/*
Copyright 2019 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 tainttoleration

import (
	"context"
	"fmt"

	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/runtime"
	v1helper "k8s.io/component-helpers/scheduling/corev1"
	"k8s.io/kubernetes/pkg/scheduler/framework"
	pluginhelper "k8s.io/kubernetes/pkg/scheduler/framework/plugins/helper"
)

// TaintToleration is a plugin that checks if a pod tolerates a node's taints.
type TaintToleration struct {
	handle framework.Handle
}

var _ framework.FilterPlugin = &TaintToleration{}
var _ framework.PreScorePlugin = &TaintToleration{}
var _ framework.ScorePlugin = &TaintToleration{}

const (
	// Name is the name of the plugin used in the plugin registry and configurations.
	Name = "TaintToleration"
	// preScoreStateKey is the key in CycleState to TaintToleration pre-computed data for Scoring.
	preScoreStateKey = "PreScore" + Name
	// ErrReasonNotMatch is the Filter reason status when not matching.
	ErrReasonNotMatch = "node(s) had taints that the pod didn't tolerate"
)

// Name returns name of the plugin. It is used in logs, etc.
func (pl *TaintToleration) Name() string {
	return Name
}

// Filter invoked at the filter extension point.
func (pl *TaintToleration) Filter(ctx context.Context, state *framework.CycleState, pod *v1.Pod, nodeInfo *framework.NodeInfo) *framework.Status {
	if nodeInfo == nil || nodeInfo.Node() == nil {
		return framework.AsStatus(fmt.Errorf("invalid nodeInfo"))
	}

	filterPredicate := func(t *v1.Taint) bool {
		// PodToleratesNodeTaints is only interested in NoSchedule and NoExecute taints.
		return t.Effect == v1.TaintEffectNoSchedule || t.Effect == v1.TaintEffectNoExecute
	}

	taint, isUntolerated := v1helper.FindMatchingUntoleratedTaint(nodeInfo.Node().Spec.Taints, pod.Spec.Tolerations, filterPredicate)
	if !isUntolerated {
		return nil
	}

	errReason := fmt.Sprintf("node(s) had taint {%s: %s}, that the pod didn't tolerate",
		taint.Key, taint.Value)
	return framework.NewStatus(framework.UnschedulableAndUnresolvable, errReason)
}

// preScoreState computed at PreScore and used at Score.
type preScoreState struct {
	tolerationsPreferNoSchedule []v1.Toleration
}

// Clone implements the mandatory Clone interface. We don't really copy the data since
// there is no need for that.
func (s *preScoreState) Clone() framework.StateData {
	return s
}

// getAllTolerationEffectPreferNoSchedule gets the list of all Tolerations with Effect PreferNoSchedule or with no effect.
func getAllTolerationPreferNoSchedule(tolerations []v1.Toleration) (tolerationList []v1.Toleration) {
	for _, toleration := range tolerations {
		// Empty effect means all effects which includes PreferNoSchedule, so we need to collect it as well.
		if len(toleration.Effect) == 0 || toleration.Effect == v1.TaintEffectPreferNoSchedule {
			tolerationList = append(tolerationList, toleration)
		}
	}
	return
}

// PreScore builds and writes cycle state used by Score and NormalizeScore.
func (pl *TaintToleration) PreScore(ctx context.Context, cycleState *framework.CycleState, pod *v1.Pod, nodes []*v1.Node) *framework.Status {
	if len(nodes) == 0 {
		return nil
	}
	tolerationsPreferNoSchedule := getAllTolerationPreferNoSchedule(pod.Spec.Tolerations)
	state := &preScoreState{
		tolerationsPreferNoSchedule: tolerationsPreferNoSchedule,
	}
	cycleState.Write(preScoreStateKey, state)
	return nil
}

func getPreScoreState(cycleState *framework.CycleState) (*preScoreState, error) {
	c, err := cycleState.Read(preScoreStateKey)
	if err != nil {
		return nil, fmt.Errorf("failed to read %q from cycleState: %v", preScoreStateKey, err)
	}

	s, ok := c.(*preScoreState)
	if !ok {
		return nil, fmt.Errorf("%+v convert to tainttoleration.preScoreState error", c)
	}
	return s, nil
}

// CountIntolerableTaintsPreferNoSchedule gives the count of intolerable taints of a pod with effect PreferNoSchedule
func countIntolerableTaintsPreferNoSchedule(taints []v1.Taint, tolerations []v1.Toleration) (intolerableTaints int) {
	for _, taint := range taints {
		// check only on taints that have effect PreferNoSchedule
		if taint.Effect != v1.TaintEffectPreferNoSchedule {
			continue
		}

		if !v1helper.TolerationsTolerateTaint(tolerations, &taint) {
			intolerableTaints++
		}
	}
	return
}

// Score invoked at the Score extension point.
func (pl *TaintToleration) Score(ctx context.Context, state *framework.CycleState, pod *v1.Pod, nodeName string) (int64, *framework.Status) {
	nodeInfo, err := pl.handle.SnapshotSharedLister().NodeInfos().Get(nodeName)
	if err != nil || nodeInfo.Node() == nil {
		return 0, framework.AsStatus(fmt.Errorf("getting node %q from Snapshot: %w", nodeName, err))
	}
	node := nodeInfo.Node()

	s, err := getPreScoreState(state)
	if err != nil {
		return 0, framework.AsStatus(err)
	}

	score := int64(countIntolerableTaintsPreferNoSchedule(node.Spec.Taints, s.tolerationsPreferNoSchedule))
	return score, nil
}

// NormalizeScore invoked after scoring all nodes.
func (pl *TaintToleration) NormalizeScore(ctx context.Context, _ *framework.CycleState, pod *v1.Pod, scores framework.NodeScoreList) *framework.Status {
	return pluginhelper.DefaultNormalizeScore(framework.MaxNodeScore, true, scores)
}

// ScoreExtensions of the Score plugin.
func (pl *TaintToleration) ScoreExtensions() framework.ScoreExtensions {
	return pl
}

// New initializes a new plugin and returns it.
func New(_ runtime.Object, h framework.Handle) (framework.Plugin, error) {
	return &TaintToleration{handle: h}, nil
}
