feat(json-crdt-extensions): 🎸 support left char retrieval for deleted points

Author: streamich

src/json-crdt-extensions/peritext/point/Point.ts

@@ -195,7 +195,13 @@ export class Point implements Pick<Stateful, 'refresh'>, Printable {
 
   public leftChar(): ChunkSlice | undefined {
     let chunk = this.chunk();
-    if (!chunk || chunk.del) return;
+    if (!chunk) return;
+    if (chunk.del) {
+      const prevId = this.prevId();
+      if (!prevId) return;
+      const tmp = new Point(this.txt, prevId, Anchor.After);
+      return tmp.leftChar();
+    }
     if (this.anchor === Anchor.After) {
       const off = this.id.time - chunk.id.time;
       return new ChunkSlice(chunk, off, 1);

src/json-crdt-extensions/peritext/point/__tests__/Point.spec.ts

@@ -551,6 +551,14 @@ describe('.rightChar()', () => {
     const end = peritext.pointAt(res.length - 1, Anchor.After);
     expect(end.rightChar()).toBe(undefined);
   });
+
+  test('retrieves left char of a deleted point', () => {
+    const {peritext, chunkD1} = setupWithChunkedText();
+    const p1 = peritext.point(chunkD1.id, Anchor.Before);
+    expect(p1.leftChar()!.view()).toBe('3');
+    const p2 = peritext.point(chunkD1.id, Anchor.After);
+    expect(p2.leftChar()!.view()).toBe('3');
+  });
 });
 
 describe('.leftChar()', () => {