Partially improve threading UI for adjacent inline comments

Summary:
Ref T10563. This isn't a complete fix, but should make viewing complex inline threads a little more manageable.

This just tries to put stuff in thread order instead of in pure chronological order. We can likely improve the display treatment -- this is a pretty minimal approach, but should improve clarity.

Test Plan:
T10563 has a "before" shot. Here's the "after":

{F1169018}

This makes it a bit easier to follow the conversations.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10563

Differential Revision: https://secure.phabricator.com/D15459

resources/celerity/map.php

@@ -10,7 +10,7 @@ return array(
     'core.pkg.css' => '9c8e888d',
     'core.pkg.js' => '7d8faf57',
     'darkconsole.pkg.js' => 'e7393ebb',
-    'differential.pkg.css' => '2de124c9',
+    'differential.pkg.css' => '7d0a63a7',
     'differential.pkg.js' => 'd0cd0df6',
     'diffusion.pkg.css' => 'f45955ed',
     'diffusion.pkg.js' => '3a9a8bfa',
@@ -59,7 +59,7 @@ return array(
     'rsrc/css/application/differential/add-comment.css' => 'c47f8c40',
     'rsrc/css/application/differential/changeset-view.css' => 'b6b0d1bb',
     'rsrc/css/application/differential/core.css' => '7ac3cabc',
-    'rsrc/css/application/differential/phui-inline-comment.css' => '0fdb3667',
+    'rsrc/css/application/differential/phui-inline-comment.css' => '5953c28e',
     'rsrc/css/application/differential/revision-comment.css' => '14b8565a',
     'rsrc/css/application/differential/revision-history.css' => '0e8eb855',
     'rsrc/css/application/differential/revision-list.css' => 'f3c47d33',
@@ -831,7 +831,7 @@ return array(
     'phui-image-mask-css' => 'a8498f9c',
     'phui-info-panel-css' => '27ea50a1',
     'phui-info-view-css' => '6d7c3509',
-    'phui-inline-comment-view-css' => '0fdb3667',
+    'phui-inline-comment-view-css' => '5953c28e',
     'phui-list-view-css' => '9da2aa00',
     'phui-object-box-css' => '91628842',
     'phui-object-item-list-view-css' => '18b2ce8e',

src/applications/differential/parser/DifferentialChangesetParser.php

@@ -1000,7 +1000,8 @@ final class DifferentialChangesetParser extends Phobject {
         }
       }
 
-      $this->comments = msort($this->comments, 'getID');
+      $this->comments = $this->reorderAndThreadComments($this->comments);
+
       foreach ($this->comments as $comment) {
         $final = $comment->getLineNumber() +
           $comment->getLineLength();
@@ -1569,4 +1570,67 @@ final class DifferentialChangesetParser extends Phobject {
     return array($old_back, $new_back);
   }
 
+  private function reorderAndThreadComments(array $comments) {
+    $comments = msort($comments, 'getID');
+
+    // Build an empty map of all the comments we actually have. If a comment
+    // is a reply but the parent has gone missing, we don't want it to vanish
+    // completely.
+    $comment_phids = mpull($comments, 'getPHID');
+    $replies = array_fill_keys($comment_phids, array());
+
+    // Now, remove all comments which are replies, leaving only the top-level
+    // comments.
+    foreach ($comments as $key => $comment) {
+      $reply_phid = $comment->getReplyToCommentPHID();
+      if (isset($replies[$reply_phid])) {
+        $replies[$reply_phid][] = $comment;
+        unset($comments[$key]);
+      }
+    }
+
+    // For each top level comment, add the comment, then add any replies
+    // to it. Do this recursively so threads are shown in threaded order.
+    $results = array();
+    foreach ($comments as $comment) {
+      $results[] = $comment;
+      $phid = $comment->getPHID();
+      $descendants = $this->getInlineReplies($replies, $phid, 1);
+      foreach ($descendants as $descendant) {
+        $results[] = $descendant;
+      }
+    }
+
+    // If we have anything left, they were cyclic references. Just dump
+    // them in a the end. This should be impossible, but users are very
+    // creative.
+    foreach ($replies as $phid => $comments) {
+      foreach ($comments as $comment) {
+        $results[] = $comment;
+      }
+    }
+
+    return $results;
+  }
+
+  private function getInlineReplies(array &$replies, $phid, $depth) {
+    $comments = idx($replies, $phid, array());
+    unset($replies[$phid]);
+
+    $results = array();
+    foreach ($comments as $comment) {
+      $results[] = $comment;
+      $descendants = $this->getInlineReplies(
+        $replies,
+        $comment->getPHID(),
+        $depth + 1);
+      foreach ($descendants as $descendant) {
+        $results[] = $descendant;
+      }
+    }
+
+    return $results;
+  }
+
+
 }

src/infrastructure/diff/view/PHUIDiffInlineCommentDetailView.php

@@ -176,7 +176,7 @@ final class PHUIDiffInlineCommentDetailView
     if ($inline->getHasReplies()) {
       $classes[] = 'inline-comment-has-reply';
     }
-    // I think this is unused
+
     if ($inline->getReplyToCommentPHID()) {
       $classes[] = 'inline-comment-is-reply';
     }

webroot/rsrc/css/application/differential/phui-inline-comment.css

@@ -61,7 +61,7 @@
 
 /* Tighten up spacing on replies */
 .differential-inline-comment.inline-comment-is-reply {
-  margin-top: -4px;
+  margin-top: -12px;
 }
 
 .differential-inline-comment .inline-head-right {