build: add Optimizely SDK logger classes

- Add FlutterOptimizelyLogger class implementing OPTLogger protocol
- Add constants for customLogger and loggerChannel
- Implement FlutterMethodChannel for invoking log method
- Add logger field to OptimizelyFlutterSdk constructor
- Initialize custom logger in OptimizelyClientWrapper
- Create LoggerBridge to handle log method calls
- Implement OptimizelyLogger interface and DefaultOptimizelyLogger class

Author: muzahidul-opti

ios/Classes/FlutterOptimizelyLogger.swift

@@ -0,0 +1,25 @@
+import Flutter
+import Optimizely
+
+public class FlutterOptimizelyLogger: NSObject, OPTLogger {
+    public static var logLevel: OptimizelyLogLevel = .info
+    
+    private static let loggerChannel = FlutterMethodChannel(
+        name: "optimizely_flutter_sdk_logger",
+        binaryMessenger: SwiftOptimizelyFlutterSdkPlugin.registrar?.messenger() ?? FlutterEngine().binaryMessenger
+    )
+    
+    public required override init() {
+        super.init()
+    }
+    
+    public func log(level: OptimizelyLogLevel, message: String) {
+        // Ensure we're on the main thread when calling Flutter
+        DispatchQueue.main.async {
+            Self.loggerChannel.invokeMethod("log", arguments: [
+                "level": level.rawValue,
+                "message": message
+            ])
+        }
+    }
+}

ios/Classes/HelperClasses/Constants.swift

@@ -91,6 +91,7 @@ struct RequestParameterKey {
     static let reasons = "reasons"
     static let decideOptions = "optimizelyDecideOption"
     static let defaultLogLevel = "defaultLogLevel"
+    static let customLogger = "customLogger"
     static let eventBatchSize = "eventBatchSize"
     static let eventTimeInterval = "eventTimeInterval"
     static let eventMaxQueueSize = "eventMaxQueueSize"

ios/Classes/SwiftOptimizelyFlutterSdkPlugin.swift

@@ -36,8 +36,10 @@ public class SwiftOptimizelyFlutterSdkPlugin: NSObject, FlutterPlugin {
         return UUID().uuidString
     }
 
+    static var registrar: FlutterPluginRegistrar?
     /// Registers optimizely_flutter_sdk channel to communicate with the flutter sdk to receive requests and send responses
     public static func register(with registrar: FlutterPluginRegistrar) {
+        self.registrar = registrar
         channel = FlutterMethodChannel(name: "optimizely_flutter_sdk", binaryMessenger: registrar.messenger())
         let instance = SwiftOptimizelyFlutterSdkPlugin()
         registrar.addMethodCallDelegate(instance, channel: channel)
@@ -163,9 +165,16 @@ public class SwiftOptimizelyFlutterSdkPlugin: NSObject, FlutterPlugin {
         notificationIdsTracker.removeValue(forKey: sdkKey)
         optimizelyClientsTracker.removeValue(forKey: sdkKey)
 
+        // Check if custom logger is requested
+        var logger: OPTLogger?
+        if let useCustomLogger = parameters[RequestParameterKey.customLogger] as? Bool, useCustomLogger {
+            logger = FlutterOptimizelyLogger()
+        }
+
         // Creating new instance
         let optimizelyInstance = OptimizelyClient(
             sdkKey:sdkKey, 
+            logger:logger,
             eventDispatcher: eventDispatcher, 
             datafileHandler: datafileHandler, 
             periodicDownloadInterval: datafilePeriodicDownloadInterval, 

lib/optimizely_flutter_sdk.dart

@@ -28,6 +28,8 @@ import 'package:optimizely_flutter_sdk/src/data_objects/optimizely_config_respon
 import 'package:optimizely_flutter_sdk/src/optimizely_client_wrapper.dart';
 import 'package:optimizely_flutter_sdk/src/user_context/optimizely_user_context.dart';
 import 'package:optimizely_flutter_sdk/src/data_objects/log_level.dart';
+import 'package:optimizely_flutter_sdk/src/logger/OptimizelyLogger.dart';
+import 'package:optimizely_flutter_sdk/src/logger/LoggerBridge.dart';
 
 export 'package:optimizely_flutter_sdk/src/optimizely_client_wrapper.dart'
     show ClientPlatform, ListenerType;
@@ -68,20 +70,37 @@ class OptimizelyFlutterSdk {
   final Set<OptimizelyDecideOption> _defaultDecideOptions;
   final OptimizelyLogLevel _defaultLogLevel;
   final SDKSettings _sdkSettings;
+  final OptimizelyLogger? _logger; // Add logger field
+  static OptimizelyLogger? _customLogger;
+  /// Set a custom logger for the SDK
+  static void setLogger(OptimizelyLogger logger) {
+    _customLogger = logger;
+    LoggerBridge.initialize();
+  }
+  /// Get the current logger
+  static OptimizelyLogger? get logger {
+    return _customLogger;
+  }
   OptimizelyFlutterSdk(this._sdkKey,
-      {EventOptions eventOptions = const EventOptions(),
-      int datafilePeriodicDownloadInterval =
-          10 * 60, // Default time interval in seconds
-      Map<ClientPlatform, DatafileHostOptions> datafileHostOptions = const {},
-      Set<OptimizelyDecideOption> defaultDecideOptions = const {},
-      OptimizelyLogLevel defaultLogLevel = OptimizelyLogLevel.info,
-      SDKSettings sdkSettings = const SDKSettings()})
-      : _eventOptions = eventOptions,
-        _datafilePeriodicDownloadInterval = datafilePeriodicDownloadInterval,
-        _datafileHostOptions = datafileHostOptions,
-        _defaultDecideOptions = defaultDecideOptions,
-        _defaultLogLevel = defaultLogLevel,
-        _sdkSettings = sdkSettings;
+    {EventOptions eventOptions = const EventOptions(),
+    int datafilePeriodicDownloadInterval = 10 * 60,
+    Map<ClientPlatform, DatafileHostOptions> datafileHostOptions = const {},
+    Set<OptimizelyDecideOption> defaultDecideOptions = const {},
+    OptimizelyLogLevel defaultLogLevel = OptimizelyLogLevel.info,
+    SDKSettings sdkSettings = const SDKSettings(),
+    OptimizelyLogger? logger}) // Add logger parameter
+    : _eventOptions = eventOptions,
+      _datafilePeriodicDownloadInterval = datafilePeriodicDownloadInterval,
+      _datafileHostOptions = datafileHostOptions,
+      _defaultDecideOptions = defaultDecideOptions,
+      _defaultLogLevel = defaultLogLevel,
+      _sdkSettings = sdkSettings,
+      _logger = logger {
+      // Set the logger if provided
+      if (logger != null) {
+        setLogger(logger);
+      }
+  }
 
   /// Starts Optimizely SDK (Synchronous) with provided sdkKey.
   Future<BaseResponse> initializeClient() async {
@@ -92,7 +111,9 @@ class OptimizelyFlutterSdk {
         _datafileHostOptions,
         _defaultDecideOptions,
         _defaultLogLevel,
-        _sdkSettings);
+        _sdkSettings,
+        _logger
+    );
   }
 
   /// Use the activate method to start an experiment.

lib/src/logger/LoggerBridge.dart

@@ -0,0 +1,26 @@
+import 'dart:async';
+import 'package:flutter/services.dart';
+import 'package:optimizely_flutter_sdk/src/data_objects/log_level.dart';
+
+import 'package:optimizely_flutter_sdk/optimizely_flutter_sdk.dart';
+
+class LoggerBridge {
+  static const MethodChannel _loggerChannel =
+      MethodChannel('optimizely_flutter_sdk_logger');
+
+  static void initialize() {
+    _loggerChannel.setMethodCallHandler(_handleMethodCall);
+  }
+
+  static Future<void> _handleMethodCall(MethodCall call) async {
+    switch (call.method) {
+      case 'log':
+        final args = call.arguments as Map<String, dynamic>;
+        final level = OptimizelyLogLevel.values[args['level'] as int];
+        final message = args['message'] as String;
+
+        OptimizelyFlutterSdk.logger?.log(level, message);
+        break;
+    }
+  }
+}

lib/src/logger/OptimizelyLogger.dart

@@ -0,0 +1,28 @@
+import 'package:optimizely_flutter_sdk/src/data_objects/log_level.dart';
+
+abstract class OptimizelyLogger {
+  /// The log level for the logger
+  OptimizelyLogLevel get logLevel;
+  set logLevel(OptimizelyLogLevel level);
+
+  /// Log a message at a certain level
+  void log(OptimizelyLogLevel level, String message);
+}
+
+// enum OptimizelyLogLevel { error, warning, info, debug }
+
+class DefaultOptimizelyLogger implements OptimizelyLogger {
+  @override
+  OptimizelyLogLevel logLevel = OptimizelyLogLevel.info;
+
+  @override
+  void log(OptimizelyLogLevel level, String message) {
+    if (_shouldLog(level)) {
+      print('[Optimizely ${level.name.toUpperCase()}] $message');
+    }
+  }
+
+  bool _shouldLog(OptimizelyLogLevel messageLevel) {
+    return messageLevel.index <= logLevel.index;
+  }
+}

lib/src/optimizely_client_wrapper.dart

@@ -27,6 +27,8 @@ import 'package:optimizely_flutter_sdk/src/data_objects/get_vuid_response.dart';
 import 'package:optimizely_flutter_sdk/src/data_objects/optimizely_config_response.dart';
 import 'package:optimizely_flutter_sdk/src/utils/constants.dart';
 import 'package:optimizely_flutter_sdk/src/utils/utils.dart';
+import 'package:optimizely_flutter_sdk/src/logger/OptimizelyLogger.dart';
+import 'package:optimizely_flutter_sdk/src/logger/LoggerBridge.dart';
 
 enum ListenerType { activate, track, decision, logEvent, projectConfigUpdate }
 
@@ -63,8 +65,13 @@ class OptimizelyClientWrapper {
       Map<ClientPlatform, DatafileHostOptions> datafileHostOptions,
       Set<OptimizelyDecideOption> defaultDecideOptions,
       OptimizelyLogLevel defaultLogLevel,
-      SDKSettings sdkSettings) async {
+      SDKSettings sdkSettings,
+      OptimizelyLogger? logger) async {
     _channel.setMethodCallHandler(methodCallHandler);
+    // Initialize logger bridge if custom logger is provided
+    if (logger != null) {
+      LoggerBridge.initialize();
+    }
     final convertedOptions = Utils.convertDecideOptions(defaultDecideOptions);
     final convertedLogLevel = Utils.convertLogLevel(defaultLogLevel);
     const sdkVersion = PackageInfo.version;
@@ -79,6 +86,7 @@ class OptimizelyClientWrapper {
       Constants.eventBatchSize: eventOptions.batchSize,
       Constants.eventTimeInterval: eventOptions.timeInterval,
       Constants.eventMaxQueueSize: eventOptions.maxQueueSize,
+      Constants.customLogger: logger != null,
     };
 
     // Odp Request params

lib/src/utils/constants.dart

@@ -86,6 +86,7 @@ class Constants {
   static const String optimizelyDecideOption = "optimizelyDecideOption";
   static const String optimizelySegmentOption = "optimizelySegmentOption";
   static const String optimizelySdkSettings = "optimizelySdkSettings";
+  static const String customLogger = 'customLogger';
   static const String defaultLogLevel = "defaultLogLevel";
   static const String payload = "payload";
   static const String value = "value";