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merge.go
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merge.go
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package jsonpatch
import (
"bytes"
"encoding/json"
"fmt"
"reflect"
)
func merge(cur, patch *lazyNode, mergeMerge bool) *lazyNode {
curDoc, err := cur.intoDoc()
if err != nil {
pruneNulls(patch)
return patch
}
patchDoc, err := patch.intoDoc()
if err != nil {
return patch
}
mergeDocs(curDoc, patchDoc, mergeMerge)
return cur
}
func mergeDocs(doc, patch *partialDoc, mergeMerge bool) {
for k, v := range *patch {
if v == nil {
if mergeMerge {
(*doc)[k] = nil
} else {
delete(*doc, k)
}
} else {
cur, ok := (*doc)[k]
if !ok || cur == nil {
pruneNulls(v)
(*doc)[k] = v
} else {
(*doc)[k] = merge(cur, v, mergeMerge)
}
}
}
}
func pruneNulls(n *lazyNode) {
sub, err := n.intoDoc()
if err == nil {
pruneDocNulls(sub)
} else {
ary, err := n.intoAry()
if err == nil {
pruneAryNulls(ary)
}
}
}
func pruneDocNulls(doc *partialDoc) *partialDoc {
for k, v := range *doc {
if v == nil {
delete(*doc, k)
} else {
pruneNulls(v)
}
}
return doc
}
func pruneAryNulls(ary *partialArray) *partialArray {
newAry := []*lazyNode{}
for _, v := range *ary {
if v != nil {
pruneNulls(v)
newAry = append(newAry, v)
}
}
*ary = newAry
return ary
}
var errBadJSONDoc = fmt.Errorf("Invalid JSON Document")
var errBadJSONPatch = fmt.Errorf("Invalid JSON Patch")
var errBadMergeTypes = fmt.Errorf("Mismatched JSON Documents")
// MergeMergePatches merges two merge patches together, such that
// applying this resulting merged merge patch to a document yields the same
// as merging each merge patch to the document in succession.
func MergeMergePatches(patch1Data, patch2Data []byte) ([]byte, error) {
return doMergePatch(patch1Data, patch2Data, true)
}
// MergePatch merges the patchData into the docData.
func MergePatch(docData, patchData []byte) ([]byte, error) {
return doMergePatch(docData, patchData, false)
}
func doMergePatch(docData, patchData []byte, mergeMerge bool) ([]byte, error) {
doc := &partialDoc{}
docErr := json.Unmarshal(docData, doc)
patch := &partialDoc{}
patchErr := json.Unmarshal(patchData, patch)
if _, ok := docErr.(*json.SyntaxError); ok {
return nil, errBadJSONDoc
}
if _, ok := patchErr.(*json.SyntaxError); ok {
return nil, errBadJSONPatch
}
if docErr == nil && *doc == nil {
return nil, errBadJSONDoc
}
if patchErr == nil && *patch == nil {
return nil, errBadJSONPatch
}
if docErr != nil || patchErr != nil {
// Not an error, just not a doc, so we turn straight into the patch
if patchErr == nil {
if mergeMerge {
doc = patch
} else {
doc = pruneDocNulls(patch)
}
} else {
patchAry := &partialArray{}
patchErr = json.Unmarshal(patchData, patchAry)
if patchErr != nil {
return nil, errBadJSONPatch
}
pruneAryNulls(patchAry)
out, patchErr := json.Marshal(patchAry)
if patchErr != nil {
return nil, errBadJSONPatch
}
return out, nil
}
} else {
mergeDocs(doc, patch, mergeMerge)
}
return json.Marshal(doc)
}
// 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
}
// CreateMergePatch will return a merge patch document capable of converting
// the original document(s) to the modified document(s).
// The parameters can be bytes of either two JSON Documents, or two arrays of
// JSON documents.
// The merge patch returned follows the specification defined at http://tools.ietf.org/html/draft-ietf-appsawg-json-merge-patch-07
func CreateMergePatch(originalJSON, modifiedJSON []byte) ([]byte, error) {
originalResemblesArray := resemblesJSONArray(originalJSON)
modifiedResemblesArray := resemblesJSONArray(modifiedJSON)
// Do both byte-slices seem like JSON arrays?
if originalResemblesArray && modifiedResemblesArray {
return createArrayMergePatch(originalJSON, modifiedJSON)
}
// Are both byte-slices are not arrays? Then they are likely JSON objects...
if !originalResemblesArray && !modifiedResemblesArray {
return createObjectMergePatch(originalJSON, modifiedJSON)
}
// None of the above? Then return an error because of mismatched types.
return nil, errBadMergeTypes
}
// createObjectMergePatch will return a merge-patch document capable of
// converting the original document to the modified document.
func createObjectMergePatch(originalJSON, modifiedJSON []byte) ([]byte, error) {
originalDoc := map[string]interface{}{}
modifiedDoc := map[string]interface{}{}
err := json.Unmarshal(originalJSON, &originalDoc)
if err != nil {
return nil, errBadJSONDoc
}
err = json.Unmarshal(modifiedJSON, &modifiedDoc)
if err != nil {
return nil, errBadJSONDoc
}
dest, err := getDiff(originalDoc, modifiedDoc)
if err != nil {
return nil, err
}
return json.Marshal(dest)
}
// createArrayMergePatch will return an array of merge-patch documents capable
// of converting the original document to the modified document for each
// pair of JSON documents provided in the arrays.
// Arrays of mismatched sizes will result in an error.
func createArrayMergePatch(originalJSON, modifiedJSON []byte) ([]byte, error) {
originalDocs := []json.RawMessage{}
modifiedDocs := []json.RawMessage{}
err := json.Unmarshal(originalJSON, &originalDocs)
if err != nil {
return nil, errBadJSONDoc
}
err = json.Unmarshal(modifiedJSON, &modifiedDocs)
if err != nil {
return nil, errBadJSONDoc
}
total := len(originalDocs)
if len(modifiedDocs) != total {
return nil, errBadJSONDoc
}
result := []json.RawMessage{}
for i := 0; i < len(originalDocs); i++ {
original := originalDocs[i]
modified := modifiedDocs[i]
patch, err := createObjectMergePatch(original, modified)
if err != nil {
return nil, err
}
result = append(result, json.RawMessage(patch))
}
return json.Marshal(result)
}
// Returns true if the array matches (must be json types).
// As is idiomatic for go, an empty array is not the same as a nil array.
func matchesArray(a, b []interface{}) bool {
if len(a) != len(b) {
return false
}
if (a == nil && b != nil) || (a != nil && b == nil) {
return false
}
for i := range a {
if !matchesValue(a[i], b[i]) {
return false
}
}
return true
}
// 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 float64:
bt := bv.(float64)
if bt == at {
return true
}
case bool:
bt := bv.(bool)
if bt == at {
return true
}
case nil:
// Both nil, fine.
return true
case map[string]interface{}:
bt := bv.(map[string]interface{})
if len(bt) != len(at) {
return false
}
for key := range bt {
if !matchesValue(at[key], bt[key]) {
return false
}
}
return true
case []interface{}:
bt := bv.([]interface{})
return matchesArray(at, bt)
}
return false
}
// getDiff returns the (recursive) difference between a and b as a map[string]interface{}.
func getDiff(a, b map[string]interface{}) (map[string]interface{}, error) {
into := map[string]interface{}{}
for key, bv := range b {
av, ok := a[key]
// value was added
if !ok {
into[key] = bv
continue
}
// If types have changed, replace completely
if reflect.TypeOf(av) != reflect.TypeOf(bv) {
into[key] = bv
continue
}
// Types are the same, compare values
switch at := av.(type) {
case map[string]interface{}:
bt := bv.(map[string]interface{})
dst := make(map[string]interface{}, len(bt))
dst, err := getDiff(at, bt)
if err != nil {
return nil, err
}
if len(dst) > 0 {
into[key] = dst
}
case string, float64, bool:
if !matchesValue(av, bv) {
into[key] = bv
}
case []interface{}:
bt := bv.([]interface{})
if !matchesArray(at, bt) {
into[key] = bv
}
case nil:
switch bv.(type) {
case nil:
// Both nil, fine.
default:
into[key] = bv
}
default:
panic(fmt.Sprintf("Unknown type:%T in key %s", av, key))
}
}
// Now add all deleted values as nil
for key := range a {
_, found := b[key]
if !found {
into[key] = nil
}
}
return into, nil
}