Improve placeholder API

api/src/main/java/me/filoghost/holographicdisplays/api/HolographicDisplaysAPI.java

@@ -8,6 +8,7 @@ package me.filoghost.holographicdisplays.api;
 import me.filoghost.holographicdisplays.api.hologram.Hologram;
 import me.filoghost.holographicdisplays.api.internal.HolographicDisplaysAPIProvider;
 import me.filoghost.holographicdisplays.api.placeholder.GlobalPlaceholderReplacer;
+import me.filoghost.holographicdisplays.api.placeholder.RegisteredPlaceholder;
 import org.bukkit.Location;
 import org.bukkit.plugin.Plugin;
 import org.jetbrains.annotations.NotNull;
@@ -92,7 +93,7 @@ public interface HolographicDisplaysAPI {
      * @return a collection of placeholder identifiers
      * @since 1
      */
-    @NotNull Collection<String> getRegisteredPlaceholders();
+    @NotNull Collection<RegisteredPlaceholder> getRegisteredPlaceholders();
 
     /**
      * Unregisters a placeholder.

api/src/main/java/me/filoghost/holographicdisplays/api/placeholder/RegisteredPlaceholder.java

@@ -0,0 +1,12 @@
+/*
+ * Copyright (C) filoghost and contributors
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+package me.filoghost.holographicdisplays.api.placeholder;
+
+public interface RegisteredPlaceholder {
+
+    String getIdentifier();
+
+}

plugin/src/main/java/me/filoghost/holographicdisplays/plugin/api/current/DefaultHolographicDisplaysAPI.java

@@ -10,6 +10,7 @@ import me.filoghost.holographicdisplays.api.HolographicDisplaysAPI;
 import me.filoghost.holographicdisplays.api.hologram.Hologram;
 import me.filoghost.holographicdisplays.api.Position;
 import me.filoghost.holographicdisplays.api.placeholder.GlobalPlaceholderReplacer;
+import me.filoghost.holographicdisplays.api.placeholder.RegisteredPlaceholder;
 import me.filoghost.holographicdisplays.plugin.hologram.base.ImmutablePosition;
 import me.filoghost.holographicdisplays.plugin.placeholder.registry.PlaceholderRegistry;
 import org.bukkit.Location;
@@ -86,8 +87,8 @@ class DefaultHolographicDisplaysAPI implements HolographicDisplaysAPI {
     }
 
     @Override
-    public @NotNull Collection<String> getRegisteredPlaceholders() {
+    public @NotNull Collection<RegisteredPlaceholder> getRegisteredPlaceholders() {
-        return placeholderRegistry.getRegisteredIdentifiers(plugin);
+        return placeholderRegistry.getRegisteredPlaceholders(plugin);
     }
 
     @Override

plugin/src/main/java/me/filoghost/holographicdisplays/plugin/api/v2/V2HologramsAPIProvider.java

@@ -9,6 +9,8 @@ import com.gmail.filoghost.holographicdisplays.api.Hologram;
 import com.gmail.filoghost.holographicdisplays.api.internal.HologramsAPIProvider;
 import com.gmail.filoghost.holographicdisplays.api.placeholder.PlaceholderReplacer;
 import me.filoghost.fcommons.Preconditions;
+import me.filoghost.fcommons.collection.CollectionUtils;
+import me.filoghost.holographicdisplays.api.placeholder.RegisteredPlaceholder;
 import me.filoghost.holographicdisplays.plugin.hologram.base.ImmutablePosition;
 import me.filoghost.holographicdisplays.plugin.placeholder.registry.PlaceholderRegistry;
 import org.bukkit.Location;
@@ -81,7 +83,8 @@ public class V2HologramsAPIProvider extends HologramsAPIProvider {
     public Collection<String> getRegisteredPlaceholders(Plugin plugin) {
         Preconditions.notNull(plugin, "plugin");
 
-        return placeholderRegistry.getRegisteredIdentifiers(plugin);
+        List<RegisteredPlaceholder> registeredPlaceholders = placeholderRegistry.getRegisteredPlaceholders(plugin);
+        return CollectionUtils.toArrayList(registeredPlaceholders, RegisteredPlaceholder::getIdentifier);
     }
 
     @Override

plugin/src/main/java/me/filoghost/holographicdisplays/plugin/placeholder/registry/PlaceholderExpansion.java

@@ -5,6 +5,7 @@
  */
 package me.filoghost.holographicdisplays.plugin.placeholder.registry;
 
+import me.filoghost.holographicdisplays.api.placeholder.RegisteredPlaceholder;
 import me.filoghost.holographicdisplays.plugin.placeholder.PlaceholderException;
 import me.filoghost.holographicdisplays.plugin.placeholder.StandardPlaceholder;
 import me.filoghost.holographicdisplays.plugin.placeholder.parsing.PlaceholderIdentifier;
@@ -16,10 +17,12 @@ public abstract class PlaceholderExpansion {
 
     private final PluginName pluginName;
     private final PlaceholderIdentifier identifier;
+    private final RegisteredPlaceholder registeredPlaceholder;
 
     public PlaceholderExpansion(Plugin plugin, String identifier) {
         this.pluginName = new PluginName(plugin);
         this.identifier = new PlaceholderIdentifier(identifier);
+        this.registeredPlaceholder = identifier::toString;
     }
 
     public PluginName getPluginName() {
@@ -30,6 +33,10 @@ public abstract class PlaceholderExpansion {
         return identifier;
     }
 
+    public RegisteredPlaceholder asRegisteredPlaceholder() {
+        return registeredPlaceholder;
+    }
+
     public abstract boolean isIndividual();
 
     public abstract @Nullable StandardPlaceholder createPlaceholder(String argument) throws PlaceholderException;

plugin/src/main/java/me/filoghost/holographicdisplays/plugin/placeholder/registry/PlaceholderRegistry.java

@@ -14,6 +14,7 @@ import me.filoghost.holographicdisplays.api.placeholder.IndividualPlaceholderRep
 import me.filoghost.holographicdisplays.api.placeholder.GlobalPlaceholder;
 import me.filoghost.holographicdisplays.api.placeholder.GlobalPlaceholderFactory;
 import me.filoghost.holographicdisplays.api.placeholder.GlobalPlaceholderReplacer;
+import me.filoghost.holographicdisplays.api.placeholder.RegisteredPlaceholder;
 import me.filoghost.holographicdisplays.plugin.placeholder.parsing.PlaceholderIdentifier;
 import me.filoghost.holographicdisplays.plugin.placeholder.parsing.PlaceholderOccurrence;
 import me.filoghost.holographicdisplays.plugin.placeholder.parsing.PluginName;
@@ -96,12 +97,12 @@ public class PlaceholderRegistry {
         }
     }
 
-    public List<String> getRegisteredIdentifiers(Plugin plugin) {
+    public List<RegisteredPlaceholder> getRegisteredPlaceholders(Plugin plugin) {
         PluginName pluginName = new PluginName(plugin);
-        List<String> identifiers = new ArrayList<>();
+        List<RegisteredPlaceholder> identifiers = new ArrayList<>();
 
         for (PlaceholderExpansion expansion : placeholderExpansions.column(pluginName).values()) {
-            identifiers.add(expansion.getIdentifier().toString());
+            identifiers.add(expansion.asRegisteredPlaceholder());
         }
 
         return identifiers;