/*
Copyright 2016 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 validation

import (
	"fmt"
	"strings"

	apimachineryvalidation "k8s.io/apimachinery/pkg/api/validation"
	pathvalidation "k8s.io/apimachinery/pkg/api/validation/path"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/validation/field"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	"k8s.io/kubernetes/pkg/apis/autoscaling"
	apivalidation "k8s.io/kubernetes/pkg/apis/core/validation"
	"k8s.io/kubernetes/pkg/features"
)

const (
	// MaxPeriodSeconds is the largest allowed scaling policy period (in seconds)
	MaxPeriodSeconds int32 = 1800
	// MaxStabilizationWindowSeconds is the largest allowed stabilization window (in seconds)
	MaxStabilizationWindowSeconds int32 = 3600
)

// ValidateScale validates a Scale and returns an ErrorList with any errors.
func ValidateScale(scale *autoscaling.Scale) field.ErrorList {
	allErrs := field.ErrorList{}
	allErrs = append(allErrs, apivalidation.ValidateObjectMeta(&scale.ObjectMeta, true, apimachineryvalidation.NameIsDNSSubdomain, field.NewPath("metadata"))...)

	if scale.Spec.Replicas < 0 {
		allErrs = append(allErrs, field.Invalid(field.NewPath("spec", "replicas"), scale.Spec.Replicas, "must be greater than or equal to 0"))
	}

	return allErrs
}

// ValidateHorizontalPodAutoscalerName can be used to check whether the given autoscaler name is valid.
// Prefix indicates this name will be used as part of generation, in which case trailing dashes are allowed.
var ValidateHorizontalPodAutoscalerName = apivalidation.ValidateReplicationControllerName

func validateHorizontalPodAutoscalerSpec(autoscaler autoscaling.HorizontalPodAutoscalerSpec, fldPath *field.Path, minReplicasLowerBound int32) field.ErrorList {
	allErrs := field.ErrorList{}

	if autoscaler.MinReplicas != nil && *autoscaler.MinReplicas < minReplicasLowerBound {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("minReplicas"), *autoscaler.MinReplicas,
			fmt.Sprintf("must be greater than or equal to %d", minReplicasLowerBound)))
	}
	if autoscaler.MaxReplicas < 1 {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("maxReplicas"), autoscaler.MaxReplicas, "must be greater than 0"))
	}
	if autoscaler.MinReplicas != nil && autoscaler.MaxReplicas < *autoscaler.MinReplicas {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("maxReplicas"), autoscaler.MaxReplicas, "must be greater than or equal to `minReplicas`"))
	}
	if refErrs := ValidateCrossVersionObjectReference(autoscaler.ScaleTargetRef, fldPath.Child("scaleTargetRef")); len(refErrs) > 0 {
		allErrs = append(allErrs, refErrs...)
	}
	if refErrs := validateMetrics(autoscaler.Metrics, fldPath.Child("metrics"), autoscaler.MinReplicas); len(refErrs) > 0 {
		allErrs = append(allErrs, refErrs...)
	}
	if refErrs := validateBehavior(autoscaler.Behavior, fldPath.Child("behavior")); len(refErrs) > 0 {
		allErrs = append(allErrs, refErrs...)
	}
	return allErrs
}

// ValidateCrossVersionObjectReference validates a CrossVersionObjectReference and returns an
// ErrorList with any errors.
func ValidateCrossVersionObjectReference(ref autoscaling.CrossVersionObjectReference, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}
	if len(ref.Kind) == 0 {
		allErrs = append(allErrs, field.Required(fldPath.Child("kind"), ""))
	} else {
		for _, msg := range pathvalidation.IsValidPathSegmentName(ref.Kind) {
			allErrs = append(allErrs, field.Invalid(fldPath.Child("kind"), ref.Kind, msg))
		}
	}

	if len(ref.Name) == 0 {
		allErrs = append(allErrs, field.Required(fldPath.Child("name"), ""))
	} else {
		for _, msg := range pathvalidation.IsValidPathSegmentName(ref.Name) {
			allErrs = append(allErrs, field.Invalid(fldPath.Child("name"), ref.Name, msg))
		}
	}

	return allErrs
}

// ValidateHorizontalPodAutoscaler validates a HorizontalPodAutoscaler and returns an
// ErrorList with any errors.
func ValidateHorizontalPodAutoscaler(autoscaler *autoscaling.HorizontalPodAutoscaler) field.ErrorList {
	allErrs := apivalidation.ValidateObjectMeta(&autoscaler.ObjectMeta, true, ValidateHorizontalPodAutoscalerName, field.NewPath("metadata"))

	// MinReplicasLowerBound represents a minimum value for minReplicas
	// 0 when HPA scale-to-zero feature is enabled
	var minReplicasLowerBound int32

	if utilfeature.DefaultFeatureGate.Enabled(features.HPAScaleToZero) {
		minReplicasLowerBound = 0
	} else {
		minReplicasLowerBound = 1
	}
	allErrs = append(allErrs, validateHorizontalPodAutoscalerSpec(autoscaler.Spec, field.NewPath("spec"), minReplicasLowerBound)...)
	return allErrs
}

// ValidateHorizontalPodAutoscalerUpdate validates an update to a HorizontalPodAutoscaler and returns an
// ErrorList with any errors.
func ValidateHorizontalPodAutoscalerUpdate(newAutoscaler, oldAutoscaler *autoscaling.HorizontalPodAutoscaler) field.ErrorList {
	allErrs := apivalidation.ValidateObjectMetaUpdate(&newAutoscaler.ObjectMeta, &oldAutoscaler.ObjectMeta, field.NewPath("metadata"))

	// minReplicasLowerBound represents a minimum value for minReplicas
	// 0 when HPA scale-to-zero feature is enabled or HPA object already has minReplicas=0
	var minReplicasLowerBound int32

	if utilfeature.DefaultFeatureGate.Enabled(features.HPAScaleToZero) || (oldAutoscaler.Spec.MinReplicas != nil && *oldAutoscaler.Spec.MinReplicas == 0) {
		minReplicasLowerBound = 0
	} else {
		minReplicasLowerBound = 1
	}

	allErrs = append(allErrs, validateHorizontalPodAutoscalerSpec(newAutoscaler.Spec, field.NewPath("spec"), minReplicasLowerBound)...)
	return allErrs
}

// ValidateHorizontalPodAutoscalerStatusUpdate validates an update to status on a HorizontalPodAutoscaler and
// returns an ErrorList with any errors.
func ValidateHorizontalPodAutoscalerStatusUpdate(newAutoscaler, oldAutoscaler *autoscaling.HorizontalPodAutoscaler) field.ErrorList {
	allErrs := apivalidation.ValidateObjectMetaUpdate(&newAutoscaler.ObjectMeta, &oldAutoscaler.ObjectMeta, field.NewPath("metadata"))
	status := newAutoscaler.Status
	allErrs = append(allErrs, apivalidation.ValidateNonnegativeField(int64(status.CurrentReplicas), field.NewPath("status", "currentReplicas"))...)
	allErrs = append(allErrs, apivalidation.ValidateNonnegativeField(int64(status.DesiredReplicas), field.NewPath("status", "desiredReplicas"))...)
	return allErrs
}

func validateMetrics(metrics []autoscaling.MetricSpec, fldPath *field.Path, minReplicas *int32) field.ErrorList {
	allErrs := field.ErrorList{}
	hasObjectMetrics := false
	hasExternalMetrics := false

	for i, metricSpec := range metrics {
		idxPath := fldPath.Index(i)
		if targetErrs := validateMetricSpec(metricSpec, idxPath); len(targetErrs) > 0 {
			allErrs = append(allErrs, targetErrs...)
		}
		if metricSpec.Type == autoscaling.ObjectMetricSourceType {
			hasObjectMetrics = true
		}
		if metricSpec.Type == autoscaling.ExternalMetricSourceType {
			hasExternalMetrics = true
		}
	}

	if minReplicas != nil && *minReplicas == 0 {
		if !hasObjectMetrics && !hasExternalMetrics {
			allErrs = append(allErrs, field.Forbidden(fldPath, "must specify at least one Object or External metric to support scaling to zero replicas"))
		}
	}

	return allErrs
}

func validateBehavior(behavior *autoscaling.HorizontalPodAutoscalerBehavior, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}
	if behavior != nil {
		if scaleUpErrs := validateScalingRules(behavior.ScaleUp, fldPath.Child("scaleUp")); len(scaleUpErrs) > 0 {
			allErrs = append(allErrs, scaleUpErrs...)
		}
		if scaleDownErrs := validateScalingRules(behavior.ScaleDown, fldPath.Child("scaleDown")); len(scaleDownErrs) > 0 {
			allErrs = append(allErrs, scaleDownErrs...)
		}
	}
	return allErrs
}

var validSelectPolicyTypes = sets.NewString(string(autoscaling.MaxPolicySelect), string(autoscaling.MinPolicySelect), string(autoscaling.DisabledPolicySelect))
var validSelectPolicyTypesList = validSelectPolicyTypes.List()

func validateScalingRules(rules *autoscaling.HPAScalingRules, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}
	if rules != nil {
		if rules.StabilizationWindowSeconds != nil && *rules.StabilizationWindowSeconds < 0 {
			allErrs = append(allErrs, field.Invalid(fldPath.Child("stabilizationWindowSeconds"), rules.StabilizationWindowSeconds, "must be greater than or equal to zero"))
		}
		if rules.StabilizationWindowSeconds != nil && *rules.StabilizationWindowSeconds > MaxStabilizationWindowSeconds {
			allErrs = append(allErrs, field.Invalid(fldPath.Child("stabilizationWindowSeconds"), rules.StabilizationWindowSeconds,
				fmt.Sprintf("must be less than or equal to %v", MaxStabilizationWindowSeconds)))
		}
		if rules.SelectPolicy != nil && !validSelectPolicyTypes.Has(string(*rules.SelectPolicy)) {
			allErrs = append(allErrs, field.NotSupported(fldPath.Child("selectPolicy"), rules.SelectPolicy, validSelectPolicyTypesList))
		}
		policiesPath := fldPath.Child("policies")
		if len(rules.Policies) == 0 {
			allErrs = append(allErrs, field.Required(policiesPath, "must specify at least one Policy"))
		}
		for i, policy := range rules.Policies {
			idxPath := policiesPath.Index(i)
			if policyErrs := validateScalingPolicy(policy, idxPath); len(policyErrs) > 0 {
				allErrs = append(allErrs, policyErrs...)
			}
		}
	}
	return allErrs
}

var validPolicyTypes = sets.NewString(string(autoscaling.PodsScalingPolicy), string(autoscaling.PercentScalingPolicy))
var validPolicyTypesList = validPolicyTypes.List()

func validateScalingPolicy(policy autoscaling.HPAScalingPolicy, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}
	if policy.Type != autoscaling.PodsScalingPolicy && policy.Type != autoscaling.PercentScalingPolicy {
		allErrs = append(allErrs, field.NotSupported(fldPath.Child("type"), policy.Type, validPolicyTypesList))
	}
	if policy.Value <= 0 {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("value"), policy.Value, "must be greater than zero"))
	}
	if policy.PeriodSeconds <= 0 {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("periodSeconds"), policy.PeriodSeconds, "must be greater than zero"))
	}
	if policy.PeriodSeconds > MaxPeriodSeconds {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("periodSeconds"), policy.PeriodSeconds,
			fmt.Sprintf("must be less than or equal to %v", MaxPeriodSeconds)))
	}
	return allErrs
}

var validMetricSourceTypes = sets.NewString(string(autoscaling.ObjectMetricSourceType), string(autoscaling.PodsMetricSourceType), string(autoscaling.ResourceMetricSourceType), string(autoscaling.ExternalMetricSourceType))
var validMetricSourceTypesList = validMetricSourceTypes.List()

func validateMetricSpec(spec autoscaling.MetricSpec, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	if len(string(spec.Type)) == 0 {
		allErrs = append(allErrs, field.Required(fldPath.Child("type"), "must specify a metric source type"))
	}

	if !validMetricSourceTypes.Has(string(spec.Type)) {
		allErrs = append(allErrs, field.NotSupported(fldPath.Child("type"), spec.Type, validMetricSourceTypesList))
	}

	typesPresent := sets.NewString()
	if spec.Object != nil {
		typesPresent.Insert("object")
		if typesPresent.Len() == 1 {
			allErrs = append(allErrs, validateObjectSource(spec.Object, fldPath.Child("object"))...)
		}
	}

	if spec.External != nil {
		typesPresent.Insert("external")
		if typesPresent.Len() == 1 {
			allErrs = append(allErrs, validateExternalSource(spec.External, fldPath.Child("external"))...)
		}
	}

	if spec.Pods != nil {
		typesPresent.Insert("pods")
		if typesPresent.Len() == 1 {
			allErrs = append(allErrs, validatePodsSource(spec.Pods, fldPath.Child("pods"))...)
		}
	}

	if spec.Resource != nil {
		typesPresent.Insert("resource")
		if typesPresent.Len() == 1 {
			allErrs = append(allErrs, validateResourceSource(spec.Resource, fldPath.Child("resource"))...)
		}
	}

	expectedField := strings.ToLower(string(spec.Type))

	if !typesPresent.Has(expectedField) {
		allErrs = append(allErrs, field.Required(fldPath.Child(expectedField), "must populate information for the given metric source"))
	}

	if typesPresent.Len() != 1 {
		typesPresent.Delete(expectedField)
		for typ := range typesPresent {
			allErrs = append(allErrs, field.Forbidden(fldPath.Child(typ), "must populate the given metric source only"))
		}
	}

	return allErrs
}

func validateObjectSource(src *autoscaling.ObjectMetricSource, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	allErrs = append(allErrs, ValidateCrossVersionObjectReference(src.DescribedObject, fldPath.Child("describedObject"))...)
	allErrs = append(allErrs, validateMetricIdentifier(src.Metric, fldPath.Child("metric"))...)
	allErrs = append(allErrs, validateMetricTarget(src.Target, fldPath.Child("target"))...)

	if src.Target.Value == nil && src.Target.AverageValue == nil {
		allErrs = append(allErrs, field.Required(fldPath.Child("target").Child("averageValue"), "must set either a target value or averageValue"))
	}

	return allErrs
}

func validateExternalSource(src *autoscaling.ExternalMetricSource, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	allErrs = append(allErrs, validateMetricIdentifier(src.Metric, fldPath.Child("metric"))...)
	allErrs = append(allErrs, validateMetricTarget(src.Target, fldPath.Child("target"))...)

	if src.Target.Value == nil && src.Target.AverageValue == nil {
		allErrs = append(allErrs, field.Required(fldPath.Child("target").Child("averageValue"), "must set either a target value for metric or a per-pod target"))
	}

	if src.Target.Value != nil && src.Target.AverageValue != nil {
		allErrs = append(allErrs, field.Forbidden(fldPath.Child("target").Child("value"), "may not set both a target value for metric and a per-pod target"))
	}

	return allErrs
}

func validatePodsSource(src *autoscaling.PodsMetricSource, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	allErrs = append(allErrs, validateMetricIdentifier(src.Metric, fldPath.Child("metric"))...)
	allErrs = append(allErrs, validateMetricTarget(src.Target, fldPath.Child("target"))...)

	if src.Target.AverageValue == nil {
		allErrs = append(allErrs, field.Required(fldPath.Child("target").Child("averageValue"), "must specify a positive target averageValue"))
	}

	return allErrs
}

func validateResourceSource(src *autoscaling.ResourceMetricSource, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	if len(src.Name) == 0 {
		allErrs = append(allErrs, field.Required(fldPath.Child("name"), "must specify a resource name"))
	}

	allErrs = append(allErrs, validateMetricTarget(src.Target, fldPath.Child("target"))...)

	if src.Target.AverageUtilization == nil && src.Target.AverageValue == nil {
		allErrs = append(allErrs, field.Required(fldPath.Child("target").Child("averageUtilization"), "must set either a target raw value or a target utilization"))
	}

	if src.Target.AverageUtilization != nil && src.Target.AverageValue != nil {
		allErrs = append(allErrs, field.Forbidden(fldPath.Child("target").Child("averageValue"), "may not set both a target raw value and a target utilization"))
	}

	return allErrs
}

func validateMetricTarget(mt autoscaling.MetricTarget, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	if len(mt.Type) == 0 {
		allErrs = append(allErrs, field.Required(fldPath.Child("type"), "must specify a metric target type"))
	}

	if mt.Type != autoscaling.UtilizationMetricType &&
		mt.Type != autoscaling.ValueMetricType &&
		mt.Type != autoscaling.AverageValueMetricType {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("type"), mt.Type, "must be either Utilization, Value, or AverageValue"))
	}

	if mt.Value != nil && mt.Value.Sign() != 1 {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("value"), mt.Value, "must be positive"))
	}

	if mt.AverageValue != nil && mt.AverageValue.Sign() != 1 {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("averageValue"), mt.AverageValue, "must be positive"))
	}

	if mt.AverageUtilization != nil && *mt.AverageUtilization < 1 {
		allErrs = append(allErrs, field.Invalid(fldPath.Child("averageUtilization"), mt.AverageUtilization, "must be greater than 0"))
	}

	return allErrs
}

func validateMetricIdentifier(id autoscaling.MetricIdentifier, fldPath *field.Path) field.ErrorList {
	allErrs := field.ErrorList{}

	if len(id.Name) == 0 {
		allErrs = append(allErrs, field.Required(fldPath.Child("name"), "must specify a metric name"))
	} else {
		for _, msg := range pathvalidation.IsValidPathSegmentName(id.Name) {
			allErrs = append(allErrs, field.Invalid(fldPath.Child("name"), id.Name, msg))
		}
	}
	return allErrs
}
