/*
Copyright 2014 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 bearertoken

import (
	"errors"
	"net/http"
	"strings"

	"k8s.io/apiserver/pkg/authentication/authenticator"
	"k8s.io/apiserver/pkg/warning"
)

const (
	invalidTokenWithSpaceWarning = "the provided Authorization header contains extra space before the bearer token, and is ignored"
)

type Authenticator struct {
	auth authenticator.Token
}

func New(auth authenticator.Token) *Authenticator {
	return &Authenticator{auth}
}

var invalidToken = errors.New("invalid bearer token")

func (a *Authenticator) AuthenticateRequest(req *http.Request) (*authenticator.Response, bool, error) {
	auth := strings.TrimSpace(req.Header.Get("Authorization"))
	if auth == "" {
		return nil, false, nil
	}
	parts := strings.SplitN(auth, " ", 3)
	if len(parts) < 2 || strings.ToLower(parts[0]) != "bearer" {
		return nil, false, nil
	}

	token := parts[1]

	// Empty bearer tokens aren't valid
	if len(token) == 0 {
		// The space before the token case
		if len(parts) == 3 {
			warning.AddWarning(req.Context(), "", invalidTokenWithSpaceWarning)
		}
		return nil, false, nil
	}

	resp, ok, err := a.auth.AuthenticateToken(req.Context(), token)
	// if we authenticated successfully, go ahead and remove the bearer token so that no one
	// is ever tempted to use it inside of the API server
	if ok {
		req.Header.Del("Authorization")
	}

	// If the token authenticator didn't error, provide a default error
	if !ok && err == nil {
		err = invalidToken
	}

	return resp, ok, err
}