fix: calculate message read status for the first message in a channel (ported from v13) (#3056)

Author: MartinCupela

src/components/MessageList/hooks/__tests__/useLastOwnMessage.test.js

@@ -0,0 +1,60 @@
+import { renderHook } from '@testing-library/react';
+
+import { generateMessage, generateUser } from '../../../../mock-builders';
+import { useLastOwnMessage } from '../useLastOwnMessage';
+
+describe('useLastOwnMessage', () => {
+  it('returns undefined when there are no messages', () => {
+    const ownUser = generateUser();
+
+    const { result } = renderHook(() =>
+      useLastOwnMessage({ messages: undefined, ownUserId: ownUser.id }),
+    );
+
+    expect(result.current).toBeUndefined();
+  });
+
+  it('returns undefined when there are no own messages', () => {
+    const ownUser = generateUser();
+    const otherUser = generateUser();
+    const messages = [generateMessage({ user: otherUser })];
+
+    const { result } = renderHook(() =>
+      useLastOwnMessage({ messages, ownUserId: ownUser.id }),
+    );
+
+    expect(result.current).toBeUndefined();
+  });
+
+  it('returns the first message when it is the only own message', () => {
+    const ownUser = generateUser();
+    const otherUser = generateUser();
+    const ownMessage = generateMessage({ user: ownUser });
+    const messages = [ownMessage, generateMessage({ user: otherUser })];
+
+    const { result } = renderHook(() =>
+      useLastOwnMessage({ messages, ownUserId: ownUser.id }),
+    );
+
+    expect(result.current).toBe(ownMessage);
+  });
+
+  it('returns the latest own message', () => {
+    const ownUser = generateUser();
+    const otherUser = generateUser();
+    const firstOwnMessage = generateMessage({ user: ownUser });
+    const lastOwnMessage = generateMessage({ user: ownUser });
+    const messages = [
+      firstOwnMessage,
+      generateMessage({ user: otherUser }),
+      lastOwnMessage,
+      generateMessage({ user: otherUser }),
+    ];
+
+    const { result } = renderHook(() =>
+      useLastOwnMessage({ messages, ownUserId: ownUser.id }),
+    );
+
+    expect(result.current).toBe(lastOwnMessage);
+  });
+});

src/utils/findReverse.ts

@@ -3,7 +3,7 @@ export const findReverse = <T>(
   items: T[],
   matches: (items: T) => boolean,
 ): T | undefined => {
-  for (let i = items.length - 1; i > 0; i -= 1) {
+  for (let i = items.length - 1; i >= 0; i -= 1) {
     if (matches(items[i])) {
       return items[i];
     }