From 69e59a75d2ba5198f2240a0598b61f6847e2e538 Mon Sep 17 00:00:00 2001
From: Christopher Gurnee <chris@gurneeconsulting.net>
Date: Fri, 8 Apr 2022 17:54:32 +0000
Subject: [PATCH] Improve scrolling with parent and permalinks

Visiting a permalink (from an internal or external link) now scrolls to
just past the post, and both parent and permalinks scroll smoothly where
appropriate; it makes sense for internal permalinks to immediately jump.
---
 src/pages/common/Post.js    |  4 ++--
 src/pages/thread/Comment.js |  7 ++++---
 src/pages/thread/index.js   | 29 ++++++++++++++++++++++++-----
 3 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/src/pages/common/Post.js b/src/pages/common/Post.js
index 3857463..6c547cb 100644
--- a/src/pages/common/Post.js
+++ b/src/pages/common/Post.js
@@ -18,7 +18,7 @@ export default (props) => {
             <Link class="thread-title" to={permalink}>[removed too quickly to be archived]</Link>
             <div class="total-comments">
               <a href={`https://www.reddit.com${permalink}`}>reddit</a>&nbsp;
-              <a href={`https://reveddit.com${permalink}`}>reveddit</a>
+              <a href={`https://www.reveddit.com${permalink}`}>reveddit</a>
             </div>
           </div>
         </div>
@@ -76,7 +76,7 @@ export default (props) => {
       <span>{props.num_comments} comments</span> :
       <Link to={props.permalink}>{props.num_comments}&nbsp;comments</Link>}&nbsp;
     <a href={`https://www.reddit.com${props.permalink}`}>reddit</a>&nbsp;
-    <a href={`https://reveddit.com${props.permalink}`}>reveddit</a>
+    <a href={`https://www.reveddit.com${props.permalink}`}>reveddit</a>
     {props.hasOwnProperty('edited_selftext') &&
       <a onClick=  {() => setShowEdited(!showEdited)}
          onKeyDown={e => e.key == 'Enter' && setShowEdited(!showEdited)}
diff --git a/src/pages/thread/Comment.js b/src/pages/thread/Comment.js
index ada629f..3aaf702 100644
--- a/src/pages/thread/Comment.js
+++ b/src/pages/thread/Comment.js
@@ -45,7 +45,8 @@ const Comment = (props) => {
         activeClassName='wait'
       >parent</NavLink>
     :
-      <a href={`#${props.parent_id}`}>parent</a>
+      // Use a function, not just an object--state is recreated and scrollBehavior is always initialized
+      <Link to={() => ({hash: `#${props.parent_id}`, state: {scrollBehavior: 'smooth'}})}>parent</Link>
   )
 
   return (
@@ -75,9 +76,9 @@ const Comment = (props) => {
       <div style={collapsed ? {display: 'none'} : {}}>
         <div className='comment-body' dangerouslySetInnerHTML={{ __html: showEdited ? editedInnerHTML : innerHTML }} />
         <div className='comment-links'>
-          <Link to={permalink}>permalink</Link>
+          <Link to={() => ({pathname: permalink, hash: '#comment-info', state: {scrollBehavior: 'auto'}})}>permalink</Link>
           <a href={`https://www.reddit.com${permalink}`}>reddit</a>
-          <a href={`https://reveddit.com${permalink}`}>reveddit</a>
+          <a href={`https://www.reveddit.com${permalink}`}>reveddit</a>
           {parentlink}
           {props.hasOwnProperty('edited_body') &&
             <a onClick=  {() => setShowEdited(!showEdited)}
diff --git a/src/pages/thread/index.js b/src/pages/thread/index.js
index ab40de4..3da586d 100644
--- a/src/pages/thread/index.js
+++ b/src/pages/thread/index.js
@@ -214,6 +214,11 @@ class Thread extends React.Component {
           this.contigs.unshift({firstCreated: EARLIEST_CREATED})
           this.getComments(maxComments)
         })
+
+      // Set the scroll location to just below the post if not already set (only with permalinks)
+      if (!this.props.location.hash)
+        this.props.location.hash = '#comment-info'
+      this.props.location.state = {scrollBehavior: 'smooth'}
     }
   }
 
@@ -243,6 +248,7 @@ class Thread extends React.Component {
   }
 
   componentDidUpdate () {
+    let { loadingComments } = this.state
 
     // If the max-to-download Reload button or 'load more comments' was clicked
     const { loadingMoreComments } = this.props.global.state
@@ -255,12 +261,13 @@ class Thread extends React.Component {
       this.getComments(loadingMoreComments, true)
 
     // Otherwise if we're loading a comment tree we haven't downloaded yet
-    } else if (!this.state.loadingComments && !this.state.reloadingComments && !this.updateCurContig()) {
+    } else if (!loadingComments && !this.state.reloadingComments && !this.updateCurContig()) {
 
       // If we haven't downloaded from the earliest available yet (not a permalink)
       const { commentID } = this.props.match.params
       if (commentID === undefined) {
-        this.setState({loadingComments: true})
+        loadingComments = true
+        this.setState({loadingComments})
         this.props.global.setLoading('Loading comments...')
         console.time('Load comments')
         this.contigs.unshift({firstCreated: EARLIEST_CREATED})
@@ -296,7 +303,8 @@ class Thread extends React.Component {
                 this.setCurContig(insertBefore - 1)  // (this was the failed earlier attempt)
                 console.timeEnd('Load comments')
                 this.props.global.setSuccess()
-                this.setState({pushshiftCommentLookup, loadingComments: false, reloadingComments: false})
+                loadingComments = false
+                this.setState({pushshiftCommentLookup, loadingComments, reloadingComments: false})
               }
             } else
               createdUtcNotFound = true
@@ -316,6 +324,14 @@ class Thread extends React.Component {
           })
       }
     }
+
+    if (!loadingComments && this.props.location.state?.scrollBehavior) {
+      const { location } = this.props
+      const id = location.hash.substring(1)
+      if (id)
+        document.getElementById(id)?.scrollIntoView({behavior: location.state.scrollBehavior})
+      delete location.state
+    }
   }
 
   // Before calling, either create (and set to current) a new contig to begin downloading
@@ -484,7 +500,6 @@ class Thread extends React.Component {
     const reloadingComments = this.state.loadingComments ||
                               this.state.reloadingComments ||
                               this.props.global.state.loadingMoreComments
-    const linkToRestOfComments = `/r/${subreddit}/comments/${id}/_/`
 
     const isSingleComment = commentID !== undefined
     const root = isSingleComment ? commentID : id
@@ -510,7 +525,11 @@ class Thread extends React.Component {
                 <div>you are viewing a single comment's thread.</div>
                 {this.state.reloadingComments ?
                   <div className='faux-link'>view the rest of the comments</div> :
-                  <Link to={linkToRestOfComments}>view the rest of the comments</Link>
+                  <Link to={() => ({
+                    pathname: `/r/${subreddit}/comments/${id}/_/`,
+                    hash: '#comment-info',
+                    state: {scrollBehavior: 'smooth'}}
+                  )}>view the rest of the comments</Link>
                 }
               </div>
             }