[Bleeding] Moved HelpTopicComparator to Bukkit.jar. Addresses BUKKIT-1193

By: rmichela <deltahat@gmail.com>

paper-api/src/main/java/org/bukkit/help/HelpTopicComparator.java

@@ -0,0 +1,46 @@
+package org.bukkit.help;
+
+import org.bukkit.help.HelpTopic;
+
+import java.util.Comparator;
+
+/**
+ * Used to impose a custom total ordering on help topics. All topics are listed in alphabetic order, but topics
+ * that start with a slash come after topics that don't.
+ */
+public class HelpTopicComparator implements Comparator<HelpTopic> {
+    
+    // Singleton implementations
+    private static final TopicNameComparator tnc = new TopicNameComparator();
+    public static TopicNameComparator topicNameComparatorInstance() {
+        return tnc;
+    }
+    
+    private static final HelpTopicComparator htc = new HelpTopicComparator();
+    public static HelpTopicComparator helpTopicComparatorInstance() {
+        return htc;
+    }
+    
+    private HelpTopicComparator() {}
+
+    public int compare(HelpTopic lhs, HelpTopic rhs) {
+        return tnc.compare(lhs.getName(), rhs.getName());
+    }
+
+    public static class TopicNameComparator implements Comparator<String> {
+        private TopicNameComparator(){}
+        
+        public int compare(String lhs, String rhs) {
+            boolean lhsStartSlash = lhs.startsWith("/");
+            boolean rhsStartSlash = rhs.startsWith("/");
+            
+            if (lhsStartSlash && !rhsStartSlash) {
+                return 1;
+            } else if (!lhsStartSlash && rhsStartSlash) {
+                return -1;
+            } else {
+                return lhs.compareToIgnoreCase(rhs);
+            }
+        }
+    }
+}