/*
Copyright 2019 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 service

import (
	"context"
	"encoding/json"
	"fmt"

	v1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/strategicpatch"
	v1core "k8s.io/client-go/kubernetes/typed/core/v1"
)

// patch patches service's Status or ObjectMeta given the origin and
// updated ones. Change to spec will be ignored.
func patch(c v1core.CoreV1Interface, oldSvc *v1.Service, newSvc *v1.Service) (*v1.Service, error) {
	// Reset spec to make sure only patch for Status or ObjectMeta.
	newSvc.Spec = oldSvc.Spec

	patchBytes, err := getPatchBytes(oldSvc, newSvc)
	if err != nil {
		return nil, err
	}

	return c.Services(oldSvc.Namespace).Patch(context.TODO(), oldSvc.Name, types.StrategicMergePatchType, patchBytes, metav1.PatchOptions{}, "status")
}

func getPatchBytes(oldSvc *v1.Service, newSvc *v1.Service) ([]byte, error) {
	oldData, err := json.Marshal(oldSvc)
	if err != nil {
		return nil, fmt.Errorf("failed to Marshal oldData for svc %s/%s: %v", oldSvc.Namespace, oldSvc.Name, err)
	}

	newData, err := json.Marshal(newSvc)
	if err != nil {
		return nil, fmt.Errorf("failed to Marshal newData for svc %s/%s: %v", newSvc.Namespace, newSvc.Name, err)
	}

	patchBytes, err := strategicpatch.CreateTwoWayMergePatch(oldData, newData, v1.Service{})
	if err != nil {
		return nil, fmt.Errorf("failed to CreateTwoWayMergePatch for svc %s/%s: %v", oldSvc.Namespace, oldSvc.Name, err)
	}
	return patchBytes, nil
}
