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335 lines
8.1 KiB
335 lines
8.1 KiB
package jsonpatch
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import (
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"bytes"
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"encoding/json"
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"fmt"
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"reflect"
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"strings"
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)
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var errBadJSONDoc = fmt.Errorf("invalid JSON Document")
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type JsonPatchOperation = Operation
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type Operation struct {
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Operation string `json:"op"`
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Path string `json:"path"`
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Value interface{} `json:"value,omitempty"`
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}
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func (j *Operation) Json() string {
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b, _ := json.Marshal(j)
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return string(b)
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}
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func (j *Operation) MarshalJSON() ([]byte, error) {
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var b bytes.Buffer
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b.WriteString("{")
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b.WriteString(fmt.Sprintf(`"op":"%s"`, j.Operation))
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b.WriteString(fmt.Sprintf(`,"path":"%s"`, j.Path))
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// Consider omitting Value for non-nullable operations.
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if j.Value != nil || j.Operation == "replace" || j.Operation == "add" {
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v, err := json.Marshal(j.Value)
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if err != nil {
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return nil, err
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}
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b.WriteString(`,"value":`)
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b.Write(v)
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}
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b.WriteString("}")
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return b.Bytes(), nil
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}
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type ByPath []Operation
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func (a ByPath) Len() int { return len(a) }
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func (a ByPath) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
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func (a ByPath) Less(i, j int) bool { return a[i].Path < a[j].Path }
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func NewOperation(op, path string, value interface{}) Operation {
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return Operation{Operation: op, Path: path, Value: value}
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}
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// CreatePatch creates a patch as specified in http://jsonpatch.com/
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//
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// 'a' is original, 'b' is the modified document. Both are to be given as json encoded content.
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// The function will return an array of JsonPatchOperations
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//
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// An error will be returned if any of the two documents are invalid.
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func CreatePatch(a, b []byte) ([]Operation, error) {
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var aI interface{}
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var bI interface{}
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err := json.Unmarshal(a, &aI)
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if err != nil {
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return nil, errBadJSONDoc
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}
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err = json.Unmarshal(b, &bI)
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if err != nil {
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return nil, errBadJSONDoc
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}
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return handleValues(aI, bI, "", []Operation{})
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}
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// Returns true if the values matches (must be json types)
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// The types of the values must match, otherwise it will always return false
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// If two map[string]interface{} are given, all elements must match.
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func matchesValue(av, bv interface{}) bool {
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if reflect.TypeOf(av) != reflect.TypeOf(bv) {
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return false
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}
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switch at := av.(type) {
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case string:
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bt, ok := bv.(string)
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if ok && bt == at {
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return true
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}
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case float64:
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bt, ok := bv.(float64)
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if ok && bt == at {
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return true
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}
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case bool:
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bt, ok := bv.(bool)
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if ok && bt == at {
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return true
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}
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case map[string]interface{}:
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bt, ok := bv.(map[string]interface{})
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if !ok {
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return false
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}
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for key := range at {
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if !matchesValue(at[key], bt[key]) {
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return false
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}
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}
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for key := range bt {
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if !matchesValue(at[key], bt[key]) {
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return false
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}
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}
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return true
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case []interface{}:
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bt, ok := bv.([]interface{})
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if !ok {
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return false
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}
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if len(bt) != len(at) {
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return false
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}
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for key := range at {
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if !matchesValue(at[key], bt[key]) {
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return false
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}
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}
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for key := range bt {
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if !matchesValue(at[key], bt[key]) {
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return false
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}
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}
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return true
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}
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return false
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}
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// From http://tools.ietf.org/html/rfc6901#section-4 :
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//
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// Evaluation of each reference token begins by decoding any escaped
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// character sequence. This is performed by first transforming any
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// occurrence of the sequence '~1' to '/', and then transforming any
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// occurrence of the sequence '~0' to '~'.
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// TODO decode support:
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// var rfc6901Decoder = strings.NewReplacer("~1", "/", "~0", "~")
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var rfc6901Encoder = strings.NewReplacer("~", "~0", "/", "~1")
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func makePath(path string, newPart interface{}) string {
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key := rfc6901Encoder.Replace(fmt.Sprintf("%v", newPart))
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if path == "" {
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return "/" + key
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}
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if strings.HasSuffix(path, "/") {
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return path + key
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}
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return path + "/" + key
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}
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// diff returns the (recursive) difference between a and b as an array of JsonPatchOperations.
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func diff(a, b map[string]interface{}, path string, patch []Operation) ([]Operation, error) {
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for key, bv := range b {
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p := makePath(path, key)
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av, ok := a[key]
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// value was added
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if !ok {
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patch = append(patch, NewOperation("add", p, bv))
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continue
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}
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// Types are the same, compare values
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var err error
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patch, err = handleValues(av, bv, p, patch)
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if err != nil {
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return nil, err
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}
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}
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// Now add all deleted values as nil
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for key := range a {
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_, found := b[key]
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if !found {
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p := makePath(path, key)
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patch = append(patch, NewOperation("remove", p, nil))
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}
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}
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return patch, nil
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}
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func handleValues(av, bv interface{}, p string, patch []Operation) ([]Operation, error) {
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{
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at := reflect.TypeOf(av)
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bt := reflect.TypeOf(bv)
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if at == nil && bt == nil {
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// do nothing
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return patch, nil
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} else if at != bt {
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// If types have changed, replace completely (preserves null in destination)
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return append(patch, NewOperation("replace", p, bv)), nil
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}
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}
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var err error
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switch at := av.(type) {
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case map[string]interface{}:
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bt := bv.(map[string]interface{})
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patch, err = diff(at, bt, p, patch)
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if err != nil {
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return nil, err
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}
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case string, float64, bool:
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if !matchesValue(av, bv) {
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patch = append(patch, NewOperation("replace", p, bv))
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}
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case []interface{}:
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bt := bv.([]interface{})
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if isSimpleArray(at) && isSimpleArray(bt) {
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patch = append(patch, compareEditDistance(at, bt, p)...)
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} else {
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n := min(len(at), len(bt))
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for i := len(at) - 1; i >= n; i-- {
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patch = append(patch, NewOperation("remove", makePath(p, i), nil))
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}
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for i := n; i < len(bt); i++ {
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patch = append(patch, NewOperation("add", makePath(p, i), bt[i]))
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}
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for i := 0; i < n; i++ {
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var err error
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patch, err = handleValues(at[i], bt[i], makePath(p, i), patch)
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if err != nil {
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return nil, err
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}
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}
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}
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default:
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panic(fmt.Sprintf("Unknown type:%T ", av))
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}
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return patch, nil
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}
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func isBasicType(a interface{}) bool {
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switch a.(type) {
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case string, float64, bool:
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default:
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return false
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}
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return true
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}
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func isSimpleArray(a []interface{}) bool {
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for i := range a {
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switch a[i].(type) {
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case string, float64, bool:
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default:
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val := reflect.ValueOf(a[i])
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if val.Kind() == reflect.Map {
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for _, k := range val.MapKeys() {
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av := val.MapIndex(k)
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if av.Kind() == reflect.Ptr || av.Kind() == reflect.Interface {
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if av.IsNil() {
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continue
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}
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av = av.Elem()
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}
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if av.Kind() != reflect.String && av.Kind() != reflect.Float64 && av.Kind() != reflect.Bool {
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return false
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}
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}
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return true
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}
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return false
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}
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}
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return true
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}
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// https://en.wikipedia.org/wiki/Wagner%E2%80%93Fischer_algorithm
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// Adapted from https://github.com/texttheater/golang-levenshtein
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func compareEditDistance(s, t []interface{}, p string) []Operation {
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m := len(s)
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n := len(t)
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d := make([][]int, m+1)
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for i := 0; i <= m; i++ {
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d[i] = make([]int, n+1)
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d[i][0] = i
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}
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for j := 0; j <= n; j++ {
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d[0][j] = j
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}
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for j := 1; j <= n; j++ {
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for i := 1; i <= m; i++ {
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if reflect.DeepEqual(s[i-1], t[j-1]) {
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d[i][j] = d[i-1][j-1] // no op required
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} else {
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del := d[i-1][j] + 1
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add := d[i][j-1] + 1
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rep := d[i-1][j-1] + 1
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d[i][j] = min(rep, min(add, del))
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}
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}
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}
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return backtrace(s, t, p, m, n, d)
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}
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func min(x int, y int) int {
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if y < x {
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return y
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}
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return x
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}
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func backtrace(s, t []interface{}, p string, i int, j int, matrix [][]int) []Operation {
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if i > 0 && matrix[i-1][j]+1 == matrix[i][j] {
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op := NewOperation("remove", makePath(p, i-1), nil)
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return append([]Operation{op}, backtrace(s, t, p, i-1, j, matrix)...)
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}
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if j > 0 && matrix[i][j-1]+1 == matrix[i][j] {
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op := NewOperation("add", makePath(p, i), t[j-1])
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return append([]Operation{op}, backtrace(s, t, p, i, j-1, matrix)...)
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}
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if i > 0 && j > 0 && matrix[i-1][j-1]+1 == matrix[i][j] {
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if isBasicType(s[0]) {
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op := NewOperation("replace", makePath(p, i-1), t[j-1])
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return append([]Operation{op}, backtrace(s, t, p, i-1, j-1, matrix)...)
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}
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p2, _ := handleValues(s[i-1], t[j-1], makePath(p, i-1), []Operation{})
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return append(p2, backtrace(s, t, p, i-1, j-1, matrix)...)
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}
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if i > 0 && j > 0 && matrix[i-1][j-1] == matrix[i][j] {
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return backtrace(s, t, p, i-1, j-1, matrix)
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}
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return []Operation{}
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}
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