typemeta.go

/*
Copyright 2014 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 runtime

import (
	"fmt"
	"reflect"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/conversion"
)

// FindTypeMeta takes an arbitary api type, returns pointer to its TypeMeta field.
// obj must be a pointer to an api type.
func FindTypeMeta(obj Object) (TypeMetaInterface, error) {
	v, err := conversion.EnforcePtr(obj)
	if err != nil {
		return nil, err
	}
	t := v.Type()
	name := t.Name()
	if v.Kind() != reflect.Struct {
		return nil, fmt.Errorf("expected struct, but got %v: %v (%#v)", v.Kind(), name, v.Interface())
	}
	typeMeta := v.FieldByName("TypeMeta")
	if !typeMeta.IsValid() {
		return nil, fmt.Errorf("struct %v lacks embedded JSON type", name)
	}
	g, err := newGenericTypeMeta(typeMeta)
	if err != nil {
		return nil, err
	}
	return g, nil
}

// NewTypeMetaResourceVersioner returns a ResourceVersioner that can set or
// retrieve ResourceVersion on objects derived from TypeMeta.
func NewTypeMetaResourceVersioner() ResourceVersioner {
	return jsonBaseModifier{}
}

// jsonBaseModifier implements ResourceVersioner and SelfLinker.
type jsonBaseModifier struct{}

func (v jsonBaseModifier) ResourceVersion(obj Object) (string, error) {
	json, err := FindTypeMeta(obj)
	if err != nil {
		return "", err
	}
	return json.ResourceVersion(), nil
}

func (v jsonBaseModifier) SetResourceVersion(obj Object, version string) error {
	json, err := FindTypeMeta(obj)
	if err != nil {
		return err
	}
	json.SetResourceVersion(version)
	return nil
}

func (v jsonBaseModifier) ID(obj Object) (string, error) {
	json, err := FindTypeMeta(obj)
	if err != nil {
		return "", err
	}
	return json.ID(), nil
}

func (v jsonBaseModifier) SelfLink(obj Object) (string, error) {
	json, err := FindTypeMeta(obj)
	if err != nil {
		return "", err
	}
	return json.SelfLink(), nil
}

func (v jsonBaseModifier) SetSelfLink(obj Object, selfLink string) error {
	json, err := FindTypeMeta(obj)
	if err != nil {
		return err
	}
	json.SetSelfLink(selfLink)
	return nil
}

// NewTypeMetaSelfLinker returns a SelfLinker that works on all TypeMeta SelfLink fields.
func NewTypeMetaSelfLinker() SelfLinker {
	return jsonBaseModifier{}
}

// TypeMetaInterface lets you work with a TypeMeta from any of the versioned or
// internal APIObjects.
type TypeMetaInterface interface {
	ID() string
	SetID(ID string)
	APIVersion() string
	SetAPIVersion(version string)
	Kind() string
	SetKind(kind string)
	ResourceVersion() string
	SetResourceVersion(version string)
	SelfLink() string
	SetSelfLink(selfLink string)
}

type genericTypeMeta struct {
	id              *string
	apiVersion      *string
	kind            *string
	resourceVersion *string
	selfLink        *string
}

func (g genericTypeMeta) ID() string {
	return *g.id
}

func (g genericTypeMeta) SetID(id string) {
	*g.id = id
}

func (g genericTypeMeta) APIVersion() string {
	return *g.apiVersion
}

func (g genericTypeMeta) SetAPIVersion(version string) {
	*g.apiVersion = version
}

func (g genericTypeMeta) Kind() string {
	return *g.kind
}

func (g genericTypeMeta) SetKind(kind string) {
	*g.kind = kind
}

func (g genericTypeMeta) ResourceVersion() string {
	return *g.resourceVersion
}

func (g genericTypeMeta) SetResourceVersion(version string) {
	*g.resourceVersion = version
}

func (g genericTypeMeta) SelfLink() string {
	return *g.selfLink
}

func (g genericTypeMeta) SetSelfLink(selfLink string) {
	*g.selfLink = selfLink
}

// fieldPtr puts the address of fieldName, which must be a member of v,
// into dest, which must be an address of a variable to which this field's
// address can be assigned.
func fieldPtr(v reflect.Value, fieldName string, dest interface{}) error {
	field := v.FieldByName(fieldName)
	if !field.IsValid() {
		return fmt.Errorf("Couldn't find %v field in %#v", fieldName, v.Interface())
	}
	v = reflect.ValueOf(dest)
	if v.Kind() != reflect.Ptr {
		return fmt.Errorf("dest should be ptr")
	}
	v = v.Elem()
	field = field.Addr()
	if field.Type().AssignableTo(v.Type()) {
		v.Set(field)
		return nil
	}
	if field.Type().ConvertibleTo(v.Type()) {
		v.Set(field.Convert(v.Type()))
		return nil
	}
	return fmt.Errorf("Couldn't assign/convert %v to %v", field.Type(), v.Type())
}

// newGenericTypeMeta creates a new generic TypeMeta from v, which must be an
// addressable/setable reflect.Value having the same fields as api.TypeMeta.
// Returns an error if this isn't the case.
func newGenericTypeMeta(v reflect.Value) (genericTypeMeta, error) {
	g := genericTypeMeta{}
	if err := fieldPtr(v, "ID", &g.id); err != nil {
		return g, err
	}
	if err := fieldPtr(v, "APIVersion", &g.apiVersion); err != nil {
		return g, err
	}
	if err := fieldPtr(v, "Kind", &g.kind); err != nil {
		return g, err
	}
	if err := fieldPtr(v, "ResourceVersion", &g.resourceVersion); err != nil {
		return g, err
	}
	if err := fieldPtr(v, "SelfLink", &g.selfLink); err != nil {
		return g, err
	}
	return g, nil
}