/*
Copyright 2015 Google Inc. All rights reserved.

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 lifecycle

import (
	"fmt"
	"io"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/admission"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
	apierrors "github.com/GoogleCloudPlatform/kubernetes/pkg/api/errors"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/latest"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/meta"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/client"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/client/cache"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/fields"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/labels"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
	"github.com/GoogleCloudPlatform/kubernetes/pkg/watch"
)

func init() {
	admission.RegisterPlugin("NamespaceLifecycle", func(client client.Interface, config io.Reader) (admission.Interface, error) {
		return NewLifecycle(client), nil
	})
}

// lifecycle is an implementation of admission.Interface.
// It enforces life-cycle constraints around a Namespace depending on its Phase
type lifecycle struct {
	client client.Interface
	store  cache.Store
}

func (l *lifecycle) Admit(a admission.Attributes) (err error) {
	if a.GetOperation() != "CREATE" {
		return nil
	}
	defaultVersion, kind, err := latest.RESTMapper.VersionAndKindForResource(a.GetResource())
	if err != nil {
		return err
	}
	mapping, err := latest.RESTMapper.RESTMapping(kind, defaultVersion)
	if err != nil {
		return err
	}
	if mapping.Scope.Name() != meta.RESTScopeNameNamespace {
		return nil
	}
	namespaceObj, exists, err := l.store.Get(&api.Namespace{
		ObjectMeta: api.ObjectMeta{
			Name:      a.GetNamespace(),
			Namespace: "",
		},
	})
	if err != nil {
		return err
	}
	if !exists {
		return nil
	}
	namespace := namespaceObj.(*api.Namespace)
	if namespace.Status.Phase != api.NamespaceTerminating {
		return nil
	}

	name := "Unknown"
	obj := a.GetObject()
	if obj != nil {
		name, _ = meta.NewAccessor().Name(obj)
	}
	return apierrors.NewForbidden(kind, name, fmt.Errorf("Namespace %s is terminating", a.GetNamespace()))
}

func NewLifecycle(c client.Interface) admission.Interface {
	store := cache.NewStore(cache.MetaNamespaceKeyFunc)
	reflector := cache.NewReflector(
		&cache.ListWatch{
			ListFunc: func() (runtime.Object, error) {
				return c.Namespaces().List(labels.Everything(), fields.Everything())
			},
			WatchFunc: func(resourceVersion string) (watch.Interface, error) {
				return c.Namespaces().Watch(labels.Everything(), fields.Everything(), resourceVersion)
			},
		},
		&api.Namespace{},
		store,
		0,
	)
	reflector.Run()
	return &lifecycle{
		client: c,
		store:  store,
	}
}