return NULL;
}
+ /**
+ * Get an array of the fields that can be edited on the recurring contribution.
+ *
+ * Some payment processors support editing the amount and other scheduling details of recurring payments, especially
+ * those which use tokens. Others are fixed. This function allows the processor to return an array of the fields that
+ * can be updated from the contribution recur edit screen.
+ *
+ * The fields are likely to be a subset of these
+ * - 'amount',
+ * - 'installments',
+ * - 'frequency_interval',
+ * - 'frequency_unit',
+ * - 'cycle_day',
+ * - 'next_sched_contribution_date',
+ * - 'end_date',
+ * - 'failure_retry_day',
+ *
+ * The form does not restrict which fields from the contribution_recur table can be added (although if the html_type
+ * metadata is not defined in the xml for the field it will cause an error.
+ *
+ * Open question - would it make sense to return membership_id in this - which is sometimes editable and is on that
+ * form (UpdateSubscription).
+ *
+ * @return array
+ */
+ public function getEditableRecurringScheduleFields() {
+ return array('amount', 'next_sched_contribution_date');
+ }
+
}