Added events for placeholder requests

src/main/java/me/clip/placeholderapi/PlaceholderAPI.java

@@ -32,6 +32,7 @@ import me.clip.placeholderapi.expansion.PlaceholderExpansion;
 import me.clip.placeholderapi.expansion.Relational;
 import me.clip.placeholderapi.expansion.manager.LocalExpansionManager;
 import me.clip.placeholderapi.replacer.CharsReplacer;
+import me.clip.placeholderapi.replacer.DelegatorReplacer;
 import me.clip.placeholderapi.replacer.Replacer;
 import me.clip.placeholderapi.replacer.Replacer.Closure;
 import me.clip.placeholderapi.util.Msg;
@@ -43,8 +44,8 @@ import org.jetbrains.annotations.NotNull;
 
 public final class PlaceholderAPI {
 
-  private static Replacer REPLACER_PERCENT = new CharsReplacer(Closure.PERCENT);
-  private static Replacer REPLACER_BRACKET = new CharsReplacer(Closure.BRACKET);
+  private static final Replacer REPLACER_PERCENT = new DelegatorReplacer(new CharsReplacer(Closure.PERCENT));
+  private static final Replacer REPLACER_BRACKET = new DelegatorReplacer(new CharsReplacer(Closure.BRACKET));
 
   private static final Pattern PLACEHOLDER_PATTERN = Pattern.compile("[%]([^%]+)[%]");
   private static final Pattern BRACKET_PLACEHOLDER_PATTERN = Pattern.compile("[{]([^{}]+)[}]");

src/main/java/me/clip/placeholderapi/events/PlaceholderRequestEvent.java

@@ -0,0 +1,78 @@
+package me.clip.placeholderapi.events;
+
+import org.bukkit.OfflinePlayer;
+import org.bukkit.event.Event;
+import org.bukkit.event.HandlerList;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import me.clip.placeholderapi.replacer.Replacer;
+
+
+/**
+ * Fired when user requests for placeholder replacement via {@link Replacer}
+ * */
+public class PlaceholderRequestEvent extends Event
+{
+
+    private static final HandlerList HANDLER_LIST = new HandlerList();
+
+    private final String input;
+    private final OfflinePlayer player;
+    private final Replacer defaultReplacer;
+    private String output;
+
+    public PlaceholderRequestEvent(String input, OfflinePlayer player, Replacer defaultReplacer) {
+        this.input = input;
+        this.player = player;
+        this.defaultReplacer = defaultReplacer;
+    }
+
+    /**
+     * @return Input string of the request with no replacements
+     * */
+    public @NotNull String getInput() {
+        return input;
+    }
+
+    /**
+     * @return Player that was used for replacement
+     */
+    public @Nullable OfflinePlayer getPlayer() {
+        return player;
+    }
+
+    /**
+     * Returns output that will be provided for this request.
+     * <br>If the output is equal to null, replacer will be used to provide final result
+     * @return Output that will be provided for this request
+     */
+    public @Nullable String getOutput() {
+        return output;
+    }
+
+    /**
+     * Sets output that will be provided for this request
+     * <br>If the output is equal to null, replacer will be used to provide final result
+     * @param output Output that will be provided for this request
+     */
+    public void setOutput(@Nullable String output) {
+        this.output = output;
+    }
+
+    /**
+     * @return {@link Replacer} that will be used to provide final result if {@link PlaceholderRequestEvent#getOutput()} is null
+     */
+    public Replacer getDefaultReplacer() {
+        return defaultReplacer;
+    }
+
+    @NotNull
+    @Override
+    public HandlerList getHandlers() {
+        return HANDLER_LIST;
+    }
+
+    public static HandlerList getHandlerList() {
+        return HANDLER_LIST;
+    }
+}

src/main/java/me/clip/placeholderapi/replacer/DelegatorReplacer.java

@@ -0,0 +1,28 @@
+package me.clip.placeholderapi.replacer;
+
+import me.clip.placeholderapi.events.PlaceholderRequestEvent;
+import me.clip.placeholderapi.expansion.PlaceholderExpansion;
+import org.bukkit.Bukkit;
+import org.bukkit.OfflinePlayer;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.function.Function;
+
+public class DelegatorReplacer implements Replacer {
+
+    private final Replacer defaultReplacer;
+
+    public DelegatorReplacer(Replacer defaultReplacer) {
+        this.defaultReplacer = defaultReplacer;
+    }
+
+
+    @Override
+    public @NotNull String apply(@NotNull String text, @Nullable OfflinePlayer player, @NotNull Function<String, @Nullable PlaceholderExpansion> lookup) {
+        PlaceholderRequestEvent placeholderRequestEvent = new PlaceholderRequestEvent(text, player, defaultReplacer);
+        Bukkit.getPluginManager().callEvent(placeholderRequestEvent);
+        return placeholderRequestEvent.getOutput() == null ? defaultReplacer.apply(text, player, lookup)
+                : placeholderRequestEvent.getOutput();
+    }
+}