feat(json-crdt): 🎸 implement view .read() retrieval method

Author: streamich

src/json-crdt/model/api/ModelApi.ts

@@ -266,6 +266,18 @@ export class ModelApi<N extends JsonNode = JsonNode> implements SyncStore<JsonNo
     return this.model.view();
   }
 
+  /**
+   * Reads the value at the given path in the model. If no path is provided,
+   * returns the root node's view.
+   *
+   * @param path Path at which to read the value.
+   * @returns The value at the given path, or the root node's view if no path
+   *     is provided.
+   */
+  public read(path?: ApiPath): unknown {
+    return this.r.read(path);
+  }
+
   private inTx = false;
   public transaction(callback: () => void) {
     if (this.inTx) callback();

src/json-crdt/model/api/__tests__/NodeApi.spec.ts

@@ -0,0 +1,51 @@
+import {Model} from '../../Model';
+
+describe('.read()', () => {
+  test('can retrieve own view', () => {
+    const doc = Model.create();
+    doc.api.root({
+      arr: [1, 2, 3],
+    });
+    const arr = doc.api.arr(['arr']);
+    expect(arr.read()).toEqual([1, 2, 3]);
+    expect(arr.read('')).toEqual([1, 2, 3]);
+    expect(arr.read([])).toEqual([1, 2, 3]);
+  });
+
+  test('can retrieve array element', () => {
+    const doc = Model.create();
+    doc.api.root({
+      arr: [1, 2, 3],
+    });
+    const arr = doc.api.arr(['arr']);
+    expect(arr.read('/0')).toEqual(1);
+    expect(arr.read([0])).toEqual(1);
+    expect(arr.read('/2')).toEqual(3);
+    expect(arr.read([2])).toEqual(3);
+    expect(arr.read(['2'])).toEqual(3);
+  });
+
+  test('retrieve deep within document', () => {
+    const doc = Model.create();
+    doc.api.root({
+      foo: 'bar',
+      obj: {
+        nested: {
+          value: 42,
+          deep: {
+            another: 'value',
+          },
+        },
+      },
+      arr: [1, 2, {
+        nested: [1, 2, 3],
+        deep: {
+          value: 4
+        }
+      }],
+    });
+    expect(doc.api.r.read('/foo')).toEqual('bar');
+    expect(doc.api.read('/foo')).toEqual('bar');
+    expect((doc.s as any).foo.toView()).toEqual('bar');
+  });
+});

src/json-crdt/model/api/nodes.ts

@@ -175,6 +175,10 @@ export class NodeApi<N extends JsonNode = JsonNode> implements Printable {
     return this.node.view() as unknown as JsonNodeView<N>;
   }
 
+  public read(path?: ApiPath): unknown {
+    return !path ? this.view() : this.in(path).view();
+  }
+
   public proxy(): types.ProxyNode<N> {
     return {
       toApi: () => <any>this,