From 3e4e52b165b3379f6d85405e8dbc8d2463ef77dc Mon Sep 17 00:00:00 2001
From: Christopher Neugebauer <chrisjrn@gmail.com>
Date: Sun, 27 Mar 2016 14:41:43 +1100
Subject: [PATCH] Adds more constraints around payment and voiding of invoices

---
 registrasion/controllers/invoice.py | 21 ++++++++++++---
 registrasion/tests/test_invoice.py  | 41 +++++++++++++++++++++++++++--
 2 files changed, 56 insertions(+), 6 deletions(-)

diff --git a/registrasion/controllers/invoice.py b/registrasion/controllers/invoice.py
index 47765358..19da7525 100644
--- a/registrasion/controllers/invoice.py
+++ b/registrasion/controllers/invoice.py
@@ -1,5 +1,6 @@
 from decimal import Decimal
 from django.core.exceptions import ObjectDoesNotExist
+from django.core.exceptions import ValidationError
 from django.db.models import Sum
 
 from registrasion import models as rego
@@ -11,7 +12,7 @@ class InvoiceController(object):
 
     def __init__(self, invoice):
         self.invoice = invoice
-        self.update_validity() # Make sure this invoice is up-to-date
+        self.update_validity()  # Make sure this invoice is up-to-date
 
     @classmethod
     def for_cart(cls, cart):
@@ -21,13 +22,16 @@ class InvoiceController(object):
 
         try:
             invoice = rego.Invoice.objects.get(
-                cart=cart, cart_revision=cart.revision)
+                cart=cart,
+                cart_revision=cart.revision,
+                void=False,
+            )
         except ObjectDoesNotExist:
             cart_controller = CartController(cart)
             cart_controller.validate_cart()  # Raises ValidationError on fail.
 
             # Void past invoices for this cart
-            invoices = rego.Invoice.objects.filter(cart=cart).update(void=True)
+            rego.Invoice.objects.filter(cart=cart).update(void=True)
 
             invoice = cls._generate(cart)
 
@@ -104,7 +108,10 @@ class InvoiceController(object):
                 self.void()
 
     def void(self):
-        ''' Voids the invoice. '''
+        ''' Voids the invoice if it is valid to do so. '''
+        if self.invoice.paid:
+            raise ValidationError("Paid invoices cannot be voided, "
+                                  "only refunded.")
         self.invoice.void = True
         self.invoice.save()
 
@@ -117,6 +124,12 @@ class InvoiceController(object):
             cart = CartController(self.invoice.cart)
             cart.validate_cart()  # Raises ValidationError if invalid
 
+        if self.invoice.void:
+            raise ValidationError("Void invoices cannot be paid")
+
+        if self.invoice.paid:
+            raise ValidationError("Paid invoices cannot be paid again")
+
         ''' Adds a payment '''
         payment = rego.Payment.objects.create(
             invoice=self.invoice,
diff --git a/registrasion/tests/test_invoice.py b/registrasion/tests/test_invoice.py
index b3f80314..37265a2a 100644
--- a/registrasion/tests/test_invoice.py
+++ b/registrasion/tests/test_invoice.py
@@ -127,8 +127,45 @@ class InvoiceTestCase(RegistrationCartTestCase):
 
         # Viewing invoice_1's invoice should show it as void
         invoice_1_new = InvoiceController(invoice_1.invoice)
-        self.assertTrue(invoice_1.invoice.void)
+        self.assertTrue(invoice_1_new.invoice.void)
 
         # Viewing invoice_2's invoice should *not* show it as void
         invoice_2_new = InvoiceController(invoice_2.invoice)
-        self.assertFalse(invoice_2.invoice.void)
+        self.assertFalse(invoice_2_new.invoice.void)
+
+    def test_voiding_invoice_creates_new_invoice(self):
+        current_cart = CartController.for_user(self.USER_1)
+
+        # Should be able to create an invoice after the product is added
+        current_cart.add_to_cart(self.PROD_1, 1)
+        invoice_1 = InvoiceController.for_cart(current_cart.cart)
+
+        self.assertFalse(invoice_1.invoice.void)
+        invoice_1.void()
+
+        invoice_2 = InvoiceController.for_cart(current_cart.cart)
+        self.assertNotEqual(invoice_1.invoice, invoice_2.invoice)
+
+    def test_cannot_pay_void_invoice(self):
+        current_cart = CartController.for_user(self.USER_1)
+
+        # Should be able to create an invoice after the product is added
+        current_cart.add_to_cart(self.PROD_1, 1)
+        invoice_1 = InvoiceController.for_cart(current_cart.cart)
+
+        invoice_1.void()
+
+        with self.assertRaises(ValidationError):
+            invoice_1.pay("Reference", invoice_1.invoice.value)
+
+    def test_cannot_void_paid_invoice(self):
+        current_cart = CartController.for_user(self.USER_1)
+
+        # Should be able to create an invoice after the product is added
+        current_cart.add_to_cart(self.PROD_1, 1)
+        invoice_1 = InvoiceController.for_cart(current_cart.cart)
+
+        invoice_1.pay("Reference", invoice_1.invoice.value)
+
+        with self.assertRaises(ValidationError):
+            invoice_1.void()