[IMP] purchase: add global discount support on RFQ lines

purchase_discount/__init__.py

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+from . import wizard

purchase_discount/__manifest__.py

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+{
+    "name": "purchase discount",
+    "version": "1.0.0",
+    "depends": ["base", "purchase"],
+    "author": "Mehul Kotak",
+    "category": "Task-1",
+    "description": "This perfrom global discount in purchase",
+    "license": "LGPL-3",
+    "auto_install": True,
+    "installable": True,
+    "data": [
+        "security/ir.model.access.csv",
+        "wizard/purchase_order_discount.xml",
+        "views/purchase_order_view.xml",
+    ],
+}

purchase_discount/security/ir.model.access.csv

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+id,name,model_id:id,group_id:id,perm_read,perm_write,perm_create,perm_unlink
+access_purchase_order_discount,access_purchase_order_discount,model_purchase_order_discount,purchase.group_purchase_user,1,1,1,1

purchase_discount/views/purchase_order_view.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<odoo>
+    <record id="view_purchase_order_form" model="ir.ui.view">
+        <field name="name">purchase.order.view.form.discount</field>
+        <field name="model">purchase.order</field>
+        <field name="inherit_id" ref="purchase.purchase_order_form"/>
+        <field name="arch" type="xml">
+            <xpath expr="//field[@name='order_line']" position="after">
+                <div class="d-flex justify-content-end mt-2 mb-2">
+                    <button string="Discount" name="%(purchase_discount.action_purchase_order_discount)d" type="action" class="btn btn-secondary"/>
+                </div>
+            </xpath>
+        </field>
+    </record>
+</odoo>
+

purchase_discount/wizard/__init__.py

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+from . import purchase_order_discount

purchase_discount/wizard/purchase_order_discount.py

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+from odoo import models, fields, api
+from odoo.exceptions import UserError, ValidationError
+
+
+class PurchaseOrderDiscount(models.TransientModel):
+    _name = "purchase.order.discount"
+    _description = "Apply Global Discount on Purchase Order"
+
+    discount = fields.Float(string="discount", required=True)
+    discount_type = fields.Selection(
+        [("amount", "$"), ("percent", "%")],
+        default="percent",
+        string="Discount Type",
+        required=True,
+    )
+    discount_percent = fields.Float(
+        compute="_calculate_percentage", string="Calculated Percentage"
+    )
+    order_id = fields.Many2one(
+        "purchase.order",
+        string="Purchase Order",
+        required=True,
+    )
+
+    @api.constrains("discount", "discount_type")
+    def _check_discount_limit(self):
+        if (
+            self.discount < 0 or self.discount > 100
+        ) and self.discount_type == "percent":
+            raise ValidationError("Discount value is invalid")
+
+    def _get_base_untaxed_amount(self, order):
+        total = 0.0
+        for line in order.order_line:
+            total += line.price_unit * line.product_qty
+        return total
+
+    @api.depends("discount", "discount_type")
+    def _calculate_percentage(self):
+        base_amount = self._get_base_untaxed_amount(self.order_id)
+        if self.discount_type == "percent":
+            self.discount_percent = self.discount
+        elif base_amount > 0:
+            self.discount_percent = (self.discount * 100) / base_amount
+        else:
+            self.discount_percent = 0
+
+    def action_apply_discount(self):
+        self.ensure_one()
+        if not self.order_id.order_line:
+            raise UserError("There are no lines on this order to discount.")
+
+        base_amount = self._get_base_untaxed_amount(self.order_id)
+
+        if self.discount_type == "percent":
+            target_discount = self.discount
+        else:
+            if base_amount <= 0:
+                raise UserError("Cannot apply an amount discount to a $0 order.")
+            target_discount = (self.discount * 100) / base_amount
+
+        # Final check to ensure calculated amount doesn't exceed 100%
+        if target_discount > 100:
+            raise UserError("The discount amount exceeds the total value of the order.")
+
+        self.order_id.order_line.write({"discount": target_discount})

purchase_discount/wizard/purchase_order_discount.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<odoo>
+
+    <record id="action_purchase_order_discount" model="ir.actions.act_window">
+        <field name="name">Discount</field>
+        <field name="res_model">purchase.order.discount</field>
+        <field name="view_mode">form</field>
+        <field name="target">new</field>
+        <field name="context">{'default_order_id': active_id}</field>
+    </record>
+
+    <record id="purchase_order_line_wizard_form" model="ir.ui.view">
+        <field name="name">purchase.order.discount.form</field>
+        <field name="model">purchase.order.discount</field>
+        <field name="arch" type="xml">
+            <form>
+                <sheet>
+                    <group>
+                        <div class="d-flex align-items-center gap-2">
+                            <label for="discount" string="Discount"/>
+                            <div class="col-1">
+                                <field name="discount"/>
+                            </div>
+                            <div class="col-1">
+                                <field name="discount_type" nolabel="1"/>
+                            </div>
+                            <span class="text-muted" invisible="discount_type =='percent'">
+ (
+                                <field name="discount_percent" nolabel="1" class="w-auto d-inline"/>
+    %
+    )    
+                            </span>
+                        </div>
+                    </group>
+                    <footer>
+                        <button name="action_apply_discount" string="Apply" type="object" class="btn btn-primary"/>
+                        <button special="cancel" string="Discard" class="btn btn-secondary" data-hotkey="x"/>
+                    </footer>
+                </sheet>
+            </form>
+        </field>
+    </record>
+
+</odoo>