From fac71d1749c5dcc8992dd560816ef046be7796fb Mon Sep 17 00:00:00 2001
From: Dessalines <dessalines@users.noreply.github.com>
Date: Tue, 16 Nov 2021 09:46:12 -0500
Subject: [PATCH] Adding post comment scrolling hack. Fixes #480 (#486)

---
 .../components/comment/comment-nodes.tsx      |  7 ++++-
 src/shared/components/post/post.tsx           | 28 +++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/shared/components/comment/comment-nodes.tsx b/src/shared/components/comment/comment-nodes.tsx
index 3605358f..af1610a2 100644
--- a/src/shared/components/comment/comment-nodes.tsx
+++ b/src/shared/components/comment/comment-nodes.tsx
@@ -15,6 +15,7 @@ interface CommentNodesProps {
   markable?: boolean;
   showContext?: boolean;
   showCommunity?: boolean;
+  maxCommentsShown?: number;
   enableDownvotes: boolean;
 }
 
@@ -24,9 +25,13 @@ export class CommentNodes extends Component<CommentNodesProps, any> {
   }
 
   render() {
+    let maxComments = this.props.maxCommentsShown
+      ? this.props.maxCommentsShown
+      : this.props.nodes.length;
+
     return (
       <div className="comments">
-        {this.props.nodes.map(node => (
+        {this.props.nodes.slice(0, maxComments).map(node => (
           <CommentNode
             key={node.comment_view.comment.id}
             node={node}
diff --git a/src/shared/components/post/post.tsx b/src/shared/components/post/post.tsx
index f1a7a8ae..1213c5a8 100644
--- a/src/shared/components/post/post.tsx
+++ b/src/shared/components/post/post.tsx
@@ -39,6 +39,7 @@ import {
   commentsToFlatNodes,
   createCommentLikeRes,
   createPostLikeRes,
+  debounce,
   editCommentRes,
   getCommentIdFromProps,
   getIdFromProps,
@@ -66,6 +67,8 @@ import { Icon, Spinner } from "../common/icon";
 import { Sidebar } from "../community/sidebar";
 import { PostListing } from "./post-listing";
 
+const commentsShownInterval = 15;
+
 interface PostState {
   postRes: GetPostResponse;
   postId: number;
@@ -79,6 +82,7 @@ interface PostState {
   siteRes: GetSiteResponse;
   commentSectionRef?: RefObject<HTMLDivElement>;
   showSidebarMobile: boolean;
+  maxCommentsShown: number;
 }
 
 export class Post extends Component<any, PostState> {
@@ -97,6 +101,7 @@ export class Post extends Component<any, PostState> {
     siteRes: this.isoData.site_res,
     commentSectionRef: null,
     showSidebarMobile: false,
+    maxCommentsShown: commentsShownInterval,
   };
 
   constructor(props: any, context: any) {
@@ -173,6 +178,7 @@ export class Post extends Component<any, PostState> {
 
   componentWillUnmount() {
     this.subscription.unsubscribe();
+    document.removeEventListener("scroll", this.trackCommentsBoxScrolling);
     window.isoData.path = undefined;
     saveScrollPosition(this.context);
   }
@@ -182,6 +188,11 @@ export class Post extends Component<any, PostState> {
       wsClient.postJoin({ post_id: this.state.postId })
     );
     autosize(document.querySelectorAll("textarea"));
+
+    document.addEventListener(
+      "scroll",
+      debounce(this.trackCommentsBoxScrolling, 100)
+    );
   }
 
   componentDidUpdate(_lastProps: any, lastState: PostState) {
@@ -253,6 +264,21 @@ export class Post extends Component<any, PostState> {
     }
   }
 
+  isBottom(el: Element) {
+    return el.getBoundingClientRect().bottom <= window.innerHeight;
+  }
+
+  /**
+   * Shows new comments when scrolling to the bottom of the comments div
+   */
+  trackCommentsBoxScrolling = () => {
+    const wrappedElement = document.getElementsByClassName("comments")[0];
+    if (this.isBottom(wrappedElement)) {
+      this.state.maxCommentsShown += commentsShownInterval;
+      this.setState(this.state);
+    }
+  };
+
   get documentTitle(): string {
     return `${this.state.postRes.post_view.post.name} - ${this.state.siteRes.site_view.site.name}`;
   }
@@ -416,6 +442,7 @@ export class Post extends Component<any, PostState> {
       <div>
         <CommentNodes
           nodes={commentsToFlatNodes(this.state.postRes.comments)}
+          maxCommentsShown={this.state.maxCommentsShown}
           noIndent
           locked={this.state.postRes.post_view.post.locked}
           moderators={this.state.postRes.moderators}
@@ -473,6 +500,7 @@ export class Post extends Component<any, PostState> {
       <div>
         <CommentNodes
           nodes={this.state.commentTree}
+          maxCommentsShown={this.state.maxCommentsShown}
           locked={this.state.postRes.post_view.post.locked}
           moderators={this.state.postRes.moderators}
           admins={this.state.siteRes.admins}