/*
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"
	"time"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/client/cache"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/controller/framework"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/fields"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/labels"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/registry/secret"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/util"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
	"github.com/golang/glog"
)

// TokensControllerOptions contains options for the TokensController
type TokensControllerOptions struct {
	// TokenGenerator is the generator to use to create new tokens
	TokenGenerator TokenGenerator
	// ServiceAccountResync is the time.Duration at which to fully re-list service accounts.
	// If zero, re-list will be delayed as long as possible
	ServiceAccountResync time.Duration
	// SecretResync is the time.Duration at which to fully re-list secrets.
	// If zero, re-list will be delayed as long as possible
	SecretResync time.Duration
}

// DefaultTokenControllerOptions returns
func DefaultTokenControllerOptions(tokenGenerator TokenGenerator) TokensControllerOptions {
	return TokensControllerOptions{TokenGenerator: tokenGenerator}
}

// NewTokensController returns a new *TokensController.
func NewTokensController(cl client.Interface, options TokensControllerOptions) *TokensController {
	e := &TokensController{
		client: cl,
		token:  options.TokenGenerator,
	}

	e.serviceAccounts, e.serviceAccountController = framework.NewIndexerInformer(
		&cache.ListWatch{
			ListFunc: func() (runtime.Object, error) {
				return e.client.ServiceAccounts(api.NamespaceAll).List(labels.Everything(), fields.Everything())
			},
			WatchFunc: func(rv string) (watch.Interface, error) {
				return e.client.ServiceAccounts(api.NamespaceAll).Watch(labels.Everything(), fields.Everything(), rv)
			},
		},
		&api.ServiceAccount{},
		options.ServiceAccountResync,
		framework.ResourceEventHandlerFuncs{
			AddFunc:    e.serviceAccountAdded,
			UpdateFunc: e.serviceAccountUpdated,
			DeleteFunc: e.serviceAccountDeleted,
		},
		cache.Indexers{"namespace": cache.MetaNamespaceIndexFunc},
	)

	tokenSelector := fields.SelectorFromSet(map[string]string{client.SecretType: string(api.SecretTypeServiceAccountToken)})
	e.secrets, e.secretController = framework.NewIndexerInformer(
		&cache.ListWatch{
			ListFunc: func() (runtime.Object, error) {
				return e.client.Secrets(api.NamespaceAll).List(labels.Everything(), tokenSelector)
			},
			WatchFunc: func(rv string) (watch.Interface, error) {
				return e.client.Secrets(api.NamespaceAll).Watch(labels.Everything(), tokenSelector, rv)
			},
		},
		&api.Secret{},
		options.SecretResync,
		framework.ResourceEventHandlerFuncs{
			AddFunc:    e.secretAdded,
			UpdateFunc: e.secretUpdated,
			DeleteFunc: e.secretDeleted,
		},
		cache.Indexers{"namespace": cache.MetaNamespaceIndexFunc},
	)

	return e
}

// TokensController manages ServiceAccountToken secrets for ServiceAccount objects
type TokensController struct {
	stopChan chan struct{}

	client client.Interface
	token  TokenGenerator

	serviceAccounts cache.Indexer
	secrets         cache.Indexer

	// Since we join two objects, we'll watch both of them with controllers.
	serviceAccountController *framework.Controller
	secretController         *framework.Controller
}

// Runs controller loops and returns immediately
func (e *TokensController) Run() {
	if e.stopChan == nil {
		e.stopChan = make(chan struct{})
		go e.serviceAccountController.Run(e.stopChan)
		go e.secretController.Run(e.stopChan)
	}
}

// Stop gracefully shuts down this controller
func (e *TokensController) Stop() {
	if e.stopChan != nil {
		close(e.stopChan)
		e.stopChan = nil
	}
}

// serviceAccountAdded reacts to a ServiceAccount creation by creating a corresponding ServiceAccountToken Secret
func (e *TokensController) serviceAccountAdded(obj interface{}) {
	serviceAccount := obj.(*api.ServiceAccount)
	err := e.createSecretIfNeeded(serviceAccount)
	if err != nil {
		glog.Error(err)
	}
}

// serviceAccountUpdated reacts to a ServiceAccount update (or re-list) by ensuring a corresponding ServiceAccountToken Secret exists
func (e *TokensController) serviceAccountUpdated(oldObj interface{}, newObj interface{}) {
	newServiceAccount := newObj.(*api.ServiceAccount)
	err := e.createSecretIfNeeded(newServiceAccount)
	if err != nil {
		glog.Error(err)
	}
}

// serviceAccountDeleted reacts to a ServiceAccount deletion by deleting all corresponding ServiceAccountToken Secrets
func (e *TokensController) serviceAccountDeleted(obj interface{}) {
	serviceAccount, ok := obj.(*api.ServiceAccount)
	if !ok {
		// Unknown type. If we missed a ServiceAccount deletion, the
		// corresponding secrets will be cleaned up during the Secret re-list
		return
	}
	secrets, err := e.listTokenSecrets(serviceAccount)
	if err != nil {
		glog.Error(err)
		return
	}
	for _, secret := range secrets {
		if err := e.deleteSecret(secret); err != nil {
			glog.Errorf("Error deleting secret %s/%s: %v", secret.Namespace, secret.Name, err)
		}
	}
}

// secretAdded reacts to a Secret create by ensuring the referenced ServiceAccount exists, and by adding a token to the secret if needed
func (e *TokensController) secretAdded(obj interface{}) {
	secret := obj.(*api.Secret)
	serviceAccount, err := e.getServiceAccount(secret)
	if err != nil {
		glog.Error(err)
		return
	}
	if serviceAccount == nil {
		if err := e.deleteSecret(secret); err != nil {
			glog.Errorf("Error deleting secret %s/%s: %v", secret.Namespace, secret.Name, err)
		}
	} else {
		e.generateTokenIfNeeded(serviceAccount, secret)
	}
}

// secretUpdated reacts to a Secret update (or re-list) by deleting the secret (if the referenced ServiceAccount does not exist)
func (e *TokensController) secretUpdated(oldObj interface{}, newObj interface{}) {
	newSecret := newObj.(*api.Secret)
	newServiceAccount, err := e.getServiceAccount(newSecret)
	if err != nil {
		glog.Error(err)
		return
	}
	if newServiceAccount == nil {
		if err := e.deleteSecret(newSecret); err != nil {
			glog.Errorf("Error deleting secret %s/%s: %v", newSecret.Namespace, newSecret.Name, err)
		}
	} else {
		e.generateTokenIfNeeded(newServiceAccount, newSecret)
	}
}

// secretDeleted reacts to a Secret being deleted by removing a reference from the corresponding ServiceAccount if needed
func (e *TokensController) secretDeleted(obj interface{}) {
	secret, ok := obj.(*api.Secret)
	if !ok {
		// Unknown type. If we missed a Secret deletion, the corresponding ServiceAccount (if it exists)
		// will get a secret recreated (if needed) during the ServiceAccount re-list
		return
	}

	serviceAccount, err := e.getServiceAccount(secret)
	if err != nil {
		glog.Error(err)
		return
	}
	if serviceAccount == nil {
		return
	}

	if _, err := e.removeSecretReferenceIfNeeded(serviceAccount, secret.Name); err != nil {
		glog.Error(err)
	}
}

// createSecretIfNeeded makes sure at least one ServiceAccountToken secret exists, and is included in the serviceAccount's Secrets list
func (e *TokensController) createSecretIfNeeded(serviceAccount *api.ServiceAccount) error {
	// If the service account references no secrets, short-circuit and create a new one
	if len(serviceAccount.Secrets) == 0 {
		return e.createSecret(serviceAccount)
	}

	// If any existing token secrets are referenced by the service account, return
	allSecrets, err := e.listTokenSecrets(serviceAccount)
	if err != nil {
		return err
	}
	referencedSecrets := getSecretReferences(serviceAccount)
	for _, secret := range allSecrets {
		if referencedSecrets.Has(secret.Name) {
			return nil
		}
	}

	// Otherwise create a new token secret
	return e.createSecret(serviceAccount)
}

// createSecret creates a secret of type ServiceAccountToken for the given ServiceAccount
func (e *TokensController) createSecret(serviceAccount *api.ServiceAccount) error {
	// Build the secret
	secret := &api.Secret{
		ObjectMeta: api.ObjectMeta{
			Name:      secret.Strategy.GenerateName(fmt.Sprintf("%s-token-", serviceAccount.Name)),
			Namespace: serviceAccount.Namespace,
			Annotations: map[string]string{
				api.ServiceAccountNameKey: serviceAccount.Name,
				api.ServiceAccountUIDKey:  string(serviceAccount.UID),
			},
		},
		Type: api.SecretTypeServiceAccountToken,
		Data: map[string][]byte{},
	}

	// Generate the token
	token, err := e.token.GenerateToken(*serviceAccount, *secret)
	if err != nil {
		return err
	}
	secret.Data[api.ServiceAccountTokenKey] = []byte(token)

	// Save the secret
	if _, err := e.client.Secrets(serviceAccount.Namespace).Create(secret); err != nil {
		return err
	}

	// We don't want to update the cache's copy of the service account
	// so add the secret to a freshly retrieved copy of the service account
	serviceAccounts := e.client.ServiceAccounts(serviceAccount.Namespace)
	serviceAccount, err = serviceAccounts.Get(serviceAccount.Name)
	if err != nil {
		return err
	}
	serviceAccount.Secrets = append(serviceAccount.Secrets, api.ObjectReference{Name: secret.Name})

	_, err = serviceAccounts.Update(serviceAccount)
	if err != nil {
		return err
	}
	return nil
}

// generateTokenIfNeeded populates the token data for the given Secret if not already set
func (e *TokensController) generateTokenIfNeeded(serviceAccount *api.ServiceAccount, secret *api.Secret) error {
	if secret.Annotations == nil {
		secret.Annotations = map[string]string{}
	}
	if secret.Data == nil {
		secret.Data = map[string][]byte{}
	}

	tokenData, ok := secret.Data[api.ServiceAccountTokenKey]
	if ok && len(tokenData) > 0 {
		return nil
	}

	// Generate the token
	token, err := e.token.GenerateToken(*serviceAccount, *secret)
	if err != nil {
		return err
	}

	// Set the token and annotations
	secret.Data[api.ServiceAccountTokenKey] = []byte(token)
	secret.Annotations[api.ServiceAccountNameKey] = serviceAccount.Name
	secret.Annotations[api.ServiceAccountUIDKey] = string(serviceAccount.UID)

	// Save the secret
	if _, err := e.client.Secrets(secret.Namespace).Update(secret); err != nil {
		return err
	}
	return nil
}

// deleteSecret deletes the given secret
func (e *TokensController) deleteSecret(secret *api.Secret) error {
	return e.client.Secrets(secret.Namespace).Delete(secret.Name)
}

// removeSecretReferenceIfNeeded updates the given ServiceAccount to remove a reference to the given secretName if needed.
// Returns whether an update was performed, and any error that occurred
func (e *TokensController) removeSecretReferenceIfNeeded(serviceAccount *api.ServiceAccount, secretName string) (bool, error) {
	// See if the account even referenced the secret
	if !getSecretReferences(serviceAccount).Has(secretName) {
		return false, nil
	}

	// We don't want to update the cache's copy of the service account
	// so remove the secret from a freshly retrieved copy of the service account
	serviceAccounts := e.client.ServiceAccounts(serviceAccount.Namespace)
	serviceAccount, err := serviceAccounts.Get(serviceAccount.Name)
	if err != nil {
		return false, err
	}

	// Double-check to see if the account still references the secret
	if !getSecretReferences(serviceAccount).Has(secretName) {
		return false, nil
	}

	secrets := []api.ObjectReference{}
	for _, s := range serviceAccount.Secrets {
		if s.Name != secretName {
			secrets = append(secrets, s)
		}
	}
	serviceAccount.Secrets = secrets

	_, err = serviceAccounts.Update(serviceAccount)
	if err != nil {
		return false, err
	}

	return true, nil
}

// getServiceAccount returns the ServiceAccount referenced by the given secret. If the secret is not
// of type ServiceAccountToken, or if the referenced ServiceAccount does not exist, nil is returned
func (e *TokensController) getServiceAccount(secret *api.Secret) (*api.ServiceAccount, error) {
	name, uid := serviceAccountNameAndUID(secret)
	if len(name) == 0 {
		return nil, nil
	}

	key := &api.ServiceAccount{ObjectMeta: api.ObjectMeta{Namespace: secret.Namespace}}
	namespaceAccounts, err := e.serviceAccounts.Index("namespace", key)
	if err != nil {
		return nil, err
	}

	for _, obj := range namespaceAccounts {
		serviceAccount := obj.(*api.ServiceAccount)
		if name != serviceAccount.Name {
			// Name must match
			continue
		}
		if len(uid) > 0 && uid != string(serviceAccount.UID) {
			// If UID is specified, it must match
			continue
		}
		return serviceAccount, nil
	}

	return nil, nil
}

// listTokenSecrets returns a list of all of the ServiceAccountToken secrets that
// reference the given service account's name and uid
func (e *TokensController) listTokenSecrets(serviceAccount *api.ServiceAccount) ([]*api.Secret, error) {
	key := &api.Secret{ObjectMeta: api.ObjectMeta{Namespace: serviceAccount.Namespace}}
	namespaceSecrets, err := e.secrets.Index("namespace", key)
	if err != nil {
		return nil, err
	}

	items := []*api.Secret{}
	for _, obj := range namespaceSecrets {
		secret := obj.(*api.Secret)
		name, uid := serviceAccountNameAndUID(secret)
		if name != serviceAccount.Name {
			// Name must match
			continue
		}
		if len(uid) > 0 && uid != string(serviceAccount.UID) {
			// If UID is specified, it must match
			continue
		}
		items = append(items, secret)
	}
	return items, nil
}

// serviceAccountNameAndUID is a helper method to get the ServiceAccount Name and UID from the given secret
// Returns "","" if the secret is not a ServiceAccountToken secret
// If the name or uid annotation is missing, "" is returned instead
func serviceAccountNameAndUID(secret *api.Secret) (string, string) {
	if secret.Type != api.SecretTypeServiceAccountToken {
		return "", ""
	}
	return secret.Annotations[api.ServiceAccountNameKey], secret.Annotations[api.ServiceAccountUIDKey]
}

func getSecretReferences(serviceAccount *api.ServiceAccount) util.StringSet {
	references := util.NewStringSet()
	for _, secret := range serviceAccount.Secrets {
		references.Insert(secret.Name)
	}
	return references
}