Openerp invoice merge

    def action_invoice_create(self, cursor, user, ids, journal_id=False,
            group=False, type='out_invoice', context=None):
        '''Return ids of created invoices for the pickings'''
        invoice_obj = self.pool.get('account.invoice')
        invoice_line_obj = self.pool.get('account.invoice.line')
        invoices_group = {}
        res = {}

        for picking in self.browse(cursor, user, ids, context=context):
            if picking.invoice_state != '2binvoiced':
                continue
            payment_term_id = False
            partner = picking.address_id and picking.address_id.partner_id
            if not partner:
                raise osv.except_osv(_('Error, no partner !'),
                    _('Please put a partner on the picking list if you want to generate invoice.'))

            if type in ('out_invoice', 'out_refund'):
                account_id = partner.property_account_receivable.id
                payment_term_id = self._get_payment_term(cursor, user, picking)
            else:
                account_id = partner.property_account_payable.id

            address_contact_id, address_invoice_id = \
                    self._get_address_invoice(cursor, user, picking).values()

            comment = self._get_comment_invoice(cursor, user, picking)
            if group and partner.id and payment_term_id invoices_group:
                invoice_id = invoices_group[partner.id]
                invoice = invoice_obj.browse(cursor, user, invoice_id)
                invoice_vals = {
                    'name': (invoice.name or '') + ', ' + (picking.name or ''),
                    'origin': (invoice.origin or '') + ', ' + (picking.name or '') + (picking.origin and (':' + picking.origin) or ''),
                    'comment': (comment and (invoice.comment and invoice.comment+"\n"+comment or comment)) or (invoice.comment and invoice.comment or ''),
                }
                invoice_obj.write(cursor, user, [invoice_id], invoice_vals, context=context)
            else:
                invoice_vals = {
                    'name': picking.name,
                    'origin': (picking.name or '') + (picking.origin and (':' + picking.origin) or ''),
                    'type': type,
                    'account_id': account_id,
                    'partner_id': partner.id,
                    'address_invoice_id': address_invoice_id,
                    'address_contact_id': address_contact_id,
                    'comment': comment,
                    'payment_term': payment_term_id,
                    'fiscal_position': partner.property_account_position.id
                    }
                cur_id = self.get_currency_id(cursor, user, picking)
                if cur_id:
                    invoice_vals['currency_id'] = cur_id
                if journal_id:
                    invoice_vals['journal_id'] = journal_id
                invoice_id = invoice_obj.create(cursor, user, invoice_vals,
                        context=context)
                invoices_group[partner.id] = invoice_id
            res[picking.id] = invoice_id
            for move_line in picking.move_lines:
                if move_line.state == 'cancel':
                    continue
                origin = move_line.picking_id.name
                if move_line.picking_id.origin:
                    origin += ':' + move_line.picking_id.origin
                if group:
                    name = (picking.name or '') + '-' + move_line.name
                else:
                    name = move_line.name

                if type in ('out_invoice', 'out_refund'):
                    account_id = move_line.product_id.product_tmpl_id.\
                            property_account_income.id
                    if not account_id:
                        account_id = move_line.product_id.categ_id.\
                                property_account_income_categ.id
                else:
                    account_id = move_line.product_id.product_tmpl_id.\
                            property_account_expense.id
                    if not account_id:
                        account_id = move_line.product_id.categ_id.\
                                property_account_expense_categ.id

                price_unit = self._get_price_unit_invoice(cursor, user,
                        move_line, type)
                discount = self._get_discount_invoice(cursor, user, move_line)
                discount1 = self._get_discount1_invoice(cursor, user, move_line)
                discount2 = self._get_discount2_invoice(cursor, user, move_line)
                discount3 = self._get_discount3_invoice(cursor, user, move_line)
                tax_ids = self._get_taxes_invoice(cursor, user, move_line, type)
                account_analytic_id = self._get_account_analytic_invoice(cursor,
                        user, picking, move_line)

                #set UoS if it's a sale and the picking doesn't have one
                uos_id = move_line.product_uos and move_line.product_uos.id or False
                if not uos_id and type in ('out_invoice', 'out_refund'):
                    uos_id = move_line.product_uom.id

#                print picking.origin
#                print picking.name
#                print move_line.customer_origin

                account_id = self.pool.get('account.fiscal.position').map_account(cursor, user, partner.property_account_position, account_id)
                invoice_line_id = invoice_line_obj.create(cursor, user, {
                    'name': name,
                    'origin': origin,
                    'invoice_id': invoice_id,
                    'uos_id': uos_id,
                    'product_id': move_line.product_id.id,
                    'account_id': account_id,
                    'price_unit': price_unit,
                    'discount': discount,
                    'discount1': discount1,
                    'discount2': discount2,
                    'discount3': discount3,
                    'sale_origin': picking.origin,
                    'ddt_origin': picking.name,
                    'customer_origin': move_line.customer_origin,
                    'quantity': move_line.product_uos_qty or move_line.product_qty,
                    'invoice_line_tax_id': [(6, 0, tax_ids)],
                    'account_analytic_id': account_analytic_id,
                    }, context=context)
                self._invoice_line_hook(cursor, user, move_line, invoice_line_id)

            invoice_obj.button_compute(cursor, user, [invoice_id], context=context,
                    set_total=(type in ('in_invoice', 'in_refund')))
            self.write(cursor, user, [picking.id], {
                'invoice_state': 'invoiced',
                }, context=context)
            self._invoice_hook(cursor, user, picking, invoice_id)
        self.write(cursor, user, res.keys(), {
            'invoice_state': 'invoiced',
            }, context=context)
        return res