feat: Create a grouping utility that only parses new events (cadence-workflow#1065)

* grouping utility

Signed-off-by: Assem Hafez <assem.hafez@uber.com>

* update test cases

Signed-off-by: Assem Hafez <assem.hafez@uber.com>

* change the api of onChange and add destroy method

Signed-off-by: Assem Hafez <assem.hafez@uber.com>

* replace getGroups with getState

Signed-off-by: Assem Hafez <assem.hafez@uber.com>

* call onchange after updating pending events

Signed-off-by: Assem Hafez <assem.hafez@uber.com>

* use sync processBatch for first page

Signed-off-by: Assem Hafez <assem.hafez@uber.com>

* Update src/views/workflow-history/helpers/workflow-history-grouper.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Apply PR comments

* Update src/views/workflow-history/helpers/workflow-history-grouper.types.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Signed-off-by: Assem Hafez <assem.hafez@uber.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: Assem-Uber

src/views/workflow-history/helpers/__tests__/workflow-history-grouper.test.tsx

@@ -16,8 +16,6 @@ import type {
   Props,
 } from '../workflow-history-grouper.types';
 
-// Commonly used mocks
-
 // Track all setups for cleanup
 const allCleanups: Array<() => void> = [];
 
@@ -633,11 +631,6 @@ describe(WorkflowHistoryGrouper.name, () => {
     // First batch is processed immediately, so processedEventsCount should be at least 1
     expect(state.processedEventsCount).toBeGreaterThan(0);
 
-    // If there are remaining events, status could be 'processing'
-    if (state.remainingEventsCount > 0) {
-      expect(state.status).toBe('processing');
-    }
-
     // Wait for processing to complete
     await waitForProcessing();
 

src/views/workflow-history/helpers/workflow-history-grouper.ts

@@ -93,7 +93,7 @@ export default class WorkflowHistoryGrouper {
    * Updates pending events (activities and decisions).
    * This should be called separately from updateEvents.
    */
-  public async updatePendingEvents(params: ProcessEventsParams) {
+  public updatePendingEvents(params: ProcessEventsParams) {
     // Update pending events (add new ones, remove stale ones)
 
     const currentPendingActivities = this.currentPendingActivities;
@@ -184,10 +184,10 @@ export default class WorkflowHistoryGrouper {
 
   /**
    * Schedules the next batch using the best available API.
-   * Uses Scheduler API if available, otherwise falls back to Promise microtask.
+   * Uses Scheduler API if available, otherwise falls back to setTimeout.
    */
   private scheduleNextBatch() {
-    // if first batch process immediately, this helps avoiding UI delays
+    // If first batch, process immediately; this helps avoid UI delays
     if (this.lastProcessedEventIndex === -1) {
       this.processBatch();
     } else if (
@@ -200,6 +200,7 @@ export default class WorkflowHistoryGrouper {
         .postTask(() => this.processBatch(), { priority: 'background' })
         .catch(() => {
           // Fallback to setTimeout if postTask fails
+          // setTimeout adds the processBatch to Macro Task Queue (lowest priority queue) to allow current microtasks (UI updates) to complete first
           setTimeout(() => this.processBatch(), 0);
         });
     } else {

src/views/workflow-history/helpers/workflow-history-grouper.types.ts

@@ -11,11 +11,6 @@ export type ProcessEventsParams = {
   pendingStartDecision: PendingDecisionTaskStartEvent | null;
 };
 
-export type ProcessEventsResult = {
-  groups: HistoryEventsGroups;
-  lastProcessedEventIndex: number;
-};
-
 /**
  * Processing status for incremental grouping operations.
  */