Add placeholders api

src/main/java/net/citizensnpcs/api/npc/NPC.java

@@ -470,11 +470,11 @@ public enum Metadata {
          * The Minecart item data. Byte.
          */
         MINECART_ITEM_DATA("minecart-item-data"),
+
         /**
          * The Minecart item offset as defined by Minecraft. {@link Minecart#setDisplayBlockOffset(int)}
          */
         MINECART_OFFSET("minecart-item-offset"),
-
         /**
          * Whether the NPC's nameplate should be visible. Boolean.
          */

src/main/java/net/citizensnpcs/api/util/Placeholders.java

@@ -12,21 +12,50 @@
 import org.bukkit.command.BlockCommandSender;
 import org.bukkit.command.CommandSender;
 import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 
 import me.clip.placeholderapi.PlaceholderAPI;
 import net.citizensnpcs.api.CitizensAPI;
+import net.citizensnpcs.api.event.CitizensDisableEvent;
 import net.citizensnpcs.api.npc.NPC;
 import net.citizensnpcs.api.trait.trait.Owner;
 
-public class Placeholders {
+public class Placeholders implements Listener {
+    public static interface PlaceholderFunction {
+        public String apply(NPC npc, CommandSender sender, String input);
+    }
+
+    private static class PlaceholderProvider {
+        PlaceholderFunction func;
+        Pattern regex;
+
+        PlaceholderProvider(Pattern regex, PlaceholderFunction func) {
+            this.regex = regex;
+            this.func = func;
+        }
+    }
+
     private static OfflinePlayer getPlayer(BlockCommandSender sender) {
         return CitizensAPI.getNMSHelper().getPlayer(sender);
     }
 
+    @EventHandler
+    private static void onCitizensDisable(CitizensDisableEvent event) {
+        PLACEHOLDERS.clear();
+    }
+
+    public static void registerNPCPlaceholder(Pattern regex, PlaceholderFunction func) {
+        if (regex.pattern().charAt(0) != '<') {
+            regex = Pattern.compile('<' + regex.pattern() + '>', regex.flags());
+        }
+        PLACEHOLDERS.add(new PlaceholderProvider(regex, func));
+    }
+
     public static String replace(String text, CommandSender sender, NPC npc) {
         text = replace(text, sender instanceof OfflinePlayer ? (OfflinePlayer) sender
                 : sender instanceof BlockCommandSender ? getPlayer((BlockCommandSender) sender) : null);
@@ -49,6 +78,16 @@ public static String replace(String text, CommandSender sender, NPC npc) {
             out.append(replacement);
         }
         matcher.appendTail(out);
+        for (PlaceholderProvider entry : PLACEHOLDERS) {
+            matcher = entry.regex.matcher(out.toString());
+            out = new StringBuffer();
+            while (matcher.find()) {
+                String group = matcher.group().substring(1, matcher.group().length() - 1);
+                matcher.appendReplacement(out, "");
+                out.append(entry.func.apply(npc, sender, group));
+            }
+            matcher.appendTail(out);
+        }
         return out.toString();
     }
 
@@ -130,6 +169,7 @@ private static String setPlaceholderAPIPlaceholders(String text, OfflinePlayer p
 
     private static final Pattern PLACEHOLDER_MATCHER = Pattern.compile("<(id|npc|owner)>");
     private static boolean PLACEHOLDERAPI_ENABLED = true;
+    private static final List<PlaceholderProvider> PLACEHOLDERS = Lists.newArrayList();
     private static final Pattern PLAYER_PLACEHOLDER_MATCHER = Pattern.compile(
             "(<player>|<p>|@p|%player%|<random_player>|<random_npc>|<random_npc_id>|<nearest_player>|<world>)");
     private static final String[] PLAYER_PLACEHOLDERS = { "<player>", "<p>", "@p", "%player%" };