Re-work API for payment settings fields

src/pretix/base/payment.py

@@ -1,8 +1,12 @@
+from collections import OrderedDict
 from decimal import Decimal
+from django import forms
 
 from django.forms import Form
 from django.template import Context
 from django.template.loader import get_template
+from django.utils.translation import ugettext_lazy as _
+from pretix.base.forms import SettingsForm
 
 from pretix.base.settings import SettingsSandbox
 
@@ -20,45 +24,74 @@ class BasePaymentProvider:
         return self.identifier
 
     @property
-    def is_enabled(self):
+    def is_enabled(self) -> bool:
         """
         Returns, whether or whether not this payment provider is enabled.
-        By default, this is determined by the value of a setting.
+        By default, this is determined by the value of the ``_enabled`` setting.
         """
         return self.settings.get('_enabled', as_type=bool)
 
-    def calculate_fee(self, price):
+    def calculate_fee(self, price: Decimal) -> Decimal:
         """
         Calculate the fee for this payment provider which will be added to
-        the final price if the price before fees (but after taxes) is 'price'.
+        final price before fees (but after taxes). It should include any taxes.
+        The default implementation makes use of the setting ``_fee_abs`` for an
+        absolute fee and ``_fee_percent`` for a percentage.
+
+        :param price: The total value without the payment method fee, after taxes.
         """
         fee_abs = self.settings.get('_fee_abs', as_type=Decimal, default=0)
         fee_percent = self.settings.get('_fee_percent', as_type=Decimal, default=0)
-        return price * fee_percent / 100 + fee_abs
+        return Decimal(price * fee_percent / 100 + fee_abs)
 
     @property
     def verbose_name(self) -> str:
         """
-        A human-readable name for this payment provider
+        A human-readable name for this payment provider. This should
+        be short but self-explaining. Good examples include 'Bank transfer'
+        and 'Credit card via Stripe'.
         """
         raise NotImplementedError()  # NOQA
 
     @property
     def identifier(self) -> str:
         """
-        A unique identifier for this payment provider
+        A short and unique identifier for this payment provider.
+        This should only contain lowercase letters and in most
+        cases will be the same as your packagename.
         """
         raise NotImplementedError()  # NOQA
 
     @property
     def settings_form_fields(self) -> dict:
         """
+        When the event's administrator administrator visits the event configuration
+        page,
         A dictionary. The keys should be (unprefixed) EventSetting keys,
         the values should be corresponding django form fields.
 
         We suggest returning a collections.OrderedDict object instead of a dict.
         """
-        raise NotImplementedError()  # NOQA
+        return OrderedDict([
+            ('_enabled',
+             forms.ChoiceField(
+                 label=_('Enable payment method'),
+                 required=False,
+                 choices=SettingsForm.BOOL_CHOICES,
+             )),
+            ('_fee_abs',
+             forms.DecimalField(
+                 label=_('Additional fee'),
+                 help_text=_('Absolute value'),
+                 required=False
+             )),
+            ('_fee_percent',
+             forms.DecimalField(
+                 label=_('Additional fee'),
+                 help_text=_('Percentage'),
+                 required=False
+             )),
+        ])
 
     @property
     def checkout_form_fields(self) -> dict: