/*
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 scheduler

import (
	"context"
	"errors"
	"fmt"
	"sort"
	"time"

	"github.com/google/go-cmp/cmp"
	v1 "k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/types"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/sets"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	"k8s.io/client-go/informers"
	coreinformers "k8s.io/client-go/informers/core/v1"
	clientset "k8s.io/client-go/kubernetes"
	corelisters "k8s.io/client-go/listers/core/v1"
	policylisters "k8s.io/client-go/listers/policy/v1beta1"
	"k8s.io/client-go/tools/cache"
	"k8s.io/klog"
	"k8s.io/kubernetes/pkg/controller/volume/scheduling"
	kubefeatures "k8s.io/kubernetes/pkg/features"
	"k8s.io/kubernetes/pkg/scheduler/algorithmprovider"
	schedulerapi "k8s.io/kubernetes/pkg/scheduler/apis/config"
	"k8s.io/kubernetes/pkg/scheduler/apis/config/validation"
	"k8s.io/kubernetes/pkg/scheduler/core"
	frameworkplugins "k8s.io/kubernetes/pkg/scheduler/framework/plugins"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/defaultbinder"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/interpodaffinity"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/noderesources"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/queuesort"
	framework "k8s.io/kubernetes/pkg/scheduler/framework/v1alpha1"
	internalcache "k8s.io/kubernetes/pkg/scheduler/internal/cache"
	cachedebugger "k8s.io/kubernetes/pkg/scheduler/internal/cache/debugger"
	internalqueue "k8s.io/kubernetes/pkg/scheduler/internal/queue"
	"k8s.io/kubernetes/pkg/scheduler/profile"
)

const (
	initialGetBackoff = 100 * time.Millisecond
	maximalGetBackoff = time.Minute
)

// Binder knows how to write a binding.
type Binder interface {
	Bind(binding *v1.Binding) error
}

// Configurator defines I/O, caching, and other functionality needed to
// construct a new scheduler.
type Configurator struct {
	client clientset.Interface

	recorderFactory profile.RecorderFactory

	informerFactory informers.SharedInformerFactory

	podInformer coreinformers.PodInformer

	// Close this to stop all reflectors
	StopEverything <-chan struct{}

	schedulerCache internalcache.Cache

	// Handles volume binding decisions
	volumeBinder scheduling.SchedulerVolumeBinder

	// Disable pod preemption or not.
	disablePreemption bool

	// Always check all predicates even if the middle of one predicate fails.
	alwaysCheckAllPredicates bool

	// percentageOfNodesToScore specifies percentage of all nodes to score in each scheduling cycle.
	percentageOfNodesToScore int32

	bindTimeoutSeconds int64

	podInitialBackoffSeconds int64

	podMaxBackoffSeconds int64

	enableNonPreempting bool

	profiles         []schedulerapi.KubeSchedulerProfile
	registry         framework.Registry
	nodeInfoSnapshot *internalcache.Snapshot
	extenders        []schedulerapi.Extender
}

func (c *Configurator) buildFramework(p schedulerapi.KubeSchedulerProfile) (framework.Framework, error) {
	return framework.NewFramework(
		c.registry,
		p.Plugins,
		p.PluginConfig,
		framework.WithClientSet(c.client),
		framework.WithInformerFactory(c.informerFactory),
		framework.WithSnapshotSharedLister(c.nodeInfoSnapshot),
		framework.WithRunAllFilters(c.alwaysCheckAllPredicates),
		framework.WithVolumeBinder(c.volumeBinder),
	)
}

// create a scheduler from a set of registered plugins.
func (c *Configurator) create() (*Scheduler, error) {
	var extenders []core.SchedulerExtender
	var ignoredExtendedResources []string
	if len(c.extenders) != 0 {
		var ignorableExtenders []core.SchedulerExtender
		for ii := range c.extenders {
			klog.V(2).Infof("Creating extender with config %+v", c.extenders[ii])
			extender, err := core.NewHTTPExtender(&c.extenders[ii])
			if err != nil {
				return nil, err
			}
			if !extender.IsIgnorable() {
				extenders = append(extenders, extender)
			} else {
				ignorableExtenders = append(ignorableExtenders, extender)
			}
			for _, r := range c.extenders[ii].ManagedResources {
				if r.IgnoredByScheduler {
					ignoredExtendedResources = append(ignoredExtendedResources, r.Name)
				}
			}
		}
		// place ignorable extenders to the tail of extenders
		extenders = append(extenders, ignorableExtenders...)
	}

	// If there are any extended resources found from the Extenders, append them to the pluginConfig for each profile.
	// This should only have an effect on ComponentConfig v1alpha2, where it is possible to configure Extenders and
	// plugin args (and in which case the extender ignored resources take precedence).
	// For earlier versions, using both policy and custom plugin config is disallowed, so this should be the only
	// plugin config for this plugin.
	if len(ignoredExtendedResources) > 0 {
		for i := range c.profiles {
			prof := &c.profiles[i]
			prof.PluginConfig = append(prof.PluginConfig,
				frameworkplugins.NewPluginConfig(
					noderesources.FitName,
					noderesources.FitArgs{IgnoredResources: ignoredExtendedResources},
				),
			)
		}
	}

	profiles, err := profile.NewMap(c.profiles, c.buildFramework, c.recorderFactory)
	if err != nil {
		return nil, fmt.Errorf("initializing profiles: %v", err)
	}
	if len(profiles) == 0 {
		return nil, errors.New("at least one profile is required")
	}
	// Profiles are required to have equivalent queue sort plugins.
	lessFn := profiles[c.profiles[0].SchedulerName].Framework.QueueSortFunc()
	podQueue := internalqueue.NewSchedulingQueue(
		lessFn,
		internalqueue.WithPodInitialBackoffDuration(time.Duration(c.podInitialBackoffSeconds)*time.Second),
		internalqueue.WithPodMaxBackoffDuration(time.Duration(c.podMaxBackoffSeconds)*time.Second),
	)

	// Setup cache debugger.
	debugger := cachedebugger.New(
		c.informerFactory.Core().V1().Nodes().Lister(),
		c.podInformer.Lister(),
		c.schedulerCache,
		podQueue,
	)
	debugger.ListenForSignal(c.StopEverything)

	algo := core.NewGenericScheduler(
		c.schedulerCache,
		podQueue,
		c.nodeInfoSnapshot,
		extenders,
		c.informerFactory.Core().V1().PersistentVolumeClaims().Lister(),
		GetPodDisruptionBudgetLister(c.informerFactory),
		c.disablePreemption,
		c.percentageOfNodesToScore,
		c.enableNonPreempting,
	)

	return &Scheduler{
		SchedulerCache:  c.schedulerCache,
		Algorithm:       algo,
		Profiles:        profiles,
		NextPod:         internalqueue.MakeNextPodFunc(podQueue),
		Error:           MakeDefaultErrorFunc(c.client, podQueue, c.schedulerCache),
		StopEverything:  c.StopEverything,
		VolumeBinder:    c.volumeBinder,
		SchedulingQueue: podQueue,
	}, nil
}

// createFromProvider creates a scheduler from the name of a registered algorithm provider.
func (c *Configurator) createFromProvider(providerName string) (*Scheduler, error) {
	klog.V(2).Infof("Creating scheduler from algorithm provider '%v'", providerName)
	r := algorithmprovider.NewRegistry()
	defaultPlugins, exist := r[providerName]
	if !exist {
		return nil, fmt.Errorf("algorithm provider %q is not registered", providerName)
	}

	for i := range c.profiles {
		prof := &c.profiles[i]
		plugins := &schedulerapi.Plugins{}
		plugins.Append(defaultPlugins)
		plugins.Apply(prof.Plugins)
		prof.Plugins = plugins
	}
	return c.create()
}

// createFromConfig creates a scheduler from the configuration file
// Only reachable when using v1alpha1 component config
func (c *Configurator) createFromConfig(policy schedulerapi.Policy) (*Scheduler, error) {
	lr := frameworkplugins.NewLegacyRegistry()
	args := &frameworkplugins.ConfigProducerArgs{}

	klog.V(2).Infof("Creating scheduler from configuration: %v", policy)

	// validate the policy configuration
	if err := validation.ValidatePolicy(policy); err != nil {
		return nil, err
	}

	predicateKeys := sets.NewString()
	if policy.Predicates == nil {
		klog.V(2).Infof("Using predicates from algorithm provider '%v'", schedulerapi.SchedulerDefaultProviderName)
		predicateKeys = lr.DefaultPredicates
	} else {
		for _, predicate := range policy.Predicates {
			klog.V(2).Infof("Registering predicate: %s", predicate.Name)
			predicateKeys.Insert(lr.ProcessPredicatePolicy(predicate, args))
		}
	}

	priorityKeys := make(map[string]int64)
	if policy.Priorities == nil {
		klog.V(2).Infof("Using default priorities")
		priorityKeys = lr.DefaultPriorities
	} else {
		for _, priority := range policy.Priorities {
			if priority.Name == frameworkplugins.EqualPriority {
				klog.V(2).Infof("Skip registering priority: %s", priority.Name)
				continue
			}
			klog.V(2).Infof("Registering priority: %s", priority.Name)
			priorityKeys[lr.ProcessPriorityPolicy(priority, args)] = priority.Weight
		}
	}

	// HardPodAffinitySymmetricWeight in the policy config takes precedence over
	// CLI configuration.
	if policy.HardPodAffinitySymmetricWeight != 0 {
		v := policy.HardPodAffinitySymmetricWeight
		args.InterPodAffinityArgs = &interpodaffinity.Args{
			HardPodAffinityWeight: &v,
		}
	}

	// When AlwaysCheckAllPredicates is set to true, scheduler checks all the configured
	// predicates even after one or more of them fails.
	if policy.AlwaysCheckAllPredicates {
		c.alwaysCheckAllPredicates = policy.AlwaysCheckAllPredicates
	}

	klog.V(2).Infof("Creating scheduler with fit predicates '%v' and priority functions '%v'", predicateKeys, priorityKeys)

	pluginsForPredicates, pluginConfigForPredicates, err := getPredicateConfigs(predicateKeys, lr, args)
	if err != nil {
		return nil, err
	}

	pluginsForPriorities, pluginConfigForPriorities, err := getPriorityConfigs(priorityKeys, lr, args)
	if err != nil {
		return nil, err
	}
	// Combine all framework configurations. If this results in any duplication, framework
	// instantiation should fail.
	var defPlugins schedulerapi.Plugins
	// "PrioritySort" and "DefaultBinder" were neither predicates nor priorities
	// before. We add them by default.
	defPlugins.Append(&schedulerapi.Plugins{
		QueueSort: &schedulerapi.PluginSet{
			Enabled: []schedulerapi.Plugin{{Name: queuesort.Name}},
		},
		Bind: &schedulerapi.PluginSet{
			Enabled: []schedulerapi.Plugin{{Name: defaultbinder.Name}},
		},
	})
	defPlugins.Append(pluginsForPredicates)
	defPlugins.Append(pluginsForPriorities)
	defPluginConfig, err := mergePluginConfigsFromPolicy(pluginConfigForPredicates, pluginConfigForPriorities)
	if err != nil {
		return nil, err
	}
	for i := range c.profiles {
		prof := &c.profiles[i]
		if prof.Plugins != nil {
			return nil, errors.New("using Plugins and Policy simultaneously is not supported")
		}
		prof.Plugins = &schedulerapi.Plugins{}
		prof.Plugins.Append(&defPlugins)

		if len(prof.PluginConfig) != 0 {
			return nil, errors.New("using PluginConfig and Policy simultaneously is not supported")
		}
		prof.PluginConfig = append(prof.PluginConfig, defPluginConfig...)
	}

	return c.create()
}

// mergePluginConfigsFromPolicy merges the giving plugin configs ensuring that,
// if a plugin name is repeated, the arguments are the same.
func mergePluginConfigsFromPolicy(pc1, pc2 []schedulerapi.PluginConfig) ([]schedulerapi.PluginConfig, error) {
	args := make(map[string]runtime.Unknown)
	for _, c := range pc1 {
		args[c.Name] = c.Args
	}
	for _, c := range pc2 {
		if v, ok := args[c.Name]; ok && !cmp.Equal(v, c.Args) {
			// This should be unreachable.
			return nil, fmt.Errorf("inconsistent configuration produced for plugin %s", c.Name)
		}
		args[c.Name] = c.Args
	}
	pc := make([]schedulerapi.PluginConfig, 0, len(args))
	for k, v := range args {
		pc = append(pc, schedulerapi.PluginConfig{
			Name: k,
			Args: v,
		})
	}
	return pc, nil
}

// getPriorityConfigs returns priorities configuration: ones that will run as priorities and ones that will run
// as framework plugins. Specifically, a priority will run as a framework plugin if a plugin config producer was
// registered for that priority.
func getPriorityConfigs(keys map[string]int64, lr *frameworkplugins.LegacyRegistry, args *frameworkplugins.ConfigProducerArgs) (*schedulerapi.Plugins, []schedulerapi.PluginConfig, error) {
	var plugins schedulerapi.Plugins
	var pluginConfig []schedulerapi.PluginConfig

	// Sort the keys so that it is easier for unit tests to do compare.
	var sortedKeys []string
	for k := range keys {
		sortedKeys = append(sortedKeys, k)
	}
	sort.Strings(sortedKeys)

	for _, priority := range sortedKeys {
		weight := keys[priority]
		producer, exist := lr.PriorityToConfigProducer[priority]
		if !exist {
			return nil, nil, fmt.Errorf("no config producer registered for %q", priority)
		}
		a := *args
		a.Weight = int32(weight)
		pl, plc := producer(a)
		plugins.Append(&pl)
		pluginConfig = append(pluginConfig, plc...)
	}
	return &plugins, pluginConfig, nil
}

// getPredicateConfigs returns predicates configuration: ones that will run as fitPredicates and ones that will run
// as framework plugins. Specifically, a predicate will run as a framework plugin if a plugin config producer was
// registered for that predicate.
// Note that the framework executes plugins according to their order in the Plugins list, and so predicates run as plugins
// are added to the Plugins list according to the order specified in predicates.Ordering().
func getPredicateConfigs(keys sets.String, lr *frameworkplugins.LegacyRegistry, args *frameworkplugins.ConfigProducerArgs) (*schedulerapi.Plugins, []schedulerapi.PluginConfig, error) {
	allPredicates := keys.Union(lr.MandatoryPredicates)

	// Create the framework plugin configurations, and place them in the order
	// that the corresponding predicates were supposed to run.
	var plugins schedulerapi.Plugins
	var pluginConfig []schedulerapi.PluginConfig

	for _, predicateKey := range frameworkplugins.PredicateOrdering() {
		if allPredicates.Has(predicateKey) {
			producer, exist := lr.PredicateToConfigProducer[predicateKey]
			if !exist {
				return nil, nil, fmt.Errorf("no framework config producer registered for %q", predicateKey)
			}
			pl, plc := producer(*args)
			plugins.Append(&pl)
			pluginConfig = append(pluginConfig, plc...)
			allPredicates.Delete(predicateKey)
		}
	}

	// Third, add the rest in no specific order.
	for predicateKey := range allPredicates {
		producer, exist := lr.PredicateToConfigProducer[predicateKey]
		if !exist {
			return nil, nil, fmt.Errorf("no framework config producer registered for %q", predicateKey)
		}
		pl, plc := producer(*args)
		plugins.Append(&pl)
		pluginConfig = append(pluginConfig, plc...)
	}

	return &plugins, pluginConfig, nil
}

type podInformer struct {
	informer cache.SharedIndexInformer
}

func (i *podInformer) Informer() cache.SharedIndexInformer {
	return i.informer
}

func (i *podInformer) Lister() corelisters.PodLister {
	return corelisters.NewPodLister(i.informer.GetIndexer())
}

// NewPodInformer creates a shared index informer that returns only non-terminal pods.
func NewPodInformer(client clientset.Interface, resyncPeriod time.Duration) coreinformers.PodInformer {
	selector := fields.ParseSelectorOrDie(
		"status.phase!=" + string(v1.PodSucceeded) +
			",status.phase!=" + string(v1.PodFailed))
	lw := cache.NewListWatchFromClient(client.CoreV1().RESTClient(), string(v1.ResourcePods), metav1.NamespaceAll, selector)
	return &podInformer{
		informer: cache.NewSharedIndexInformer(lw, &v1.Pod{}, resyncPeriod, cache.Indexers{cache.NamespaceIndex: cache.MetaNamespaceIndexFunc}),
	}
}

// MakeDefaultErrorFunc construct a function to handle pod scheduler error
func MakeDefaultErrorFunc(client clientset.Interface, podQueue internalqueue.SchedulingQueue, schedulerCache internalcache.Cache) func(*framework.PodInfo, error) {
	return func(podInfo *framework.PodInfo, err error) {
		pod := podInfo.Pod
		if err == core.ErrNoNodesAvailable {
			klog.V(2).Infof("Unable to schedule %v/%v: no nodes are registered to the cluster; waiting", pod.Namespace, pod.Name)
		} else {
			if _, ok := err.(*core.FitError); ok {
				klog.V(2).Infof("Unable to schedule %v/%v: no fit: %v; waiting", pod.Namespace, pod.Name, err)
			} else if apierrors.IsNotFound(err) {
				klog.V(2).Infof("Unable to schedule %v/%v: possibly due to node not found: %v; waiting", pod.Namespace, pod.Name, err)
				if errStatus, ok := err.(apierrors.APIStatus); ok && errStatus.Status().Details.Kind == "node" {
					nodeName := errStatus.Status().Details.Name
					// when node is not found, We do not remove the node right away. Trying again to get
					// the node and if the node is still not found, then remove it from the scheduler cache.
					_, err := client.CoreV1().Nodes().Get(context.TODO(), nodeName, metav1.GetOptions{})
					if err != nil && apierrors.IsNotFound(err) {
						node := v1.Node{ObjectMeta: metav1.ObjectMeta{Name: nodeName}}
						if err := schedulerCache.RemoveNode(&node); err != nil {
							klog.V(4).Infof("Node %q is not found; failed to remove it from the cache.", node.Name)
						}
					}
				}
			} else {
				klog.Errorf("Error scheduling %v/%v: %v; retrying", pod.Namespace, pod.Name, err)
			}
		}

		podSchedulingCycle := podQueue.SchedulingCycle()
		// Retry asynchronously.
		// Note that this is extremely rudimentary and we need a more real error handling path.
		go func() {
			defer utilruntime.HandleCrash()
			podID := types.NamespacedName{
				Namespace: pod.Namespace,
				Name:      pod.Name,
			}

			// An unschedulable pod will be placed in the unschedulable queue.
			// This ensures that if the pod is nominated to run on a node,
			// scheduler takes the pod into account when running predicates for the node.
			// Get the pod again; it may have changed/been scheduled already.
			getBackoff := initialGetBackoff
			for {
				pod, err := client.CoreV1().Pods(podID.Namespace).Get(context.TODO(), podID.Name, metav1.GetOptions{})
				if err == nil {
					if len(pod.Spec.NodeName) == 0 {
						podInfo.Pod = pod
						if err := podQueue.AddUnschedulableIfNotPresent(podInfo, podSchedulingCycle); err != nil {
							klog.Error(err)
						}
					}
					break
				}
				if apierrors.IsNotFound(err) {
					klog.Warningf("A pod %v no longer exists", podID)
					return
				}
				klog.Errorf("Error getting pod %v for retry: %v; retrying...", podID, err)
				if getBackoff = getBackoff * 2; getBackoff > maximalGetBackoff {
					getBackoff = maximalGetBackoff
				}
				time.Sleep(getBackoff)
			}
		}()
	}
}

// GetPodDisruptionBudgetLister returns pdb lister from the given informer factory. Returns nil if PodDisruptionBudget feature is disabled.
func GetPodDisruptionBudgetLister(informerFactory informers.SharedInformerFactory) policylisters.PodDisruptionBudgetLister {
	if utilfeature.DefaultFeatureGate.Enabled(kubefeatures.PodDisruptionBudget) {
		return informerFactory.Policy().V1beta1().PodDisruptionBudgets().Lister()
	}
	return nil
}