handler.go

// Copyright 2017 The Kubernetes Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package errors

import (
	"log"
	"net/http"

	restful "github.com/emicklei/go-restful"
	"k8s.io/apimachinery/pkg/api/errors"
)

// NonCriticalErrors is an array of error statuses, that are non-critical. That means, that this error can be
// silenced and displayed to the user as a warning on the frontend side.
var NonCriticalErrors = []int32{http.StatusForbidden, http.StatusUnauthorized}

// HandleError handles single error, that occurred during API GET call. If it is not critical, then it will be
// returned as a part of error array. Otherwise, it will be returned as a second value. Usage of this functions
// allows to distinguish critical errors from non-critical ones. It is needed to handle them in a different way.
func HandleError(err error) ([]error, error) {
	nonCriticalErrors := make([]error, 0)
	return AppendError(err, nonCriticalErrors)
}

// AppendError handles single error, that occurred during API GET call. If it is not critical, then it will be
// returned as a part of error array. Otherwise, it will be returned as a second value. Usage of this functions
// allows to distinguish critical errors from non-critical ones. It is needed to handle them in a different way.
func AppendError(err error, nonCriticalErrors []error) ([]error, error) {
	if err != nil {
		if isErrorCritical(err) {
			return nonCriticalErrors, LocalizeError(err)
		} else {
			log.Printf("Non-critical error occurred during resource retrieval: %s", err)
			nonCriticalErrors = appendMissing(nonCriticalErrors, LocalizeError(err))
		}
	}
	return nonCriticalErrors, nil
}

// MergeErrors merges multiple non-critical error arrays into one array.
func MergeErrors(errorArraysToMerge ...[]error) (mergedErrors []error) {
	for _, errorArray := range errorArraysToMerge {
		mergedErrors = appendMissing(mergedErrors, errorArray...)
	}
	return
}

func isErrorCritical(err error) bool {
	status, ok := err.(*errors.StatusError)
	if !ok {
		// Assume, that error is critical if it cannot be mapped.
		return true
	}
	return !contains(NonCriticalErrors, status.ErrStatus.Code)
}

func appendMissing(slice []error, toAppend ...error) []error {
	m := make(map[string]bool, 0)

	for _, s := range slice {
		m[s.Error()] = true
	}

	for _, a := range toAppend {
		_, ok := m[a.Error()]
		if !ok {
			slice = append(slice, a)
			m[a.Error()] = true
		}
	}

	return slice
}

func contains(s []int32, e int32) bool {
	for _, a := range s {
		if a == e {
			return true
		}
	}
	return false
}

// IsForbiddenError returns true if given error has code 403, false otherwise.
func IsForbiddenError(err error) bool {
	status, ok := err.(*errors.StatusError)
	if !ok {
		return false
	}

	return status.ErrStatus.Code == http.StatusForbidden
}

// IsNotFoundError returns true when the given error is 404-NotFound error.
func IsNotFoundError(err error) bool {
	status, ok := err.(*errors.StatusError)
	if !ok {
		return false
	}

	return status.ErrStatus.Code == http.StatusNotFound
}

// HandleInternalError writes the given error to the response and sets appropriate HTTP status headers.
func HandleInternalError(response *restful.Response, err error) {
	log.Print(err)
	statusCode := http.StatusInternalServerError
	statusError, ok := err.(*errors.StatusError)
	if ok && statusError.Status().Code > 0 {
		statusCode = int(statusError.Status().Code)
	}
	response.AddHeader("Content-Type", "text/plain")
	response.WriteErrorString(statusCode, err.Error()+"\n")
}

// Handle HTTP Errors more accurately based on the localized consts
func HandleHTTPError(err error) int {
	if err == nil {
		return http.StatusInternalServerError
	}
	if err.Error() == MSG_TOKEN_EXPIRED_ERROR || err.Error() == MSG_LOGIN_UNAUTHORIZED_ERROR || err.Error() == MSG_ENCRYPTION_KEY_CHANGED {
		return http.StatusUnauthorized
	}
	return http.StatusInternalServerError
}