feat(json-crdt): 🎸 implement string deletion undo in Log

Author: streamich

src/json-crdt/log/Log.ts

@@ -226,9 +226,15 @@ export class Log<N extends JsonNode = JsonNode<any>> implements Printable {
         if (node) {
           const rga = node.v;
           if (rga instanceof StrNode) {
-            for (const span of op.what) {
-              // TODO: SPAN to view: ...
+            let str = '';
+            for (const span of op.what) str += rga.spanView(span).join('');
+            let after = op.obj;
+            const firstDelSpan = op.what[0];
+            if (firstDelSpan) {
+              const after2 = rga.prevId(firstDelSpan);
+              if (after2) after = after2;
             }
+            builder.insStr(op.obj, after, str);
           }
         }
       }

src/json-crdt/nodes/rga/AbstractRga.ts

@@ -793,6 +793,10 @@ export abstract class AbstractRga<T> {
     return chunk;
   }
 
+  /**
+   * @param id ID of character to start the search from.
+   * @returns Previous ID in the RGA sequence.
+   */
   public prevId(id: ITimestampStruct): ITimestampStruct | undefined {
     let chunk = this.findById(id);
     if (!chunk) return;