Chats: add the building blocks for pagination

app/soapbox/actions/chats.js

@@ -34,13 +34,13 @@ export function fetchChats() {
   };
 }
 
-export function fetchChatMessages(chatId) {
+export function fetchChatMessages(chatId, maxId = null) {
   return (dispatch, getState) => {
-    dispatch({ type: CHAT_MESSAGES_FETCH_REQUEST, chatId });
-    return api(getState).get(`/api/v1/pleroma/chats/${chatId}/messages`).then(({ data }) => {
-      dispatch({ type: CHAT_MESSAGES_FETCH_SUCCESS, chatId, chatMessages: data });
+    dispatch({ type: CHAT_MESSAGES_FETCH_REQUEST, chatId, maxId });
+    return api(getState).get(`/api/v1/pleroma/chats/${chatId}/messages`, { params: { max_id: maxId } }).then(({ data }) => {
+      dispatch({ type: CHAT_MESSAGES_FETCH_SUCCESS, chatId, maxId, chatMessages: data });
     }).catch(error => {
-      dispatch({ type: CHAT_MESSAGES_FETCH_FAIL, chatId, error });
+      dispatch({ type: CHAT_MESSAGES_FETCH_FAIL, chatId, maxId, error });
     });
   };
 }

app/soapbox/features/chats/components/chat_box.js

@@ -98,12 +98,12 @@ class ChatBox extends ImmutablePureComponent {
   }
 
   render() {
-    const { chatMessageIds, intl } = this.props;
+    const { chatMessageIds, chatId, intl } = this.props;
     if (!chatMessageIds) return null;
 
     return (
       <div className='chat-box' onMouseOver={this.handleHover}>
-        <ChatMessageList chatMessageIds={chatMessageIds} />
+        <ChatMessageList chatMessageIds={chatMessageIds} chatId={chatId} />
         <div className='chat-box__actions simple_form'>
           <textarea
             rows={1}

app/soapbox/features/chats/components/chat_message_list.js

@@ -5,9 +5,10 @@ import ImmutablePropTypes from 'react-immutable-proptypes';
 import { injectIntl } from 'react-intl';
 import ImmutablePureComponent from 'react-immutable-pure-component';
 import { Map as ImmutableMap, List as ImmutableList } from 'immutable';
+import { fetchChatMessages } from 'soapbox/actions/chats';
 import emojify from 'soapbox/features/emoji/emoji';
 import classNames from 'classnames';
-import { escape } from 'lodash';
+import { escape, throttle } from 'lodash';
 
 const makeEmojiMap = record => record.get('emojis', ImmutableList()).reduce((map, emoji) => {
   return map.set(`:${emoji.get('shortcode')}:`, emoji);
@@ -28,6 +29,7 @@ class ChatMessageList extends ImmutablePureComponent {
   static propTypes = {
     dispatch: PropTypes.func.isRequired,
     intl: PropTypes.object.isRequired,
+    chatId: PropTypes.string,
     chatMessages: ImmutablePropTypes.list,
     chatMessageIds: ImmutablePropTypes.orderedSet,
     me: PropTypes.node,
@@ -61,7 +63,7 @@ class ChatMessageList extends ImmutablePureComponent {
     );
   };
 
-  setRef = (c) => {
+  setBubbleRef = (c) => {
     if (!c) return;
     const links = c.querySelectorAll('a[rel="ugc"]');
 
@@ -72,11 +74,30 @@ class ChatMessageList extends ImmutablePureComponent {
     });
   }
 
+  componentDidMount() {
+  }
+
   componentDidUpdate(prevProps) {
     if (prevProps.chatMessages !== this.props.chatMessages)
       this.scrollToBottom();
   }
 
+  componentWillUnmount() {
+    this.node.removeEventListener('scroll', this.handleScroll);
+  }
+
+  handleLoadMore = () => {
+    const { dispatch, chatId, chatMessageIds } = this.props;
+    const maxId = chatMessageIds.last();
+    dispatch(fetchChatMessages(chatId, maxId));
+  }
+
+  handleScroll = throttle(() => {
+    if (this.node.scrollTop < 100) this.handleLoadMore();
+  }, 150, {
+    trailing: true,
+  });
+
   parsePendingContent = content => {
     return escape(content).replace(/(?:\r\n|\r|\n)/g, '<br>');
   }
@@ -89,11 +110,16 @@ class ChatMessageList extends ImmutablePureComponent {
     return emojify(formatted, emojiMap.toJS());
   }
 
+  setRef = (c) => {
+    this.node = c;
+    this.node.addEventListener('scroll', this.handleScroll);
+  }
+
   render() {
     const { chatMessages, me } = this.props;
 
     return (
-      <div className='chat-messages'>
+      <div className='chat-messages' ref={this.setRef}>
         {chatMessages.map(chatMessage => (
           <div
             className={classNames('chat-message', {
@@ -106,7 +132,7 @@ class ChatMessageList extends ImmutablePureComponent {
               title={this.getFormattedTimestamp(chatMessage)}
               className='chat-message__bubble'
               dangerouslySetInnerHTML={{ __html: this.parseContent(chatMessage) }}
-              ref={this.setRef}
+              ref={this.setBubbleRef}
             />
           </div>
         ))}