[FIX] account_factux: discount taken only for gross price

How to reproduce the bug:

- Install the account app
- Get a FacturX invoice with a discount on item
- Upload the invoice
- Check that the price of the discounted item takes the
  discount into account

Bug:

If you want to upload a FacturX invoice that contains a discount,
Odoo will take the original price into account instead of the
discounted one.

opw-2705291

closes odoo/odoo#87126

X-original-commit: fc853c21
Signed-off-by: Adrien Minet <admi@odoo.com>
Signed-off-by: William André (wan) <wan@odoo.com>

addons/account_edi_facturx/models/account_edi_format.py

@@ -310,6 +310,24 @@ class AccountEdiFormat(models.Model):
                                 invoice_line_form.price_unit = float(line_elements[0].text) / float(quantity_elements[0].text)
                             else:
                                 invoice_line_form.price_unit = float(line_elements[0].text)
+                            # For Gross price, we need to check if a discount must be taken into account
+                            discount_elements = element.xpath('.//ram:AppliedTradeAllowanceCharge',
+                                                          namespaces=tree.nsmap)
+                            if discount_elements:
+                                discount_percent_elements = element.xpath(
+                                    './/ram:AppliedTradeAllowanceCharge/ram:CalculationPercent', namespaces=tree.nsmap)
+                                if discount_percent_elements:
+                                    invoice_line_form.discount = float(discount_percent_elements[0].text)
+                                else:
+                                    # if discount not available, it will be computed from the gross and net prices.
+                                    net_price_elements = element.xpath('.//ram:NetPriceProductTradePrice/ram:ChargeAmount',
+                                                                  namespaces=tree.nsmap)
+                                    if net_price_elements:
+                                        quantity_elements = element.xpath(
+                                            './/ram:NetPriceProductTradePrice/ram:BasisQuantity', namespaces=tree.nsmap)
+                                        net_unit_price = float(net_price_elements[0].text) / float(quantity_elements[0].text) \
+                                            if quantity_elements else float(net_price_elements[0].text)
+                                        invoice_line_form.discount = (invoice_line_form.price_unit - net_unit_price) / invoice_line_form.price_unit * 100.0
                         else:
                             line_elements = element.xpath('.//ram:NetPriceProductTradePrice/ram:ChargeAmount', namespaces=tree.nsmap)
                             if line_elements:
@@ -318,10 +336,6 @@ class AccountEdiFormat(models.Model):
                                     invoice_line_form.price_unit = float(line_elements[0].text) / float(quantity_elements[0].text)
                                 else:
                                     invoice_line_form.price_unit = float(line_elements[0].text)
-                        # Discount.
-                        line_elements = element.xpath('.//ram:AppliedTradeAllowanceCharge/ram:CalculationPercent', namespaces=tree.nsmap)
-                        if line_elements:
-                            invoice_line_form.discount = float(line_elements[0].text)
 
                         # Taxes
                         tax_element = element.xpath('.//ram:SpecifiedLineTradeSettlement/ram:ApplicableTradeTax/ram:RateApplicablePercent', namespaces=tree.nsmap)