From abee9e3c6231d77d76b7d8b7ccce83704405055d Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@gmail.com>
Date: Thu, 22 Sep 2016 11:04:43 +1000
Subject: [PATCH] Adds support for refunds

---
 registripe/forms.py | 51 +++++++++++++++++++++++++++++++++
 registripe/urls.py  |  1 +
 registripe/views.py | 70 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 122 insertions(+)

diff --git a/registripe/forms.py b/registripe/forms.py
index 4f8915fb..0f4a4db0 100644
--- a/registripe/forms.py
+++ b/registripe/forms.py
@@ -1,8 +1,10 @@
 import copy
+import models
 
 from django import forms
 from django.core.urlresolvers import reverse
 from django.core.exceptions import ValidationError
+from django.db.models import F, Q
 from django.forms import widgets
 from django.utils import timezone
 
@@ -10,6 +12,8 @@ from django_countries import countries
 from django_countries.fields import LazyTypedChoiceField
 from django_countries.widgets import CountrySelectWidget
 
+from pinax.stripe import models as pinax_stripe_models
+
 
 class NoRenderWidget(forms.widgets.HiddenInput):
 
@@ -140,6 +144,53 @@ class CreditCardForm(forms.Form):
     ))
 
 
+class StripeRefundForm(forms.Form):
+
+    def __init__(self, *args, **kwargs):
+        '''
+
+        Arguments:
+            user (User): The user whose charges we should filter to.
+            min_value (Decimal): The minimum value of the charges we should
+                show (currently, credit notes can only be cashed out in full.)
+
+        '''
+        user = kwargs.pop('user', None)
+        min_value = kwargs.pop('min_value', None)
+        super(StripeRefundForm, self).__init__(*args, **kwargs)
+
+        payment_field = self.fields['payment']
+        qs = payment_field.queryset
+
+        if user:
+            qs = qs.filter(
+                charge__customer__user=user,
+            )
+
+        if min_value is not None:
+            # amount >= amount_to_refund + amount_refunded
+            # No refunds yet
+            q1 = (
+                Q(charge__amount_refunded__isnull=True) &
+                Q(charge__amount__gte=min_value)
+            )
+            # There are some refunds
+            q2 = (
+                Q(charge__amount_refunded__isnull=False) &
+                Q(charge__amount__gte=(
+                    F("charge__amount_refunded") + min_value)
+                )
+            )
+            qs = qs.filter(q1 | q2)
+
+        payment_field.queryset = qs
+
+    payment = forms.ModelChoiceField(
+        required=True,
+        queryset=models.StripePayment.objects.all(),
+    )
+
+
 '''{
 From stripe.js details:
 
diff --git a/registripe/urls.py b/registripe/urls.py
index e5958902..04a249ba 100644
--- a/registripe/urls.py
+++ b/registripe/urls.py
@@ -10,5 +10,6 @@ from pinax.stripe.views import (
 urlpatterns = [
     url(r"^card/([0-9]*)/$", views.card, name="registripe_card"),
     url(r"^pubkey/$", views.pubkey_script, name="registripe_pubkey"),
+    url(r"^refund/([0-9]*)/$", views.refund, name="registripe_refund"),
     url(r"^webhook/$", Webhook.as_view(), name="pinax_stripe_webhook"),
 ]
diff --git a/registripe/views.py b/registripe/views.py
index 8207e2b7..bd54a528 100644
--- a/registripe/views.py
+++ b/registripe/views.py
@@ -4,14 +4,18 @@ import models
 from django.core.exceptions import ValidationError
 from django.conf import settings
 from django.contrib import messages
+from django.contrib.auth.decorators import user_passes_test
 from django.db import transaction
 from django.http import HttpResponse
 from django.shortcuts import redirect, render
 
+from registrasion.controllers.credit_note import CreditNoteController
 from registrasion.controllers.invoice import InvoiceController
 from registrasion.models import commerce
 
 from pinax.stripe import actions
+from pinax.stripe.actions import refunds as pinax_stripe_actions_refunds
+
 from stripe.error import StripeError
 
 from symposion.conference.models import Conference
@@ -20,6 +24,11 @@ CURRENCY = settings.INVOICE_CURRENCY
 CONFERENCE_ID = settings.CONFERENCE_ID
 
 
+def _staff_only(user):
+    ''' Returns true if the user is staff. '''
+    return user.is_staff
+
+
 def pubkey_script(request):
     ''' Returns a JS snippet that sets the Stripe public key for Stripe.js. '''
 
@@ -126,3 +135,64 @@ def process_card(request, form, inv):
     inv.update_status()
 
     messages.success(request, "This invoice was successfully paid.")
+
+
+@user_passes_test(_staff_only)
+def refund(request, credit_note_id):
+    ''' Allows staff to select a Stripe charge for the owner of the credit
+    note, and refund the credit note into stripe. '''
+
+    cn = CreditNoteController.for_id_or_404(str(credit_note_id))
+
+    to_credit_note = redirect("credit_note", cn.credit_note.id)
+
+    if not cn.credit_note.is_unclaimed:
+        return to_credit_note
+
+    form = forms.StripeRefundForm(
+        request.POST or None,
+        user=cn.credit_note.invoice.user,
+        min_value=cn.credit_note.value,
+    )
+
+    if request.POST and form.is_valid():
+        try:
+            process_refund(cn, form)
+            return to_credit_note
+        except StripeError as se:
+            form.add_error(None, ValidationError(se))
+
+    data = {
+        "credit_note": cn.credit_note,
+        "form": form,
+    }
+
+    return render(
+        request, "registrasion/stripe/refund.html", data
+    )
+
+
+def process_refund(cn, form):
+    payment = form.cleaned_data["payment"]
+    charge = payment.charge
+
+    to_refund = cn.credit_note.value
+    stripe_charge_id = charge.stripe_charge.id
+
+    # Test that the given charge is allowed to be refunded.
+    max_refund = actions.charges.calculate_refund_amount(charge)
+
+    if max_refund < to_refund:
+        raise ValidationError(
+            "You must select a payment holding greater value than "
+            "the credit note."
+        )
+
+    refund = actions.refunds.create(charge, to_refund)
+
+    commerce.CreditNoteRefund.objects.create(
+        parent=cn.credit_note,
+        reference="Refunded %s to Stripe charge %s" % (
+            to_refund, stripe_charge_id
+        )
+    )