Extract common message-sending methods into a shared utility class

service/src/main/java/org/whispersystems/textsecuregcm/push/MessageUtil.java

@@ -0,0 +1,128 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.push;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.signal.libsignal.protocol.SealedSenderMultiRecipientMessage;
+import org.whispersystems.textsecuregcm.identity.ServiceIdentifier;
+import org.whispersystems.textsecuregcm.storage.Account;
+import org.whispersystems.textsecuregcm.storage.AccountsManager;
+import org.whispersystems.textsecuregcm.storage.Device;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import reactor.util.function.Tuple2;
+import reactor.util.function.Tuples;
+
+public class MessageUtil {
+
+  public static final int DEFAULT_MAX_FETCH_ACCOUNT_CONCURRENCY = 8;
+
+  private MessageUtil() {
+  }
+
+  /**
+   * Finds account records for all recipients named in the given multi-recipient manager. Note that the returned map
+   * of recipients to account records will omit entries for recipients that could not be resolved to active accounts;
+   * callers that require full resolution should check for a missing entries and take appropriate action.
+   *
+   * @param accountsManager the {@code AccountsManager} instance to use to find account records
+   * @param multiRecipientMessage the message for which to resolve recipients
+   *
+   * @return a map of recipients to account records
+   *
+   * @see #getUnresolvedRecipients(SealedSenderMultiRecipientMessage, Map)
+   */
+  public static Map<SealedSenderMultiRecipientMessage.Recipient, Account> resolveRecipients(
+      final AccountsManager accountsManager,
+      final SealedSenderMultiRecipientMessage multiRecipientMessage) {
+
+    return resolveRecipients(accountsManager, multiRecipientMessage, DEFAULT_MAX_FETCH_ACCOUNT_CONCURRENCY);
+  }
+
+  /**
+   * Finds account records for all recipients named in the given multi-recipient manager. Note that the returned map
+   * of recipients to account records will omit entries for recipients that could not be resolved to active accounts;
+   * callers that require full resolution should check for a missing entries and take appropriate action.
+   *
+   * @param accountsManager the {@code AccountsManager} instance to use to find account records
+   * @param multiRecipientMessage the message for which to resolve recipients
+   * @param maxFetchAccountConcurrency the maximum number of concurrent account-retrieval operations
+   *
+   * @return a map of recipients to account records
+   *
+   * @see #getUnresolvedRecipients(SealedSenderMultiRecipientMessage, Map)
+   */
+  public static Map<SealedSenderMultiRecipientMessage.Recipient, Account> resolveRecipients(
+      final AccountsManager accountsManager,
+      final SealedSenderMultiRecipientMessage multiRecipientMessage,
+      final int maxFetchAccountConcurrency) {
+
+    return Flux.fromIterable(multiRecipientMessage.getRecipients().entrySet())
+        .flatMap(serviceIdAndRecipient -> {
+          final ServiceIdentifier serviceIdentifier =
+              ServiceIdentifier.fromLibsignal(serviceIdAndRecipient.getKey());
+
+          return Mono.fromFuture(() -> accountsManager.getByServiceIdentifierAsync(serviceIdentifier))
+              .flatMap(Mono::justOrEmpty)
+              .map(account -> Tuples.of(serviceIdAndRecipient.getValue(), account));
+        }, maxFetchAccountConcurrency)
+        .collectMap(Tuple2::getT1, Tuple2::getT2)
+        .blockOptional()
+        .orElse(Collections.emptyMap());
+  }
+
+  /**
+   * Returns a list of recipients missing from the map of resolved recipients for a multi-recipient message.
+   *
+   * @param multiRecipientMessage the multi-recipient message
+   * @param resolvedRecipients the map of resolved recipients to check for missing entries
+   *
+   * @return a list of {@code ServiceIdentifiers} belonging to multi-recipient message recipients that are not present
+   * in the given map of {@code resolvedRecipients}
+   */
+  public static List<ServiceIdentifier> getUnresolvedRecipients(
+      final SealedSenderMultiRecipientMessage multiRecipientMessage,
+      final Map<SealedSenderMultiRecipientMessage.Recipient, Account> resolvedRecipients) {
+
+    return multiRecipientMessage.getRecipients().entrySet().stream()
+        .filter(entry -> !resolvedRecipients.containsKey(entry.getValue()))
+        .map(entry -> ServiceIdentifier.fromLibsignal(entry.getKey()))
+        .toList();
+  }
+
+  /**
+   * Checks if a multi-recipient message contains duplicate recipients.
+   *
+   * @param multiRecipientMessage the message to check for duplicate recipients
+   *
+   * @return {@code true} if the message contains duplicate recipients or {@code false} otherwise
+   */
+  public static boolean hasDuplicateDevices(final SealedSenderMultiRecipientMessage multiRecipientMessage) {
+    final boolean[] usedDeviceIds = new boolean[Device.MAXIMUM_DEVICE_ID + 1];
+
+    for (final SealedSenderMultiRecipientMessage.Recipient recipient : multiRecipientMessage.getRecipients().values()) {
+      if (recipient.getDevices().length == 1) {
+        // A recipient can't have repeated devices if they only have one device
+        continue;
+      }
+
+      Arrays.fill(usedDeviceIds, false);
+
+      for (final byte deviceId : recipient.getDevices()) {
+        if (usedDeviceIds[deviceId]) {
+          return true;
+        }
+
+        usedDeviceIds[deviceId] = true;
+      }
+    }
+
+    return false;
+  }
+}