Fix: Disable Auto-scroll when user looks back through historical chat-Bug 9062 (#9107)

### What problem does this PR solve?

This code allows user chat to auto-scroll down when entered, but if user
scrolls up away from the generative feedback, autoscroll is disabled.
Close #9062 

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

---------

Co-authored-by: Charles Copley <ccopley@ancera.com>

web/src/hooks/__tests__/logic-hooks.useScrollToBottom.test.tsx

@@ -0,0 +1,127 @@
+jest.mock('eventsource-parser/stream', () => ({}));
+
+import { act, renderHook } from '@testing-library/react';
+import { useScrollToBottom } from '../logic-hooks';
+
+function createMockContainer({ atBottom = true } = {}) {
+  const scrollTop = atBottom ? 100 : 0;
+  const clientHeight = 100;
+  const scrollHeight = 200;
+  const listeners = {};
+  return {
+    current: {
+      scrollTop,
+      clientHeight,
+      scrollHeight,
+      addEventListener: jest.fn((event, cb) => {
+        listeners[event] = cb;
+      }),
+      removeEventListener: jest.fn(),
+    },
+    listeners,
+  } as any;
+}
+
+// Helper to flush all timers and microtasks
+async function flushAll() {
+  jest.runAllTimers();
+  // Flush microtasks
+  await Promise.resolve();
+  // Sometimes, effects queue more timers, so run again
+  jest.runAllTimers();
+  await Promise.resolve();
+}
+
+describe('useScrollToBottom', () => {
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+  afterEach(() => {
+    jest.useRealTimers();
+  });
+
+  it('should set isAtBottom true when user is at bottom', () => {
+    const containerRef = createMockContainer({ atBottom: true });
+    const { result } = renderHook(() => useScrollToBottom([], containerRef));
+    expect(result.current.isAtBottom).toBe(true);
+  });
+
+  it('should set isAtBottom false when user is not at bottom', () => {
+    const containerRef = createMockContainer({ atBottom: false });
+    const { result } = renderHook(() => useScrollToBottom([], containerRef));
+    expect(result.current.isAtBottom).toBe(false);
+  });
+
+  it('should scroll to bottom when isAtBottom is true and messages change', async () => {
+    const containerRef = createMockContainer({ atBottom: true });
+    const mockScroll = jest.fn();
+
+    function useTestScrollToBottom(messages: any, containerRef: any) {
+      const hook = useScrollToBottom(messages, containerRef);
+      hook.scrollRef.current = { scrollIntoView: mockScroll } as any;
+      return hook;
+    }
+
+    const { rerender } = renderHook(
+      ({ messages }) => useTestScrollToBottom(messages, containerRef),
+      { initialProps: { messages: [] } },
+    );
+
+    rerender({ messages: ['msg1'] });
+    await flushAll();
+
+    expect(mockScroll).toHaveBeenCalled();
+  });
+
+  it('should NOT scroll to bottom when isAtBottom is false and messages change', async () => {
+    const containerRef = createMockContainer({ atBottom: false });
+    const mockScroll = jest.fn();
+
+    function useTestScrollToBottom(messages: any, containerRef: any) {
+      const hook = useScrollToBottom(messages, containerRef);
+      hook.scrollRef.current = { scrollIntoView: mockScroll } as any;
+      console.log('HOOK: isAtBottom:', hook.isAtBottom);
+      return hook;
+    }
+
+    const { result, rerender } = renderHook(
+      ({ messages }) => useTestScrollToBottom(messages, containerRef),
+      { initialProps: { messages: [] } },
+    );
+
+    // Simulate user scrolls up before messages change
+    await act(async () => {
+      containerRef.current.scrollTop = 0;
+      containerRef.current.addEventListener.mock.calls[0][1]();
+      await flushAll();
+      // Advance fake timers by 10ms instead of real setTimeout
+      jest.advanceTimersByTime(10);
+      console.log('AFTER SCROLL: isAtBottom:', result.current.isAtBottom);
+    });
+
+    rerender({ messages: ['msg1'] });
+    await flushAll();
+
+    console.log('AFTER RERENDER: isAtBottom:', result.current.isAtBottom);
+
+    expect(mockScroll).not.toHaveBeenCalled();
+
+    // Optionally, flush again after the assertion to see if it gets called late
+    await flushAll();
+  });
+
+  it('should indicate button should appear when user is not at bottom', () => {
+    const containerRef = createMockContainer({ atBottom: false });
+    const { result } = renderHook(() => useScrollToBottom([], containerRef));
+    // The button should appear in the UI when isAtBottom is false
+    expect(result.current.isAtBottom).toBe(false);
+  });
+});
+
+const originalRAF = global.requestAnimationFrame;
+beforeAll(() => {
+  global.requestAnimationFrame = (cb) => setTimeout(cb, 0);
+});
+afterAll(() => {
+  global.requestAnimationFrame = originalRAF;
+});

web/src/hooks/logic-hooks.ts

@@ -27,6 +27,14 @@ import { useTranslate } from './common-hooks';
 import { useSetPaginationParams } from './route-hook';
 import { useFetchTenantInfo, useSaveSetting } from './user-setting-hooks';
 
+function usePrevious<T>(value: T) {
+  const ref = useRef<T>();
+  useEffect(() => {
+    ref.current = value;
+  }, [value]);
+  return ref.current;
+}
+
 export const useSetSelectedRecord = <T = IKnowledgeFile>() => {
   const [currentRecord, setCurrentRecord] = useState<T>({} as T);
 
@@ -210,7 +218,6 @@ export const useSendMessageWithSse = (
           if (x) {
             const { done, value } = x;
             if (done) {
-              console.info('done');
               resetAnswer();
               break;
             }
@@ -218,26 +225,23 @@ export const useSendMessageWithSse = (
               const val = JSON.parse(value?.data || '');
               const d = val?.data;
               if (typeof d !== 'boolean') {
-                console.info('data:', d);
                 setAnswer({
                   ...d,
                   conversationId: body?.conversation_id,
                 });
               }
             } catch (e) {
-              console.warn(e);
+              // Swallow parse errors silently
             }
           }
         }
-        console.info('done?');
         setDone(true);
         resetAnswer();
         return { data: await res, response };
       } catch (e) {
         setDone(true);
         resetAnswer();
-
-        console.warn(e);
+        // Swallow fetch errors silently
       }
     },
     [initializeSseRef, url, resetAnswer],
@@ -267,7 +271,7 @@ export const useSpeechWithSse = (url: string = api.tts) => {
           message.error(res?.message);
         }
       } catch (error) {
-        console.warn('🚀 ~ error:', error);
+        // Swallow errors silently
       }
       return response;
     },
@@ -279,20 +283,55 @@ export const useSpeechWithSse = (url: string = api.tts) => {
 
 //#region chat hooks
 
-export const useScrollToBottom = (messages?: unknown) => {
+export const useScrollToBottom = (
+  messages?: unknown,
+  containerRef?: React.RefObject<HTMLDivElement>,
+) => {
   const ref = useRef<HTMLDivElement>(null);
+  const [isAtBottom, setIsAtBottom] = useState(true);
+  const isAtBottomRef = useRef(true);
 
-  const scrollToBottom = useCallback(() => {
-    if (messages) {
-      ref.current?.scrollIntoView({ behavior: 'instant' });
-    }
-  }, [messages]); // If the message changes, scroll to the bottom
+  useEffect(() => {
+    isAtBottomRef.current = isAtBottom;
+  }, [isAtBottom]);
+
+  const checkIfUserAtBottom = useCallback(() => {
+    if (!containerRef?.current) return true;
+    const { scrollTop, scrollHeight, clientHeight } = containerRef.current;
+    return Math.abs(scrollTop + clientHeight - scrollHeight) < 25;
+  }, [containerRef]);
 
   useEffect(() => {
-    scrollToBottom();
-  }, [scrollToBottom]);
+    if (!containerRef?.current) return;
+    const container = containerRef.current;
+
+    const handleScroll = () => {
+      setIsAtBottom(checkIfUserAtBottom());
+    };
+
+    container.addEventListener('scroll', handleScroll);
+    handleScroll();
+    return () => container.removeEventListener('scroll', handleScroll);
+  }, [containerRef, checkIfUserAtBottom]);
+
+  useEffect(() => {
+    if (!messages) return;
+    if (!containerRef?.current) return;
+    requestAnimationFrame(() => {
+      setTimeout(() => {
+        if (isAtBottomRef.current) {
+          ref.current?.scrollIntoView({ behavior: 'smooth' });
+        }
+      }, 30);
+    });
+  }, [messages, containerRef]);
+
+  // Imperative scroll function
+  const scrollToBottom = useCallback(() => {
+    ref.current?.scrollIntoView({ behavior: 'smooth' });
+  }, []);
 
-  return ref;
+  return { scrollRef: ref, isAtBottom, scrollToBottom };
 };
 
 export const useHandleMessageInputChange = () => {

web/src/pages/chat/chat-container/index.tsx

@@ -1,6 +1,7 @@
 import MessageItem from '@/components/message-item';
 import { MessageType } from '@/constants/chat';
 import { Flex, Spin } from 'antd';
+import { useRef } from 'react';
 import {
   useCreateConversationBeforeUploadDocument,
   useGetFileIcon,
@@ -15,9 +16,10 @@ import PdfDrawer from '@/components/pdf-drawer';
 import { useClickDrawer } from '@/components/pdf-drawer/hooks';
 import {
   useFetchNextConversation,
-  useGetChatSearchParams,
   useFetchNextDialog,
+  useGetChatSearchParams,
 } from '@/hooks/chat-hooks';
+import { useScrollToBottom } from '@/hooks/logic-hooks';
 import { useFetchUserInfo } from '@/hooks/user-setting-hooks';
 import { buildMessageUuidWithRole } from '@/utils/chat';
 import { memo } from 'react';
@@ -31,8 +33,8 @@ const ChatContainer = ({ controller }: IProps) => {
   const { conversationId } = useGetChatSearchParams();
   const { data: conversation } = useFetchNextConversation();
   const { data: currentDialog } = useFetchNextDialog();
-    
 
+  const messageContainerRef = useRef<HTMLDivElement>(null);
   const {
     value,
     ref,
@@ -45,6 +47,10 @@ const ChatContainer = ({ controller }: IProps) => {
     removeMessageById,
     stopOutputMessage,
   } = useSendNextMessage(controller);
+  const { scrollRef, isAtBottom, scrollToBottom } = useScrollToBottom(
+    derivedMessages,
+    messageContainerRef,
+  );
 
   const { visible, hideModal, documentId, selectedChunk, clickDocumentButton } =
     useClickDrawer();
@@ -55,10 +61,20 @@ const ChatContainer = ({ controller }: IProps) => {
   const { createConversationBeforeUploadDocument } =
     useCreateConversationBeforeUploadDocument();
 
+  const handleSend = (msg) => {
+    // your send logic
+    setTimeout(scrollToBottom, 0);
+  };
+
   return (
     <>
       <Flex flex={1} className={styles.chatContainer} vertical>
-        <Flex flex={1} vertical className={styles.messageContainer}>
+        <Flex
+          flex={1}
+          vertical
+          className={styles.messageContainer}
+          ref={messageContainerRef}
+        >
           <div>
             <Spin spinning={loading}>
               {derivedMessages?.map((message, i) => {
@@ -91,7 +107,7 @@ const ChatContainer = ({ controller }: IProps) => {
               })}
             </Spin>
           </div>
-          <div ref={ref} />
+          <div ref={scrollRef} />
         </Flex>
         <MessageInput
           disabled={disabled}