interface.go

/*
Copyright 2018 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 describe

import (
	"fmt"
	"k8s.io/apimachinery/pkg/api/meta"
	"k8s.io/cli-runtime/pkg/genericclioptions"
)

const (
	// LoadBalancerWidth is the width how we describe load balancer
	LoadBalancerWidth = 16

	// LabelNodeRolePrefix is a label prefix for node roles
	// It's copied over to here until it's merged in core: https://github.com/kubernetes/kubernetes/pull/39112
	LabelNodeRolePrefix = "node-role.kubernetes.io/"

	// NodeLabelRole specifies the role of a node
	NodeLabelRole = "kubernetes.io/role"
)

// DescriberFunc gives a way to display the specified RESTMapping type
type DescriberFunc func(restClientGetter genericclioptions.RESTClientGetter, mapping *meta.RESTMapping) (Describer, error)

// Describer generates output for the named resource or an error
// if the output could not be generated. Implementers typically
// abstract the retrieval of the named object from a remote server.
type Describer interface {
	Describe(namespace, name string, describerSettings DescriberSettings) (output string, err error)
}

// DescriberSettings holds display configuration for each object
// describer to control what is printed.
type DescriberSettings struct {
	ShowEvents bool
}

// ObjectDescriber is an interface for displaying arbitrary objects with extra
// information. Use when an object is in hand (on disk, or already retrieved).
// Implementers may ignore the additional information passed on extra, or use it
// by default. ObjectDescribers may return ErrNoDescriber if no suitable describer
// is found.
type ObjectDescriber interface {
	DescribeObject(object interface{}, extra ...interface{}) (output string, err error)
}

// ErrNoDescriber is a structured error indicating the provided object or objects
// cannot be described.
type ErrNoDescriber struct {
	Types []string
}

// Error implements the error interface.
func (e ErrNoDescriber) Error() string {
	return fmt.Sprintf("no describer has been defined for %v", e.Types)
}