Add payments to refunds in admin

refunding/admin.py

@@ -1,4 +1,5 @@
 from django.contrib import admin
+from refunding.forms import RefundForm
 from refunding.models import Refund, Payment
 
 
@@ -8,11 +9,13 @@ class RefundAdmin(admin.ModelAdmin):
     list_display_links = ('title',)
     search_fields = ('title',)
     date_hierarchy = 'date'
+    form = RefundForm
+    readonly_fields = ('amount',)
 
 
 @admin.register(Payment)
 class PaymentAdmin(admin.ModelAdmin):
-    list_display = ('title', 'date', 'value', 'user', 'refund')
+    list_display = ('title', 'date', 'eur_value', 'user', 'refund')
     list_display_links = ('title',)
     search_fields = ('title',)
     date_hierarchy = 'date'

refunding/forms.py

@@ -0,0 +1,24 @@
+from django import forms
+from refunding.models import Refund, Payment
+
+
+class RefundForm(forms.ModelForm):
+    class Meta:
+        model = Refund
+        fields = '__all__'
+
+    payments = forms.ModelMultipleChoiceField(queryset=Payment.objects.all())
+
+    def __init__(self, *args, **kwargs):
+        super(RefundForm, self).__init__(*args, **kwargs)
+        if self.instance:
+            self.fields['payments'].initial = self.instance.payment_set.all()
+
+    def save(self, *args, **kwargs):
+        # Save the refund
+        instance = super(RefundForm, self).save(commit=False)
+        # Remove the refund from payments it was previously assigned to
+        self.fields['payments'].initial.update(refund=None)
+        # Add the refund to the selected payments
+        self.cleaned_data['payments'].update(refund=instance)
+        return instance

refunding/models.py

@@ -1,5 +1,6 @@
 from django.db import models
 from django.conf import settings
+from django.db.models import Sum
 
 AUTH_USER_MODEL = getattr(settings, 'AUTH_USER_MODEL', 'auth.User')
 
@@ -14,6 +15,12 @@ class Refund(models.Model):
         on_delete=models.PROTECT
     )
 
+    def amount(self) -> float:
+        return self.payment_set.all().aggregate(Sum('value')).get('value__sum') / 100
+
+    def __str__(self) -> str:
+        return "{0} on {1} for {2}".format(self.title, self.date, self.amount())
+
 
 class Payment(models.Model):
     title = models.CharField(max_length=100)
@@ -31,3 +38,9 @@ class Payment(models.Model):
         null=True,
         blank=True
     )
+
+    def __str__(self) -> str:
+        return '{0} on {1} for {2}'.format(self.title, self.date, self.value / 100)
+
+    def eur_value(self) -> float:
+        return self.value / 100