From 4de20c81dac3c43b8068778d80af6c3c3a3db383 Mon Sep 17 00:00:00 2001
From: zak <zak.knill@ably.com>
Date: Wed, 18 Oct 2023 14:10:22 +0100
Subject: [PATCH] Correlate events only on Mutation ID

Update the comparator to be uuid only.
---
 src/Model.ts             | 10 ++++++----
 src/MutationsRegistry.ts | 32 ++------------------------------
 2 files changed, 8 insertions(+), 34 deletions(-)

diff --git a/src/Model.ts b/src/Model.ts
index f0f54a8d..07e2e77e 100644
--- a/src/Model.ts
+++ b/src/Model.ts
@@ -3,7 +3,7 @@ import type { Logger } from 'pino';
 import { Subject, Subscription } from 'rxjs';
 
 import { toError } from './Errors.js';
-import MutationsRegistry, { defaultComparator } from './MutationsRegistry.js';
+import MutationsRegistry, { mutationIdComparator } from './MutationsRegistry.js';
 import PendingConfirmationRegistry from './PendingConfirmationRegistry.js';
 import { IStream } from './stream/Stream.js';
 import StreamFactory, { IStreamFactory as IStreamFactory } from './stream/StreamFactory.js';
@@ -57,7 +57,9 @@ export default class Model<T> extends EventEmitter<Record<ModelState, ModelState
   private readonly mutationsRegistry: MutationsRegistry;
 
   private optimisticEvents: OptimisticEventWithParams[] = [];
-  private pendingConfirmationRegistry: PendingConfirmationRegistry = new PendingConfirmationRegistry(defaultComparator);
+  private pendingConfirmationRegistry: PendingConfirmationRegistry = new PendingConfirmationRegistry(
+    mutationIdComparator,
+  );
 
   private readonly subscriptions = new Subject<{ confirmed: boolean; data: T }>();
   private subscriptionMap: WeakMap<StandardCallback<T>, Subscription> = new WeakMap();
@@ -432,7 +434,7 @@ export default class Model<T> extends EventEmitter<Record<ModelState, ModelState
     // additional data on the confirmed event in the updated data.
     for (let i = 0; i < this.optimisticEvents.length; i++) {
       let e = this.optimisticEvents[i];
-      if (defaultComparator(e, event)) {
+      if (mutationIdComparator(e, event)) {
         this.optimisticEvents.splice(i, 1);
         await this.applyWithRebase(event, this.optimisticEvents);
         return;
@@ -469,7 +471,7 @@ export default class Model<T> extends EventEmitter<Record<ModelState, ModelState
     // remove any matching events from the optimisticEvents and re-apply the remaining events
     // on top of the latest confirmed state
     for (let event of events) {
-      this.optimisticEvents = this.optimisticEvents.filter((e) => !defaultComparator(e, event));
+      this.optimisticEvents = this.optimisticEvents.filter((e) => !mutationIdComparator(e, event));
     }
     let nextData = this.confirmedData;
     for (const e of this.optimisticEvents) {
diff --git a/src/MutationsRegistry.ts b/src/MutationsRegistry.ts
index b76e3f96..34d93b3e 100644
--- a/src/MutationsRegistry.ts
+++ b/src/MutationsRegistry.ts
@@ -1,46 +1,18 @@
-import isEqual from 'lodash/isEqual.js';
-
 import { toError } from './Errors.js';
 import type { Event, OptimisticEventWithParams } from './types/model.js';
 import type { EventComparator, OptimisticEventOptions } from './types/optimistic.js';
 
 /**
- * This comparator compares events by equality of channel, event name and deep equality on the event data.
- *
- * @param optimistic - The optimistic event to compare.
- * @param confirmed - The confirmed event to compare.
- * @returns {boolean} Whether the two events are equal.
- */
-export const equalityComparator: EventComparator = (optimistic: Event, confirmed: Event) => {
-  return optimistic.name === confirmed.name && isEqual(optimistic.data, confirmed.data);
-};
-
-/**
- * This comparator compares events by their `uuid` property.
+ * This comparator compares events by their `mutationId` property.
  *
  * @param optimistic - The optimistic event to compare.
  * @param confirmed - The confirmed event to compare.
  * @returns {boolean} Whether the two events are equal.
  */
-export const uuidComparator: EventComparator = (optimistic: Event, confirmed: Event) => {
+export const mutationIdComparator: EventComparator = (optimistic: Event, confirmed: Event) => {
   return !!optimistic.mutationId && !!confirmed.mutationId && optimistic.mutationId === confirmed.mutationId;
 };
 
-/**
- * The default event comparator. Compares events by uuid, if provided on both the optimistic and confirmed events.
- * Otherwise, compares events by equality of channel, event name and deep equality on the event data.
- *
- * @param optimistic - The optimistic event to compare.
- * @param confirmed - The confirmed event to compare.
- * @returns {boolean} Whether the two events are equal.
- */
-export const defaultComparator: EventComparator = (optimistic: Event, confirmed: Event) => {
-  if (optimistic.mutationId && confirmed.mutationId) {
-    return uuidComparator(optimistic, confirmed);
-  }
-  return equalityComparator(optimistic, confirmed);
-};
-
 /**
  * Default options applied to all optimistic events.
  */