feat(json-crdt): 🎸 add str_ins JSON Patch+ operation support

Author: streamich

src/json-crdt/json-patch/JsonPatch.ts

@@ -1,4 +1,3 @@
-import {Draft} from '../../json-crdt-patch/Draft';
 import {JsonPatchDraft} from './JsonPatchDraft';
 import type {Model} from '../model/Model';
 import type {Operation} from '../../json-patch';

src/json-crdt/json-patch/JsonPatchDraft.ts

@@ -6,7 +6,7 @@ import {ObjectType} from '../types/lww-object/ObjectType';
 import {UNDEFINED_ID} from '../../json-crdt-patch/constants';
 import {toPath} from '../../json-pointer/util';
 import type {Model} from '../model';
-import type {Operation, OperationAdd, OperationRemove, OperationReplace, OperationMove, OperationCopy, OperationTest} from '../../json-patch';
+import type {Operation, OperationAdd, OperationRemove, OperationReplace, OperationMove, OperationCopy, OperationTest, OperationStrIns} from '../../json-patch';
 
 export class JsonPatchDraft {
   public readonly draft = new Draft();
@@ -25,6 +25,7 @@ export class JsonPatchDraft {
       case 'move': this.applyMove(op); break;
       case 'copy': this.applyCopy(op); break;
       case 'test': this.applyTest(op); break;
+      case 'str_ins': this.applyStrIns(op); break;
     }
   }
 
@@ -107,6 +108,15 @@ export class JsonPatchDraft {
     if (!deepEqual(json, op.value)) throw new Error('TEST');
   }
 
+  public applyStrIns(op: OperationStrIns): void {
+    const path = toPath(op.path);
+    const {node} = this.model.api.str(path);
+    const {builder} = this.draft;
+    const length = node.length();
+    const after = op.pos ? node.findId(length < op.pos ? length - 1 : op.pos - 1) : node.id;
+    builder.insStr(node.id, after, op.str);
+  }
+
   private get(steps: Path): unknown {
     if (!steps.length) return this.model.toView();
     else {

src/json-crdt/json-patch/__tests__/JsonPatch.str.spec.ts

@@ -0,0 +1,85 @@
+import {Operation} from '../../../json-patch';
+import {Model} from '../../model/Model';
+import {JsonPatch} from '../JsonPatch';
+
+interface TestCase {
+  name: string;
+  doc1?: unknown;
+  patches: Operation[][];
+  doc2?: unknown;
+  throws?: string;
+  only?: true;
+}
+
+const testCases: TestCase[] = [
+  {
+    name: 'can insert char in empty string',
+    doc1: '',
+    patches: [[{op: 'str_ins', path: '', pos: 0, str: 'a'}]],
+    doc2: 'a',
+  },
+  {
+    name: 'can insert char at the end of string',
+    doc1: '1',
+    patches: [[{op: 'str_ins', path: '', pos: 1, str: '2'}]],
+    doc2: '12',
+  },
+  {
+    name: 'can insert char beyond end of string',
+    doc1: '1',
+    patches: [[{op: 'str_ins', path: '', pos: 111, str: '2'}]],
+    doc2: '12',
+  },
+  {
+    name: 'can insert char beyond end of string - 2',
+    doc1: '1',
+    patches: [[{op: 'str_ins', path: '', pos: 2, str: '2'}]],
+    doc2: '12',
+  },
+  {
+    name: 'can insert char at the beginning of string',
+    doc1: '1',
+    patches: [[{op: 'str_ins', path: '', pos: 0, str: '0'}]],
+    doc2: '01',
+  },
+  {
+    name: 'can insert char in the middle of string',
+    doc1: '25',
+    patches: [[{op: 'str_ins', path: '', pos: 1, str: '.'}]],
+    doc2: '2.5',
+  },
+  {
+    name: 'can insert text in nested object',
+    doc1: null,
+    patches: [
+      [{op: 'add', path: '', value: {foo: [{bar: 'baz'}]}}],
+      [{op: 'str_ins', path: '/foo/0/bar', pos: 3, str: '!'}]
+    ],
+    doc2: {foo: [{bar: 'baz!'}]},
+  },
+  {
+    name: 'can insert text in nested object - 2',
+    doc1: null,
+    patches: [
+      [{op: 'add', path: '', value: {foo: [{bar: 'baz'}]}}],
+      [{op: 'str_ins', path: ['foo', 0, 'bar'], pos: 3, str: '!'}]
+    ],
+    doc2: {foo: [{bar: 'baz!'}]},
+  },
+];
+
+for (const {only, name, doc1, doc2, patches, throws} of testCases) {
+  (only ? test.only : test)(name, () => {
+    const model = Model.withLogicalClock();
+    const jsonPatch = new JsonPatch(model);
+    if (doc1 !== undefined) model.api.root(doc1).commit();
+    if (throws) {
+      expect(() => {
+        for (const patch of patches) jsonPatch.apply(patch).commit();
+      }).toThrow(new Error(throws));
+    } else {
+      for (const patch of patches) jsonPatch.apply(patch).commit();
+      expect(model.toView()).toEqual(doc2);
+    }
+  });
+}

src/json-crdt/types/rga-string/StringType.ts

@@ -184,7 +184,10 @@ export class StringType implements JsonNode {
     return size;
   }
 
-  /** String length. */
+  /**
+   * String length.
+   * @todo This could be cached same as .toJson().
+   */
   public length(): number {
     let curr: StringChunk | null = this.start;
     let size: number = 0;