[Web support] Add init method to load JS SDK and create factory instance

splitio_web/lib/splitio_web.dart

@@ -1,5 +1,15 @@
+import 'dart:async';
+import 'dart:js_interop';
+import 'dart:js_interop_unsafe';
 import 'package:flutter_web_plugins/flutter_web_plugins.dart' show Registrar;
 import 'package:splitio_platform_interface/splitio_platform_interface.dart';
+import 'package:splitio_web/src/js_interop.dart';
+import 'package:web/web.dart';
+
+extension on Window {
+  @JS()
+  external JS_BrowserSDKPackage? splitio;
+}
 
 /// Web implementation of [SplitioPlatform].
 class SplitioWeb extends SplitioPlatform {
@@ -8,4 +18,84 @@ class SplitioWeb extends SplitioPlatform {
     SplitioPlatform.instance = SplitioWeb();
   }
 
+  // Future to queue method calls until SDK is initialized
+  Future<void>? _initFuture;
+
+  late JS_IBrowserSDK _factory;
+
+  @override
+  Future<void> init({
+    required String apiKey,
+    required String matchingKey,
+    required String? bucketingKey,
+    SplitConfiguration? sdkConfiguration,
+  }) async {
+    if (_initFuture == null) {
+      _initFuture = this._init(apiKey: apiKey, matchingKey: matchingKey, bucketingKey: bucketingKey, sdkConfiguration: sdkConfiguration);
+    }
+    return _initFuture;
+  }
+
+  Future<void> _init({
+    required String apiKey,
+    required String matchingKey,
+    required String? bucketingKey,
+    SplitConfiguration? sdkConfiguration,
+  }) async {
+    await _loadSplitSdk();
+
+    final config = _buildConfig(apiKey, matchingKey, bucketingKey, sdkConfiguration);
+
+    // Create factory instance
+    this._factory = window.splitio!.SplitFactory.callAsFunction(null, config) as JS_IBrowserSDK;
+
+    return;
+  }
+
+  // Checks whether the Split Browser SDK was manually loaded (`window.splitio != null`).
+  // If not, loads it by injecting a script tag.
+  static Future<void> _loadSplitSdk() async {
+    if (window.splitio != null) {
+      return; // Already loaded
+    }
+
+    // Create and inject script tag
+    final script = document.createElement('script') as HTMLScriptElement;
+    script.type = 'text/javascript';
+    script.src = 'packages/splitio_web/web/split-browser-1.6.0.full.min.js';
+
+    // Wait for script to load
+    final completer = Completer<void>();
+
+    script.onload = (Event event) {
+      completer.complete();
+    }.toJS;
+
+    script.onerror = (Event event) {
+      completer.completeError(Exception('Failed to load Split SDK'));
+    }.toJS;
+
+    document.head!.appendChild(script);
+
+    await completer.future;
+
+    if (window.splitio == null) {
+      throw Exception('Split Browser SDK failed to initialize after loading');
+    }
+  }
+
+  // Map SplitConfiguration to JS equivalent object
+  JSObject _buildConfig(String apiKey, String matchingKey, String? bucketingKey, SplitConfiguration? configuration) {
+    final core = JSObject();
+    core.setProperty('authorizationKey'.toJS, apiKey.toJS);
+    // @TODO: set bucketingKey if provided
+    core.setProperty('key'.toJS, matchingKey.toJS);
+
+    final config = JSObject();
+    config.setProperty('core'.toJS, core);
+
+    // @TODO: complete config
+    return config;
+  }
+
 }

splitio_web/lib/src/js_interop.dart

@@ -0,0 +1,9 @@
+import 'dart:js_interop';
+
+@JS()
+extension type JS_IBrowserSDK._(JSObject _) implements JSObject {}
+
+@JS()
+extension type JS_BrowserSDKPackage._(JSObject _) implements JSObject {
+  external JSFunction SplitFactory;
+}