From 4ec4062274fdf5ebcc4da9f2feb0f8206b966035 Mon Sep 17 00:00:00 2001
From: Marcel <marcel@familienarchiv>
Date: Fri, 17 Apr 2026 07:45:40 +0200
Subject: [PATCH] refactor(#248): simplify TagService.buildTree() to
 single-pass LinkedHashMap approach

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../familienarchiv/service/TagService.java    | 40 +++++--------------
 1 file changed, 11 insertions(+), 29 deletions(-)

diff --git a/backend/src/main/java/org/raddatz/familienarchiv/service/TagService.java b/backend/src/main/java/org/raddatz/familienarchiv/service/TagService.java
index b82b0be5..042b7943 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/service/TagService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/service/TagService.java
@@ -4,6 +4,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -208,39 +209,20 @@ public class TagService {
     }
 
     private List<TagTreeNodeDTO> buildTree(List<Tag> tags, Map<UUID, Long> counts) {
-        Map<UUID, List<TagTreeNodeDTO>> childrenByParent = new HashMap<>();
-
-        for (Tag tag : tags) {
-            childrenByParent.putIfAbsent(tag.getId(), new ArrayList<>());
-            if (tag.getParentId() != null) {
-                childrenByParent.computeIfAbsent(tag.getParentId(), k -> new ArrayList<>());
-            }
-        }
-
+        Map<UUID, TagTreeNodeDTO> nodeById = new LinkedHashMap<>();
         for (Tag tag : tags) {
             int documentCount = counts.getOrDefault(tag.getId(), 0L).intValue();
-            TagTreeNodeDTO node = new TagTreeNodeDTO(
+            nodeById.put(tag.getId(), new TagTreeNodeDTO(
                     tag.getId(), tag.getName(), tag.getColor(), documentCount,
-                    childrenByParent.getOrDefault(tag.getId(), new ArrayList<>()),
-                    tag.getParentId()
-            );
-            if (tag.getParentId() != null) {
-                childrenByParent.get(tag.getParentId()).add(node);
+                    new ArrayList<>(), tag.getParentId()
+            ));
+        }
+        for (TagTreeNodeDTO node : nodeById.values()) {
+            if (node.parentId() != null) {
+                TagTreeNodeDTO parent = nodeById.get(node.parentId());
+                if (parent != null) parent.children().add(node);
             }
         }
-
-        // Collect root nodes (tags without a parent)
-        List<TagTreeNodeDTO> roots = new ArrayList<>();
-        for (Tag tag : tags) {
-            if (tag.getParentId() == null) {
-                int documentCount = counts.getOrDefault(tag.getId(), 0L).intValue();
-                roots.add(new TagTreeNodeDTO(
-                        tag.getId(), tag.getName(), tag.getColor(), documentCount,
-                        childrenByParent.getOrDefault(tag.getId(), new ArrayList<>()),
-                        null
-                ));
-            }
-        }
-        return roots;
+        return nodeById.values().stream().filter(n -> n.parentId() == null).toList();
     }
 }