/*
Copyright 2019 The Knative 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 v1alpha1

import (
	"fmt"
	"strconv"
	"time"

	corev1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/runtime/schema"

	"knative.dev/pkg/apis"
	"knative.dev/serving/pkg/apis/autoscaling"
)

const hasBeenActiveAnnotation = "HasBeenActive"

var podCondSet = apis.NewLivingConditionSet(
	PodAutoscalerConditionActive,
)

// GetConditionSet retrieves the condition set for this resource. Implements the KRShaped interface.
func (*PodAutoscaler) GetConditionSet() apis.ConditionSet {
	return podCondSet
}

// GetGroupVersionKind returns the GVK for the PodAutoscaler.
func (pa *PodAutoscaler) GetGroupVersionKind() schema.GroupVersionKind {
	return SchemeGroupVersion.WithKind("PodAutoscaler")
}

// Class returns the Autoscaler class from Annotation or `KPA` if none is set.
func (pa *PodAutoscaler) Class() string {
	if c, ok := pa.Annotations[autoscaling.ClassAnnotationKey]; ok {
		return c
	}
	// Default to "kpa" class for backward compatibility.
	return autoscaling.KPA
}

// Metric returns the contents of the metric annotation or a default.
func (pa *PodAutoscaler) Metric() string {
	if m, ok := pa.Annotations[autoscaling.MetricAnnotationKey]; ok {
		return m
	}
	// TODO: defaulting here is awkward and is already taken care of by defaulting logic.
	return defaultMetric(pa.Class())
}

func (pa *PodAutoscaler) annotationInt32(key string) (int32, bool) {
	if s, ok := pa.Annotations[key]; ok {
		i, err := strconv.ParseInt(s, 10, 32)
		return int32(i), err == nil
	}
	return 0, false
}

func (pa *PodAutoscaler) annotationFloat64(key string) (float64, bool) {
	if s, ok := pa.Annotations[key]; ok {
		f, err := strconv.ParseFloat(s, 64)
		return f, err == nil
	}
	return 0.0, false
}

// ScaleBounds returns scale bounds annotations values as a tuple:
// `(min, max int32)`. The value of 0 for any of min or max means the bound is
// not set.
// Note: min will be ignored if the PA is not reachable
func (pa *PodAutoscaler) ScaleBounds() (min, max int32) {
	if pa.Spec.Reachability != ReachabilityUnreachable {
		min, _ = pa.annotationInt32(autoscaling.MinScaleAnnotationKey)
	}
	max, _ = pa.annotationInt32(autoscaling.MaxScaleAnnotationKey)

	return
}

// Target returns the target annotation value or false if not present, or invalid.
func (pa *PodAutoscaler) Target() (float64, bool) {
	return pa.annotationFloat64(autoscaling.TargetAnnotationKey)
}

// TargetUtilization returns the target capacity utilization as a fraction,
// if the corresponding annotation is set.
func (pa *PodAutoscaler) TargetUtilization() (float64, bool) {
	if tu, ok := pa.annotationFloat64(autoscaling.TargetUtilizationPercentageKey); ok {
		return tu / 100, true
	}
	return 0, false
}

// TargetBC returns the target burst capacity,
// if the corresponding annotation is set.
func (pa *PodAutoscaler) TargetBC() (float64, bool) {
	// The value is validated in the webhook.
	return pa.annotationFloat64(autoscaling.TargetBurstCapacityKey)
}

func (pa *PodAutoscaler) annotationDuration(key string) (time.Duration, bool) {
	if s, ok := pa.Annotations[key]; ok {
		d, err := time.ParseDuration(s)
		return d, err == nil
	}
	return 0, false
}

// ScaleToZeroPodRetention returns the window annotation value or false if not present.
func (pa *PodAutoscaler) ScaleToZeroPodRetention() (time.Duration, bool) {
	// The value is validated in the webhook.
	return pa.annotationDuration(autoscaling.ScaleToZeroPodRetentionPeriodKey)
}

// Window returns the window annotation value or false if not present.
func (pa *PodAutoscaler) Window() (time.Duration, bool) {
	// The value is validated in the webhook.
	return pa.annotationDuration(autoscaling.WindowAnnotationKey)
}

// PanicWindowPercentage returns panic window annotation value or false if not present.
func (pa *PodAutoscaler) PanicWindowPercentage() (percentage float64, ok bool) {
	// The value is validated in the webhook.
	return pa.annotationFloat64(autoscaling.PanicWindowPercentageAnnotationKey)
}

// PanicThresholdPercentage return the panic target annotation value or false if not present.
func (pa *PodAutoscaler) PanicThresholdPercentage() (percentage float64, ok bool) {
	// The value is validated in the webhook.
	return pa.annotationFloat64(autoscaling.PanicThresholdPercentageAnnotationKey)
}

// InitialScale returns the initial scale on the revision if present, or false if not present.
func (pa *PodAutoscaler) InitialScale() (int32, bool) {
	// The value is validated in the webhook.
	return pa.annotationInt32(autoscaling.InitialScaleAnnotationKey)
}

// IsReady returns true if the Status condition PodAutoscalerConditionReady
// is true and the latest spec has been observed.
func (pa *PodAutoscaler) IsReady() bool {
	pas := pa.Status
	return pa.Generation == pas.ObservedGeneration &&
		pas.GetCondition(PodAutoscalerConditionReady).IsTrue()
}

// IsActive returns true if the pod autoscaler is finished scaling.
func (pas *PodAutoscalerStatus) IsActive() bool {
	return pas.GetCondition(PodAutoscalerConditionActive).IsTrue()
}

// IsActivating returns true if the pod autoscaler is Activating if it is neither
// Active nor Inactive.
func (pas *PodAutoscalerStatus) IsActivating() bool {
	return pas.GetCondition(PodAutoscalerConditionActive).IsUnknown()
}

// IsInactive returns true if the pod autoscaler is Inactive.
func (pas *PodAutoscalerStatus) IsInactive() bool {
	return pas.GetCondition(PodAutoscalerConditionActive).IsFalse()
}

// HasBeenActive returns true if the pod autoscaler has reached its initial scale.
func (pas *PodAutoscalerStatus) HasBeenActive() bool {
	if val, ok := pas.Annotations[hasBeenActiveAnnotation]; !ok || val != "true" {
		return false
	}
	return true
}

// MarkHasBeenActive marks the PA's PodAutoscalerConditionInitiallyActive condition true.
func (pas *PodAutoscalerStatus) MarkHasBeenActive() {
	if pas.Annotations == nil {
		pas.Annotations = map[string]string{}
	}
	pas.Annotations[hasBeenActiveAnnotation] = "true"
}

// GetCondition gets the condition `t`.
func (pas *PodAutoscalerStatus) GetCondition(t apis.ConditionType) *apis.Condition {
	return podCondSet.Manage(pas).GetCondition(t)
}

// InitializeConditions initializes the conditions of the PA.
func (pas *PodAutoscalerStatus) InitializeConditions() {
	podCondSet.Manage(pas).InitializeConditions()
}

// MarkActive marks the PA active.
func (pas *PodAutoscalerStatus) MarkActive() {
	podCondSet.Manage(pas).MarkTrue(PodAutoscalerConditionActive)
}

// MarkActivating marks the PA as activating.
func (pas *PodAutoscalerStatus) MarkActivating(reason, message string) {
	podCondSet.Manage(pas).MarkUnknown(PodAutoscalerConditionActive, reason, message)
}

// MarkInactive marks the PA as inactive.
func (pas *PodAutoscalerStatus) MarkInactive(reason, message string) {
	podCondSet.Manage(pas).MarkFalse(PodAutoscalerConditionActive, reason, message)
}

// MarkResourceNotOwned changes the "Active" condition to false to reflect that the
// resource of the given kind and name has already been created, and we do not own it.
func (pas *PodAutoscalerStatus) MarkResourceNotOwned(kind, name string) {
	pas.MarkInactive("NotOwned",
		fmt.Sprintf("There is an existing %s %q that we do not own.", kind, name))
}

// MarkResourceFailedCreation changes the "Active" condition to false to reflect that a
// critical resource of the given kind and name was unable to be created.
func (pas *PodAutoscalerStatus) MarkResourceFailedCreation(kind, name string) {
	pas.MarkInactive("FailedCreate",
		fmt.Sprintf("Failed to create %s %q.", kind, name))
}

// CanScaleToZero checks whether the pod autoscaler has been in an inactive state
// for at least the specified grace period.
func (pas *PodAutoscalerStatus) CanScaleToZero(now time.Time, gracePeriod time.Duration) bool {
	return pas.InactiveFor(now) >= gracePeriod
}

// InactiveFor returns the time PA spent being inactive.
func (pas *PodAutoscalerStatus) InactiveFor(now time.Time) time.Duration {
	return pas.inStatusFor(corev1.ConditionFalse, now, 0)
}

// ActiveFor returns the time PA spent being active.
func (pas *PodAutoscalerStatus) ActiveFor(now time.Time) time.Duration {
	return pas.inStatusFor(corev1.ConditionTrue, now, 0)
}

// CanFailActivation checks whether the pod autoscaler has been activating
// for at least the specified idle period.
func (pas *PodAutoscalerStatus) CanFailActivation(now time.Time, idlePeriod time.Duration) bool {
	return pas.inStatusFor(corev1.ConditionUnknown, now, idlePeriod) > 0
}

// inStatusFor returns positive duration if the PodAutoscalerStatus's Active condition has stayed in
// the specified status for at least the specified duration. Otherwise it returns negative duration,
// including when the status is undetermined (Active condition is not found.)
func (pas *PodAutoscalerStatus) inStatusFor(status corev1.ConditionStatus, now time.Time, dur time.Duration) time.Duration {
	cond := pas.GetCondition(PodAutoscalerConditionActive)
	if cond == nil || cond.Status != status {
		return -1
	}
	return now.Sub(cond.LastTransitionTime.Inner.Add(dur))
}

// GetDesiredScale returns the desired scale if ever set, or -1.
func (pas *PodAutoscalerStatus) GetDesiredScale() int32 {
	if pas.DesiredScale != nil {
		return *pas.DesiredScale
	}
	return -1
}

// GetActualScale returns the desired scale if ever set, or -1.
func (pas *PodAutoscalerStatus) GetActualScale() int32 {
	if pas.ActualScale != nil {
		return *pas.ActualScale
	}
	return -1
}
