/*
Copyright 2014 The Kubernetes Authors All rights reserved.

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 serviceaccount

import (
	"fmt"
	"strings"

	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/api/validation"
	"k8s.io/kubernetes/pkg/auth/user"
)

const (
	ServiceAccountUsernamePrefix    = "system:serviceaccount:"
	ServiceAccountUsernameSeparator = ":"
	ServiceAccountGroupPrefix       = "system:serviceaccounts:"
	AllServiceAccountsGroup         = "system:serviceaccounts"
)

// MakeUsername generates a username from the given namespace and ServiceAccount name.
// The resulting username can be passed to SplitUsername to extract the original namespace and ServiceAccount name.
func MakeUsername(namespace, name string) string {
	return ServiceAccountUsernamePrefix + namespace + ServiceAccountUsernameSeparator + name
}

var invalidUsernameErr = fmt.Errorf("Username must be in the form %s", MakeUsername("namespace", "name"))

// SplitUsername returns the namespace and ServiceAccount name embedded in the given username,
// or an error if the username is not a valid name produced by MakeUsername
func SplitUsername(username string) (string, string, error) {
	if !strings.HasPrefix(username, ServiceAccountUsernamePrefix) {
		return "", "", invalidUsernameErr
	}
	trimmed := strings.TrimPrefix(username, ServiceAccountUsernamePrefix)
	parts := strings.Split(trimmed, ServiceAccountUsernameSeparator)
	if len(parts) != 2 {
		return "", "", invalidUsernameErr
	}
	namespace, name := parts[0], parts[1]
	if len(validation.ValidateNamespaceName(namespace, false)) != 0 {
		return "", "", invalidUsernameErr
	}
	if len(validation.ValidateServiceAccountName(name, false)) != 0 {
		return "", "", invalidUsernameErr
	}
	return namespace, name, nil
}

// MakeGroupNames generates service account group names for the given namespace and ServiceAccount name
func MakeGroupNames(namespace, name string) []string {
	return []string{
		AllServiceAccountsGroup,
		MakeNamespaceGroupName(namespace),
	}
}

// MakeNamespaceGroupName returns the name of the group all service accounts in the namespace are included in
func MakeNamespaceGroupName(namespace string) string {
	return ServiceAccountGroupPrefix + namespace
}

// UserInfo returns a user.Info interface for the given namespace, service account name and UID
func UserInfo(namespace, name, uid string) user.Info {
	return &user.DefaultInfo{
		Name:   MakeUsername(namespace, name),
		UID:    uid,
		Groups: MakeGroupNames(namespace, name),
	}
}

// IsServiceAccountToken returns true if the secret is a valid api token for the service account
func IsServiceAccountToken(secret *api.Secret, sa *api.ServiceAccount) bool {
	if secret.Type != api.SecretTypeServiceAccountToken {
		return false
	}

	name := secret.Annotations[api.ServiceAccountNameKey]
	uid := secret.Annotations[api.ServiceAccountUIDKey]
	if name != sa.Name {
		// Name must match
		return false
	}
	if len(uid) > 0 && uid != string(sa.UID) {
		// If UID is specified, it must match
		return false
	}

	return true
}
