from odoo import models, fields, api, _
from odoo.exceptions import UserError

class PosOrder(models.Model):
    _inherit = 'pos.order'

    payer_id = fields.Many2one('hr.employee', string='Cashier', help='Employee who processed the payment')
    
    # Existing Odoo/POS fields renamed for clarity
    user_id = fields.Many2one('res.users', string='Session User', help='Odoo user who opened the session')
    employee_id = fields.Many2one('hr.employee', string='Order Taker', help='Employee who uses the cash register')

    def _refund(self):
        for order in self:
            if order.state == 'cancel':
                raise UserError(_("You cannot refund a cancelled order."))
        return super()._refund()

    @api.model
    def _process_order(self, order, existing_order):
        res = super()._process_order(order, existing_order)
        pos_order = self.browse(res)
        if pos_order.state in ['paid', 'done', 'invoiced'] and not pos_order.payer_id:
            if pos_order.employee_id:
                pos_order.write({'payer_id': pos_order.employee_id.id})
            elif pos_order.session_id.user_id.employee_id:
                pos_order.write({'payer_id': pos_order.session_id.user_id.employee_id.id})
            else:
                employee = self.env['hr.employee'].sudo().search([('user_id', '=', pos_order.user_id.id)], limit=1)
                if employee:
                    pos_order.write({'payer_id': employee.id})
        return res