/*
Copyright 2016 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 cluster

import (
	"strings"
	"sync"
	"time"

	"github.com/golang/glog"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/apimachinery/pkg/watch"
	restclient "k8s.io/client-go/rest"
	"k8s.io/client-go/tools/cache"
	federationv1beta1 "k8s.io/kubernetes/federation/apis/federation/v1beta1"
	clustercache "k8s.io/kubernetes/federation/client/cache"
	federationclientset "k8s.io/kubernetes/federation/client/clientset_generated/federation_clientset"
	"k8s.io/kubernetes/pkg/controller"
)

type ClusterController struct {
	// federationClient used to operate cluster
	federationClient federationclientset.Interface

	// clusterMonitorPeriod is the period for updating status of cluster
	clusterMonitorPeriod time.Duration

	mu              sync.RWMutex
	knownClusterSet sets.String
	// clusterClusterStatusMap is a mapping of clusterName and cluster status of last sampling
	clusterClusterStatusMap map[string]federationv1beta1.ClusterStatus
	// clusterKubeClientMap is a mapping of clusterName and restclient
	clusterKubeClientMap map[string]ClusterClient

	// cluster framework and store
	clusterController cache.Controller
	clusterStore      clustercache.StoreToClusterLister
}

// StartClusterController starts a new cluster controller
func StartClusterController(config *restclient.Config, stopChan <-chan struct{}, clusterMonitorPeriod time.Duration) {
	restclient.AddUserAgent(config, "cluster-controller")
	client := federationclientset.NewForConfigOrDie(config)
	controller := newClusterController(client, clusterMonitorPeriod)
	glog.Infof("Starting cluster controller")
	controller.Run(stopChan)
}

// newClusterController returns a new cluster controller
func newClusterController(federationClient federationclientset.Interface, clusterMonitorPeriod time.Duration) *ClusterController {
	cc := &ClusterController{
		knownClusterSet:         make(sets.String),
		federationClient:        federationClient,
		clusterMonitorPeriod:    clusterMonitorPeriod,
		clusterClusterStatusMap: make(map[string]federationv1beta1.ClusterStatus),
		clusterKubeClientMap:    make(map[string]ClusterClient),
	}
	cc.clusterStore.Store, cc.clusterController = cache.NewInformer(
		&cache.ListWatch{
			ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
				return cc.federationClient.Federation().Clusters().List(options)
			},
			WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
				return cc.federationClient.Federation().Clusters().Watch(options)
			},
		},
		&federationv1beta1.Cluster{},
		controller.NoResyncPeriodFunc(),
		cache.ResourceEventHandlerFuncs{
			DeleteFunc: cc.delFromClusterSet,
			AddFunc:    cc.addToClusterSet,
		},
	)
	return cc
}

// delFromClusterSet delete a cluster from clusterSet and
// delete the corresponding restclient from the map clusterKubeClientMap
func (cc *ClusterController) delFromClusterSet(obj interface{}) {
	cc.mu.Lock()
	defer cc.mu.Unlock()
	cluster := obj.(*federationv1beta1.Cluster)
	cc.delFromClusterSetByName(cluster.Name)
}

// delFromClusterSetByName delete a cluster from clusterSet by name and
// delete the corresponding restclient from the map clusterKubeClientMap.
// Caller must make sure that they hold the mutex
func (cc *ClusterController) delFromClusterSetByName(clusterName string) {
	glog.V(1).Infof("ClusterController observed a cluster deletion: %v", clusterName)
	cc.knownClusterSet.Delete(clusterName)
	delete(cc.clusterKubeClientMap, clusterName)
	delete(cc.clusterClusterStatusMap, clusterName)
}

func (cc *ClusterController) addToClusterSet(obj interface{}) {
	cc.mu.Lock()
	defer cc.mu.Unlock()
	cluster := obj.(*federationv1beta1.Cluster)
	cc.addToClusterSetWithoutLock(cluster)
}

// addToClusterSetWithoutLock inserts the new cluster to clusterSet and create
// a corresponding restclient to map clusterKubeClientMap if the cluster is not
// known. Caller must make sure that they hold the mutex.
func (cc *ClusterController) addToClusterSetWithoutLock(cluster *federationv1beta1.Cluster) {
	if cc.knownClusterSet.Has(cluster.Name) {
		return
	}
	glog.V(1).Infof("ClusterController observed a new cluster: %v", cluster.Name)
	cc.knownClusterSet.Insert(cluster.Name)
	// create the restclient of cluster
	restClient, err := NewClusterClientSet(cluster)
	if err != nil || restClient == nil {
		glog.Errorf("Failed to create corresponding restclient of kubernetes cluster: %v", err)
		return
	}
	cc.clusterKubeClientMap[cluster.Name] = *restClient
}

// Run begins watching and syncing.
func (cc *ClusterController) Run(stopChan <-chan struct{}) {
	defer utilruntime.HandleCrash()
	go cc.clusterController.Run(stopChan)
	// monitor cluster status periodically, in phase 1 we just get the health state from "/healthz"
	go wait.Until(func() {
		if err := cc.updateClusterStatus(); err != nil {
			glog.Errorf("Error monitoring cluster status: %v", err)
		}
	}, cc.clusterMonitorPeriod, stopChan)
}

// updateClusterStatus checks cluster status and get the metrics from cluster's restapi
func (cc *ClusterController) updateClusterStatus() error {
	clusters, err := cc.federationClient.Federation().Clusters().List(metav1.ListOptions{})
	if err != nil {
		return err
	}

	for _, cluster := range clusters.Items {
		cc.mu.RLock()
		// skip updating status of the cluster which is not yet added to knownClusterSet.
		if !cc.knownClusterSet.Has(cluster.Name) {
			cc.mu.RUnlock()
			continue
		}
		clusterClient, clientFound := cc.clusterKubeClientMap[cluster.Name]
		clusterStatusOld, statusFound := cc.clusterClusterStatusMap[cluster.Name]
		cc.mu.RUnlock()

		if !clientFound {
			glog.Warningf("Failed to get client for cluster %s", cluster.Name)
			continue
		}
		clusterStatusNew := clusterClient.GetClusterHealthStatus()
		if !statusFound {
			glog.Infof("There is no status stored for cluster: %v before", cluster.Name)
		} else {
			hasTransition := false
			if len(clusterStatusNew.Conditions) != len(clusterStatusOld.Conditions) {
				hasTransition = true
			} else {
				for i := 0; i < len(clusterStatusNew.Conditions); i++ {
					if !(strings.EqualFold(string(clusterStatusNew.Conditions[i].Type), string(clusterStatusOld.Conditions[i].Type)) &&
						strings.EqualFold(string(clusterStatusNew.Conditions[i].Status), string(clusterStatusOld.Conditions[i].Status))) {
						hasTransition = true
						break
					}
				}
			}

			if !hasTransition {
				for j := 0; j < len(clusterStatusNew.Conditions); j++ {
					clusterStatusNew.Conditions[j].LastTransitionTime = clusterStatusOld.Conditions[j].LastTransitionTime
				}
			}
		}

		cc.mu.Lock()
		cc.clusterClusterStatusMap[cluster.Name] = *clusterStatusNew
		cc.mu.Unlock()
		cluster.Status = *clusterStatusNew
		cluster, err := cc.federationClient.Federation().Clusters().UpdateStatus(&cluster)
		if err != nil {
			glog.Warningf("Failed to update the status of cluster: %v ,error is : %v", cluster.Name, err)
			// Don't return err here, as we want to continue processing remaining clusters.
			continue
		}
	}
	return nil
}