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{}) 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{}) 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 }