/*
Copyright 2017 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 configuration

import (
	"fmt"
	"sort"

	"k8s.io/api/admissionregistration/v1"
	"k8s.io/apimachinery/pkg/labels"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apiserver/pkg/admission/plugin/webhook"
	"k8s.io/apiserver/pkg/admission/plugin/webhook/generic"
	"k8s.io/client-go/informers"
	admissionregistrationlisters "k8s.io/client-go/listers/admissionregistration/v1"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/cache/synctrack"
)

// mutatingWebhookConfigurationManager collects the mutating webhook objects so that they can be called.
type mutatingWebhookConfigurationManager struct {
	lister    admissionregistrationlisters.MutatingWebhookConfigurationLister
	hasSynced func() bool
	lazy      synctrack.Lazy[[]webhook.WebhookAccessor]
}

var _ generic.Source = &mutatingWebhookConfigurationManager{}

func NewMutatingWebhookConfigurationManager(f informers.SharedInformerFactory) generic.Source {
	informer := f.Admissionregistration().V1().MutatingWebhookConfigurations()
	manager := &mutatingWebhookConfigurationManager{
		lister: informer.Lister(),
	}
	manager.lazy.Evaluate = manager.getConfiguration

	handle, _ := informer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc:    func(_ interface{}) { manager.lazy.Notify() },
		UpdateFunc: func(_, _ interface{}) { manager.lazy.Notify() },
		DeleteFunc: func(_ interface{}) { manager.lazy.Notify() },
	})
	manager.hasSynced = handle.HasSynced

	return manager
}

// Webhooks returns the merged MutatingWebhookConfiguration.
func (m *mutatingWebhookConfigurationManager) Webhooks() []webhook.WebhookAccessor {
	out, err := m.lazy.Get()
	if err != nil {
		utilruntime.HandleError(fmt.Errorf("error getting webhook configuration: %v", err))
	}
	return out
}

// HasSynced returns true if the initial set of mutating webhook configurations
// has been loaded.
func (m *mutatingWebhookConfigurationManager) HasSynced() bool { return m.hasSynced() }

func (m *mutatingWebhookConfigurationManager) getConfiguration() ([]webhook.WebhookAccessor, error) {
	configurations, err := m.lister.List(labels.Everything())
	if err != nil {
		return []webhook.WebhookAccessor{}, err
	}
	return mergeMutatingWebhookConfigurations(configurations), nil
}

func mergeMutatingWebhookConfigurations(configurations []*v1.MutatingWebhookConfiguration) []webhook.WebhookAccessor {
	// The internal order of webhooks for each configuration is provided by the user
	// but configurations themselves can be in any order. As we are going to run these
	// webhooks in serial, they are sorted here to have a deterministic order.
	sort.SliceStable(configurations, MutatingWebhookConfigurationSorter(configurations).ByName)
	accessors := []webhook.WebhookAccessor{}
	for _, c := range configurations {
		// webhook names are not validated for uniqueness, so we check for duplicates and
		// add a int suffix to distinguish between them
		names := map[string]int{}
		for i := range c.Webhooks {
			n := c.Webhooks[i].Name
			uid := fmt.Sprintf("%s/%s/%d", c.Name, n, names[n])
			names[n]++
			accessors = append(accessors, webhook.NewMutatingWebhookAccessor(uid, c.Name, &c.Webhooks[i]))
		}
	}
	return accessors
}

type MutatingWebhookConfigurationSorter []*v1.MutatingWebhookConfiguration

func (a MutatingWebhookConfigurationSorter) ByName(i, j int) bool {
	return a[i].Name < a[j].Name
}