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package jsonpatch
import (
"bytes"
"encoding/json"
"fmt"
"reflect"
"strings"
)
var errBadJSONDoc = fmt.Errorf("invalid JSON Document")
type JsonPatchOperation = Operation
type Operation struct {
Operation string `json:"op"`
Path string `json:"path"`
Value interface{} `json:"value,omitempty"`
}
func (j *Operation) Json() string {
b, _ := json.Marshal(j)
return string(b)
}
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
}
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 }
func NewOperation(op, path string, value interface{}) Operation {
return Operation{Operation: op, 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 JsonPatchOperations
//
// An error will be returned if any of the two documents are invalid.
func CreatePatch(a, b []byte) ([]Operation, error) {
var aI interface{}
var bI interface{}
err := json.Unmarshal(a, &aI)
if err != nil {
return nil, errBadJSONDoc
}
err = json.Unmarshal(b, &bI)
if err != nil {
return nil, errBadJSONDoc
}
return handleValues(aI, bI, "", []Operation{})
}
// 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, ok := bv.(string)
if ok && bt == at {
return true
}
case float64:
bt, ok := bv.(float64)
if ok && bt == at {
return true
}
case bool:
bt, ok := bv.(bool)
if ok && bt == at {
return true
}
case map[string]interface{}:
bt, ok := bv.(map[string]interface{})
if !ok {
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
case []interface{}:
bt, ok := bv.([]interface{})
if !ok {
return false
}
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 JsonPatchOperations.
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(patch, NewOperation("add", p, bv))
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(patch, NewOperation("remove", p, nil))
}
}
return patch, nil
}
func handleValues(av, bv interface{}, p string, patch []Operation) ([]Operation, error) {
{
at := reflect.TypeOf(av)
bt := reflect.TypeOf(bv)
if at == nil && bt == nil {
// do nothing
return patch, nil
} else if at != bt {
// If types have changed, replace completely (preserves null in destination)
return append(patch, NewOperation("replace", p, bv)), nil
}
}
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, float64, bool:
if !matchesValue(av, bv) {
patch = append(patch, NewOperation("replace", p, bv))
}
case []interface{}:
bt := bv.([]interface{})
if isSimpleArray(at) && isSimpleArray(bt) {
patch = append(patch, compareEditDistance(at, bt, p)...)
} else {
n := min(len(at), len(bt))
for i := len(at) - 1; i >= n; i-- {
patch = append(patch, NewOperation("remove", makePath(p, i), nil))
}
for i := n; i < len(bt); i++ {
patch = append(patch, NewOperation("add", makePath(p, i), bt[i]))
}
for i := 0; i < n; i++ {
var err error
patch, err = handleValues(at[i], bt[i], makePath(p, i), patch)
if err != nil {
return nil, err
}
}
}
default:
panic(fmt.Sprintf("Unknown type:%T ", av))
}
return patch, nil
}
func isBasicType(a interface{}) bool {
switch a.(type) {
case string, float64, bool:
default:
return false
}
return true
}
func isSimpleArray(a []interface{}) bool {
for i := range a {
switch a[i].(type) {
case string, float64, bool:
default:
val := reflect.ValueOf(a[i])
if val.Kind() == reflect.Map {
for _, k := range val.MapKeys() {
av := val.MapIndex(k)
if av.Kind() == reflect.Ptr || av.Kind() == reflect.Interface {
if av.IsNil() {
continue
}
av = av.Elem()
}
if av.Kind() != reflect.String && av.Kind() != reflect.Float64 && av.Kind() != reflect.Bool {
return false
}
}
return true
}
return false
}
}
return true
}
// https://en.wikipedia.org/wiki/Wagner%E2%80%93Fischer_algorithm
// Adapted from https://github.com/texttheater/golang-levenshtein
func compareEditDistance(s, t []interface{}, p string) []Operation {
m := len(s)
n := len(t)
d := make([][]int, m+1)
for i := 0; i <= m; i++ {
d[i] = make([]int, n+1)
d[i][0] = i
}
for j := 0; j <= n; j++ {
d[0][j] = j
}
for j := 1; j <= n; j++ {
for i := 1; i <= m; i++ {
if reflect.DeepEqual(s[i-1], t[j-1]) {
d[i][j] = d[i-1][j-1] // no op required
} else {
del := d[i-1][j] + 1
add := d[i][j-1] + 1
rep := d[i-1][j-1] + 1
d[i][j] = min(rep, min(add, del))
}
}
}
return backtrace(s, t, p, m, n, d)
}
func min(x int, y int) int {
if y < x {
return y
}
return x
}
func backtrace(s, t []interface{}, p string, i int, j int, matrix [][]int) []Operation {
if i > 0 && matrix[i-1][j]+1 == matrix[i][j] {
op := NewOperation("remove", makePath(p, i-1), nil)
return append([]Operation{op}, backtrace(s, t, p, i-1, j, matrix)...)
}
if j > 0 && matrix[i][j-1]+1 == matrix[i][j] {
op := NewOperation("add", makePath(p, i), t[j-1])
return append([]Operation{op}, backtrace(s, t, p, i, j-1, matrix)...)
}
if i > 0 && j > 0 && matrix[i-1][j-1]+1 == matrix[i][j] {
if isBasicType(s[0]) {
op := NewOperation("replace", makePath(p, i-1), t[j-1])
return append([]Operation{op}, backtrace(s, t, p, i-1, j-1, matrix)...)
}
p2, _ := handleValues(s[i-1], t[j-1], makePath(p, i-1), []Operation{})
return append(p2, backtrace(s, t, p, i-1, j-1, matrix)...)
}
if i > 0 && j > 0 && matrix[i-1][j-1] == matrix[i][j] {
return backtrace(s, t, p, i-1, j-1, matrix)
}
return []Operation{}
}