Matthias Andreas Benkard | 832a54e | 2019-01-29 09:27:38 +0100 | [diff] [blame^] | 1 | package jsonpatch |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "encoding/json" |
| 6 | "fmt" |
| 7 | "reflect" |
| 8 | ) |
| 9 | |
| 10 | func merge(cur, patch *lazyNode, mergeMerge bool) *lazyNode { |
| 11 | curDoc, err := cur.intoDoc() |
| 12 | |
| 13 | if err != nil { |
| 14 | pruneNulls(patch) |
| 15 | return patch |
| 16 | } |
| 17 | |
| 18 | patchDoc, err := patch.intoDoc() |
| 19 | |
| 20 | if err != nil { |
| 21 | return patch |
| 22 | } |
| 23 | |
| 24 | mergeDocs(curDoc, patchDoc, mergeMerge) |
| 25 | |
| 26 | return cur |
| 27 | } |
| 28 | |
| 29 | func mergeDocs(doc, patch *partialDoc, mergeMerge bool) { |
| 30 | for k, v := range *patch { |
| 31 | if v == nil { |
| 32 | if mergeMerge { |
| 33 | (*doc)[k] = nil |
| 34 | } else { |
| 35 | delete(*doc, k) |
| 36 | } |
| 37 | } else { |
| 38 | cur, ok := (*doc)[k] |
| 39 | |
| 40 | if !ok || cur == nil { |
| 41 | pruneNulls(v) |
| 42 | (*doc)[k] = v |
| 43 | } else { |
| 44 | (*doc)[k] = merge(cur, v, mergeMerge) |
| 45 | } |
| 46 | } |
| 47 | } |
| 48 | } |
| 49 | |
| 50 | func pruneNulls(n *lazyNode) { |
| 51 | sub, err := n.intoDoc() |
| 52 | |
| 53 | if err == nil { |
| 54 | pruneDocNulls(sub) |
| 55 | } else { |
| 56 | ary, err := n.intoAry() |
| 57 | |
| 58 | if err == nil { |
| 59 | pruneAryNulls(ary) |
| 60 | } |
| 61 | } |
| 62 | } |
| 63 | |
| 64 | func pruneDocNulls(doc *partialDoc) *partialDoc { |
| 65 | for k, v := range *doc { |
| 66 | if v == nil { |
| 67 | delete(*doc, k) |
| 68 | } else { |
| 69 | pruneNulls(v) |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | return doc |
| 74 | } |
| 75 | |
| 76 | func pruneAryNulls(ary *partialArray) *partialArray { |
| 77 | newAry := []*lazyNode{} |
| 78 | |
| 79 | for _, v := range *ary { |
| 80 | if v != nil { |
| 81 | pruneNulls(v) |
| 82 | newAry = append(newAry, v) |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | *ary = newAry |
| 87 | |
| 88 | return ary |
| 89 | } |
| 90 | |
| 91 | var errBadJSONDoc = fmt.Errorf("Invalid JSON Document") |
| 92 | var errBadJSONPatch = fmt.Errorf("Invalid JSON Patch") |
| 93 | var errBadMergeTypes = fmt.Errorf("Mismatched JSON Documents") |
| 94 | |
| 95 | // MergeMergePatches merges two merge patches together, such that |
| 96 | // applying this resulting merged merge patch to a document yields the same |
| 97 | // as merging each merge patch to the document in succession. |
| 98 | func MergeMergePatches(patch1Data, patch2Data []byte) ([]byte, error) { |
| 99 | return doMergePatch(patch1Data, patch2Data, true) |
| 100 | } |
| 101 | |
| 102 | // MergePatch merges the patchData into the docData. |
| 103 | func MergePatch(docData, patchData []byte) ([]byte, error) { |
| 104 | return doMergePatch(docData, patchData, false) |
| 105 | } |
| 106 | |
| 107 | func doMergePatch(docData, patchData []byte, mergeMerge bool) ([]byte, error) { |
| 108 | doc := &partialDoc{} |
| 109 | |
| 110 | docErr := json.Unmarshal(docData, doc) |
| 111 | |
| 112 | patch := &partialDoc{} |
| 113 | |
| 114 | patchErr := json.Unmarshal(patchData, patch) |
| 115 | |
| 116 | if _, ok := docErr.(*json.SyntaxError); ok { |
| 117 | return nil, errBadJSONDoc |
| 118 | } |
| 119 | |
| 120 | if _, ok := patchErr.(*json.SyntaxError); ok { |
| 121 | return nil, errBadJSONPatch |
| 122 | } |
| 123 | |
| 124 | if docErr == nil && *doc == nil { |
| 125 | return nil, errBadJSONDoc |
| 126 | } |
| 127 | |
| 128 | if patchErr == nil && *patch == nil { |
| 129 | return nil, errBadJSONPatch |
| 130 | } |
| 131 | |
| 132 | if docErr != nil || patchErr != nil { |
| 133 | // Not an error, just not a doc, so we turn straight into the patch |
| 134 | if patchErr == nil { |
| 135 | if mergeMerge { |
| 136 | doc = patch |
| 137 | } else { |
| 138 | doc = pruneDocNulls(patch) |
| 139 | } |
| 140 | } else { |
| 141 | patchAry := &partialArray{} |
| 142 | patchErr = json.Unmarshal(patchData, patchAry) |
| 143 | |
| 144 | if patchErr != nil { |
| 145 | return nil, errBadJSONPatch |
| 146 | } |
| 147 | |
| 148 | pruneAryNulls(patchAry) |
| 149 | |
| 150 | out, patchErr := json.Marshal(patchAry) |
| 151 | |
| 152 | if patchErr != nil { |
| 153 | return nil, errBadJSONPatch |
| 154 | } |
| 155 | |
| 156 | return out, nil |
| 157 | } |
| 158 | } else { |
| 159 | mergeDocs(doc, patch, mergeMerge) |
| 160 | } |
| 161 | |
| 162 | return json.Marshal(doc) |
| 163 | } |
| 164 | |
| 165 | // resemblesJSONArray indicates whether the byte-slice "appears" to be |
| 166 | // a JSON array or not. |
| 167 | // False-positives are possible, as this function does not check the internal |
| 168 | // structure of the array. It only checks that the outer syntax is present and |
| 169 | // correct. |
| 170 | func resemblesJSONArray(input []byte) bool { |
| 171 | input = bytes.TrimSpace(input) |
| 172 | |
| 173 | hasPrefix := bytes.HasPrefix(input, []byte("[")) |
| 174 | hasSuffix := bytes.HasSuffix(input, []byte("]")) |
| 175 | |
| 176 | return hasPrefix && hasSuffix |
| 177 | } |
| 178 | |
| 179 | // CreateMergePatch will return a merge patch document capable of converting |
| 180 | // the original document(s) to the modified document(s). |
| 181 | // The parameters can be bytes of either two JSON Documents, or two arrays of |
| 182 | // JSON documents. |
| 183 | // The merge patch returned follows the specification defined at http://tools.ietf.org/html/draft-ietf-appsawg-json-merge-patch-07 |
| 184 | func CreateMergePatch(originalJSON, modifiedJSON []byte) ([]byte, error) { |
| 185 | originalResemblesArray := resemblesJSONArray(originalJSON) |
| 186 | modifiedResemblesArray := resemblesJSONArray(modifiedJSON) |
| 187 | |
| 188 | // Do both byte-slices seem like JSON arrays? |
| 189 | if originalResemblesArray && modifiedResemblesArray { |
| 190 | return createArrayMergePatch(originalJSON, modifiedJSON) |
| 191 | } |
| 192 | |
| 193 | // Are both byte-slices are not arrays? Then they are likely JSON objects... |
| 194 | if !originalResemblesArray && !modifiedResemblesArray { |
| 195 | return createObjectMergePatch(originalJSON, modifiedJSON) |
| 196 | } |
| 197 | |
| 198 | // None of the above? Then return an error because of mismatched types. |
| 199 | return nil, errBadMergeTypes |
| 200 | } |
| 201 | |
| 202 | // createObjectMergePatch will return a merge-patch document capable of |
| 203 | // converting the original document to the modified document. |
| 204 | func createObjectMergePatch(originalJSON, modifiedJSON []byte) ([]byte, error) { |
| 205 | originalDoc := map[string]interface{}{} |
| 206 | modifiedDoc := map[string]interface{}{} |
| 207 | |
| 208 | err := json.Unmarshal(originalJSON, &originalDoc) |
| 209 | if err != nil { |
| 210 | return nil, errBadJSONDoc |
| 211 | } |
| 212 | |
| 213 | err = json.Unmarshal(modifiedJSON, &modifiedDoc) |
| 214 | if err != nil { |
| 215 | return nil, errBadJSONDoc |
| 216 | } |
| 217 | |
| 218 | dest, err := getDiff(originalDoc, modifiedDoc) |
| 219 | if err != nil { |
| 220 | return nil, err |
| 221 | } |
| 222 | |
| 223 | return json.Marshal(dest) |
| 224 | } |
| 225 | |
| 226 | // createArrayMergePatch will return an array of merge-patch documents capable |
| 227 | // of converting the original document to the modified document for each |
| 228 | // pair of JSON documents provided in the arrays. |
| 229 | // Arrays of mismatched sizes will result in an error. |
| 230 | func createArrayMergePatch(originalJSON, modifiedJSON []byte) ([]byte, error) { |
| 231 | originalDocs := []json.RawMessage{} |
| 232 | modifiedDocs := []json.RawMessage{} |
| 233 | |
| 234 | err := json.Unmarshal(originalJSON, &originalDocs) |
| 235 | if err != nil { |
| 236 | return nil, errBadJSONDoc |
| 237 | } |
| 238 | |
| 239 | err = json.Unmarshal(modifiedJSON, &modifiedDocs) |
| 240 | if err != nil { |
| 241 | return nil, errBadJSONDoc |
| 242 | } |
| 243 | |
| 244 | total := len(originalDocs) |
| 245 | if len(modifiedDocs) != total { |
| 246 | return nil, errBadJSONDoc |
| 247 | } |
| 248 | |
| 249 | result := []json.RawMessage{} |
| 250 | for i := 0; i < len(originalDocs); i++ { |
| 251 | original := originalDocs[i] |
| 252 | modified := modifiedDocs[i] |
| 253 | |
| 254 | patch, err := createObjectMergePatch(original, modified) |
| 255 | if err != nil { |
| 256 | return nil, err |
| 257 | } |
| 258 | |
| 259 | result = append(result, json.RawMessage(patch)) |
| 260 | } |
| 261 | |
| 262 | return json.Marshal(result) |
| 263 | } |
| 264 | |
| 265 | // Returns true if the array matches (must be json types). |
| 266 | // As is idiomatic for go, an empty array is not the same as a nil array. |
| 267 | func matchesArray(a, b []interface{}) bool { |
| 268 | if len(a) != len(b) { |
| 269 | return false |
| 270 | } |
| 271 | if (a == nil && b != nil) || (a != nil && b == nil) { |
| 272 | return false |
| 273 | } |
| 274 | for i := range a { |
| 275 | if !matchesValue(a[i], b[i]) { |
| 276 | return false |
| 277 | } |
| 278 | } |
| 279 | return true |
| 280 | } |
| 281 | |
| 282 | // Returns true if the values matches (must be json types) |
| 283 | // The types of the values must match, otherwise it will always return false |
| 284 | // If two map[string]interface{} are given, all elements must match. |
| 285 | func matchesValue(av, bv interface{}) bool { |
| 286 | if reflect.TypeOf(av) != reflect.TypeOf(bv) { |
| 287 | return false |
| 288 | } |
| 289 | switch at := av.(type) { |
| 290 | case string: |
| 291 | bt := bv.(string) |
| 292 | if bt == at { |
| 293 | return true |
| 294 | } |
| 295 | case float64: |
| 296 | bt := bv.(float64) |
| 297 | if bt == at { |
| 298 | return true |
| 299 | } |
| 300 | case bool: |
| 301 | bt := bv.(bool) |
| 302 | if bt == at { |
| 303 | return true |
| 304 | } |
| 305 | case nil: |
| 306 | // Both nil, fine. |
| 307 | return true |
| 308 | case map[string]interface{}: |
| 309 | bt := bv.(map[string]interface{}) |
| 310 | for key := range at { |
| 311 | if !matchesValue(at[key], bt[key]) { |
| 312 | return false |
| 313 | } |
| 314 | } |
| 315 | for key := range bt { |
| 316 | if !matchesValue(at[key], bt[key]) { |
| 317 | return false |
| 318 | } |
| 319 | } |
| 320 | return true |
| 321 | case []interface{}: |
| 322 | bt := bv.([]interface{}) |
| 323 | return matchesArray(at, bt) |
| 324 | } |
| 325 | return false |
| 326 | } |
| 327 | |
| 328 | // getDiff returns the (recursive) difference between a and b as a map[string]interface{}. |
| 329 | func getDiff(a, b map[string]interface{}) (map[string]interface{}, error) { |
| 330 | into := map[string]interface{}{} |
| 331 | for key, bv := range b { |
| 332 | av, ok := a[key] |
| 333 | // value was added |
| 334 | if !ok { |
| 335 | into[key] = bv |
| 336 | continue |
| 337 | } |
| 338 | // If types have changed, replace completely |
| 339 | if reflect.TypeOf(av) != reflect.TypeOf(bv) { |
| 340 | into[key] = bv |
| 341 | continue |
| 342 | } |
| 343 | // Types are the same, compare values |
| 344 | switch at := av.(type) { |
| 345 | case map[string]interface{}: |
| 346 | bt := bv.(map[string]interface{}) |
| 347 | dst := make(map[string]interface{}, len(bt)) |
| 348 | dst, err := getDiff(at, bt) |
| 349 | if err != nil { |
| 350 | return nil, err |
| 351 | } |
| 352 | if len(dst) > 0 { |
| 353 | into[key] = dst |
| 354 | } |
| 355 | case string, float64, bool: |
| 356 | if !matchesValue(av, bv) { |
| 357 | into[key] = bv |
| 358 | } |
| 359 | case []interface{}: |
| 360 | bt := bv.([]interface{}) |
| 361 | if !matchesArray(at, bt) { |
| 362 | into[key] = bv |
| 363 | } |
| 364 | case nil: |
| 365 | switch bv.(type) { |
| 366 | case nil: |
| 367 | // Both nil, fine. |
| 368 | default: |
| 369 | into[key] = bv |
| 370 | } |
| 371 | default: |
| 372 | panic(fmt.Sprintf("Unknown type:%T in key %s", av, key)) |
| 373 | } |
| 374 | } |
| 375 | // Now add all deleted values as nil |
| 376 | for key := range a { |
| 377 | _, found := b[key] |
| 378 | if !found { |
| 379 | into[key] = nil |
| 380 | } |
| 381 | } |
| 382 | return into, nil |
| 383 | } |