public function is_transaction_valid_post()
 {
     $main_id = $this->input->post('mainId');
     $branch_id = $this->input->post('branchId');
     $delivery_id_from_main = $this->input->post('deliveryIdFromMain');
     $transaction = $this->input->post('transaction');
     $settings_repo = new Settings_Repository($this->base_model->get_db_instance());
     $deliveries_repo = new Deliveries_Repository($this->base_model->get_db_instance());
     if ($transaction == Transaction_Type::Deliver_Items) {
         if ($settings_repo->get_settings()->main_id != $main_id) {
             echo -2;
         } else {
             if ($settings_repo->get_settings()->app_id != $branch_id) {
                 echo -1;
             } else {
                 if ($deliveries_repo->delivery_exists_via_delivery_id_from_main($delivery_id_from_main)) {
                     echo 0;
                 } else {
                     echo 2;
                 }
             }
         }
         // valid delivery
     } else {
         echo 1;
         // invalid transaction
     }
 }