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jsonpatch.go
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jsonpatch.go
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package jsonpatch
import (
"bytes"
"fmt"
"reflect"
"strconv"
"strings"
"github.com/goccy/go-json"
)
var errBadMergeTypes = fmt.Errorf("mismatched json documents")
// Operation operation struct
type Operation struct {
Operation string `json:"op"`
Path string `json:"path"`
Value interface{} `json:"value,omitempty"`
}
// resemblesJSONArray indicates whether the byte-slice "appears" to be
// a JSON array or not.
// False-positives are possible, as this function does not check the internal
// structure of the array. It only checks that the outer syntax is present and
// correct.
func resemblesJSONArray(input []byte) bool {
input = bytes.TrimSpace(input)
hasPrefix := bytes.HasPrefix(input, []byte("["))
hasSuffix := bytes.HasSuffix(input, []byte("]"))
return hasPrefix && hasSuffix
}
// JSON returns a patch operation Json representation
func (j *Operation) JSON() string {
b, _ := json.Marshal(j)
return string(b)
}
// MarshalJSON for patch operations
func (j *Operation) MarshalJSON() ([]byte, error) {
var b bytes.Buffer
b.WriteString("{")
b.WriteString(fmt.Sprintf(`"op":"%s"`, j.Operation))
b.WriteString(fmt.Sprintf(`,"path":"%s"`, j.Path))
// Consider omitting Value for non-nullable operations.
if j.Value != nil || j.Operation == "replace" || j.Operation == "add" {
v, err := json.Marshal(j.Value)
if err != nil {
return nil, err
}
b.WriteString(`,"value":`)
b.Write(v)
}
b.WriteString("}")
return b.Bytes(), nil
}
// ByPath array of patch operation structs
type ByPath []Operation
func (a ByPath) Len() int { return len(a) }
func (a ByPath) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a ByPath) Less(i, j int) bool { return a[i].Path < a[j].Path }
// NewPatch creates a patch operation struct
func NewPatch(operation, path string, value interface{}) Operation {
return Operation{Operation: operation, Path: path, Value: value}
}
// CreatePatch creates a patch as specified in http://jsonpatch.com/
//
// 'a' is original, 'b' is the modified document. Both are to be given as json encoded content.
// The function will return an array of Operations
//
// An error will be returned if any of the two documents are invalid.
func CreatePatch(a, b []byte) ([]Operation, error) {
if bytes.Equal(a, b) {
return []Operation{}, nil
}
originalResemblesArray := resemblesJSONArray(a)
modifiedResemblesArray := resemblesJSONArray(b)
// Do both byte-slices seem like JSON arrays?
if originalResemblesArray && modifiedResemblesArray {
original := []json.RawMessage{}
modified := []json.RawMessage{}
d := json.NewDecoder(bytes.NewReader(a))
d.UseNumber()
err := d.Decode(&original)
if err != nil {
return nil, err
}
db := json.NewDecoder(bytes.NewReader(b))
db.UseNumber()
err = db.Decode(&modified)
if err != nil {
return nil, err
}
patch := []Operation{}
path := ""
keysModified := map[int]bool{}
keysOriginal := map[int]bool{}
for k := range original {
keysOriginal[k] = true
}
if len(modified) == len(original) && len(original) > 2 {
// moving window of collections in ascending order
diffAsc := 0
length := len(modified) - 1
for key := range modified {
// first element of the original cant be found in the modified
if key < length && string(original[0]) == string(modified[key]) {
diffAsc++
break
}
// last element of the modified cant be found in the original
if key > 0 && string(modified[length]) == string(original[key]) {
diffAsc++
break
}
// other than the first original and last modified all elements are the same
if key < length && string(original[key+1]) != string(modified[key]) {
diffAsc++
break
}
}
if diffAsc == 0 {
pFirst := makePath(path, 0)
pLast := makePath(path, length)
patch = append([]Operation{NewPatch("add", pLast, modified[length])}, patch...)
patch = append([]Operation{NewPatch("remove", pFirst, nil)}, patch...)
return patch, nil
}
// moving window of collections in descending order
diffDsc := 0
for key := range modified {
// first element of the modified cant be found in the original
if key < length && string(modified[0]) == string(original[key]) {
diffDsc++
break
}
// last element of the original cant be found in the modified
if key > 0 && string(original[length]) == string(modified[key]) {
diffDsc++
break
}
// other than the first modified and last original all elements are the same
if key < length && string(modified[key+1]) != string(original[key]) {
diffDsc++
break
}
}
if diffDsc == 0 {
pFirst := makePath(path, 0)
pLast := makePath(path, length+1)
patch = append([]Operation{NewPatch("remove", pLast, nil)}, patch...)
patch = append([]Operation{NewPatch("add", pFirst, modified[0])}, patch...)
return patch, nil
}
}
for key, bv := range modified {
keysModified[key] = true
p := makePath(path, key)
_, found := keysOriginal[key]
// value was added
if !found {
patch = append(patch, NewPatch("add", p, bv))
continue
}
av := original[key]
// If types have changed, replace completely
if reflect.TypeOf(av) != reflect.TypeOf(bv) {
patch = append([]Operation{NewPatch("replace", p, bv)}, patch...)
continue
}
// Types are the same, compare values
patch, err = diffObjects(av, bv, "/"+strconv.Itoa(key)+"/", patch)
if err != nil {
return nil, err
}
}
// Now add all deleted values as nil
for key := range original {
_, found := keysModified[key]
if !found {
p := makePath(path, key)
patch = append([]Operation{NewPatch("remove", p, nil)}, patch...)
}
}
return patch, nil
}
// Are both byte-slices are not arrays? Then they are likely JSON objects...
if !originalResemblesArray && !modifiedResemblesArray {
return diffObjects(a, b, "", []Operation{})
}
// None of the above? Then return an error because of mismatched types.
return nil, errBadMergeTypes
}
func diffObjects(a, b []byte, key string, patch []Operation) ([]Operation, error) {
aI := map[string]interface{}{}
bI := map[string]interface{}{}
d := json.NewDecoder(bytes.NewReader(a))
d.UseNumber()
err := d.Decode(&aI)
if err != nil {
return nil, err
}
db := json.NewDecoder(bytes.NewReader(b))
db.UseNumber()
err = db.Decode(&bI)
if err != nil {
return nil, err
}
return diff(aI, bI, key, patch)
}
// Returns true if the values matches (must be json types)
// The types of the values must match, otherwise it will always return false
// If two map[string]interface{} are given, all elements must match.
func matchesValue(av, bv interface{}) bool {
if reflect.TypeOf(av) != reflect.TypeOf(bv) {
return false
}
switch at := av.(type) {
case string:
bt := bv.(string)
if bt == at {
return true
}
case json.Number:
bt := bv.(json.Number)
if bt == at {
return true
}
case bool:
bt := bv.(bool)
if bt == at {
return true
}
case map[string]interface{}:
bt := bv.(map[string]interface{})
for key := range at {
if !matchesValue(at[key], bt[key]) {
return false
}
}
for key := range bt {
if !matchesValue(at[key], bt[key]) {
return false
}
}
return true
case []interface{}:
bt := bv.([]interface{})
if len(bt) != len(at) {
return false
}
for key := range at {
if !matchesValue(at[key], bt[key]) {
return false
}
}
for key := range bt {
if !matchesValue(at[key], bt[key]) {
return false
}
}
return true
}
return false
}
// From http://tools.ietf.org/html/rfc6901#section-4 :
//
// Evaluation of each reference token begins by decoding any escaped
// character sequence. This is performed by first transforming any
// occurrence of the sequence '~1' to '/', and then transforming any
// occurrence of the sequence '~0' to '~'.
// TODO decode support:
// var rfc6901Decoder = strings.NewReplacer("~1", "/", "~0", "~")
var rfc6901Encoder = strings.NewReplacer("~", "~0", "/", "~1")
func makePath(path string, newPart interface{}) string {
key := rfc6901Encoder.Replace(fmt.Sprintf("%v", newPart))
if path == "" {
return "/" + key
}
if strings.HasSuffix(path, "/") {
return path + key
}
return path + "/" + key
}
// diff returns the (recursive) difference between a and b as an array of Operations.
func diff(a, b map[string]interface{}, path string, patch []Operation) ([]Operation, error) {
for key, bv := range b {
p := makePath(path, key)
av, ok := a[key]
// value was added
if !ok {
patch = append([]Operation{NewPatch("add", p, bv)}, patch...)
continue
}
// If types have changed, replace completely
if reflect.TypeOf(av) != reflect.TypeOf(bv) {
patch = append([]Operation{NewPatch("replace", p, bv)}, patch...)
continue
}
// Types are the same, compare values
var err error
patch, err = handleValues(av, bv, p, patch)
if err != nil {
return nil, err
}
}
// Now add all deleted values as nil
for key := range a {
_, found := b[key]
if !found {
p := makePath(path, key)
patch = append([]Operation{NewPatch("remove", p, nil)}, patch...)
}
}
return patch, nil
}
func handleValues(av, bv interface{}, p string, patch []Operation) ([]Operation, error) {
var err error
switch at := av.(type) {
case map[string]interface{}:
bt := bv.(map[string]interface{})
patch, err = diff(at, bt, p, patch)
if err != nil {
return nil, err
}
case string, json.Number, bool:
if !matchesValue(av, bv) {
patch = append([]Operation{NewPatch("replace", p, bv)}, patch...)
}
case []interface{}:
bt, ok := bv.([]interface{})
if !ok {
// array replaced by non-array
patch = append([]Operation{NewPatch("replace", p, bv)}, patch...)
} else if len(at) != len(bt) {
// arrays are not the same length
patch = append(patch, compareArray(at, bt, p)...)
} else {
for i := range bt {
patch, err = handleValues(at[i], bt[i], makePath(p, i), patch)
if err != nil {
return nil, err
}
}
}
case nil:
switch bv.(type) {
case nil:
// Both nil, fine.
default:
patch = append([]Operation{NewPatch("add", p, bv)}, patch...)
}
default:
panic(fmt.Sprintf("Unknown type:%T ", av))
}
return patch, nil
}
func compareArray(av, bv []interface{}, p string) []Operation {
retval := []Operation{}
// var err error
for i, v := range av {
found := false
for _, v2 := range bv {
if reflect.DeepEqual(v, v2) {
found = true
break
}
}
if !found {
retval = append([]Operation{NewPatch("remove", makePath(p, i), nil)}, retval...)
}
}
for i, v := range bv {
found := false
for _, v2 := range av {
if reflect.DeepEqual(v, v2) {
found = true
break
}
}
if !found {
retval = append([]Operation{NewPatch("add", makePath(p, i), v)}, retval...)
}
}
return retval
}