test(json-crdt-extensions): 💍 add .nextId() edge case tests

Author: streamich

src/json-crdt-extensions/peritext/Peritext.ts

@@ -24,6 +24,14 @@ export class Peritext implements Printable {
     return this.point(id, anchor);
   }
 
+  public pointAtStart(): Point {
+    return this.point(this.str.id, Anchor.After);
+  }
+
+  public pointAtEnd(): Point {
+    return this.point(this.str.id, Anchor.Before);
+  }
+
   // ---------------------------------------------------------------- Printable
 
   public toString(tab: string = ''): string {

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

@@ -125,13 +125,11 @@ export class Point implements Pick<Stateful, 'refresh'>, Printable {
    * @returns Next visible ID in string.
    */
   public nextId(move: number = 1): ITimestampStruct | undefined {
-    // TODO: add tests for when cursor is at the end.
     if (this.isEndOfStr()) return;
     let remaining: number = move;
     const {id, txt} = this;
     const str = txt.str;
     let chunk: StringChunk | undefined;
-    // TODO: add tests for when cursor starts from start of string.
     if (this.isStartOfStr()) {
       chunk = str.first();
       while (chunk && chunk.del) chunk = str.next(chunk);

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

@@ -416,6 +416,25 @@ describe('.nextId()', () => {
     p2.prevId(0);
     expect(p2.leftChar()!.view()).toBe('3');
   });
+
+  test('returns undefined, when at end of str', () => {
+    const {peritext} = setupWithChunkedText();
+    const point = peritext.pointAtEnd();
+    expect(point.nextId()).toBe(undefined);
+  });
+
+  test('returns undefined, when at last char', () => {
+    const {peritext} = setupWithChunkedText();
+    const point = peritext.pointAt(8, Anchor.Before);
+    expect(point.nextId()).toBe(undefined);
+  });
+
+  test('returns first char, when at start of str', () => {
+    const {peritext, chunk1} = setupWithChunkedText();
+    const point = peritext.pointAtStart();
+    const id = point.nextId();
+    expect(id).toEqual(chunk1.id);
+  });
 });
 
 describe('.prevId()', () => {