merge.go

//
// Copyright 2022 IBM Corporation
//
// 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 util

import (
	"encoding/json"

	"k8s.io/apimachinery/pkg/api/equality"
	"k8s.io/klog"
)

// MergeCR deep merge two custom resource spec
func MergeCR(defaultCR, changedCR []byte) map[string]interface{} {
	if len(defaultCR) == 0 && len(changedCR) == 0 {
		return make(map[string]interface{})
	}

	// Handle when only one CR is provided
	defaultCRDecoded := make(map[string]interface{})
	changedCRDecoded := make(map[string]interface{})
	if len(defaultCR) != 0 && len(changedCR) == 0 {
		defaultCRUnmarshalErr := json.Unmarshal(defaultCR, &defaultCRDecoded)
		if defaultCRUnmarshalErr != nil {
			klog.Errorf("failed to unmarshal CR Template: %v", defaultCRUnmarshalErr)
		}
		return defaultCRDecoded
	} else if len(defaultCR) == 0 && len(changedCR) != 0 {
		changedCRUnmarshalErr := json.Unmarshal(changedCR, &changedCRDecoded)
		if changedCRUnmarshalErr != nil {
			klog.Errorf("failed to unmarshal service spec: %v", changedCRUnmarshalErr)
		}
		return changedCRDecoded
	}
	defaultCRUnmarshalErr := json.Unmarshal(defaultCR, &defaultCRDecoded)
	if defaultCRUnmarshalErr != nil {
		klog.Errorf("failed to unmarshal CR Template: %v", defaultCRUnmarshalErr)
	}
	changedCRUnmarshalErr := json.Unmarshal(changedCR, &changedCRDecoded)
	if changedCRUnmarshalErr != nil {
		klog.Errorf("failed to unmarshal service spec: %v", changedCRUnmarshalErr)
	}

	// Merge both specs
	for key := range defaultCRDecoded {
		checkKeyBeforeMerging(key, defaultCRDecoded[key], changedCRDecoded[key], changedCRDecoded)
	}

	return changedCRDecoded
}

func checkKeyBeforeMerging(key string, defaultMap interface{}, changedMap interface{}, finalMap map[string]interface{}) {
	if !equality.Semantic.DeepEqual(defaultMap, changedMap) {
		switch defaultMap := defaultMap.(type) {
		case map[string]interface{}:
			//Check that the changed map value doesn't contain this map at all and is nil
			if changedMap == nil {
				finalMap[key] = defaultMap
			} else if _, ok := changedMap.(map[string]interface{}); ok { //Check that the changed map value is also a map[string]interface
				defaultMapRef := defaultMap
				changedMapRef := changedMap.(map[string]interface{})
				for newKey := range defaultMapRef {
					checkKeyBeforeMerging(newKey, defaultMapRef[newKey], changedMapRef[newKey], finalMap[key].(map[string]interface{}))
				}
			}
		case []interface{}:
			if changedMap == nil {
				finalMap[key] = defaultMap
			} else if _, ok := changedMap.([]interface{}); ok { //Check that the changed map value is also a slice []interface
				defaultMapRef := defaultMap
				changedMapRef := changedMap.([]interface{})
				for i := range defaultMapRef {
					if _, ok := defaultMapRef[i].(map[string]interface{}); ok {
						if len(changedMapRef) > i {
							for newKey := range defaultMapRef[i].(map[string]interface{}) {
								checkKeyBeforeMerging(newKey, defaultMapRef[i].(map[string]interface{})[newKey], changedMapRef[i].(map[string]interface{})[newKey], finalMap[key].([]interface{})[i].(map[string]interface{}))
							}
						}
					}
				}
			}
		default:
			//Check if the value was set, otherwise set it
			if changedMap == nil {
				finalMap[key] = defaultMap
			}
		}
	}
}