/*
Copyright 2017 Heptio Inc.

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 server

import (
	"context"
	"fmt"
	"io/ioutil"
	"os"
	"reflect"
	"sync"
	"time"

	"golang.org/x/oauth2/google"

	"github.com/golang/glog"
	"github.com/spf13/cobra"

	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/discovery"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/pkg/api/v1"
	"k8s.io/client-go/tools/cache"

	api "github.com/heptio/ark/pkg/apis/ark/v1"
	"github.com/heptio/ark/pkg/backup"
	"github.com/heptio/ark/pkg/client"
	"github.com/heptio/ark/pkg/cloudprovider"
	arkaws "github.com/heptio/ark/pkg/cloudprovider/aws"
	"github.com/heptio/ark/pkg/cloudprovider/azure"
	"github.com/heptio/ark/pkg/cloudprovider/gcp"
	"github.com/heptio/ark/pkg/cmd"
	"github.com/heptio/ark/pkg/controller"
	arkdiscovery "github.com/heptio/ark/pkg/discovery"
	"github.com/heptio/ark/pkg/generated/clientset"
	arkv1client "github.com/heptio/ark/pkg/generated/clientset/typed/ark/v1"
	informers "github.com/heptio/ark/pkg/generated/informers/externalversions"
	"github.com/heptio/ark/pkg/restore"
	"github.com/heptio/ark/pkg/restore/restorers"
	"github.com/heptio/ark/pkg/util/kube"
)

func NewCommand() *cobra.Command {
	var kubeconfig string

	var command = &cobra.Command{
		Use:   "server",
		Short: "Run the ark server",
		Long:  "Run the ark server",
		Run: func(c *cobra.Command, args []string) {
			s, err := newServer(kubeconfig)
			cmd.CheckError(err)

			cmd.CheckError(s.run())
		},
	}

	command.Flags().StringVar(&kubeconfig, "kubeconfig", "", "Path to the kubeconfig file to use to talk to the Kubernetes apiserver. If unset, try the environment variable KUBECONFIG, as well as in-cluster configuration")

	return command
}

type server struct {
	kubeClient            kubernetes.Interface
	arkClient             clientset.Interface
	backupService         cloudprovider.BackupService
	snapshotService       cloudprovider.SnapshotService
	discoveryClient       discovery.DiscoveryInterface
	clientPool            dynamic.ClientPool
	sharedInformerFactory informers.SharedInformerFactory
	ctx                   context.Context
	cancelFunc            context.CancelFunc
}

func newServer(kubeconfig string) (*server, error) {
	clientConfig, err := client.Config(kubeconfig)
	if err != nil {
		return nil, err
	}

	kubeClient, err := kubernetes.NewForConfig(clientConfig)
	if err != nil {
		return nil, err
	}

	arkClient, err := clientset.NewForConfig(clientConfig)
	if err != nil {
		return nil, err
	}

	ctx, cancelFunc := context.WithCancel(context.Background())

	s := &server{
		kubeClient:            kubeClient,
		arkClient:             arkClient,
		discoveryClient:       arkClient.Discovery(),
		clientPool:            dynamic.NewDynamicClientPool(clientConfig),
		sharedInformerFactory: informers.NewSharedInformerFactory(arkClient, 0),
		ctx:        ctx,
		cancelFunc: cancelFunc,
	}

	return s, nil
}

func (s *server) run() error {
	if err := s.ensureArkNamespace(); err != nil {
		return err
	}

	config, err := s.loadConfig()
	if err != nil {
		return err
	}
	applyConfigDefaults(config)

	s.watchConfig(config)

	if err := s.initBackupService(config); err != nil {
		return err
	}

	if err := s.initSnapshotService(config); err != nil {
		return err
	}

	if err := s.runControllers(config); err != nil {
		return err
	}

	return nil
}

func (s *server) ensureArkNamespace() error {
	glog.Infof("Ensuring %s namespace exists for backups", api.DefaultNamespace)
	defaultNamespace := v1.Namespace{
		ObjectMeta: metav1.ObjectMeta{
			Name: api.DefaultNamespace,
		},
	}

	if created, err := kube.EnsureNamespaceExists(&defaultNamespace, s.kubeClient.CoreV1().Namespaces()); created {
		glog.Infof("Namespace created")
	} else if err != nil {
		return err
	}
	glog.Infof("Namespace already exists")
	return nil
}

func (s *server) loadConfig() (*api.Config, error) {
	glog.Infof("Retrieving Ark configuration")
	var (
		config *api.Config
		err    error
	)
	for {
		config, err = s.arkClient.ArkV1().Configs(api.DefaultNamespace).Get("default", metav1.GetOptions{})
		if err == nil {
			break
		}
		if !apierrors.IsNotFound(err) {
			glog.Errorf("error retrieving configuration: %v", err)
		}
		glog.Infof("Will attempt to retrieve configuration again in 5 seconds")
		time.Sleep(5 * time.Second)
	}
	glog.Infof("Successfully retrieved Ark configuration")
	return config, nil
}

const (
	defaultGCSyncPeriod       = 60 * time.Minute
	defaultBackupSyncPeriod   = 60 * time.Minute
	defaultScheduleSyncPeriod = time.Minute
)

var defaultResourcePriorities = []string{
	"namespaces",
	"persistentvolumes",
	"persistentvolumeclaims",
	"secrets",
	"configmaps",
}

func applyConfigDefaults(c *api.Config) {
	if c.GCSyncPeriod.Duration == 0 {
		c.GCSyncPeriod.Duration = defaultGCSyncPeriod
	}

	if c.BackupSyncPeriod.Duration == 0 {
		c.BackupSyncPeriod.Duration = defaultBackupSyncPeriod
	}

	if c.ScheduleSyncPeriod.Duration == 0 {
		c.ScheduleSyncPeriod.Duration = defaultScheduleSyncPeriod
	}

	if len(c.ResourcePriorities) == 0 {
		c.ResourcePriorities = defaultResourcePriorities
		glog.Infof("Using default resource priorities: %v", c.ResourcePriorities)
	} else {
		glog.Infof("Using resource priorities from config: %v", c.ResourcePriorities)
	}
}

// watchConfig adds an update event handler to the Config shared informer, invoking s.cancelFunc
// when it sees a change.
func (s *server) watchConfig(config *api.Config) {
	s.sharedInformerFactory.Ark().V1().Configs().Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		UpdateFunc: func(oldObj, newObj interface{}) {
			updated := newObj.(*api.Config)

			if updated.Name != config.Name {
				glog.V(5).Infof("config watch channel received other config %q", updated.Name)
				return
			}

			if !reflect.DeepEqual(config, updated) {
				glog.Infof("Detected a config change. Gracefully shutting down")
				s.cancelFunc()
			}
		},
	})
}

func (s *server) initBackupService(config *api.Config) error {
	glog.Infof("Configuring cloud provider for backup service")
	objectStorage, err := getObjectStorageProvider(config.BackupStorageProvider.CloudProviderConfig, "backupStorageProvider")
	if err != nil {
		return err
	}

	s.backupService = cloudprovider.NewBackupService(objectStorage)
	return nil
}

func (s *server) initSnapshotService(config *api.Config) error {
	if config.PersistentVolumeProvider == nil {
		glog.Infof("PersistentVolumeProvider config not provided, volume snapshots and restores are disabled")
		return nil
	}

	glog.Infof("Configuring cloud provider for snapshot service")
	blockStorage, err := getBlockStorageProvider(*config.PersistentVolumeProvider, "persistentVolumeProvider")
	if err != nil {
		return err
	}
	s.snapshotService = cloudprovider.NewSnapshotService(blockStorage)
	return nil
}

func hasOneCloudProvider(cloudConfig api.CloudProviderConfig) bool {
	found := false

	if cloudConfig.AWS != nil {
		found = true
	}

	if cloudConfig.GCP != nil {
		if found {
			return false
		}
		found = true
	}

	if cloudConfig.Azure != nil {
		if found {
			return false
		}
		found = true
	}

	return found
}

func getObjectStorageProvider(cloudConfig api.CloudProviderConfig, field string) (cloudprovider.ObjectStorageAdapter, error) {
	var (
		objectStorage cloudprovider.ObjectStorageAdapter
		err           error
	)

	if !hasOneCloudProvider(cloudConfig) {
		return nil, fmt.Errorf("you must specify exactly one of aws, gcp, or azure for %s", field)
	}

	switch {
	case cloudConfig.AWS != nil:
		objectStorage, err = arkaws.NewObjectStorageAdapter(
			cloudConfig.AWS.Region,
			cloudConfig.AWS.S3Url,
			cloudConfig.AWS.KMSKeyID,
			cloudConfig.AWS.S3ForcePathStyle)
	case cloudConfig.GCP != nil:
		var email string
		var privateKey []byte

		credentialsFile := os.Getenv("GOOGLE_APPLICATION_CREDENTIALS")
		if credentialsFile != "" {
			// Get the email and private key from the credentials file so we can pre-sign download URLs
			creds, err := ioutil.ReadFile(credentialsFile)
			if err != nil {
				return nil, err
			}
			jwtConfig, err := google.JWTConfigFromJSON(creds)
			if err != nil {
				return nil, err
			}
			email = jwtConfig.Email
			privateKey = jwtConfig.PrivateKey
		} else {
			glog.Warning("GOOGLE_APPLICATION_CREDENTIALS is undefined; some features such as downloading log files will not work")
		}

		objectStorage, err = gcp.NewObjectStorageAdapter(email, privateKey)
	case cloudConfig.Azure != nil:
		objectStorage, err = azure.NewObjectStorageAdapter()
	}

	if err != nil {
		return nil, err
	}

	return objectStorage, nil
}

func getBlockStorageProvider(cloudConfig api.CloudProviderConfig, field string) (cloudprovider.BlockStorageAdapter, error) {
	var (
		blockStorage cloudprovider.BlockStorageAdapter
		err          error
	)

	if !hasOneCloudProvider(cloudConfig) {
		return nil, fmt.Errorf("you must specify exactly one of aws, gcp, or azure for %s", field)
	}

	switch {
	case cloudConfig.AWS != nil:
		blockStorage, err = arkaws.NewBlockStorageAdapter(cloudConfig.AWS.Region, cloudConfig.AWS.AvailabilityZone)
	case cloudConfig.GCP != nil:
		blockStorage, err = gcp.NewBlockStorageAdapter(cloudConfig.GCP.Project, cloudConfig.GCP.Zone)
	case cloudConfig.Azure != nil:
		blockStorage, err = azure.NewBlockStorageAdapter(cloudConfig.Azure.Location, cloudConfig.Azure.APITimeout.Duration)
	}

	if err != nil {
		return nil, err
	}

	return blockStorage, nil
}

func durationMin(a, b time.Duration) time.Duration {
	if a < b {
		return a
	}
	return b
}

func (s *server) runControllers(config *api.Config) error {
	glog.Infof("Starting controllers")

	ctx := s.ctx
	var wg sync.WaitGroup

	cloudBackupCacheResyncPeriod := durationMin(config.GCSyncPeriod.Duration, config.BackupSyncPeriod.Duration)
	glog.Infof("Caching cloud backups every %s", cloudBackupCacheResyncPeriod)
	s.backupService = cloudprovider.NewBackupServiceWithCachedBackupGetter(
		ctx,
		s.backupService,
		cloudBackupCacheResyncPeriod,
	)

	backupSyncController := controller.NewBackupSyncController(
		s.arkClient.ArkV1(),
		s.backupService,
		config.BackupStorageProvider.Bucket,
		config.BackupSyncPeriod.Duration,
	)
	wg.Add(1)
	go func() {
		backupSyncController.Run(ctx, 1)
		wg.Done()
	}()

	discoveryHelper, err := arkdiscovery.NewHelper(s.discoveryClient)
	if err != nil {
		return err
	}
	go wait.Until(
		func() {
			if err := discoveryHelper.Refresh(); err != nil {
				glog.Errorf("error refreshing discovery: %v", err)
			}
		},
		5*time.Minute,
		ctx.Done(),
	)

	if config.RestoreOnlyMode {
		glog.Infof("Restore only mode - not starting the backup, schedule or GC controllers")
	} else {
		backupper, err := newBackupper(discoveryHelper, s.clientPool, s.backupService, s.snapshotService)
		cmd.CheckError(err)
		backupController := controller.NewBackupController(
			s.sharedInformerFactory.Ark().V1().Backups(),
			s.arkClient.ArkV1(),
			backupper,
			s.backupService,
			config.BackupStorageProvider.Bucket,
			s.snapshotService != nil,
		)
		wg.Add(1)
		go func() {
			backupController.Run(ctx, 1)
			wg.Done()
		}()

		scheduleController := controller.NewScheduleController(
			s.arkClient.ArkV1(),
			s.arkClient.ArkV1(),
			s.sharedInformerFactory.Ark().V1().Schedules(),
			config.ScheduleSyncPeriod.Duration,
		)
		wg.Add(1)
		go func() {
			scheduleController.Run(ctx, 1)
			wg.Done()
		}()

		gcController := controller.NewGCController(
			s.backupService,
			s.snapshotService,
			config.BackupStorageProvider.Bucket,
			config.GCSyncPeriod.Duration,
			s.sharedInformerFactory.Ark().V1().Backups(),
			s.arkClient.ArkV1(),
			s.sharedInformerFactory.Ark().V1().Restores(),
			s.arkClient.ArkV1(),
		)
		wg.Add(1)
		go func() {
			gcController.Run(ctx, 1)
			wg.Done()
		}()
	}

	restorer, err := newRestorer(
		discoveryHelper,
		s.clientPool,
		s.backupService,
		s.snapshotService,
		config.ResourcePriorities,
		s.arkClient.ArkV1(),
		s.kubeClient,
	)
	cmd.CheckError(err)

	restoreController := controller.NewRestoreController(
		s.sharedInformerFactory.Ark().V1().Restores(),
		s.arkClient.ArkV1(),
		s.arkClient.ArkV1(),
		restorer,
		s.backupService,
		config.BackupStorageProvider.Bucket,
		s.sharedInformerFactory.Ark().V1().Backups(),
		s.snapshotService != nil,
	)
	wg.Add(1)
	go func() {
		restoreController.Run(ctx, 1)
		wg.Done()
	}()

	downloadRequestController := controller.NewDownloadRequestController(
		s.arkClient.ArkV1(),
		s.sharedInformerFactory.Ark().V1().DownloadRequests(),
		s.sharedInformerFactory.Ark().V1().Backups(),
		s.backupService,
		config.BackupStorageProvider.Bucket,
	)
	wg.Add(1)
	go func() {
		downloadRequestController.Run(ctx, 1)
		wg.Done()
	}()

	// SHARED INFORMERS HAVE TO BE STARTED AFTER ALL CONTROLLERS
	go s.sharedInformerFactory.Start(ctx.Done())

	glog.Infof("Server started successfully")

	<-ctx.Done()

	glog.Info("Waiting for all controllers to shut down gracefully")
	wg.Wait()

	return nil
}

func newBackupper(
	discoveryHelper arkdiscovery.Helper,
	clientPool dynamic.ClientPool,
	backupService cloudprovider.BackupService,
	snapshotService cloudprovider.SnapshotService,
) (backup.Backupper, error) {
	actions := map[string]backup.Action{}

	if snapshotService != nil {
		action, err := backup.NewVolumeSnapshotAction(snapshotService)
		if err != nil {
			return nil, err
		}

		actions["persistentvolumes"] = action
	}

	return backup.NewKubernetesBackupper(
		discoveryHelper,
		client.NewDynamicFactory(clientPool),
		actions,
	)
}

func newRestorer(
	discoveryHelper arkdiscovery.Helper,
	clientPool dynamic.ClientPool,
	backupService cloudprovider.BackupService,
	snapshotService cloudprovider.SnapshotService,
	resourcePriorities []string,
	backupClient arkv1client.BackupsGetter,
	kubeClient kubernetes.Interface,
) (restore.Restorer, error) {
	restorers := map[string]restorers.ResourceRestorer{
		"persistentvolumes":      restorers.NewPersistentVolumeRestorer(snapshotService),
		"persistentvolumeclaims": restorers.NewPersistentVolumeClaimRestorer(),
		"services":               restorers.NewServiceRestorer(),
		"namespaces":             restorers.NewNamespaceRestorer(),
		"pods":                   restorers.NewPodRestorer(),
		"jobs":                   restorers.NewJobRestorer(),
	}

	return restore.NewKubernetesRestorer(
		discoveryHelper,
		client.NewDynamicFactory(clientPool),
		restorers,
		backupService,
		resourcePriorities,
		backupClient,
		kubeClient.CoreV1().Namespaces(),
	)
}