/*
Copyright 2014 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 admission

import (
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apiserver/pkg/authentication/user"
)

// Attributes is an interface used by AdmissionController to get information about a request
// that is used to make an admission decision.
type Attributes interface {
	// GetName returns the name of the object as presented in the request.  On a CREATE operation, the client
	// may omit name and rely on the server to generate the name.  If that is the case, this method will return
	// the empty string
	GetName() string
	// GetNamespace is the namespace associated with the request (if any)
	GetNamespace() string
	// GetResource is the name of the resource being requested.  This is not the kind.  For example: pods
	GetResource() schema.GroupVersionResource
	// GetSubresource is the name of the subresource being requested.  This is a different resource, scoped to the parent resource, but it may have a different kind.
	// For instance, /pods has the resource "pods" and the kind "Pod", while /pods/foo/status has the resource "pods", the sub resource "status", and the kind "Pod"
	// (because status operates on pods). The binding resource for a pod though may be /pods/foo/binding, which has resource "pods", subresource "binding", and kind "Binding".
	GetSubresource() string
	// GetOperation is the operation being performed
	GetOperation() Operation
	// GetObject is the object from the incoming request prior to default values being applied
	GetObject() runtime.Object
	// GetOldObject is the existing object. Only populated for UPDATE requests.
	GetOldObject() runtime.Object
	// GetKind is the type of object being manipulated.  For example: Pod
	GetKind() schema.GroupVersionKind
	// GetUserInfo is information about the requesting user
	GetUserInfo() user.Info
}

// Interface is an abstract, pluggable interface for Admission Control decisions.
type Interface interface {
	// Admit makes an admission decision based on the request attributes
	Admit(a Attributes) (err error)

	// Handles returns true if this admission controller can handle the given operation
	// where operation can be one of CREATE, UPDATE, DELETE, or CONNECT
	Handles(operation Operation) bool
}

// Operation is the type of resource operation being checked for admission control
type Operation string

// Operation constants
const (
	Create  Operation = "CREATE"
	Update  Operation = "UPDATE"
	Delete  Operation = "DELETE"
	Connect Operation = "CONNECT"
)

// PluginInitializer is used for initialization of shareable resources between admission plugins.
// After initialization the resources have to be set separately
type PluginInitializer interface {
	Initialize(plugin Interface)
}

// Validator holds Validate functions, which are responsible for validation of initialized shared resources
// and should be implemented on admission plugins
type Validator interface {
	Validate() error
}