/*
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"
	"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/runtime"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/client-go/informers"
	clientset "k8s.io/client-go/kubernetes"
	corelisters "k8s.io/client-go/listers/core/v1"
	"k8s.io/klog/v2"
	"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"
	"k8s.io/kubernetes/pkg/scheduler/framework"
	frameworkplugins "k8s.io/kubernetes/pkg/scheduler/framework/plugins"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/defaultbinder"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/defaultpreemption"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/noderesources"
	"k8s.io/kubernetes/pkg/scheduler/framework/plugins/queuesort"
	frameworkruntime "k8s.io/kubernetes/pkg/scheduler/framework/runtime"
	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"
)

// 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

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

	schedulerCache internalcache.Cache

	// 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

	podInitialBackoffSeconds int64

	podMaxBackoffSeconds int64

	profiles          []schedulerapi.KubeSchedulerProfile
	registry          frameworkruntime.Registry
	nodeInfoSnapshot  *internalcache.Snapshot
	extenders         []schedulerapi.Extender
	frameworkCapturer FrameworkCapturer
}

// create a scheduler from a set of registered plugins.
func (c *Configurator) create() (*Scheduler, error) {
	var extenders []framework.Extender
	var ignoredExtendedResources []string
	if len(c.extenders) != 0 {
		var ignorableExtenders []framework.Extender
		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 v1beta1, 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]
			pc := schedulerapi.PluginConfig{
				Name: noderesources.FitName,
				Args: &schedulerapi.NodeResourcesFitArgs{
					IgnoredResources: ignoredExtendedResources,
				},
			}
			prof.PluginConfig = append(prof.PluginConfig, pc)
		}
	}

	// The nominator will be passed all the way to framework instantiation.
	nominator := internalqueue.NewPodNominator()
	profiles, err := profile.NewMap(c.profiles, c.registry, c.recorderFactory,
		frameworkruntime.WithClientSet(c.client),
		frameworkruntime.WithInformerFactory(c.informerFactory),
		frameworkruntime.WithSnapshotSharedLister(c.nodeInfoSnapshot),
		frameworkruntime.WithRunAllFilters(c.alwaysCheckAllPredicates),
		frameworkruntime.WithPodNominator(nominator),
		frameworkruntime.WithCaptureProfile(frameworkruntime.CaptureProfile(c.frameworkCapturer)),
	)
	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].QueueSortFunc()
	podQueue := internalqueue.NewSchedulingQueue(
		lessFn,
		internalqueue.WithPodInitialBackoffDuration(time.Duration(c.podInitialBackoffSeconds)*time.Second),
		internalqueue.WithPodMaxBackoffDuration(time.Duration(c.podMaxBackoffSeconds)*time.Second),
		internalqueue.WithPodNominator(nominator),
	)

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

	algo := core.NewGenericScheduler(
		c.schedulerCache,
		c.nodeInfoSnapshot,
		extenders,
		c.percentageOfNodesToScore,
	)

	return &Scheduler{
		SchedulerCache:  c.schedulerCache,
		Algorithm:       algo,
		Profiles:        profiles,
		NextPod:         internalqueue.MakeNextPodFunc(podQueue),
		Error:           MakeDefaultErrorFunc(c.client, c.informerFactory.Core().V1().Pods().Lister(), podQueue, c.schedulerCache),
		StopEverything:  c.StopEverything,
		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 {
		args.InterPodAffinityArgs = &schedulerapi.InterPodAffinityArgs{
			HardPodAffinityWeight: policy.HardPodAffinitySymmetricWeight,
		}
	}

	// 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)

	// Combine all framework configurations. If this results in any duplication, framework
	// instantiation should fail.

	// "PrioritySort", "DefaultPreemption" and "DefaultBinder" were neither predicates nor priorities
	// before. We add them by default.
	plugins := schedulerapi.Plugins{
		QueueSort: &schedulerapi.PluginSet{
			Enabled: []schedulerapi.Plugin{{Name: queuesort.Name}},
		},
		PostFilter: &schedulerapi.PluginSet{
			Enabled: []schedulerapi.Plugin{{Name: defaultpreemption.Name}},
		},
		Bind: &schedulerapi.PluginSet{
			Enabled: []schedulerapi.Plugin{{Name: defaultbinder.Name}},
		},
	}
	var pluginConfig []schedulerapi.PluginConfig
	var err error
	if plugins, pluginConfig, err = lr.AppendPredicateConfigs(predicateKeys, args, plugins, pluginConfig); err != nil {
		return nil, err
	}
	if plugins, pluginConfig, err = lr.AppendPriorityConfigs(priorityKeys, args, plugins, pluginConfig); err != nil {
		return nil, err
	}
	if pluginConfig, err = dedupPluginConfigs(pluginConfig); err != nil {
		return nil, err
	}
	for i := range c.profiles {
		prof := &c.profiles[i]
		// Plugins and PluginConfig are empty when using Policy; overriding.
		prof.Plugins = &schedulerapi.Plugins{}
		prof.Plugins.Append(&plugins)
		prof.PluginConfig = pluginConfig
	}

	return c.create()
}

// dedupPluginConfigs removes duplicates from pluginConfig, ensuring that,
// if a plugin name is repeated, the arguments are the same.
func dedupPluginConfigs(pc []schedulerapi.PluginConfig) ([]schedulerapi.PluginConfig, error) {
	args := make(map[string]runtime.Object)
	result := make([]schedulerapi.PluginConfig, 0, len(pc))
	for _, c := range pc {
		if v, found := args[c.Name]; !found {
			result = append(result, c)
			args[c.Name] = c.Args
		} else if !cmp.Equal(v, c.Args) {
			// This should be unreachable.
			return nil, fmt.Errorf("inconsistent configuration produced for plugin %s", c.Name)
		}
	}
	return result, nil
}

// MakeDefaultErrorFunc construct a function to handle pod scheduler error
func MakeDefaultErrorFunc(client clientset.Interface, podLister corelisters.PodLister, podQueue internalqueue.SchedulingQueue, schedulerCache internalcache.Cache) func(*framework.QueuedPodInfo, error) {
	return func(podInfo *framework.QueuedPodInfo, err error) {
		pod := podInfo.Pod
		if err == core.ErrNoNodesAvailable {
			klog.V(2).InfoS("Unable to schedule pod; no nodes are registered to the cluster; waiting", "pod", klog.KObj(pod))
		} else if _, ok := err.(*core.FitError); ok {
			klog.V(2).InfoS("Unable to schedule pod; no fit; waiting", "pod", klog.KObj(pod), "err", 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.ErrorS(err, "Error scheduling pod; retrying", "pod", klog.KObj(pod))
		}

		// Check if the Pod exists in informer cache.
		cachedPod, err := podLister.Pods(pod.Namespace).Get(pod.Name)
		if err != nil {
			klog.Warningf("Pod %v/%v doesn't exist in informer cache: %v", pod.Namespace, pod.Name, err)
			return
		}
		// As <cachedPod> is from SharedInformer, we need to do a DeepCopy() here.
		podInfo.Pod = cachedPod.DeepCopy()
		if err := podQueue.AddUnschedulableIfNotPresent(podInfo, podQueue.SchedulingCycle()); err != nil {
			klog.Error(err)
		}
	}
}