use IPPError in Response CheckForError method

error.go

@@ -2,6 +2,7 @@ package ipp
 
 import "fmt"
 
+// check a given error whether a printer or class does not exist
 func IsNotExistsError(err error) bool {
 	if err == nil {
 		return false
@@ -10,6 +11,7 @@ func IsNotExistsError(err error) bool {
 	return err.Error() == "The printer or class does not exist."
 }
 
+//non ok ipp status codes
 type IPPError struct {
 	Status  int16
 	Message string
@@ -19,6 +21,7 @@ func (e IPPError) Error() string {
 	return fmt.Sprintf("ipp status: %d, message: %s", e.Status, e.Message)
 }
 
+// non 200 http codes
 type HTTPError struct {
 	Code int
 }

ipp-client.go

@@ -119,19 +119,8 @@ func (c *IPPClient) SendRequest(url string, req *Request, additionalResponseData
 		return nil, err
 	}
 
-	if resp.StatusCode == StatusOk {
-		return resp, nil
-	}
-
-	msg := ""
-	if statusMessage, ok := resp.OperationAttributes[AttributeStatusMessage]; ok {
-		msg = statusMessage[0].Value.(string)
-	}
-
-	return resp, IPPError{
-		Status:  resp.StatusCode,
-		Message: msg,
-	}
+	err = resp.CheckForErrors()
+	return resp, err
 }
 
 // Print one or more `Document`s using IPP `Create-Job` followed by `Send-Document` request(s).

response.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"encoding/binary"
 	"errors"
-	"fmt"
 	"io"
 )
 
@@ -23,12 +22,17 @@ type Response struct {
 }
 
 func (r *Response) CheckForErrors() error {
-	if r.StatusCode != 0 {
-		if len(r.OperationAttributes["status-message"]) == 0 {
-			return fmt.Errorf("ipp server return error code %d but no status message", r.StatusCode)
+	if r.StatusCode != StatusOk {
+		err := IPPError{
+			Status:  r.StatusCode,
+			Message: "no status message returned",
 		}
 
-		return errors.New(r.OperationAttributes["status-message"][0].Value.(string))
+		if len(r.OperationAttributes["status-message"]) > 0 {
+			err.Message = r.OperationAttributes["status-message"][0].Value.(string)
+		}
+
+		return err
 	}
 
 	return nil