Implements confirm method of gateway transaction

gateway.py

@@ -1,7 +1,10 @@
 # This file is part account_payment_gateway_invoice module for Tryton.
 # The COPYRIGHT file at the top level of this repository contains
 # the full copyright notices and license terms.
-from trytond.pool import PoolMeta
+from trytond.pool import Pool, PoolMeta
+
+from trytond.transaction import Transaction
+
 
 __all__ = ['AccountPaymentGatewayTransaction']
 __metaclass__ = PoolMeta
@@ -15,3 +18,49 @@ class AccountPaymentGatewayTransaction:
         res = super(AccountPaymentGatewayTransaction, cls)._get_origin()
         res.append('account.invoice')
         return res
+
+    @classmethod
+    def confirm(cls, transactions):
+        pool = Pool()
+        Invoice = pool.get('account.invoice')
+        PayInvoice = pool.get('account.invoice.pay', type='wizard')
+
+        to_update = []
+        for transaction in transactions:
+            if isinstance(transaction.origin, Invoice):
+                invoice = transaction.origin
+                Invoice.workflow_to_posted([invoice])
+                if not invoice.amount_to_pay:
+                    continue
+                with Transaction().set_context({'active_id': invoice.id}):
+                    session_id, _, _ = PayInvoice.create()
+                    pay_invoice = PayInvoice(session_id)
+                    pay_invoice.start.currency = transaction.currency
+                    pay_invoice.start.currency_digits = (transaction
+                        .currency_digits)
+                    pay_invoice.start.description = transaction.description
+                    pay_invoice.start.journal = transaction.gateway.journal
+                    pay_invoice.start.date = transaction.date
+                    pay_invoice.start.amount = transaction.amount
+                    if invoice.total_amount != transaction.amount:
+                        min_percent_writeoff = invoice.total_amount * (1 -
+                            transaction.gateway.writeoff_amount_percent)
+                        max_percent_writeoff = invoice.total_amount * (1 +
+                            transaction.gateway.writeoff_amount_percent)
+                        [setattr(pay_invoice.ask, f, v)
+                            for f, v in pay_invoice.default_ask(None)
+                                .iteritems()]
+
+                        if (min_percent_writeoff < transaction.amount <
+                                max_percent_writeoff
+                                or transaction.amount > invoice.amount_to_pay):
+                            pay_invoice.ask.type = 'writeoff'
+                            pay_invoice.ask.journal_writeoff = (transaction
+                                .gateway.journal_writeoff)
+                        else:
+                            pay_invoice.ask.type = 'partial'
+                        pay_invoice.transition_pay()
+                    PayInvoice.delete(session_id)
+                to_update.append(transaction)
+
+        super(AccountPaymentGatewayTransaction, cls).confirm(to_update)

invoice.py

@@ -31,3 +31,8 @@ class Invoice:
                     if transaction.origin == invoice:
                         result[name][invoice.id] += transaction.amount
         return result
+
+    @classmethod
+    def workflow_to_posted(cls, invoices):
+        cls.validate_invoice(invoices)
+        cls.post(invoices)