refined SignEditListener to filter illegal characters more robustly by normalizing input and introducing specific character whitelists

common/src/main/java/eu/mhsl/craftattack/spawn/common/appliances/security/antiIllegalSignCharacters/SignEditListener.java

@@ -6,18 +6,73 @@ import net.kyori.adventure.text.serializer.plain.PlainTextComponentSerializer;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.block.SignChangeEvent;
 
+import java.text.Normalizer;
+import java.util.Set;
+
 class SignEditListener extends ApplianceListener<AntiIllegalSignCharacters> {
+    private static final Set<Integer> ALLOWED_CHARS = Set.of(
+        (int)' ', (int)'.', (int)',', (int)';', (int)':', (int)'!', (int)'?',
+        (int)'"', (int)'\'',
+        (int)'(', (int)')', (int)'[', (int)']', (int)'{', (int)'}',
+        (int)'-', (int)'_', (int)'+', (int)'=', (int)'/', (int)'\\',
+        (int)'@', (int)'#', (int)'$', (int)'%', (int)'&', (int)'*',
+        (int)'<', (int)'>', (int)'|',
+        (int)'~', (int)'`', (int)'^'
+    );
+
+    private static final Set<Integer> ALLOWED_EXTRA = Set.of(
+        (int)'Ä', (int)'Ö', (int)'Ü', (int)'ä', (int)'ö', (int)'ü', (int)'ß',
+        (int)'€', (int)'°', (int)'µ'
+    );
+
+
     @EventHandler
     public void onSignEdit(SignChangeEvent event) {
         for (int i = 0; i < 4; i++) {
             Component line = event.line(i);
-            if(line == null) continue;
+            if (line == null) continue;
-            String lineStr = PlainTextComponentSerializer.plainText().serialize(line);
+            String plainString = PlainTextComponentSerializer.plainText().serialize(line);
-
+            plainString = Normalizer.normalize(plainString, Normalizer.Form.NFC);
-            if (!lineStr.matches("^[ -~]*$")) {
+            String cleaned = filterAllowed(plainString);
-                String cleaned = lineStr.replaceAll("[^ -~]", "");
             event.line(i, Component.text(cleaned));
         }
     }
+
+    private static String filterAllowed(String s) {
+        StringBuilder out = new StringBuilder(s.length());
+
+        for (int off = 0; off < s.length(); ) {
+            int cp = s.codePointAt(off);
+            off += Character.charCount(cp);
+
+            if (isForbidden(cp)) continue;
+
+            if (Character.isLetterOrDigit(cp)) {
+                out.appendCodePoint(cp);
+                continue;
+            }
+
+            if (ALLOWED_CHARS.contains(cp) || ALLOWED_EXTRA.contains(cp)) {
+                out.appendCodePoint(cp);
+            }
+        }
+        return out.toString();
+    }
+
+    private static boolean isForbidden(int cp) {
+        // Surrogates / invalid
+        if (cp >= 0xD800 && cp <= 0xDFFF) return true;
+
+        // Private Use Area (Mod/Pack-Icons/Placeholder)
+        if (cp >= 0xE000 && cp <= 0xF8FF) return true;
+
+        // Zero-width and control characters
+        if (cp == 0x200B || cp == 0x200C || cp == 0x200D || cp == 0xFEFF) return true;
+
+        // BiDi-Steuerzeichen
+        if (cp >= 0x202A && cp <= 0x202E) return true;
+        if (cp >= 0x2066 && cp <= 0x2069) return true;
+
+        return cp == '§';
     }
 }