book: view zeigt in listansicht bei unterkonten in fremdwährung

den korrekten wert,
book-form: feld für saldo in unternehmens-währung

book.py

@@ -11,8 +11,10 @@ from trytond.transaction import Transaction
 from trytond.pool import Pool
 from trytond.report import Report
 from decimal import Decimal
+from sql import Literal
 from sql.aggregate import Sum
-from sql.conditionals import Case
+from sql.conditionals import Case, Coalesce
+from sql.functions import CurrentDate
 from .model import order_name_hierarchical
 
 
@@ -103,15 +105,29 @@ class Book(tree(separator='/'), Workflow, ModelSQL, ModelView):
     balance = fields.Function(fields.Numeric(string='Balance', readonly=True,
         digits=(16, Eval('currency_digits', 2)),
         depends=['currency_digits']), 'on_change_with_balance')
-    currency = fields.Many2One(string='Currency',
-        model_name='currency.currency',
+
+    balance_ref = fields.Function(fields.Numeric(string='Balance (Ref.)',
+        help='Balance in company currency',
+        readonly=True, digits=(16, Eval('company_currency_digits', 2)),
+        states={
+            'invisible': ~Bool(Eval('company_currency')),
+        }, depends=['company_currency_digits', 'company_currency']),
+        'on_change_with_balance_ref')
+    company_currency = fields.Function(fields.Many2One(readonly=True,
+        string='Company Currency', states={'invisible': True},
+        model_name='currency.currency'),
+        'on_change_with_company_currency')
+    company_currency_digits = fields.Function(fields.Integer(
+        string='Currency Digits (Ref.)', readonly=True),
+        'on_change_with_currency_digits')
+
+    currency = fields.Many2One(string='Currency', select=True,
+        model_name='currency.currency', readonly=True,
         states={
             'readonly': Or(
                 STATES2['readonly'],
                 Bool(Eval('lines', [])),
                 ),
-            'invisible': STATES2['invisible'],
-            'required': ~STATES2['invisible'],
         }, depends=DEPENDS2+['lines'])
     currency_digits = fields.Function(fields.Integer(string='Currency Digits',
         readonly=True), 'on_change_with_currency_digits')
@@ -255,36 +271,95 @@ class Book(tree(separator='/'), Workflow, ModelSQL, ModelView):
         else:
             return 2
 
+    @fields.depends('company', 'currency', 'btype')
+    def on_change_with_company_currency(self, name=None):
+        """ get company-currency if its different from current
+            cashbook-currency, disable if book is a view
+        """
+        if self.company:
+            if self.currency:
+                if self.btype:
+                    if self.company.currency.id != self.currency.id:
+                        return self.company.currency.id
+
     @fields.depends('id')
     def on_change_with_balance(self, name=None):
         """ compute balance
         """
         pool = Pool()
         Book2 = pool.get('cashbook.book')
+        Book3 = pool.get('cashbook.book')
         Line = pool.get('cashbook.line')
+        Currency = pool.get('currency.currency')
+
         tab_line = Line.__table__()
+        tab_book = Book3.__table__()
         cursor = Transaction().connection.cursor()
 
+        # select cashbook-lines from current cashbook and below
         line_query = Line.search([
                 ('cashbook.id', 'in', Book2.search([
                         ('parent', 'child_of', [self.id]),
                     ], query=True)),
             ], query=True)
 
-        query = line_query.join(tab_line,
+        # sum lines by currency
+        bal_by_currency = line_query.join(tab_line,
                 condition=tab_line.id==line_query.id,
+            ).join(tab_book,
+                condition=tab_book.id==tab_line.cashbook,
             ).select(
                 Sum(tab_line.credit - tab_line.debit).as_('balance'),
+                tab_book.currency,
+                group_by=[tab_book.currency],
+            )
+
+        if self.id:
+            total = Decimal('0.0')
+
+            cursor.execute(*bal_by_currency)
+            balance_lines = cursor.fetchall()
+
+            for line in balance_lines:
+                (balance, id_currency) = line
+
+                total += Currency.compute(
+                        Currency(id_currency),  # from
+                        balance,
+                        self.currency, # to
+                    )
+            return total
+
+    @fields.depends('company', 'currency', 'id', 'btype')
+    def on_change_with_balance_ref(self, name=None):
+        """ balance converted to company-currency
+        """
+        pool = Pool()
+        Line = pool.get('cashbook.line')
+        tab_line = Line.__table__()
+        cursor = Transaction().connection.cursor()
+
+        if self.btype is None:
+            return None
+
+        query = tab_line.select(
+                Sum(tab_line.credit - tab_line.debit),
+                where = tab_line.cashbook == self.id,
             )
 
         if self.id:
-            balance = Decimal('0.0')
             cursor.execute(*query)
             result = cursor.fetchone()
+            balance = Decimal('0.0')
             if result:
                 if result[0] is not None:
                     balance += result[0]
-            return balance
+            if self.currency:
+                return self.currency.compute(
+                        self.currency,          # from
+                        balance,
+                        self.company.currency   # to
+                    )
 
     @classmethod
     @ModelView.button