feat(fcm): Enable fid and deprecate token for Send API

src/main/java/com/google/firebase/messaging/FirebaseMessaging.java

@@ -265,12 +265,14 @@ protected SendResponse execute() {
   }
 
   /**
-   * Sends the given multicast message to all the FCM registration tokens specified in it.
+   * Sends the given multicast message to all the FCM registration tokens and/or FIDs
+   * specified in it.
    *
    * <p>This method uses the {@link #sendEach(List)} API under the hood to send the given
    * message to all the target recipients. The list of responses obtained by calling
    * {@link BatchResponse#getResponses()} on the return value is in the same order as the
-   * tokens in the {@link MulticastMessage}.
+   * tokens and/or FIDs in the {@link MulticastMessage}. If both tokens and FIDs are
+   * provided, tokens are processed first, followed by FIDs.
    *
    * @param message A non-null {@link MulticastMessage}
    * @return A {@link BatchResponse} indicating the result of the operation.
@@ -285,17 +287,19 @@ public BatchResponse sendEachForMulticast(
   }
 
   /**
-   * Sends the given multicast message to all the FCM registration tokens specified in it.
+   * Sends the given multicast message to all the FCM registration tokens and/or FIDs
+   * specified in it.
    *
-   * <p>If the {@code dryRun} option is set to true, the message will not be actually sent. Instead
-   * FCM performs all the necessary validations, and emulates the send operation. The {@code dryRun}
-   * option is useful for determining whether an FCM registration has been deleted. But it cannot be
-   * used to validate APNs tokens.
+   * <p>If the {@code dryRun} option is set to true, the message will not be actually sent.
+   * Instead FCM performs all the necessary validations, and emulates the send operation.
+   * The {@code dryRun} option is useful for determining whether an FCM registration has
+   * been deleted. But it cannot be used to validate APNs tokens.
    *
    * <p>This method uses the {@link #sendEach(List)} API under the hood to send the given
    * message to all the target recipients. The list of responses obtained by calling
    * {@link BatchResponse#getResponses()} on the return value is in the same order as the
-   * tokens in the {@link MulticastMessage}.
+   * tokens and/or FIDs in the {@link MulticastMessage}. If both tokens and FIDs are
+   * provided, tokens are processed first, followed by FIDs.
    *
    * @param message A non-null {@link MulticastMessage}.
    * @param dryRun A boolean indicating whether to perform a dry run (validation only) of the send.
@@ -417,12 +421,14 @@ public ApiFuture<BatchResponse> sendAllAsync(
   }
 
   /**
-   * Sends the given multicast message to all the FCM registration tokens specified in it.
+   * Sends the given multicast message to all the FCM registration tokens and/or FIDs
+   * specified in it.
    *
    * <p>This method uses the {@link #sendAll(List)} API under the hood to send the given
    * message to all the target recipients. The responses list obtained by calling
-   * {@link BatchResponse#getResponses()} on the return value corresponds to the order of tokens
-   * in the {@link MulticastMessage}.
+   * {@link BatchResponse#getResponses()} on the return value corresponds to the order of
+   * tokens and/or FIDs in the {@link MulticastMessage}. If both tokens and FIDs are
+   * provided, tokens are processed first, followed by FIDs.
    *
    * @param message A non-null {@link MulticastMessage}
    * @return A {@link BatchResponse} indicating the result of the operation.
@@ -439,17 +445,19 @@ public BatchResponse sendMulticast(
   }
 
   /**
-   * Sends the given multicast message to all the FCM registration tokens specified in it.
+   * Sends the given multicast message to all the FCM registration tokens and/or FIDs
+   * specified in it.
    *
-   * <p>If the {@code dryRun} option is set to true, the message will not be actually sent. Instead
-   * FCM performs all the necessary validations, and emulates the send operation. The {@code dryRun}
-   * option is useful for determining whether an FCM registration has been deleted. But it cannot be
-   * used to validate APNs tokens.
+   * <p>If the {@code dryRun} option is set to true, the message will not be actually sent.
+   * Instead FCM performs all the necessary validations, and emulates the send operation.
+   * The {@code dryRun} option is useful for determining whether an FCM registration has
+   * been deleted. But it cannot be used to validate APNs tokens.
    *
    * <p>This method uses the {@link #sendAll(List)} API under the hood to send the given
    * message to all the target recipients. The responses list obtained by calling
-   * {@link BatchResponse#getResponses()} on the return value corresponds to the order of tokens
-   * in the {@link MulticastMessage}.
+   * {@link BatchResponse#getResponses()} on the return value corresponds to the order of
+   * tokens and/or FIDs in the {@link MulticastMessage}. If both tokens and FIDs are
+   * provided, tokens are processed first, followed by FIDs.
    *
    * @param message A non-null {@link MulticastMessage}.
    * @param dryRun A boolean indicating whether to perform a dry run (validation only) of the send.

src/main/java/com/google/firebase/messaging/Message.java

@@ -54,9 +54,16 @@ public class Message {
   @Key("apns")
   private final ApnsConfig apnsConfig;
 
+  /**
+   * @deprecated Use {@link #fid} instead.
+   */
+  @Deprecated
   @Key("token")
   private final String token;
 
+  @Key("fid")
+  private final String fid;
+
   @Key("topic")
   private final String topic;
 
@@ -74,11 +81,14 @@ private Message(Builder builder) {
     this.apnsConfig = builder.apnsConfig;
     int count = Booleans.countTrue(
         !Strings.isNullOrEmpty(builder.token),
+        !Strings.isNullOrEmpty(builder.fid),
         !Strings.isNullOrEmpty(builder.topic),
         !Strings.isNullOrEmpty(builder.condition)
     );
-    checkArgument(count == 1, "Exactly one of token, topic or condition must be specified");
+    checkArgument(count == 1,
+        "Exactly one of token, fid, topic or condition must be specified");
     this.token = builder.token;
+    this.fid = builder.fid;
     this.topic = stripPrefix(builder.topic);
     this.condition = builder.condition;
     this.fcmOptions = builder.fcmOptions;
@@ -109,11 +119,20 @@ ApnsConfig getApnsConfig() {
     return apnsConfig;
   }
 
+  /**
+   * @deprecated Use {@link #getFid()} instead.
+   */
+  @Deprecated
   @VisibleForTesting
   String getToken() {
     return token;
   }
 
+  @VisibleForTesting
+  String getFid() {
+    return fid;
+  }
+
   @VisibleForTesting
   String getTopic() {
     return topic;
@@ -166,7 +185,9 @@ public static class  Builder {
     private AndroidConfig androidConfig;
     private WebpushConfig webpushConfig;
     private ApnsConfig apnsConfig;
+    @Deprecated
     private String token;
+    private String fid;
     private String topic;
     private String condition;
     private FcmOptions fcmOptions;
@@ -222,12 +243,26 @@ public Builder setApnsConfig(ApnsConfig apnsConfig) {
      *
      * @param token A valid device registration token.
      * @return This builder.
+     * @deprecated Use {@link #setFid(String)} instead.
      */
+    @Deprecated
     public Builder setToken(String token) {
       this.token = token;
       return this;
     }
 
+    /**
+     * Sets the Firebase Installation ID (FID) of the app instance to which the message
+     * should be sent.
+     *
+     * @param fid A valid Firebase Installation ID.
+     * @return This builder.
+     */
+    public Builder setFid(String fid) {
+      this.fid = fid;
+      return this;
+    }
+
     /**
      * Sets the name of the FCM topic to which the message should be sent. Topic names may
      * contain the {@code /topics/} prefix.

src/main/java/com/google/firebase/messaging/MulticastMessage.java

@@ -30,22 +30,26 @@
 
 /**
  * Represents a message that can be sent to multiple devices via Firebase Cloud Messaging (FCM).
- * Contains payload information as well as the list of device registration tokens to which the
- * message should be sent. A single {@code MulticastMessage} may contain up to 500 registration
- * tokens.
+ * Contains payload information as well as the list of device registration tokens and/or
+ * Firebase Installation IDs (FIDs) to which the message should be sent. A single
+ * {@code MulticastMessage} may contain up to 500 registration tokens and FIDs combined.
  *
  * <p>Instances of this class are thread-safe and immutable. Use {@link MulticastMessage.Builder}
  * to create new instances. See {@link FirebaseMessaging#sendMulticast(MulticastMessage)} for
  * details on how to send the message to FCM for multicast delivery.
  *
- * <p>This class and the associated Builder retain the order of tokens. Therefore the order of
- * the responses list obtained by calling {@link BatchResponse#getResponses()} on the return value
- * of {@link FirebaseMessaging#sendMulticast(MulticastMessage)} corresponds to the order in which
- * tokens were added to the {@link MulticastMessage.Builder}.
+ * <p>This class and the associated Builder retain the order of tokens and FIDs. Therefore
+ * the order of the responses list obtained by calling {@link BatchResponse#getResponses()}
+ * on the return value of {@link FirebaseMessaging#sendMulticast(MulticastMessage)}
+ * corresponds to the order in which targets were added to the
+ * {@link MulticastMessage.Builder}. If both tokens and FIDs are provided, tokens are
+ * processed first, followed by FIDs.
  */
 public class MulticastMessage {
 
+  @Deprecated
   private final List<String> tokens;
+  private final List<String> fids;
   private final Map<String, String> data;
   private final Notification notification;
   private final AndroidConfig androidConfig;
@@ -55,11 +59,18 @@ public class MulticastMessage {
 
   private MulticastMessage(Builder builder) {
     this.tokens = builder.tokens.build();
-    checkArgument(!this.tokens.isEmpty(), "at least one token must be specified");
-    checkArgument(this.tokens.size() <= 500, "no more than 500 tokens can be specified");
+    this.fids = builder.fids.build();
+    int tokensSize = this.tokens.size();
+    int fidsSize = this.fids.size();
+    checkArgument(tokensSize + fidsSize > 0, "at least one token or fid must be specified");
+    checkArgument(tokensSize + fidsSize <= 500,
+        "no more than 500 tokens and fids combined can be specified");
     for (String token : this.tokens) {
       checkArgument(!Strings.isNullOrEmpty(token), "none of the tokens can be null or empty");
     }
+    for (String fid : this.fids) {
+      checkArgument(!Strings.isNullOrEmpty(fid), "none of the fids can be null or empty");
+    }
     this.data = builder.data.isEmpty() ? null : ImmutableMap.copyOf(builder.data);
     this.notification = builder.notification;
     this.androidConfig = builder.androidConfig;
@@ -69,6 +80,26 @@ private MulticastMessage(Builder builder) {
   }
 
   List<Message> getMessageList() {
+    ImmutableList.Builder<Message> messages = ImmutableList.builder();
+
+    if (!this.tokens.isEmpty()) {
+      Message.Builder tokenBuilder = getMetadataBuilder();
+      for (String token : this.tokens) {
+        messages.add(tokenBuilder.setToken(token).build());
+      }
+    }
+
+    if (!this.fids.isEmpty()) {
+      Message.Builder fidBuilder = getMetadataBuilder();
+      for (String fid : this.fids) {
+        messages.add(fidBuilder.setFid(fid).build());
+      }
+    }
+
+    return messages.build();
+  }
+
+  private Message.Builder getMetadataBuilder() {
     Message.Builder builder = Message.builder()
         .setNotification(this.notification)
         .setAndroidConfig(this.androidConfig)
@@ -78,11 +109,7 @@ List<Message> getMessageList() {
     if (this.data != null) {
       builder.putAllData(this.data);
     }
-    ImmutableList.Builder<Message> messages = ImmutableList.builder();
-    for (String token : this.tokens) {
-      messages.add(builder.setToken(token).build());
-    }
-    return messages.build();
+    return builder;
   }
 
   /**
@@ -96,7 +123,9 @@ public static Builder builder() {
 
   public static class Builder {
 
+    @Deprecated
     private final ImmutableList.Builder<String> tokens = ImmutableList.builder();
+    private final ImmutableList.Builder<String> fids = ImmutableList.builder();
     private final Map<String, String> data = new HashMap<>();
     private Notification notification;
     private AndroidConfig androidConfig;
@@ -107,29 +136,61 @@ public static class Builder {
     private Builder() {}
 
     /**
-     * Adds a token to which the message should be sent. Up to 500 tokens can be specified on
-     * a single instance of {@link MulticastMessage}.
+     * Adds a token to which the message should be sent. Up to 500 tokens
+     * and FIDs combined can be specified on a single instance of
+     * {@link MulticastMessage}.
      *
      * @param token A non-null, non-empty Firebase device registration token.
      * @return This builder.
+     * @deprecated Use {@link #addFid(String)} instead.
      */
+    @Deprecated
     public Builder addToken(@NonNull String token) {
       this.tokens.add(token);
       return this;
     }
 
     /**
-     * Adds a collection of tokens to which the message should be sent. Up to 500 tokens can be
-     * specified on a single instance of {@link MulticastMessage}.
+     * Adds a Firebase Installation ID (FID) to which the message should be sent.
+     * Up to 500 tokens and FIDs combined can be specified on a single instance
+     * of {@link MulticastMessage}.
+     *
+     * @param fid A non-null, non-empty Firebase Installation ID.
+     * @return This builder.
+     */
+    public Builder addFid(@NonNull String fid) {
+      this.fids.add(fid);
+      return this;
+    }
+
+    /**
+     * Adds a collection of tokens to which the message should be sent. Up to 500
+     * tokens and FIDs combined can be specified on a single instance of
+     * {@link MulticastMessage}.
      *
      * @param tokens Collection of Firebase device registration tokens.
      * @return This builder.
+     * @deprecated Use {@link #addAllFids(Collection)} instead.
      */
+    @Deprecated
     public Builder addAllTokens(@NonNull Collection<String> tokens) {
       this.tokens.addAll(tokens);
       return this;
     }
 
+    /**
+     * Adds a collection of Firebase Installation IDs (FIDs) to which the message
+     * should be sent. Up to 500 tokens and FIDs combined can be specified on a
+     * single instance of {@link MulticastMessage}.
+     *
+     * @param fids Collection of Firebase Installation IDs.
+     * @return This builder.
+     */
+    public Builder addAllFids(@NonNull Collection<String> fids) {
+      this.fids.addAll(fids);
+      return this;
+    }
+
     /**
      * Sets the notification information to be included in the message.
      *