Optimize ChatColor.getLastColors.

ChatColor searches from the start to the end of a string for chat format
characters but this always has to search the entire string. By starting
from the end of the string and working backwards we can stop searching once
we find a color code or a reset code as any previous formatting is wiped
out by these.

By: Travis Watkins <amaranth@ubuntu.com>

paper-api/src/main/java/org/bukkit/ChatColor.java

@@ -218,19 +218,21 @@ public enum ChatColor {
      */
     public static String getLastColors(String input) {
         String result = "";
-        int lastIndex = -1;
         int length = input.length();
 
-        while ((lastIndex = input.indexOf(COLOR_CHAR, lastIndex + 1)) != -1) {
+        // Search backwards from the end as it is faster
-            if (lastIndex < length - 1) {
+        for (int index = length - 1; index > -1; index--) {
-                char c = input.charAt(lastIndex + 1);
+            char section = input.charAt(index);
-                ChatColor col = getByChar(c);
+            if (section == COLOR_CHAR && index < length - 1) {
+                char c = input.charAt(index + 1);
+                ChatColor color = getByChar(c);
 
-                if (col != null) {
+                if (color != null) {
-                    if (col.isColor()) {
+                    result = color.toString() + result;
-                        result = col.toString();
+
-                    } else if (col.isFormat()) {
+                    // Once we find a color or reset we can stop searching
-                        result += col.toString();
+                    if (color.isColor() || color.equals(RESET)) {
+                        break;
                     }
                 }
             }

paper-api/src/test/java/org/bukkit/ChatColorTest.java

@@ -70,4 +70,14 @@ public class ChatColorTest {
         String u = ChatColor.BLACK.toString() + ChatColor.DARK_BLUE + ChatColor.DARK_GREEN + ChatColor.DARK_AQUA + ChatColor.DARK_RED + ChatColor.DARK_PURPLE + ChatColor.GOLD + ChatColor.GRAY + ChatColor.DARK_GRAY + ChatColor.BLUE + ChatColor.GREEN + ChatColor.GREEN + ChatColor.AQUA + ChatColor.AQUA + ChatColor.RED + ChatColor.RED + ChatColor.LIGHT_PURPLE + ChatColor.LIGHT_PURPLE + ChatColor.YELLOW + ChatColor.YELLOW + ChatColor.WHITE + ChatColor.WHITE + ChatColor.MAGIC + ChatColor.MAGIC + " & more";
         assertThat(t, is(u));
     }
+
+    @Test
+    public void getChatColors() {
+        String s = String.format("%c%ctest%c%ctest%c", ChatColor.COLOR_CHAR, ChatColor.RED.getChar(), ChatColor.COLOR_CHAR, ChatColor.ITALIC.getChar(), ChatColor.COLOR_CHAR);
+        String expected = ChatColor.RED.toString() + ChatColor.ITALIC;
+        assertThat(ChatColor.getLastColors(s), is(expected));
+
+        s = String.format("%c%ctest%c%ctest", ChatColor.COLOR_CHAR, ChatColor.RED.getChar(), ChatColor.COLOR_CHAR, ChatColor.BLUE.getChar());
+        assertThat(ChatColor.getLastColors(s), is(ChatColor.BLUE.toString()));
+    }
 }