Add custom signals support in Remote Config.

FirebaseRemoteConfig/Sources/FIRRemoteConfig.m

@@ -34,6 +34,9 @@
 /// Remote Config Error Domain.
 /// TODO: Rename according to obj-c style for constants.
 NSString *const FIRRemoteConfigErrorDomain = @"com.google.remoteconfig.ErrorDomain";
+// Remote Config Custom Signals Error Domain
+NSString *const FIRRemoteConfigCustomSignalsErrorDomain =
+    @"com.google.remoteconfig.customsignals.ErrorDomain";
 // Remote Config Realtime Error Domain
 NSString *const FIRRemoteConfigUpdateErrorDomain = @"com.google.remoteconfig.update.ErrorDomain";
 /// Remote Config Error Info End Time Seconds;
@@ -237,6 +240,99 @@ - (void)callListeners:(NSString *)key config:(NSDictionary *)config {
   }
 }
 
+- (void)setCustomSignals:(nullable NSDictionary<NSString *, NSObject *> *)customSignals
+          WithCompletion:(void (^_Nullable)(NSError *_Nullable error))completionHandler {
+  void (^setCustomSignalsBlock)(void) = ^{
+    if (!customSignals) {
+      if (completionHandler) {
+        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+          completionHandler(nil);
+        });
+      }
+      return;
+    }
+
+    // Validate value type, and key and value length
+    for (NSString *key in customSignals) {
+      NSObject *value = customSignals[key];
+      if (![value isKindOfClass:[NSNull class]] && ![value isKindOfClass:[NSString class]] &&
+          ![value isKindOfClass:[NSNumber class]]) {
+        if (completionHandler) {
+          dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+            NSError *error =
+                [NSError errorWithDomain:FIRRemoteConfigCustomSignalsErrorDomain
+                                    code:FIRRemoteConfigCustomSignalsErrorInvalidValueType
+                                userInfo:@{
+                                  NSLocalizedDescriptionKey :
+                                      @"Invalid value type. Must be NSString, NSNumber or NSNull"
+                                }];
+            completionHandler(error);
+          });
+        }
+        return;
+      }
+
+      if (key.length > 250 ||
+          ([value isKindOfClass:[NSString class]] && [(NSString *)value length] > 500)) {
+        if (completionHandler) {
+          dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+            NSError *error = [NSError errorWithDomain:FIRRemoteConfigCustomSignalsErrorDomain
+                                                 code:FIRRemoteConfigCustomSignalsErrorLimitExceeded
+                                             userInfo:@{
+                                               NSLocalizedDescriptionKey :
+                                                   @"Custom signal keys and string values must be "
+                                                   @"250 and 500 characters or less respectively."
+                                             }];
+            completionHandler(error);
+          });
+        }
+        return;
+      }
+    }
+
+    // Merge new signals with existing ones, overwriting existing keys.
+    // Also, remove entries where the new value is null.
+    NSMutableDictionary<NSString *, NSObject *> *newCustomSignals =
+        [[NSMutableDictionary alloc] initWithDictionary:self->_settings.customSignals];
+
+    for (NSString *key in customSignals) {
+      NSObject *value = customSignals[key];
+      if (![value isKindOfClass:[NSNull class]]) {
+        [newCustomSignals setObject:value forKey:key];
+      } else {
+        [newCustomSignals removeObjectForKey:key];
+      }
+    }
+
+    // Check the size limit.
+    if (newCustomSignals.count > 100) {
+      if (completionHandler) {
+        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+          NSError *error = [NSError
+              errorWithDomain:FIRRemoteConfigCustomSignalsErrorDomain
+                         code:FIRRemoteConfigCustomSignalsErrorLimitExceeded
+                     userInfo:@{
+                       NSLocalizedDescriptionKey : @"Custom signals count exceeds the limit of 100."
+                     }];
+          completionHandler(error);
+        });
+      }
+      return;
+    }
+
+    // Update only if there are changes.
+    if (![newCustomSignals isEqualToDictionary:self->_settings.customSignals]) {
+      self->_settings.customSignals = newCustomSignals;
+    }
+    if (completionHandler) {
+      dispatch_async(dispatch_get_main_queue(), ^{
+        completionHandler(nil);
+      });
+    }
+  };
+  dispatch_async(_queue, setCustomSignalsBlock);
+}
+
 #pragma mark - fetch
 
 - (void)fetchWithCompletionHandler:(FIRRemoteConfigFetchCompletion)completionHandler {

FirebaseRemoteConfig/Sources/Private/RCNConfigSettings.h

@@ -84,6 +84,11 @@
 /// Last active template version.
 @property(nonatomic, readwrite, assign) NSString *lastActiveTemplateVersion;
 
+#pragma mark - Custom Signals
+
+/// A dictionary to hold custom signals that are set by the developer.
+@property(nonatomic, readwrite, strong) NSMutableDictionary<NSString *, NSObject *> *customSignals;
+
 #pragma mark Throttling properties
 
 /// Throttling intervals are based on https://cloud.google.com/storage/docs/exponential-backoff

FirebaseRemoteConfig/Sources/Public/FirebaseRemoteConfig/FIRRemoteConfig.h

@@ -96,6 +96,19 @@ typedef NS_ERROR_ENUM(FIRRemoteConfigUpdateErrorDomain, FIRRemoteConfigUpdateErr
     FIRRemoteConfigUpdateErrorUnavailable = 8004,
 } NS_SWIFT_NAME(RemoteConfigUpdateError);
 
+/// Error domain for custom signals errors.
+extern NSString *const _Nonnull FIRRemoteConfigCustomSignalsErrorDomain NS_SWIFT_NAME(RemoteConfigCustomSignalsErrorDomain);
+
+/// Firebase Remote Config custom signals error.
+typedef NS_ERROR_ENUM(FIRRemoteConfigCustomSignalsErrorDomain, FIRRemoteConfigCustomSignalsError){
+    /// Unknown error.
+    FIRRemoteConfigCustomSignalsErrorUnknown = 8001,
+    /// Invalid value type in the custom signals dictionary.
+    FIRRemoteConfigCustomSignalsErrorInvalidValueType = 8002,
+    /// Limit exceeded for key length, value length, or number of signals.
+    FIRRemoteConfigCustomSignalsErrorLimitExceeded = 8003,
+} NS_SWIFT_NAME(RemoteConfigCustomSignalsError);
+
 /// Enumerated value that indicates the source of Remote Config data. Data can come from
 /// the Remote Config service, the DefaultConfig that is available when the app is first installed,
 /// or a static initialized value if data is not available from the service or DefaultConfig.
@@ -357,4 +370,8 @@ typedef void (^FIRRemoteConfigUpdateCompletion)(FIRRemoteConfigUpdate *_Nullable
     (FIRRemoteConfigUpdateCompletion _Nonnull)listener
     NS_SWIFT_NAME(addOnConfigUpdateListener(remoteConfigUpdateCompletion:));
 
+- (void)setCustomSignals:(nullable NSDictionary<NSString *, NSObject *> *)customSignals
+          WithCompletion:(void (^_Nullable)(NSError *_Nullable error))completionHandler
+    NS_REFINED_FOR_SWIFT;
+
 @end

FirebaseRemoteConfig/Sources/RCNConfigSettings.m

@@ -109,6 +109,7 @@ - (instancetype)initWithDatabaseManager:(RCNConfigDBManager *)manager
       [_userDefaultsManager resetUserDefaults];
     }
 
+    _customSignals = [_userDefaultsManager customSignals];
     _isFetchInProgress = NO;
     _lastFetchedTemplateVersion = [_userDefaultsManager lastFetchedTemplateVersion];
     _lastActiveTemplateVersion = [_userDefaultsManager lastActiveTemplateVersion];
@@ -444,6 +445,21 @@ - (NSString *)nextRequestWithUserProperties:(NSDictionary *)userProperties {
       }
     }
   }
+
+  if (_customSignals.count > 0) {
+    NSError *error;
+    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:_customSignals
+                                                       options:0
+                                                         error:&error];
+    if (!error) {
+      ret = [ret
+          stringByAppendingString:[NSString
+                                      stringWithFormat:@", custom_signals:%@",
+                                                       [[NSString alloc]
+                                                           initWithData:jsonData
+                                                               encoding:NSUTF8StringEncoding]]];
+    }
+  }
   ret = [ret stringByAppendingString:@"}"];
   return ret;
 }
@@ -517,6 +533,11 @@ - (void)setLastSetDefaultsTimeInterval:(NSTimeInterval)lastSetDefaultsTimestamp
                      completionHandler:nil];
 }
 
+- (void)setCustomSignals:(NSMutableDictionary<NSString *, NSObject *> *)customSignals {
+  _customSignals = customSignals;
+  [_userDefaultsManager setCustomSignals:customSignals];
+}
+
 #pragma mark Throttling
 
 - (BOOL)hasMinimumFetchIntervalElapsed:(NSTimeInterval)minimumFetchInterval {

FirebaseRemoteConfig/Sources/RCNUserDefaultsManager.h

@@ -47,6 +47,8 @@ NS_ASSUME_NONNULL_BEGIN
 @property(nonatomic, assign) NSString *lastFetchedTemplateVersion;
 /// Last active template version.
 @property(nonatomic, assign) NSString *lastActiveTemplateVersion;
+/// A dictionary to hold the latest custom signals set by the developer.
+@property(nonatomic, readwrite, strong) NSMutableDictionary<NSString *, NSObject *> *customSignals;
 
 /// Designated initializer.
 - (instancetype)initWithAppName:(NSString *)appName

FirebaseRemoteConfig/Sources/RCNUserDefaultsManager.m

@@ -34,6 +34,7 @@
 static NSString *const kRCNUserDefaultsKeyNameCurrentRealtimeThrottlingRetryInterval =
     @"currentRealtimeThrottlingRetryInterval";
 static NSString *const kRCNUserDefaultsKeyNameRealtimeRetryCount = @"realtimeRetryCount";
+static NSString *const kRCNUserDefaultsKeyCustomSignals = @"customSignals";
 
 @interface RCNUserDefaultsManager () {
   /// User Defaults instance for this bundleID. NSUserDefaults is guaranteed to be thread-safe.
@@ -141,6 +142,21 @@ - (void)setLastActiveTemplateVersion:(NSString *)templateVersion {
   }
 }
 
+- (NSMutableDictionary<NSString *, NSObject *> *)customSignals {
+  NSDictionary *userDefaults = [self instanceUserDefaults];
+  if ([userDefaults objectForKey:kRCNUserDefaultsKeyCustomSignals]) {
+    return [userDefaults objectForKey:kRCNUserDefaultsKeyCustomSignals];
+  }
+
+  return [[NSMutableDictionary<NSString *, NSObject *> alloc] init];
+}
+
+- (void)setCustomSignals:(NSMutableDictionary<NSString *, NSObject *> *)customSignals {
+  if (customSignals) {
+    [self setInstanceUserDefaultsValue:customSignals forKey:kRCNUserDefaultsKeyCustomSignals];
+  }
+}
+
 - (NSTimeInterval)lastETagUpdateTime {
   NSNumber *lastETagUpdateTime =
       [[self instanceUserDefaults] objectForKey:kRCNUserDefaultsKeyNamelastETagUpdateTime];

FirebaseRemoteConfig/Swift/CustomSignals.swift

@@ -0,0 +1,86 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Foundation
+#if SWIFT_PACKAGE
+  @_exported import FirebaseRemoteConfigInternal
+#endif // SWIFT_PACKAGE
+
+// TODO: Document.
+public struct CustomSignalValue {
+  private enum Kind {
+    case string(String)
+    case integer(Int)
+  }
+
+  private let kind: Kind
+
+  private init(kind: Kind) {
+    self.kind = kind
+  }
+
+  /// Returns a string backed custom signal.
+  /// - Parameter string: The given string to back the custom signal with.
+  /// - Returns: A string backed custom signal.
+  public static func string(_ string: String) -> Self {
+    Self(kind: .string(string))
+  }
+
+  /// Returns an integer backed custom signal.
+  /// - Parameter integer: The given integer to back the custom signal with.
+  /// - Returns: An integer backed custom signal.
+  public static func integer(_ integer: Int) -> Self {
+    Self(kind: .integer(integer))
+  }
+
+  fileprivate func toNSObject() -> NSObject {
+    switch kind {
+    case let .string(string):
+      return string as NSString
+    case let .integer(int):
+      return int as NSNumber
+    }
+  }
+}
+
+extension CustomSignalValue: ExpressibleByStringInterpolation {
+  public init(stringLiteral value: String) {
+    self = .string(value)
+  }
+}
+
+extension CustomSignalValue: ExpressibleByIntegerLiteral {
+  public init(integerLiteral value: Int) {
+    self = .integer(value)
+  }
+}
+
+@available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
+public extension RemoteConfig {
+  /// Sets custom signals for this Remote Config instance.
+  /// - Parameter customSignals: A dictionary mapping string keys to custom
+  /// signals to be set for the app instance.
+  func setCustomSignals(_ customSignals: [String: CustomSignalValue?]) async throws {
+    return try await withCheckedThrowingContinuation { continuation in
+      let customSignals = customSignals.mapValues { $0?.toNSObject() ?? NSNull() }
+      self.__setCustomSignals(customSignals) { error in
+        if let error {
+          continuation.resume(throwing: error)
+        } else {
+          continuation.resume()
+        }
+      }
+    }
+  }
+}

FirebaseRemoteConfig/Tests/Swift/SwiftAPI/FirebaseRemoteConfigSwift_APIBuildTests.swift

@@ -223,5 +223,17 @@ final class FirebaseRemoteConfig_APIBuildTests: XCTestCase {
 
     struct MyEncodableValue: Encodable {}
     let _: Void = try config.setDefaults(from: MyEncodableValue())
+
+    Task {
+      let signals: [String: CustomSignalValue?] = [
+        "signal_1": .integer(5),
+        "signal_2": .string("enable_feature"),
+        "signal_3": 5,
+        "signal_4": "enable_feature",
+        "signal_5": "enable_feature_\("secret")",
+        "signal_6": nil, // Used to delete the custom signal for a given key.
+      ]
+      try await config.setCustomSignals(signals)
+    }
   }
 }