/*
Copyright 2015 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 horizontalpodautoscaler

import (
	"fmt"

	"k8s.io/apimachinery/pkg/fields"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/util/validation/field"
	genericapirequest "k8s.io/apiserver/pkg/endpoints/request"
	"k8s.io/apiserver/pkg/storage"
	"k8s.io/apiserver/pkg/storage/names"
	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/apis/autoscaling"
	"k8s.io/kubernetes/pkg/apis/autoscaling/validation"
)

// autoscalerStrategy implements behavior for HorizontalPodAutoscalers
type autoscalerStrategy struct {
	runtime.ObjectTyper
	names.NameGenerator
}

// Strategy is the default logic that applies when creating and updating HorizontalPodAutoscaler
// objects via the REST API.
var Strategy = autoscalerStrategy{api.Scheme, names.SimpleNameGenerator}

// NamespaceScoped is true for autoscaler.
func (autoscalerStrategy) NamespaceScoped() bool {
	return true
}

// PrepareForCreate clears fields that are not allowed to be set by end users on creation.
func (autoscalerStrategy) PrepareForCreate(ctx genericapirequest.Context, obj runtime.Object) {
	newHPA := obj.(*autoscaling.HorizontalPodAutoscaler)

	// create cannot set status
	newHPA.Status = autoscaling.HorizontalPodAutoscalerStatus{}
}

// Validate validates a new autoscaler.
func (autoscalerStrategy) Validate(ctx genericapirequest.Context, obj runtime.Object) field.ErrorList {
	autoscaler := obj.(*autoscaling.HorizontalPodAutoscaler)
	return validation.ValidateHorizontalPodAutoscaler(autoscaler)
}

// Canonicalize normalizes the object after validation.
func (autoscalerStrategy) Canonicalize(obj runtime.Object) {
}

// AllowCreateOnUpdate is false for autoscalers.
func (autoscalerStrategy) AllowCreateOnUpdate() bool {
	return false
}

// PrepareForUpdate clears fields that are not allowed to be set by end users on update.
func (autoscalerStrategy) PrepareForUpdate(ctx genericapirequest.Context, obj, old runtime.Object) {
	newHPA := obj.(*autoscaling.HorizontalPodAutoscaler)
	oldHPA := old.(*autoscaling.HorizontalPodAutoscaler)
	// Update is not allowed to set status
	newHPA.Status = oldHPA.Status
}

// ValidateUpdate is the default update validation for an end user.
func (autoscalerStrategy) ValidateUpdate(ctx genericapirequest.Context, obj, old runtime.Object) field.ErrorList {
	return validation.ValidateHorizontalPodAutoscalerUpdate(obj.(*autoscaling.HorizontalPodAutoscaler), old.(*autoscaling.HorizontalPodAutoscaler))
}

func (autoscalerStrategy) AllowUnconditionalUpdate() bool {
	return true
}

func AutoscalerToSelectableFields(hpa *autoscaling.HorizontalPodAutoscaler) fields.Set {
	return nil
}

// GetAttrs returns labels and fields of a given object for filtering purposes.
func GetAttrs(obj runtime.Object) (labels.Set, fields.Set, error) {
	hpa, ok := obj.(*autoscaling.HorizontalPodAutoscaler)
	if !ok {
		return nil, nil, fmt.Errorf("given object is not a horizontal pod autoscaler.")
	}
	return labels.Set(hpa.ObjectMeta.Labels), AutoscalerToSelectableFields(hpa), nil
}

func MatchAutoscaler(label labels.Selector, field fields.Selector) storage.SelectionPredicate {
	return storage.SelectionPredicate{
		Label:    label,
		Field:    field,
		GetAttrs: GetAttrs,
	}
}

type autoscalerStatusStrategy struct {
	autoscalerStrategy
}

var StatusStrategy = autoscalerStatusStrategy{Strategy}

func (autoscalerStatusStrategy) PrepareForUpdate(ctx genericapirequest.Context, obj, old runtime.Object) {
	newAutoscaler := obj.(*autoscaling.HorizontalPodAutoscaler)
	oldAutoscaler := old.(*autoscaling.HorizontalPodAutoscaler)
	// status changes are not allowed to update spec
	newAutoscaler.Spec = oldAutoscaler.Spec
}

func (autoscalerStatusStrategy) ValidateUpdate(ctx genericapirequest.Context, obj, old runtime.Object) field.ErrorList {
	return validation.ValidateHorizontalPodAutoscalerStatusUpdate(obj.(*autoscaling.HorizontalPodAutoscaler), old.(*autoscaling.HorizontalPodAutoscaler))
}