Ignore signs and transactions made by players with invalid names

src/main/java/com/Acrobot/ChestShop/ChestShop.java

@@ -319,6 +319,7 @@ public class ChestShop extends JavaPlugin {
             registerEvent(new AmountAndPriceChecker());
         }
 
+        registerEvent(new InvalidNameIgnorer());
         registerEvent(new CreativeModeIgnorer());
         registerEvent(new ErrorMessageSender());
         registerEvent(new PermissionChecker());

src/main/java/com/Acrobot/ChestShop/Listeners/PreTransaction/InvalidNameIgnorer.java

@@ -0,0 +1,26 @@
+package com.Acrobot.ChestShop.Listeners.PreTransaction;
+
+import com.Acrobot.ChestShop.Events.PreTransactionEvent;
+import com.Acrobot.ChestShop.Signs.ChestShopSign;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+
+import java.util.regex.Pattern;
+
+public class InvalidNameIgnorer implements Listener {
+
+    private final static Pattern USERNAME_PATTERN = Pattern.compile("^\\w+$");
+
+    @EventHandler(priority = EventPriority.LOWEST)
+    public static void onPreTransaction(PreTransactionEvent event) {
+        if (event.isCancelled()) {
+            return;
+        }
+
+        String name = event.getClient().getName();
+        if (ChestShopSign.isAdminShop(name) || !USERNAME_PATTERN.matcher(name).matches()) {
+            event.setCancelled(PreTransactionEvent.TransactionOutcome.CLIENT_DOES_NOT_HAVE_PERMISSION);
+        }
+    }
+}

src/main/java/com/Acrobot/ChestShop/Signs/ChestShopSign.java

@@ -26,10 +26,10 @@ public class ChestShopSign {
     public static final byte ITEM_LINE = 3;
 
     public static final Pattern[] SHOP_SIGN_PATTERN = {
-            Pattern.compile("^?[\\w -.:]*$"),
+            Pattern.compile("^?[\\w \\-.:]*$"),
             Pattern.compile("^[1-9][0-9]{0,5}$"),
             Pattern.compile("(?i)^[\\d.bs(free) :]+$"),
-            Pattern.compile("^[\\w? #:-]+$")
+            Pattern.compile("^[\\w? #:\\-]+$")
     };
     public static final String AUTOFILL_CODE = "?";