from odoo import models, fields, api

class PurchaseOrderLine(models.Model):
    _inherit = 'purchase.order.line'

    @api.model_create_multi
    def create(self, vals_list):
        lines = super(PurchaseOrderLine, self).create(vals_list)
        for line in lines:
            if line.order_id:
                # Log creation
                msg = f"Line added: {line.product_id.display_name} (Qty: {line.product_qty})"
                line.order_id.message_post(body=msg)
        return lines

    def write(self, vals):
        # Capture old values for tracking
        changes = {}
        track_fields = ['product_id', 'product_qty']
        
        # Only track if relevant fields are being modified
        if any(f in vals for f in track_fields):
            for line in self:
                changes[line.id] = {
                    'product_id': line.product_id,
                    'product_qty': line.product_qty,
                }

        result = super(PurchaseOrderLine, self).write(vals)

        for line in self:
            if line.id in changes:
                old_data = changes[line.id]
                
                # Track Product Change
                if 'product_id' in vals:
                    new_product = line.product_id
                    old_product = old_data['product_id']
                    if old_product != new_product:
                        msg = f"Product changed on line: {old_product.display_name or 'None'} -> {new_product.display_name or 'None'}"
                        line.order_id.message_post(body=msg)
                
                # Track Quantity Change
                if 'product_qty' in vals:
                    new_qty = line.product_qty
                    old_qty = old_data['product_qty']
                    if old_qty != new_qty:
                        msg = f"Quantity changed for {line.product_id.display_name}: {old_qty} -> {new_qty}"
                        line.order_id.message_post(body=msg)
        
        return result

    def unlink(self):
        for line in self:
            if line.order_id and line.product_id:
                msg = f"Line removed: {line.product_id.display_name} (Qty: {line.product_qty})"
                line.order_id.message_post(body=msg)
        return super(PurchaseOrderLine, self).unlink()