filter sequences of more than 3 ltr-rtl

src/main/java/eu/siacs/conversations/entities/Message.java

@@ -606,7 +606,7 @@ public class Message extends AbstractEntity {
 	}
 
 	public SpannableStringBuilder getMergedBody() {
-		SpannableStringBuilder body = new SpannableStringBuilder(this.body.trim());
+		SpannableStringBuilder body = new SpannableStringBuilder(MessageUtils.filterLtrRtl(this.body).trim());
 		Message current = this;
 		while (current.mergeable(current.next())) {
 			current = current.next();
@@ -616,7 +616,7 @@ public class Message extends AbstractEntity {
 			body.append("\n\n");
 			body.setSpan(new MergeSeparator(), body.length() - 2, body.length(),
 					SpannableStringBuilder.SPAN_EXCLUSIVE_EXCLUSIVE);
-			body.append(current.getBody().trim());
+			body.append(MessageUtils.filterLtrRtl(current.getBody()).trim());
 		}
 		return body;
 	}

src/main/java/eu/siacs/conversations/utils/MessageUtils.java

@@ -31,11 +31,17 @@ package eu.siacs.conversations.utils;
 
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.util.regex.Pattern;
 
 import eu.siacs.conversations.entities.Message;
 import eu.siacs.conversations.http.AesGcmURLStreamHandler;
 
 public class MessageUtils {
+
+	private static final Pattern LTR_RTL = Pattern.compile("(\\u200E[^\\u200F]*\\u200F){3,}");
+
+	private static final String EMPTY_STRING = "";
+
 	public static String prepareQuote(Message message) {
 		final StringBuilder builder = new StringBuilder();
 		final String body = message.getMergedBody().toString();
@@ -79,4 +85,8 @@ public class MessageUtils {
 			return false;
 		}
 	}
+
+	public static String filterLtrRtl(String body) {
+		return LTR_RTL.matcher(body).replaceFirst(EMPTY_STRING);
+	}
 }

src/main/java/eu/siacs/conversations/utils/UIHelper.java

@@ -283,7 +283,7 @@ public class UIHelper {
 		} else if (message.getType() == Message.TYPE_FILE || message.getType() == Message.TYPE_IMAGE) {
 			return new Pair<>(getFileDescriptionString(context, message), true);
 		} else {
-			final String body = message.getBody();
+			final String body = MessageUtils.filterLtrRtl(message.getBody());
 			if (body.startsWith(Message.ME_COMMAND)) {
 				return new Pair<>(body.replaceAll("^" + Message.ME_COMMAND,
 						UIHelper.getMessageDisplayName(message) + " "), false);