/*
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 podtopologyspread

import (
	"fmt"

	"k8s.io/apimachinery/pkg/runtime"
	framework "k8s.io/kubernetes/pkg/scheduler/framework/v1alpha1"
	schedulerlisters "k8s.io/kubernetes/pkg/scheduler/listers"
)

const (
	// ErrReasonConstraintsNotMatch is used for PodTopologySpread filter error.
	ErrReasonConstraintsNotMatch = "node(s) didn't match pod topology spread constraints"
)

// PodTopologySpread is a plugin that ensures pod's topologySpreadConstraints is satisfied.
type PodTopologySpread struct {
	sharedLister schedulerlisters.SharedLister
}

var _ framework.PreFilterPlugin = &PodTopologySpread{}
var _ framework.FilterPlugin = &PodTopologySpread{}
var _ framework.PreScorePlugin = &PodTopologySpread{}
var _ framework.ScorePlugin = &PodTopologySpread{}

const (
	// Name is the name of the plugin used in the plugin registry and configurations.
	Name = "PodTopologySpread"
)

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

// New initializes a new plugin and returns it.
func New(_ *runtime.Unknown, h framework.FrameworkHandle) (framework.Plugin, error) {
	if h.SnapshotSharedLister() == nil {
		return nil, fmt.Errorf("SnapshotSharedlister is nil")
	}
	return &PodTopologySpread{sharedLister: h.SnapshotSharedLister()}, nil
}
