Move bidi methods to BidiUtil.

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/subscription/boost/Boost.kt

@@ -16,7 +16,7 @@ import androidx.appcompat.widget.AppCompatEditText
 import androidx.core.animation.doOnEnd
 import androidx.core.text.isDigitsOnly
 import com.google.android.material.button.MaterialButton
-import org.signal.core.util.StringUtil
+import org.signal.core.util.BidiUtil
 import org.signal.core.util.money.FiatMoney
 import org.thoughtcrime.securesms.R
 import org.thoughtcrime.securesms.badges.BadgeImageView
@@ -255,7 +255,7 @@ data class Boost(
       dend: Int
     ): CharSequence? {
       val result = dest.subSequence(0, dstart).toString() + source.toString() + dest.subSequence(dend, dest.length)
-      val resultWithoutCurrencyPrefix = StringUtil.stripBidiIndicator(result.removePrefix(symbol).removeSuffix(symbol).trim())
+      val resultWithoutCurrencyPrefix = BidiUtil.stripBidiIndicator(result.removePrefix(symbol).removeSuffix(symbol).trim())
 
       if (resultWithoutCurrencyPrefix.length == 1 && !resultWithoutCurrencyPrefix.isDigitsOnly() && resultWithoutCurrencyPrefix != separator.toString()) {
         return dest.subSequence(dstart, dend)

app/src/main/java/org/thoughtcrime/securesms/components/settings/app/subscription/donate/DonateToSignalViewModel.kt

@@ -11,7 +11,7 @@ import io.reactivex.rxjava3.kotlin.plusAssign
 import io.reactivex.rxjava3.kotlin.subscribeBy
 import io.reactivex.rxjava3.processors.BehaviorProcessor
 import io.reactivex.rxjava3.subjects.PublishSubject
-import org.signal.core.util.StringUtil
+import org.signal.core.util.BidiUtil
 import org.signal.core.util.logging.Log
 import org.signal.core.util.money.FiatMoney
 import org.signal.core.util.money.PlatformCurrencyUtil
@@ -158,7 +158,7 @@ class DonateToSignalViewModel(
   }
 
   fun setCustomAmount(rawAmount: String) {
-    val amount = StringUtil.stripBidiIndicator(rawAmount)
+    val amount = BidiUtil.stripBidiIndicator(rawAmount)
     val bigDecimalAmount: BigDecimal = if (amount.isEmpty() || amount == DecimalFormatSymbols.getInstance().decimalSeparator.toString()) {
       BigDecimal.ZERO
     } else {

app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationItem.java

@@ -70,6 +70,7 @@ import com.google.common.collect.Sets;
 import org.greenrobot.eventbus.EventBus;
 import org.greenrobot.eventbus.Subscribe;
 import org.greenrobot.eventbus.ThreadMode;
+import org.signal.core.util.BidiUtil;
 import org.signal.core.util.DimensionUnit;
 import org.signal.core.util.StringUtil;
 import org.signal.core.util.logging.Log;
@@ -561,7 +562,7 @@ public final class ConversationItem extends RelativeLayout implements BindableCo
         isFooterVisible(messageRecord, nextMessageRecord, groupThread) &&
         !bodyText.isJumbomoji() &&
         conversationMessage.getBottomButton() == null &&
-        !StringUtil.hasMixedTextDirection(bodyText.getText()) &&
+        !BidiUtil.hasMixedTextDirection(bodyText.getText()) &&
         !messageRecord.isRemoteDelete() &&
         bodyText.getLastLineWidth() > 0)
     {

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/items/V2FooterPositionDelegate.kt

@@ -7,7 +7,7 @@ package org.thoughtcrime.securesms.conversation.v2.items
 
 import android.view.View
 import android.widget.Space
-import org.signal.core.util.StringUtil
+import org.signal.core.util.BidiUtil
 import org.signal.core.util.dp
 import org.thoughtcrime.securesms.R
 import org.thoughtcrime.securesms.components.emoji.EmojiTextView
@@ -80,7 +80,7 @@ class V2FooterPositionDelegate private constructor(
       return false
     }
 
-    if (body.isJumbomoji || StringUtil.hasMixedTextDirection(body.text)) {
+    if (body.isJumbomoji || BidiUtil.hasMixedTextDirection(body.text)) {
       displayUnderneathBody()
       return true
     }

app/src/main/java/org/thoughtcrime/securesms/database/model/GroupsV2UpdateMessageConverter.kt

@@ -6,7 +6,7 @@
 package org.thoughtcrime.securesms.database.model
 
 import okio.ByteString
-import org.signal.core.util.StringUtil
+import org.signal.core.util.BidiUtil
 import org.signal.core.util.isNullOrEmpty
 import org.signal.storageservice.protos.groups.AccessControl
 import org.signal.storageservice.protos.groups.AccessControl.AccessRequired
@@ -340,7 +340,7 @@ object GroupsV2UpdateMessageConverter {
   fun translateNewTitle(change: DecryptedGroupChange, editorUnknown: Boolean, updates: MutableList<GroupChangeChatUpdate.Update>) {
     if (change.newTitle != null) {
       val editorAci = if (editorUnknown) null else change.editorServiceIdBytes
-      val newTitle = StringUtil.isolateBidi(change.newTitle?.value_)
+      val newTitle = BidiUtil.isolateBidi(change.newTitle?.value_)
       updates.add(
         GroupChangeChatUpdate.Update(
           groupNameUpdate = GroupNameUpdate(

app/src/main/java/org/thoughtcrime/securesms/database/model/GroupsV2UpdateMessageProducer.java

@@ -12,6 +12,7 @@ import androidx.annotation.StringRes;
 import androidx.annotation.VisibleForTesting;
 import androidx.core.content.ContextCompat;
 
+import org.signal.core.util.BidiUtil;
 import org.signal.core.util.StringUtil;
 import org.signal.storageservice.protos.groups.AccessControl;
 import org.signal.storageservice.protos.groups.Member;
@@ -551,9 +552,9 @@ final class GroupsV2UpdateMessageProducer {
 
   private void describeGroupNameUpdate(@NonNull GroupNameUpdate update, @NonNull List<UpdateDescription> updates) {
     if (update.updaterAci == null) {
-      updates.add(updateDescription(context.getString(R.string.MessageRecord_the_group_name_has_changed_to_s, StringUtil.isolateBidi(update.newGroupName)), R.drawable.ic_update_group_name_16));
+      updates.add(updateDescription(context.getString(R.string.MessageRecord_the_group_name_has_changed_to_s, BidiUtil.isolateBidi(update.newGroupName)), R.drawable.ic_update_group_name_16));
     } else {
-      String newTitle = StringUtil.isolateBidi(update.newGroupName);
+      String newTitle = BidiUtil.isolateBidi(update.newGroupName);
       if (selfIds.matches(update.updaterAci)) {
         updates.add(updateDescription(context.getString(R.string.MessageRecord_you_changed_the_group_name_to_s, newTitle), R.drawable.ic_update_group_name_16));
       } else {
@@ -1081,7 +1082,7 @@ final class GroupsV2UpdateMessageProducer {
     boolean editorIsYou = selfIds.matches(change.editorServiceIdBytes);
 
     if (change.newTitle != null) {
-      String newTitle = StringUtil.isolateBidi(change.newTitle.value_);
+      String newTitle = BidiUtil.isolateBidi(change.newTitle.value_);
       if (editorIsYou) {
         updates.add(updateDescription(context.getString(R.string.MessageRecord_you_changed_the_group_name_to_s, newTitle), R.drawable.ic_update_group_name_16));
       } else {
@@ -1104,7 +1105,7 @@ final class GroupsV2UpdateMessageProducer {
 
   private void describeUnknownEditorNewTitle(@NonNull DecryptedGroupChange change, @NonNull List<UpdateDescription> updates) {
     if (change.newTitle != null) {
-      updates.add(updateDescription(context.getString(R.string.MessageRecord_the_group_name_has_changed_to_s, StringUtil.isolateBidi(change.newTitle.value_)), R.drawable.ic_update_group_name_16));
+      updates.add(updateDescription(context.getString(R.string.MessageRecord_the_group_name_has_changed_to_s, BidiUtil.isolateBidi(change.newTitle.value_)), R.drawable.ic_update_group_name_16));
     }
   }
 
@@ -1118,7 +1119,7 @@ final class GroupsV2UpdateMessageProducer {
         updates.add(updateDescription(R.string.MessageRecord_s_changed_the_group_description, groupDescriptionUpdate.updaterAci, R.drawable.ic_update_group_name_16));
       }
     } else {
-      updates.add(updateDescription(context.getString(R.string.MessageRecord_the_group_name_has_changed_to_s, StringUtil.isolateBidi(groupDescriptionUpdate.newDescription)), R.drawable.ic_update_group_name_16));
+      updates.add(updateDescription(context.getString(R.string.MessageRecord_the_group_name_has_changed_to_s, BidiUtil.isolateBidi(groupDescriptionUpdate.newDescription)), R.drawable.ic_update_group_name_16));
     }
   }
 

app/src/main/java/org/thoughtcrime/securesms/database/model/MessageRecord.java

@@ -34,6 +34,7 @@ import androidx.core.content.ContextCompat;
 import com.annimon.stream.Stream;
 
 import org.signal.core.util.Base64;
+import org.signal.core.util.BidiUtil;
 import org.signal.core.util.StringUtil;
 import org.signal.core.util.logging.Log;
 import org.signal.storageservice.protos.groups.local.DecryptedGroup;
@@ -470,8 +471,8 @@ public abstract class MessageRecord extends DisplayRecord {
     if (profileChangeDetails != null) {
       if (profileChangeDetails.profileNameChange != null) {
         String displayName  = getFromRecipient().getDisplayName(context);
-        String newName      = StringUtil.isolateBidi(ProfileName.fromSerialized(profileChangeDetails.profileNameChange.newValue).toString());
-        String previousName = StringUtil.isolateBidi(ProfileName.fromSerialized(profileChangeDetails.profileNameChange.previous).toString());
+        String newName      = BidiUtil.isolateBidi(ProfileName.fromSerialized(profileChangeDetails.profileNameChange.newValue).toString());
+        String previousName = BidiUtil.isolateBidi(ProfileName.fromSerialized(profileChangeDetails.profileNameChange.previous).toString());
 
         String updateMessage;
         if (getFromRecipient().isSystemContact()) {

app/src/main/java/org/thoughtcrime/securesms/phonenumbers/PhoneNumberFormatter.java

@@ -10,6 +10,7 @@ import com.google.i18n.phonenumbers.PhoneNumberUtil;
 import com.google.i18n.phonenumbers.Phonenumber;
 import com.google.i18n.phonenumbers.ShortNumberInfo;
 
+import org.signal.core.util.BidiUtil;
 import org.signal.core.util.logging.Log;
 import org.signal.libsignal.protocol.util.Pair;
 import org.thoughtcrime.securesms.dependencies.AppDependencies;
@@ -80,7 +81,7 @@ public class PhoneNumberFormatter {
   }
 
   public static @NonNull String prettyPrint(@NonNull String e164) {
-    return StringUtil.forceLtr(get(AppDependencies.getApplication()).prettyPrintFormat(e164));
+    return BidiUtil.forceLtr(get(AppDependencies.getApplication()).prettyPrintFormat(e164));
   }
 
   public @NonNull String prettyPrintFormat(@NonNull String e164) {
@@ -91,13 +92,13 @@ public class PhoneNumberFormatter {
           localNumber.get().countryCode == parsedNumber.getCountryCode() &&
           NATIONAL_FORMAT_COUNTRY_CODES.contains(localNumber.get().getCountryCode()))
       {
-        return StringUtil.isolateBidi(phoneNumberUtil.format(parsedNumber, PhoneNumberUtil.PhoneNumberFormat.NATIONAL));
+        return BidiUtil.isolateBidi(phoneNumberUtil.format(parsedNumber, PhoneNumberUtil.PhoneNumberFormat.NATIONAL));
       } else {
-        return StringUtil.isolateBidi(phoneNumberUtil.format(parsedNumber, PhoneNumberUtil.PhoneNumberFormat.INTERNATIONAL));
+        return BidiUtil.isolateBidi(phoneNumberUtil.format(parsedNumber, PhoneNumberUtil.PhoneNumberFormat.INTERNATIONAL));
       }
     } catch (NumberParseException e) {
       Log.w(TAG, "Failed to format number: " + e.toString());
-      return StringUtil.isolateBidi(e164);
+      return BidiUtil.isolateBidi(e164);
     }
   }
 

app/src/main/java/org/thoughtcrime/securesms/profiles/edit/EditProfileViewModel.java

@@ -8,6 +8,7 @@ import androidx.lifecycle.Transformations;
 import androidx.lifecycle.ViewModel;
 import androidx.lifecycle.ViewModelProvider;
 
+import org.signal.core.util.BidiUtil;
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.conversation.colors.AvatarColor;
 import org.thoughtcrime.securesms.groups.GroupId;
@@ -155,9 +156,9 @@ class EditProfileViewModel extends ViewModel {
 
     repository.uploadProfile(profileName,
                              displayName,
-                             !Objects.equals(StringUtil.stripBidiProtection(oldDisplayName), displayName),
+                             !Objects.equals(BidiUtil.stripBidiProtection(oldDisplayName), displayName),
                              description,
-                             !Objects.equals(StringUtil.stripBidiProtection(oldDescription), description),
+                             !Objects.equals(BidiUtil.stripBidiProtection(oldDescription), description),
                              newAvatar,
                              !Arrays.equals(oldAvatar, newAvatar),
                              uploadResult::postValue);

app/src/main/java/org/thoughtcrime/securesms/recipients/Recipient.kt

@@ -7,7 +7,7 @@ import androidx.annotation.WorkerThread
 import io.reactivex.rxjava3.core.Observable
 import io.reactivex.rxjava3.schedulers.Schedulers
 import kotlinx.collections.immutable.toImmutableList
-import org.signal.core.util.StringUtil
+import org.signal.core.util.BidiUtil
 import org.signal.core.util.isNotNullOrBlank
 import org.signal.core.util.logging.Log
 import org.signal.core.util.nullIfBlank
@@ -532,7 +532,7 @@ class Recipient(
     if (Util.isEmpty(name)) {
       name = getUnknownDisplayName(context)
     }
-    return StringUtil.isolateBidi(name)
+    return BidiUtil.isolateBidi(name)
   }
 
   fun hasNonUsernameDisplayName(context: Context): Boolean {
@@ -569,21 +569,21 @@ class Recipient(
   /** A display name to use when rendering a mention of this user. */
   fun getMentionDisplayName(context: Context): String {
     var name: String? = if (isSelf) profileName.toString() else getGroupName(context)
-    name = StringUtil.isolateBidi(name)
+    name = BidiUtil.isolateBidi(name)
 
     if (name.isBlank()) {
       name = if (isSelf) getGroupName(context) else nickname.toString()
-      name = StringUtil.isolateBidi(name)
+      name = BidiUtil.isolateBidi(name)
     }
 
     if (name.isBlank()) {
       name = if (isSelf) getGroupName(context) else systemContactName
-      name = StringUtil.isolateBidi(name)
+      name = BidiUtil.isolateBidi(name)
     }
 
     if (name.isBlank()) {
       name = if (isSelf) getGroupName(context) else profileName.toString()
-      name = StringUtil.isolateBidi(name)
+      name = BidiUtil.isolateBidi(name)
     }
 
     if (name.isBlank() && e164Value.isNotNullOrBlank()) {
@@ -591,11 +591,11 @@ class Recipient(
     }
 
     if (name.isBlank()) {
-      name = StringUtil.isolateBidi(emailValue)
+      name = BidiUtil.isolateBidi(emailValue)
     }
 
     if (name.isBlank()) {
-      name = StringUtil.isolateBidi(context.getString(R.string.Recipient_unknown))
+      name = BidiUtil.isolateBidi(context.getString(R.string.Recipient_unknown))
     }
 
     return name
@@ -615,7 +615,7 @@ class Recipient(
       getDisplayName(context)
     ).firstOrNull { it.isNotNullOrBlank() }
 
-    return StringUtil.isolateBidi(name)
+    return BidiUtil.isolateBidi(name)
   }
 
   private fun getUnknownDisplayName(context: Context): String {

app/src/main/java/org/thoughtcrime/securesms/util/GroupUtil.java

@@ -6,6 +6,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
+import org.signal.core.util.BidiUtil;
 import org.signal.core.util.StringUtil;
 import org.signal.core.util.logging.Log;
 import org.signal.libsignal.zkgroup.InvalidInputException;
@@ -115,7 +116,7 @@ public final class GroupUtil {
         return description.toString();
       }
 
-      String title = StringUtil.isolateBidi(groupContext.getName());
+      String title = BidiUtil.isolateBidi(groupContext.getName());
 
       if (members != null && members.size() > 0) {
         description.append("\n");

app/src/test/java/org/thoughtcrime/securesms/database/model/GroupsV2UpdateMessageProducerTest.kt

@@ -14,7 +14,7 @@ import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
 import org.robolectric.annotation.Config
-import org.signal.core.util.StringUtil
+import org.signal.core.util.BidiUtil
 import org.signal.storageservice.protos.groups.AccessControl
 import org.signal.storageservice.protos.groups.AccessControl.AccessRequired
 import org.signal.storageservice.protos.groups.AccessControl.AccessRequired.ADMINISTRATOR
@@ -683,7 +683,7 @@ class GroupsV2UpdateMessageProducerTest {
       .title("New title")
       .build()
 
-    assertEquals(listOf("Alice changed the group name to \"" + StringUtil.isolateBidi("New title") + "\"."), describeChange(change))
+    assertEquals(listOf("Alice changed the group name to \"" + BidiUtil.isolateBidi("New title") + "\"."), describeChange(change))
   }
 
   @Test
@@ -692,7 +692,7 @@ class GroupsV2UpdateMessageProducerTest {
       .title("Title 2")
       .build()
 
-    assertEquals(listOf("You changed the group name to \"" + StringUtil.isolateBidi("Title 2") + "\"."), describeChange(change))
+    assertEquals(listOf("You changed the group name to \"" + BidiUtil.isolateBidi("Title 2") + "\"."), describeChange(change))
   }
 
   @Test
@@ -701,7 +701,7 @@ class GroupsV2UpdateMessageProducerTest {
       .title("Title 3")
       .build()
 
-    assertEquals(listOf("The group name has changed to \"" + StringUtil.isolateBidi("Title 3") + "\"."), describeChange(change))
+    assertEquals(listOf("The group name has changed to \"" + BidiUtil.isolateBidi("Title 3") + "\"."), describeChange(change))
   }
 
   // Avatar change
@@ -1166,7 +1166,7 @@ class GroupsV2UpdateMessageProducerTest {
       listOf(
         "Alice added you to the group.",
         "Alice added Bob.",
-        "Alice changed the group name to \"" + StringUtil.isolateBidi("Title") + "\".",
+        "Alice changed the group name to \"" + BidiUtil.isolateBidi("Title") + "\".",
         "Alice set the disappearing message timer to 5 minutes.",
         "Alice changed who can edit group membership to \"All members\"."
       ),
@@ -1219,7 +1219,7 @@ class GroupsV2UpdateMessageProducerTest {
     assertEquals(
       listOf(
         "Bob joined the group.",
-        "The group name has changed to \"" + StringUtil.isolateBidi("Title 2") + "\".",
+        "The group name has changed to \"" + BidiUtil.isolateBidi("Title 2") + "\".",
         "The group avatar has been changed.",
         "The disappearing message timer has been set to 10 minutes.",
         "Who can edit group membership has been changed to \"All members\"."
@@ -1241,7 +1241,7 @@ class GroupsV2UpdateMessageProducerTest {
       listOf(
         "Alice joined the group.",
         "Alice is now an admin.",
-        "The group name has changed to \"" + StringUtil.isolateBidi("Updated title") + "\".",
+        "The group name has changed to \"" + BidiUtil.isolateBidi("Updated title") + "\".",
         "Alice is no longer in the group."
       ),
       describeChange(change)

core-util-jvm/src/main/java/org/signal/core/util/BidiUtil.kt

@@ -0,0 +1,155 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.signal.core.util
+
+import java.util.regex.Pattern
+
+object BidiUtil {
+  private val ALL_ASCII_PATTERN: Pattern = Pattern.compile("^[\\x00-\\x7F]*$")
+
+  private object Bidi {
+    /** Override text direction   */
+    val OVERRIDES: Set<Int> = SetUtil.newHashSet(
+      "\u202a".codePointAt(0), // LRE
+      "\u202b".codePointAt(0), // RLE
+      "\u202d".codePointAt(0), // LRO
+      "\u202e".codePointAt(0) // RLO
+    )
+
+    /** Set direction and isolate surrounding text  */
+    val ISOLATES: Set<Int> = SetUtil.newHashSet(
+      "\u2066".codePointAt(0), // LRI
+      "\u2067".codePointAt(0), // RLI
+      "\u2068".codePointAt(0) // FSI
+    )
+
+    /** Closes things in [.OVERRIDES]  */
+    val PDF: Int = "\u202c".codePointAt(0)
+
+    /** Closes things in [.ISOLATES]  */
+    val PDI: Int = "\u2069".codePointAt(0)
+
+    /** Auto-detecting isolate  */
+    val FSI: Int = "\u2068".codePointAt(0)
+  }
+
+  /**
+   * @return True if the provided text contains a mix of LTR and RTL characters, otherwise false.
+   */
+  @JvmStatic
+  fun hasMixedTextDirection(text: CharSequence?): Boolean {
+    if (text == null) {
+      return false
+    }
+
+    var isLtr: Boolean? = null
+
+    var i = 0
+    val len = Character.codePointCount(text, 0, text.length)
+    while (i < len) {
+      val codePoint = Character.codePointAt(text, i)
+      val direction = Character.getDirectionality(codePoint)
+      val isLetter = Character.isLetter(codePoint)
+
+      if (isLtr != null && isLtr && direction != Character.DIRECTIONALITY_LEFT_TO_RIGHT && isLetter) {
+        return true
+      } else if (isLtr != null && !isLtr && direction != Character.DIRECTIONALITY_RIGHT_TO_LEFT && isLetter) {
+        return true
+      } else if (isLetter) {
+        isLtr = direction == Character.DIRECTIONALITY_LEFT_TO_RIGHT
+      }
+      i++
+    }
+
+    return false
+  }
+
+  /**
+   * Isolates bi-directional text from influencing surrounding text. You should use this whenever
+   * you're injecting user-generated text into a larger string.
+   *
+   * You'd think we'd be able to trust BidiFormatter, but unfortunately it just misses some
+   * corner cases, so here we are.
+   *
+   * The general idea is just to balance out the opening and closing codepoints, and then wrap the
+   * whole thing in FSI/PDI to isolate it.
+   *
+   * For more details, see:
+   * https://www.w3.org/International/questions/qa-bidi-unicode-controls
+   */
+  @JvmStatic
+  fun isolateBidi(text: String?): String {
+    if (text == null) {
+      return ""
+    }
+
+    if (text.isEmpty()) {
+      return text
+    }
+
+    if (ALL_ASCII_PATTERN.matcher(text).matches()) {
+      return text
+    }
+
+    var overrideCount = 0
+    var overrideCloseCount = 0
+    var isolateCount = 0
+    var isolateCloseCount = 0
+
+    var i = 0
+    val len = text.codePointCount(0, text.length)
+    while (i < len) {
+      val codePoint = text.codePointAt(i)
+
+      if (Bidi.OVERRIDES.contains(codePoint)) {
+        overrideCount++
+      } else if (codePoint == Bidi.PDF) {
+        overrideCloseCount++
+      } else if (Bidi.ISOLATES.contains(codePoint)) {
+        isolateCount++
+      } else if (codePoint == Bidi.PDI) {
+        isolateCloseCount++
+      }
+      i++
+    }
+
+    val suffix = StringBuilder()
+
+    while (overrideCount > overrideCloseCount) {
+      suffix.appendCodePoint(Bidi.PDF)
+      overrideCloseCount++
+    }
+
+    while (isolateCount > isolateCloseCount) {
+      suffix.appendCodePoint(Bidi.FSI)
+      isolateCloseCount++
+    }
+
+    val out = StringBuilder()
+
+    return out.appendCodePoint(Bidi.FSI)
+      .append(text)
+      .append(suffix)
+      .appendCodePoint(Bidi.PDI)
+      .toString()
+  }
+
+  @JvmStatic
+  fun stripBidiProtection(text: String?): String? {
+    if (text == null) return null
+
+    return text.replace("[\\u2068\\u2069\\u202c]".toRegex(), "")
+  }
+
+  fun stripBidiIndicator(text: String): String {
+    return text.replace("\u200F", "")
+  }
+
+  @JvmStatic
+  fun forceLtr(text: CharSequence): String {
+    return "\u202a" + text + "\u202c"
+  }
+}

core-util/src/main/java/org/signal/core/util/StringUtil.kt

@@ -4,7 +4,6 @@ import android.text.SpannableStringBuilder
 import java.io.ByteArrayOutputStream
 import java.io.IOException
 import java.nio.charset.StandardCharsets
-import java.util.regex.Pattern
 
 object StringUtil {
   private val WHITESPACE: Set<Char> = setOf(
@@ -15,34 +14,6 @@ object StringUtil {
     '\u2800' // braille blank
   )
 
-  private val ALL_ASCII_PATTERN: Pattern = Pattern.compile("^[\\x00-\\x7F]*$")
-
-  private object Bidi {
-    /** Override text direction   */
-    val OVERRIDES: Set<Int> = SetUtil.newHashSet(
-      "\u202a".codePointAt(0), /* LRE */
-      "\u202b".codePointAt(0), /* RLE */
-      "\u202d".codePointAt(0), /* LRO */
-      "\u202e".codePointAt(0) /* RLO */
-    )
-
-    /** Set direction and isolate surrounding text  */
-    val ISOLATES: Set<Int> = SetUtil.newHashSet(
-      "\u2066".codePointAt(0), /* LRI */
-      "\u2067".codePointAt(0), /* RLI */
-      "\u2068".codePointAt(0) /* FSI */
-    )
-
-    /** Closes things in [.OVERRIDES]  */
-    val PDF: Int = "\u202c".codePointAt(0)
-
-    /** Closes things in [.ISOLATES]  */
-    val PDI: Int = "\u2069".codePointAt(0)
-
-    /** Auto-detecting isolate  */
-    val FSI: Int = "\u2068".codePointAt(0)
-  }
-
   /**
    * Trims a name string to fit into the byte length requirement.
    *
@@ -172,37 +143,6 @@ object StringUtil {
     return String(Character.toChars(codePoint))
   }
 
-  /**
-   * @return True if the provided text contains a mix of LTR and RTL characters, otherwise false.
-   */
-  @JvmStatic
-  fun hasMixedTextDirection(text: CharSequence?): Boolean {
-    if (text == null) {
-      return false
-    }
-
-    var isLtr: Boolean? = null
-
-    var i = 0
-    val len = Character.codePointCount(text, 0, text.length)
-    while (i < len) {
-      val codePoint = Character.codePointAt(text, i)
-      val direction = Character.getDirectionality(codePoint)
-      val isLetter = Character.isLetter(codePoint)
-
-      if (isLtr != null && isLtr && direction != Character.DIRECTIONALITY_LEFT_TO_RIGHT && isLetter) {
-        return true
-      } else if (isLtr != null && !isLtr && direction != Character.DIRECTIONALITY_RIGHT_TO_LEFT && isLetter) {
-        return true
-      } else if (isLetter) {
-        isLtr = direction == Character.DIRECTIONALITY_LEFT_TO_RIGHT
-      }
-      i++
-    }
-
-    return false
-  }
-
   /**
    * @return True if the text is null or has a length of 0, otherwise false.
    */
@@ -211,87 +151,6 @@ object StringUtil {
     return text.isNullOrEmpty()
   }
 
-  /**
-   * Isolates bi-directional text from influencing surrounding text. You should use this whenever
-   * you're injecting user-generated text into a larger string.
-   *
-   * You'd think we'd be able to trust BidiFormatter, but unfortunately it just misses some
-   * corner cases, so here we are.
-   *
-   * The general idea is just to balance out the opening and closing codepoints, and then wrap the
-   * whole thing in FSI/PDI to isolate it.
-   *
-   * For more details, see:
-   * https://www.w3.org/International/questions/qa-bidi-unicode-controls
-   */
-  @JvmStatic
-  fun isolateBidi(text: String?): String {
-    if (text == null) {
-      return ""
-    }
-
-    if (isEmpty(text)) {
-      return text
-    }
-
-    if (ALL_ASCII_PATTERN.matcher(text).matches()) {
-      return text
-    }
-
-    var overrideCount = 0
-    var overrideCloseCount = 0
-    var isolateCount = 0
-    var isolateCloseCount = 0
-
-    var i = 0
-    val len = text.codePointCount(0, text.length)
-    while (i < len) {
-      val codePoint = text.codePointAt(i)
-
-      if (Bidi.OVERRIDES.contains(codePoint)) {
-        overrideCount++
-      } else if (codePoint == Bidi.PDF) {
-        overrideCloseCount++
-      } else if (Bidi.ISOLATES.contains(codePoint)) {
-        isolateCount++
-      } else if (codePoint == Bidi.PDI) {
-        isolateCloseCount++
-      }
-      i++
-    }
-
-    val suffix = StringBuilder()
-
-    while (overrideCount > overrideCloseCount) {
-      suffix.appendCodePoint(Bidi.PDF)
-      overrideCloseCount++
-    }
-
-    while (isolateCount > isolateCloseCount) {
-      suffix.appendCodePoint(Bidi.FSI)
-      isolateCloseCount++
-    }
-
-    val out = StringBuilder()
-
-    return out.appendCodePoint(Bidi.FSI)
-      .append(text)
-      .append(suffix)
-      .appendCodePoint(Bidi.PDI)
-      .toString()
-  }
-
-  @JvmStatic
-  fun stripBidiProtection(text: String?): String? {
-    if (text == null) return null
-
-    return text.replace("[\\u2068\\u2069\\u202c]".toRegex(), "")
-  }
-
-  fun stripBidiIndicator(text: String): String {
-    return text.replace("\u200F", "")
-  }
-
   /**
    * Trims a [CharSequence] of starting and trailing whitespace. Behavior matches
    * [String.trim] to preserve expectations around results.
@@ -341,11 +200,6 @@ object StringUtil {
     return iterator.countBreaks()
   }
 
-  @JvmStatic
-  fun forceLtr(text: CharSequence): String {
-    return "\u202a" + text + "\u202c"
-  }
-
   @JvmStatic
   fun replace(text: CharSequence, toReplace: Char, replacement: String?): CharSequence {
     var updatedText: SpannableStringBuilder? = null

core-util/src/test/java/org/signal/core/util/StringUtilTest_hasMixedTextDirection.java

@@ -49,7 +49,7 @@ public final class StringUtilTest_hasMixedTextDirection {
 
   @Test
   public void trim() {
-    boolean output = StringUtil.hasMixedTextDirection(input);
+    boolean output = BidiUtil.hasMixedTextDirection(input);
     assertEquals(expected, output);
   }
 }