[NETWORK][TreeNotes] Add TreeNotes plugin which takes over the responsibility of displaying a conversation as a tree, in order to reduce the number of queries

plugins/TreeNotes/TreeNotes.php

@@ -0,0 +1,52 @@
+<?php
+
+// {{{ License
+// This file is part of GNU social - https://www.gnu.org/software/social
+//
+// GNU social is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// GNU social is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with GNU social.  If not, see <http://www.gnu.org/licenses/>.
+// }}}
+
+namespace Plugin\TreeNotes;
+
+use App\Entity\Note;
+use App\Core\Event;
+use App\Core\Module;
+use Functional as F;
+
+class TreeNotes extends Module
+{
+    /**
+     * Format the given $notes_in_trees_out in a list of reply trees
+     */
+    public function onFormatNoteList(array &$notes_in_trees_out)
+    {
+        $roots = array_filter($notes_in_trees_out, function(Note $note) { return $note->getReplyTo() == null; }, ARRAY_FILTER_USE_BOTH);
+        $notes_in_trees_out = $this->build_tree($roots, $notes_in_trees_out);
+    }
+
+    private function build_tree(array $parents, array $notes)
+    {
+        $subtree = [];
+        foreach ($parents as $p) {
+            $subtree[] = $this->build_subtree($p, $notes);
+        }
+        return $subtree;
+    }
+
+    private function build_subtree(Note $parent, array $notes)
+    {
+        $children = array_filter($notes, function(Note $n) use ($parent) { return $parent->getId() == $n->getReplyTo(); }, ARRAY_FILTER_USE_BOTH);
+        return ['note' => $parent, 'replies' => $this->build_tree($children, $notes)];
+    }
+}