From ad0beb9dbafdad8d4f606b3c3cd29a79fdd08b4d Mon Sep 17 00:00:00 2001
From: Patrick Strawderman <pstrawderman@netflix.com>
Date: Fri, 15 Sep 2023 09:58:26 -0700
Subject: [PATCH] Simplify ArrayTagSet sort method

Get rid of unnecessary branches in ArrayTagSet's insertionSort method.
---
 .../netflix/spectator/api/ArrayTagSet.java    | 35 +++++--------------
 .../spectator/api/ArrayTagSetTest.java        | 22 ++++++++++--
 2 files changed, 29 insertions(+), 28 deletions(-)

diff --git a/spectator-api/src/main/java/com/netflix/spectator/api/ArrayTagSet.java b/spectator-api/src/main/java/com/netflix/spectator/api/ArrayTagSet.java
index 2798cc786..9810d94c3 100644
--- a/spectator-api/src/main/java/com/netflix/spectator/api/ArrayTagSet.java
+++ b/spectator-api/src/main/java/com/netflix/spectator/api/ArrayTagSet.java
@@ -304,33 +304,16 @@ private void checkForNullValues(String[] ts) {
    * tags. With the small size a simple insertion sort works well.
    */
   private static void insertionSort(String[] ts, int length) {
-    if (length == 4) {
-      // Two key/value pairs, swap if needed
-      if (ts[0].compareTo(ts[2]) > 0) {
-        // Swap key
-        String tmp = ts[0];
-        ts[0] = ts[2];
-        ts[2] = tmp;
-
-        // Swap value
-        tmp = ts[1];
-        ts[1] = ts[3];
-        ts[3] = tmp;
-      }
-    } else if (length > 4) {
-      // One entry is already sorted. Two entries handled above, for larger arrays
-      // use insertion sort.
-      for (int i = 2; i < length; i += 2) {
-        String k = ts[i];
-        String v = ts[i + 1];
-        int j = i - 2;
-        for (; j >= 0 && ts[j].compareTo(k) > 0; j -= 2) {
-          ts[j + 2] = ts[j];
-          ts[j + 3] = ts[j + 1];
-        }
-        ts[j + 2] = k;
-        ts[j + 3] = v;
+    for (int i = 2; i < length; i += 2) {
+      String k = ts[i];
+      String v = ts[i + 1];
+      int j = i - 2;
+      for (; j >= 0 && ts[j].compareTo(k) > 0; j -= 2) {
+        ts[j + 2] = ts[j];
+        ts[j + 3] = ts[j + 1];
       }
+      ts[j + 2] = k;
+      ts[j + 3] = v;
     }
   }
 
diff --git a/spectator-api/src/test/java/com/netflix/spectator/api/ArrayTagSetTest.java b/spectator-api/src/test/java/com/netflix/spectator/api/ArrayTagSetTest.java
index 161ec9091..f86e3319a 100644
--- a/spectator-api/src/test/java/com/netflix/spectator/api/ArrayTagSetTest.java
+++ b/spectator-api/src/test/java/com/netflix/spectator/api/ArrayTagSetTest.java
@@ -779,7 +779,25 @@ public void addAllDuplicates() {
     assertDistinct(updated);
   }
 
-  class TagIterator implements Iterable<Tag> {
+  @Test
+  public void testSort() {
+    Assertions.assertEquals(Arrays.asList("a", "v1"), toList(ArrayTagSet.create("a", "v1")));
+    Assertions.assertEquals(Arrays.asList("a", "v1", "b", "v2"), toList(ArrayTagSet.create("a", "v1", "b", "v2")));
+    Assertions.assertEquals(Arrays.asList("a", "v1", "b", "v2"), toList(ArrayTagSet.create("b", "v2", "a", "v1")));
+    Assertions.assertEquals(Arrays.asList("a", "v1", "b", "v3"), toList(ArrayTagSet.create("b", "v2", "a", "v1", "b", "v3")));
+    Assertions.assertEquals(Arrays.asList("a", "v1", "b", "v2", "c", "v3"), toList(ArrayTagSet.create("c", "v3", "b", "v2", "a", "v1")));
+  }
+
+  private static List<String> toList(TagList tagList) {
+    List<String> list = new ArrayList<>(tagList.size() * 2);
+    tagList.forEach(tag -> {
+      list.add(tag.key());
+      list.add(tag.value());
+    });
+    return list;
+  }
+
+  static final class TagIterator implements Iterable<Tag> {
     String[] tags;
     TagIterator(String... tags) {
       this.tags = tags;
@@ -803,7 +821,7 @@ public Tag next() {
     }
   }
 
-  class BadTagList implements TagList {
+  static final class BadTagList implements TagList {
 
     String[] tags;
     BadTagList(String... tags) {