/*
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 util

import (
	"context"
	"sort"

	apps "k8s.io/api/apps/v1"
	v1 "k8s.io/api/core/v1"
	apiequality "k8s.io/apimachinery/pkg/api/equality"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	intstrutil "k8s.io/apimachinery/pkg/util/intstr"
	"sigs.k8s.io/controller-runtime/pkg/client"
)

// deploymentutil contains a copy of a few functions from Kubernetes controller code to avoid a dependency on k8s.io/kubernetes.
// This code is copied from https://github.com/kubernetes/kubernetes/blob/e856613dd5bb00bcfaca6974431151b5c06cbed5/pkg/controller/deployment/util/deployment_util.go
// No changes to the code were made other than removing some unused functions

// RsListFunc returns the ReplicaSet from the ReplicaSet namespace and the List metav1.ListOptions.
type RsListFunc func(string, metav1.ListOptions) ([]*apps.ReplicaSet, error)

// ListReplicaSets returns a slice of RSes the given deployment targets.
// Note that this does NOT attempt to reconcile ControllerRef (adopt/orphan),
// because only the controller itself should do that.
// However, it does filter out anything whose ControllerRef doesn't match.
func ListReplicaSets(deployment *apps.Deployment, getRSList RsListFunc) ([]*apps.ReplicaSet, error) {
	// TODO: Right now we list replica sets by their labels. We should list them by selector, i.e. the replica set's selector
	//       should be a superset of the deployment's selector, see https://github.com/kubernetes/kubernetes/issues/19830.
	namespace := deployment.Namespace
	selector, err := metav1.LabelSelectorAsSelector(deployment.Spec.Selector)
	if err != nil {
		return nil, err
	}
	options := metav1.ListOptions{LabelSelector: selector.String()}
	all, err := getRSList(namespace, options)
	if err != nil {
		return nil, err
	}
	// Only include those whose ControllerRef matches the Deployment.
	owned := make([]*apps.ReplicaSet, 0, len(all))
	for _, rs := range all {
		if metav1.IsControlledBy(rs, deployment) {
			owned = append(owned, rs)
		}
	}
	return owned, nil
}

// ReplicaSetsByCreationTimestamp sorts a list of ReplicaSet by creation timestamp, using their names as a tie breaker.
type ReplicaSetsByCreationTimestamp []*apps.ReplicaSet

func (o ReplicaSetsByCreationTimestamp) Len() int      { return len(o) }
func (o ReplicaSetsByCreationTimestamp) Swap(i, j int) { o[i], o[j] = o[j], o[i] }
func (o ReplicaSetsByCreationTimestamp) Less(i, j int) bool {
	if o[i].CreationTimestamp.Equal(&o[j].CreationTimestamp) {
		return o[i].Name < o[j].Name
	}
	return o[i].CreationTimestamp.Before(&o[j].CreationTimestamp)
}

// FindNewReplicaSet returns the new RS this given deployment targets (the one with the same pod template).
func FindNewReplicaSet(deployment *apps.Deployment, rsList []*apps.ReplicaSet) *apps.ReplicaSet {
	sort.Sort(ReplicaSetsByCreationTimestamp(rsList))
	for i := range rsList {
		if EqualIgnoreHash(&rsList[i].Spec.Template, &deployment.Spec.Template) {
			// In rare cases, such as after cluster upgrades, Deployment may end up with
			// having more than one new ReplicaSets that have the same template as its template,
			// see https://github.com/kubernetes/kubernetes/issues/40415
			// We deterministically choose the oldest new ReplicaSet.
			return rsList[i]
		}
	}
	// new ReplicaSet does not exist.
	return nil
}

// EqualIgnoreHash returns true if two given podTemplateSpec are equal, ignoring the diff in value of Labels[pod-template-hash]
// We ignore pod-template-hash because:
// 1. The hash result would be different upon podTemplateSpec API changes
//    (e.g. the addition of a new field will cause the hash code to change)
// 2. The deployment template won't have hash labels
func EqualIgnoreHash(template1, template2 *v1.PodTemplateSpec) bool {
	t1Copy := template1.DeepCopy()
	t2Copy := template2.DeepCopy()
	// Remove hash labels from template.Labels before comparing
	delete(t1Copy.Labels, apps.DefaultDeploymentUniqueLabelKey)
	delete(t2Copy.Labels, apps.DefaultDeploymentUniqueLabelKey)
	return apiequality.Semantic.DeepEqual(t1Copy, t2Copy)
}

// GetNewReplicaSet returns a replica set that matches the intent of the given deployment; get ReplicaSetList from client interface.
// Returns nil if the new replica set doesn't exist yet.
func GetNewReplicaSet(deployment *apps.Deployment, c client.Client) (*apps.ReplicaSet, error) {
	rsList, err := ListReplicaSets(deployment, RsListFromClient(c))
	if err != nil {
		return nil, err
	}
	return FindNewReplicaSet(deployment, rsList), nil
}

// RsListFromClient returns an rsListFunc that wraps the given client.
func RsListFromClient(c client.Client) RsListFunc {
	return func(namespace string, options metav1.ListOptions) ([]*apps.ReplicaSet, error) {
		rsList := &apps.ReplicaSetList{}
		err := c.List(context.TODO(), rsList, client.InNamespace(namespace))
		if err != nil {
			return nil, err
		}
		var ret []*apps.ReplicaSet
		for i := range rsList.Items {
			ret = append(ret, &rsList.Items[i])
		}
		return ret, err
	}
}

// IsRollingUpdate returns true if the strategy type is a rolling update.
func IsRollingUpdate(deployment *apps.Deployment) bool {
	return deployment.Spec.Strategy.Type == apps.RollingUpdateDeploymentStrategyType
}

// MaxUnavailable returns the maximum unavailable pods a rolling deployment can take.
func MaxUnavailable(deployment apps.Deployment) int32 {
	if !IsRollingUpdate(&deployment) || *(deployment.Spec.Replicas) == 0 {
		return int32(0)
	}
	// Error caught by validation
	_, maxUnavailable, _ := ResolveFenceposts(deployment.Spec.Strategy.RollingUpdate.MaxSurge, deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, *(deployment.Spec.Replicas))
	if maxUnavailable > *deployment.Spec.Replicas {
		return *deployment.Spec.Replicas
	}
	return maxUnavailable
}

// ResolveFenceposts resolves both maxSurge and maxUnavailable. This needs to happen in one
// step. For example:
//
// 2 desired, max unavailable 1%, surge 0% - should scale old(-1), then new(+1), then old(-1), then new(+1)
// 1 desired, max unavailable 1%, surge 0% - should scale old(-1), then new(+1)
// 2 desired, max unavailable 25%, surge 1% - should scale new(+1), then old(-1), then new(+1), then old(-1)
// 1 desired, max unavailable 25%, surge 1% - should scale new(+1), then old(-1)
// 2 desired, max unavailable 0%, surge 1% - should scale new(+1), then old(-1), then new(+1), then old(-1)
// 1 desired, max unavailable 0%, surge 1% - should scale new(+1), then old(-1)
func ResolveFenceposts(maxSurge, maxUnavailable *intstrutil.IntOrString, desired int32) (int32, int32, error) {
	surge, err := intstrutil.GetValueFromIntOrPercent(intstrutil.ValueOrDefault(maxSurge, intstrutil.FromInt(0)), int(desired), true)
	if err != nil {
		return 0, 0, err
	}
	unavailable, err := intstrutil.GetValueFromIntOrPercent(intstrutil.ValueOrDefault(maxUnavailable, intstrutil.FromInt(0)), int(desired), false)
	if err != nil {
		return 0, 0, err
	}

	if surge == 0 && unavailable == 0 {
		// Validation should never allow the user to explicitly use zero values for both maxSurge
		// maxUnavailable. Due to rounding down maxUnavailable though, it may resolve to zero.
		// If both fenceposts resolve to zero, then we should set maxUnavailable to 1 on the
		// theory that surge might not work due to quota.
		unavailable = 1
	}

	return int32(surge), int32(unavailable), nil
}
