improvement: optimize ChannelMessageView and prevent sending a request for initial messages multiple times (has issues; see TODO)

src/common/store.js

@@ -13,7 +13,8 @@ const intitialState = {
         glyph: "",
         title: "",
         content: ""
-    }
+    },
+    messagesLoadedIn: []
 };
 
 const reducer = (state = intitialState, payload) => {
@@ -74,6 +75,16 @@ const reducer = (state = intitialState, payload) => {
             };
         }
 
+        case 'channels/firstmessageload': {
+            return {
+                ...state,
+                messagesLoadedIn: [
+                    ...state.messagesLoadedIn,
+                    payload.channelId
+                ]
+            };
+        }
+
         case 'channels/updatepresence': {
             return {
                 ...state,

src/components/channel/ChannelMessageView.js

@@ -1,52 +1,83 @@
-import { useRef, useEffect, useState } from 'react';
-import { useDispatch } from "react-redux";
+import { PureComponent, createRef } from 'react';
+import { connect } from "react-redux";
 
 import { authenticated } from "../../api/request";
+import { getJsonValue } from '../../common/environmentmanager';
 import Message from  "../Message";
 
-export default function ChannelMessageView({ messages, channelId }) {
-    const invisibleBottomMessageRef = useRef();
+class ChannelMessageView extends PureComponent {
+    constructor() {
+        super();
+        this.state = {
+            isLoading: false
+        };
+        this.invisibleBottomMessageRef = createRef();
+        this.scroller = createRef();
 
-    const [isLoading, setIsLoading] = useState(false);
-    const dispatch = useDispatch();
-    const scroller = useRef();
+        this.onScroll = this.onScroll.bind(this);
+    }
 
-    const loadOlderMessages = () => {
-        if (isLoading) return;
-        if (!channelId) return;
-        setIsLoading(true);
+    loadOlderMessages() {
+        if (this.state.isLoading) return;
+        if (!getJsonValue("loadMessages")) return; // parse as json to get boolean
+        if (!this.props.channelId) return;
+        this.setState({ isLoading: true });
 
-        const request = messages[0] ? `/api/v1/content/channel/${channelId}/messages?before=${messages[0]._id}` : `/api/v1/content/channel/${channelId}/messages`;
+        const request = this.props.messages[0] ? `/api/v1/content/channel/${this.props.channelId}/messages?before=${this.props.messages[0]._id}` : `/api/v1/content/channel/${this.props.channelId}/messages`;
 
         authenticated(request)
             .then((res) => {
                 if (res.json.channelMessages)
-                    dispatch({
+                    this.props.dispatch({
                         type: "messagestore/addmessagesback",
                         messages: res.json.channelMessages.reverse(),
-                        channelId
-                    })
+                        channelId: this.props.channelId
+                    });
             })
             .then(() => {
-                setIsLoading(false);
+                this.setState({ isLoading: false });
             });
-    };
-
-    const onScroll = () => {
-        if (scroller.current.scrollTop === 0) {
-            loadOlderMessages();
     }
-    };
 
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-    useEffect(loadOlderMessages, [channelId, dispatch]);
+    firstTimeMessageLoad() {
+        if (!this.props.channelId) return false;
+        if (this.props.messagesLoadedIn.includes(this.props.channelId)) return false;
+        this.props.dispatch({
+            type: "channels/firstmessageload",
+            channelId: this.props.channelId
+        });
+        this.loadOlderMessages();
+    }
 
-    useEffect(() => {
-        invisibleBottomMessageRef.current.scrollIntoView(true);
-    }, [messages]);
+    onScroll() {
+        // TODO: this triggers when switching between channels so the firstmessageload check does not take effect
+        if (this.scroller.current.scrollTop === 0)
+            this.loadOlderMessages();
+    }
 
-    return <div className="message-list" id="message-list" ref={ scroller } onScroll={ onScroll }>
-        {messages.map(message => <Message message={message} key={message._id} />)}
-        <div className="messages-scroll-div" ref={ invisibleBottomMessageRef }></div>
+    componentDidMount() {
+        this.firstTimeMessageLoad();
+    }
+
+    componentDidUpdate(prevProps) {
+        if (prevProps.messages !== this.props.messages) {
+            this.invisibleBottomMessageRef.current.scrollIntoView(true);
+        }
+        if (prevProps.channelId !== this.props.channelId) {
+            this.firstTimeMessageLoad();
+        }
+    }
+
+    render() {
+        return <div className="message-list" id="message-list" ref={ this.scroller } onScroll={ this.onScroll }>
+            {this.props.messages.map(message => <Message message={message} key={message._id} />)}
+            <div className="messages-scroll-div" ref={ this.invisibleBottomMessageRef }></div>
         </div>;
     }
+}
+
+export default connect((state) => {
+    return {
+        messagesLoadedIn: state.messagesLoadedIn
+    };
+}, null)(ChannelMessageView);

src/config.js

@@ -1,7 +1,8 @@
 const config = {
     apiUrl: "http://localhost:3000",
     gatewayUrl: "ws://localhost:3005/gateway",
-    gatewayConnectionAttributes: ["PRESENCE_UPDATES"]
+    gatewayConnectionAttributes: ["PRESENCE_UPDATES"],
+    loadMessages: true
 };
 
 export default config;