From 94b7a8676a94a454e1b21eb46eac447f2b68d2ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Krier?= <ced@b2ck.com>
Date: Thu, 15 Jan 2015 23:40:42 +0100
Subject: [PATCH] Add reverse_compute on Tax

issue4444
review6801002
---
 CHANGELOG             |  1 +
 tax.py                | 52 +++++++++++++++++++++++++++++++++++++++++--
 tests/test_account.py | 29 +++++++++++++++++++++++-
 3 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index b0d930b2b1..891a859e8d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Add reverse_compute on Tax
 * Add fix_party script
 * Allow to display only the balance in the General Ledger
 * Add TaxableMixin
diff --git a/tax.py b/tax.py
index 5ccb44d163..438861d589 100644
--- a/tax.py
+++ b/tax.py
@@ -788,11 +788,47 @@ class Tax(ModelSQL, ModelView):
         return res
 
     @classmethod
-    def sort_taxes(cls, taxes):
+    def _reverse_rate_amount(cls, taxes, date):
+        rate = None
+        amount = 0
+        for tax in taxes:
+            start_date = tax.start_date or datetime.date.min
+            end_date = tax.end_date or datetime.date.max
+            if not (start_date <= date <= end_date):
+                continue
+
+            if tax.type == 'percentage':
+                if rate is None:
+                    rate = tax.rate
+                else:
+                    rate *= tax.rate
+            elif tax.type == 'fixed':
+                amount += tax.amount
+
+            if tax.childs:
+                child_rate, child_amount = cls._reverse_rate_amount(
+                    tax.childs, date)
+                if rate is None:
+                    rate = child_rate
+                else:
+                    rate *= child_rate
+                amount += child_amount
+        return rate, amount
+
+    @classmethod
+    def _reverse_unit_compute(cls, price_unit, taxes, date):
+        rate, amount = cls._reverse_rate_amount(taxes, date)
+        price_unit -= amount
+        if rate is not None:
+            price_unit = price_unit / (1 + rate)
+        return price_unit
+
+    @classmethod
+    def sort_taxes(cls, taxes, reverse=False):
         '''
         Return a list of taxes sorted
         '''
-        return sorted(taxes, key=lambda t: (t.sequence, t.id))
+        return sorted(taxes, key=lambda t: (t.sequence, t.id), reverse=reverse)
 
     @classmethod
     def compute(cls, taxes, price_unit, quantity, date=None):
@@ -815,6 +851,18 @@ class Tax(ModelSQL, ModelView):
             row['amount'] *= quantity
         return res
 
+    @classmethod
+    def reverse_compute(cls, price_unit, taxes, date=None):
+        '''
+        Reverse compute the price_unit for taxes at the date.
+        '''
+        pool = Pool()
+        Date = pool.get('ir.date')
+        if date is None:
+            date = Date.today()
+        taxes = cls.sort_taxes(taxes, reverse=True)
+        return cls._reverse_unit_compute(price_unit, taxes, date)
+
     def update_tax(self, template2tax_code, template2account,
             template2tax=None):
         '''
diff --git a/tests/test_account.py b/tests/test_account.py
index 1ce6224b60..997f9ae1bf 100644
--- a/tests/test_account.py
+++ b/tests/test_account.py
@@ -329,7 +329,7 @@ class AccountTestCase(unittest.TestCase):
             transaction.cursor.rollback()
 
     def test0040tax_compute(self):
-        'Test tax compute'
+        'Test tax compute/reverse_compute'
         with Transaction().start(DB_NAME, USER, context=CONTEXT):
             today = datetime.date.today()
 
@@ -372,6 +372,10 @@ class AccountTestCase(unittest.TestCase):
                         'tax': child2,
                         }])
 
+            self.assertEqual(
+                self.tax.reverse_compute(Decimal('130'), [tax]),
+                Decimal('100'))
+
             child1.end_date = today + relativedelta(days=5)
             child1.save()
             self.assertEqual(self.tax.compute([tax], Decimal('100'), 2, today),
@@ -385,6 +389,10 @@ class AccountTestCase(unittest.TestCase):
                         'tax': child2,
                         }])
 
+            self.assertEqual(
+                self.tax.reverse_compute(Decimal('130'), [tax], today),
+                Decimal('100'))
+
             child1.start_date = today + relativedelta(days=1)
             child1.save()
             self.assertEqual(self.tax.compute([tax], Decimal('100'), 2, today),
@@ -393,6 +401,9 @@ class AccountTestCase(unittest.TestCase):
                         'amount': Decimal('20'),
                         'tax': child2,
                         }])
+            self.assertEqual(
+                self.tax.reverse_compute(Decimal('110'), [tax], today),
+                Decimal('100'))
             self.assertEqual(self.tax.compute([tax], Decimal('100'), 2,
                     today + relativedelta(days=1)), [{
                         'base': Decimal('200'),
@@ -403,6 +414,10 @@ class AccountTestCase(unittest.TestCase):
                         'amount': Decimal('20'),
                         'tax': child2,
                         }])
+            self.assertEqual(
+                self.tax.reverse_compute(
+                    Decimal('130'), [tax], today + relativedelta(days=1)),
+                Decimal('100'))
             self.assertEqual(self.tax.compute([tax], Decimal('100'), 2,
                     today + relativedelta(days=5)), [{
                         'base': Decimal('200'),
@@ -413,12 +428,20 @@ class AccountTestCase(unittest.TestCase):
                         'amount': Decimal('20'),
                         'tax': child2,
                         }])
+            self.assertEqual(
+                self.tax.reverse_compute(Decimal('130'), [tax],
+                    today + relativedelta(days=5)),
+                Decimal('100'))
             self.assertEqual(self.tax.compute([tax], Decimal('100'), 2,
                     today + relativedelta(days=6)), [{
                         'base': Decimal('200'),
                         'amount': Decimal('20'),
                         'tax': child2,
                         }])
+            self.assertEqual(
+                self.tax.reverse_compute(Decimal('110'), [tax],
+                    today + relativedelta(days=6)),
+                Decimal('100'))
 
             child1.end_date = None
             child1.save()
@@ -432,6 +455,10 @@ class AccountTestCase(unittest.TestCase):
                         'amount': Decimal('20'),
                         'tax': child2,
                         }])
+            self.assertEqual(
+                self.tax.reverse_compute(Decimal('130'), [tax],
+                    today + relativedelta(days=6)),
+                Decimal('100'))
 
 
 def suite():