}
         <div class="panel panel-danger">
             <div class="panel-heading">
+                <div class="pull-right">
+                    <a href="{% eventurl event "presale:event.order.pay.change" secret=order.secret order=order.code %}">
+                        <span class="fa fa-edit"></span>
+                        {% trans "Use different payment method" %}
+                    </a>
+                </div>
                 <h3 class="panel-title">
                     {% trans "Payment" %}
                 </h3>

src/pretix/presale/templates/pretixpresale/event/order_pay_change.html

@@ -0,0 +1,65 @@
+{% extends "pretixpresale/event/base.html" %}
+{% load i18n %}
+{% load eventurl %}
+{% block title %}{% trans "Change payment method" %}{% endblock %}
+{% block content %}
+    <h2>
+        {% blocktrans trimmed with code=order.code %}
+            Change payment method: {{ code }}
+        {% endblocktrans %}
+    </h2>
+    <p>
+        {% blocktrans trimmed %}
+            Please note: If you change your payment method, your order total will change by the
+            amount displayed to the right of each method.
+        {% endblocktrans %}
+    </p>
+    <form method="post">
+        {% csrf_token %}
+        <div class="panel-group" id="payment_accordion">
+            {% for p in providers %}
+                <div class="panel panel-default">
+                    <div class="panel-heading">
+                        <h4 class="panel-title">
+                            <label class="radio">
+                                <strong class="pull-right">{% if p.fee_diff >= 0 %}+{% else %}-{% endif %} {{ p.fee_diff_abs|floatformat:2 }} {{ event.currency }}</strong>
+                                <input type="radio" name="payment" value="{{ p.provider.identifier }}"
+                                        data-parent="#payment_accordion"
+                                        {% if selected == p.provider.identifier %}checked="checked"{% endif %}
+                                        data-toggle="radiocollapse" data-target="#payment_{{ p.provider.identifier }}" />
+                                <strong>{{ p.provider.verbose_name }}</strong>
+                            </label>
+                        </h4>
+                    </div>
+                    <div id="payment_{{ p.provider.identifier }}"
+                         class="panel-collapse collapsed {% if selected == p.provider.identifier %}in{% endif %}">
+                        <div class="panel-body form-horizontal">
+                            {{ p.form }}
+                        </div>
+                    </div>
+                </div>
+            {% empty %}
+                <div class="alert alert-info">
+                    {% trans "There are no alternative payment providers available for this order." %}
+                </div>
+            {% endfor %}
+        </div>
+        <div class="row checkout-button-row">
+            <div class="col-md-4">
+                <a class="btn btn-block btn-default btn-lg"
+                   href="{% eventurl request.event "presale:event.order" secret=order.secret order=order.code %}">
+                    {% trans "Cancel" %}
+                </a>
+            </div>
+            <div class="col-md-4 col-md-offset-4">
+                {% if providers %}
+                <button class="btn btn-block btn-primary btn-lg" type="submit">
+                    {% trans "Continue" %}
+                </button>
+                {% endif %}
+            </div>
+            <div class="clearfix"></div>
+        </div>
+    </form>
+
+{% endblock %}

src/pretix/presale/urls.py

@@ -40,6 +40,9 @@ event_patterns = [
     url(r'^order/(?P<order>[^/]+)/(?P<secret>[A-Za-z0-9]+)/pay/complete$',
         pretix.presale.views.order.OrderPayComplete.as_view(),
         name='event.order.pay.complete'),
+    url(r'^order/(?P<order>[^/]+)/(?P<secret>[A-Za-z0-9]+)/pay/change',
+        pretix.presale.views.order.OrderPayChangeMethod.as_view(),
+        name='event.order.pay.change'),
     url(r'^order/(?P<order>[^/]+)/(?P<secret>[A-Za-z0-9]+)/download/(?P<output>[^/]+)$',
         pretix.presale.views.order.OrderDownload.as_view(),
         name='event.order.download'),

src/pretix/presale/views/order.py

@@ -2,6 +2,8 @@ from datetime import timedelta
 
 from django.contrib import messages
 from django.core.urlresolvers import reverse
+from django.db import transaction
+from django.db.models import Sum
 from django.http import Http404
 from django.shortcuts import redirect
 from django.utils.functional import cached_property
@@ -14,7 +16,7 @@ from pretix.base.models import (
 )
 from pretix.base.models.orders import InvoiceAddress
 from pretix.base.services.invoices import (
-    generate_invoice, invoice_pdf, invoice_qualified,
+    generate_cancellation, generate_invoice, invoice_pdf, invoice_qualified,
 )
 from pretix.base.services.orders import OrderError, cancel_order
 from pretix.base.services.tickets import generate
@@ -125,9 +127,9 @@ class OrderPay(EventViewMixin, OrderDetailMixin, TemplateView):
         return super().dispatch(request, *args, **kwargs)
 
     def post(self, request, *args, **kwargs):
-        resp = self.payment_provider.retry_prepare(
-            request, self.order
-        )
+        resp = self.payment_provider.order_prepare(request, self.order)
+        if 'payment_change_{}'.format(self.order.pk) in request.session:
+            del request.session['payment_change_{}'.format(self.order.pk)]
         if isinstance(resp, str):
             return redirect(resp)
         elif resp is True:
@@ -181,7 +183,8 @@ class OrderPayDo(EventViewMixin, OrderDetailMixin, TemplateView):
         self.request = request
         if not self.order:
             raise Http404(_('Unknown order code or not authorized to access this order.'))
-        if not self.payment_provider.order_can_retry(self.order) or not self.payment_provider.is_enabled:
+        can_do = self.payment_provider.order_can_retry(self.order) or 'payment_change_{}'.format(self.order.pk) in request.session
+        if not can_do or not self.payment_provider.is_enabled:
             messages.error(request, _('The payment for this order cannot be continued.'))
             return redirect(self.get_order_url())
         if (not self.payment_provider.payment_is_valid_session(request)
@@ -192,6 +195,8 @@ class OrderPayDo(EventViewMixin, OrderDetailMixin, TemplateView):
 
     def post(self, request, *args, **kwargs):
         resp = self.payment_provider.payment_perform(request, self.order)
+        if 'payment_change_{}'.format(self.order.pk) in request.session:
+            del request.session['payment_change_{}'.format(self.order.pk)]
         return redirect(resp or self.get_order_url())
 
     def get_context_data(self, **kwargs):
@@ -213,8 +218,8 @@ class OrderPayComplete(EventViewMixin, OrderDetailMixin, View):
         self.request = request
         if not self.order:
             raise Http404(_('Unknown order code or not authorized to access this order.'))
-        if (not self.payment_provider.payment_is_valid_session(request)
-                or not self.payment_provider.is_enabled):
+        if (not self.payment_provider.payment_is_valid_session(request) or
+                not self.payment_provider.is_enabled):
             messages.error(request, _('The payment information you entered was incomplete.'))
             return redirect(self.get_payment_url())
         return super().dispatch(request, *args, **kwargs)
@@ -230,6 +235,96 @@ class OrderPayComplete(EventViewMixin, OrderDetailMixin, View):
         })
 
 
+class OrderPayChangeMethod(EventViewMixin, OrderDetailMixin, TemplateView):
+    template_name = 'pretixpresale/event/order_pay_change.html'
+
+    def dispatch(self, request, *args, **kwargs):
+        self.request = request
+        if not self.order:
+            raise Http404(_('Unknown order code or not authorized to access this order.'))
+        if self.order.status not in (Order.STATUS_PENDING, Order.STATUS_EXPIRED):
+            messages.error(request, _('The payment method for this order cannot be changed.'))
+            return redirect(self.get_order_url() + '?paid=yes')
+        return super().dispatch(request, *args, **kwargs)
+
+    def get_payment_url(self):
+        return eventreverse(self.request.event, 'presale:event.order.pay', kwargs={
+            'order': self.order.code,
+            'secret': self.order.secret
+        })
+
+    @cached_property
+    def _total_order_value(self):
+        return self.order.positions.aggregate(sum=Sum('price'))['sum']
+
+    @cached_property
+    def provider_forms(self):
+        providers = []
+        responses = register_payment_providers.send(self.request.event)
+        for receiver, response in responses:
+            provider = response(self.request.event)
+            if provider.identifier == self.order.payment_provider:
+                continue
+            if not provider.is_enabled or not provider.order_change_allowed(self.order):
+                continue
+            fee = provider.calculate_fee(self._total_order_value)
+            providers.append({
+                'provider': provider,
+                'fee': fee,
+                'fee_diff': fee - self.order.payment_fee,
+                'fee_diff_abs': abs(fee - self.order.payment_fee),
+                'form': provider.payment_form_render(self.request)
+            })
+        return providers
+
+    def post(self, request, *args, **kwargs):
+        self.request = request
+        for p in self.provider_forms:
+            if p['provider'].identifier == request.POST.get('payment', ''):
+                request.session['payment'] = p['provider'].identifier
+                request.session['payment_change_{}'.format(self.order.pk)] = '1'
+
+                resp = p['provider'].order_prepare(request, self.order)
+                if resp:
+                    with transaction.atomic():
+                        new_fee = p['provider'].calculate_fee(self._total_order_value)
+                        self.order.log_action('pretix.event.order.payment.changed', {
+                            'old_fee': self.order.payment_fee,
+                            'new_fee': new_fee,
+                            'old_provider': self.order.payment_provider,
+                            'new_provider': p['provider'].identifier
+                        })
+                        self.order.payment_provider = p['provider'].identifier
+                        self.order.payment_fee = new_fee
+                        self.order._calculate_tax()
+                        self.order.save()
+
+                        i = self.order.invoices.filter(is_cancellation=False).last()
+                        if i:
+                            generate_cancellation(i)
+                            generate_invoice(self.order)
+                if isinstance(resp, str):
+                    return redirect(resp)
+                elif resp is True:
+                    return redirect(self.get_confirm_url())
+                else:
+                    return self.get(request, *args, **kwargs)
+        messages.error(self.request, _("Please select a payment method."))
+        return self.get(request, *args, **kwargs)
+
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        ctx['order'] = self.order
+        ctx['providers'] = self.provider_forms
+        return ctx
+
+    def get_confirm_url(self):
+        return eventreverse(self.request.event, 'presale:event.order.pay.confirm', kwargs={
+            'order': self.order.code,
+            'secret': self.order.secret
+        })
+
+
 class OrderModify(EventViewMixin, OrderDetailMixin, QuestionsViewMixin, TemplateView):
     template_name = "pretixpresale/event/order_modify.html"