Player events + mail receive event

src/main/java/emu/grasscutter/game/player/Player.java

@@ -38,6 +38,7 @@ import emu.grasscutter.net.proto.ProfilePictureOuterClass.ProfilePicture;
 import emu.grasscutter.net.proto.SocialDetailOuterClass.SocialDetail;
 import emu.grasscutter.net.proto.SocialShowAvatarInfoOuterClass;
 import emu.grasscutter.server.event.game.PlayerQuitEvent;
+import emu.grasscutter.server.event.player.PlayerReceiveMailEvent;
 import emu.grasscutter.server.game.GameServer;
 import emu.grasscutter.server.game.GameSession;
 import emu.grasscutter.server.packet.send.*;
@@ -726,9 +727,13 @@ public class Player {
 	public List<Mail> getAllMail() { return this.mail; }
 
 	public void sendMail(Mail message) {
+		// Call mail receive event.
+		PlayerReceiveMailEvent event = new PlayerReceiveMailEvent(this, message); event.call();
+		if(event.isCanceled()) return; message = event.getMessage();
+		
 		this.mail.add(message);
 		this.save();
-		Grasscutter.getLogger().info("Mail sent to user [" + this.getUid()  + ":" + this.getNickname() + "]!");
+		Grasscutter.getLogger().debug("Mail sent to user [" + this.getUid()  + ":" + this.getNickname() + "]!");
 		if(this.isOnline()) {
 			this.sendPacket(new PacketMailChangeNotify(this, message));
 		} // TODO: setup a way for the mail notification to show up when someone receives mail when they were offline

src/main/java/emu/grasscutter/server/event/player/PlayerReceiveMailEvent.java

+package emu.grasscutter.server.event.player;
+
+import emu.grasscutter.game.mail.Mail;
+import emu.grasscutter.game.player.Player;
+import emu.grasscutter.server.event.Cancellable;
+import emu.grasscutter.server.event.types.PlayerEvent;
+
+public final class PlayerReceiveMailEvent extends PlayerEvent implements Cancellable {
+    private Mail message;
+    
+    public PlayerReceiveMailEvent(Player player, Mail message) {
+        super(player);
+        
+        this.message = message;
+    }
+    
+    public void setMessage(Mail message) {
+        this.message = message;
+    }
+    
+    public Mail getMessage() {
+        return this.message;
+    }
+}

src/main/java/emu/grasscutter/server/event/types/PlayerEvent.java

+package emu.grasscutter.server.event.types;
+
+import emu.grasscutter.game.player.Player;
+import emu.grasscutter.server.event.Event;
+
+/**
+ * An event that is related to player interactions.
+ */
+public abstract class PlayerEvent extends Event {
+    protected final Player player;
+
+    public PlayerEvent(Player player) {
+        this.player = player;
+    }
+
+    public Player getPlayer() {
+        return this.player;
+    }
+}