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mobile/lib/utils/hmac_utility.dart

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+import 'dart:convert';
+import 'package:crypto/crypto.dart';
+
+/// أداة توليد توقيع HMAC-SHA256 للمصادقة مع الباك إند
+class HmacUtility {
+  /// Generate HMAC-SHA256 signature
+  /// message = timestamp|api_key|payload
+  static String generateSignature({
+    required String apiKey,
+    required String apiSecret,
+    required String payload,
+    required int timestamp,
+  }) {
+    final message = '$timestamp|$apiKey|$payload';
+    final hmac = Hmac(sha256, utf8.encode(apiSecret));
+    final digest = hmac.convert(utf8.encode(message));
+    return digest.toString();
+  }
+
+  /// Build authenticated headers for API requests
+  static Map<String, String> buildHeaders({
+    required String apiKey,
+    required String apiSecret,
+    required String payload,
+  }) {
+    final timestamp = DateTime.now().millisecondsSinceEpoch ~/ 1000;
+    final signature = generateSignature(
+      apiKey: apiKey,
+      apiSecret: apiSecret,
+      payload: payload,
+      timestamp: timestamp,
+    );
+
+    return {
+      'Content-Type': 'application/json',
+      'X-API-Key': apiKey,
+      'X-Signature': signature,
+      'X-Timestamp': timestamp.toString(),
+    };
+  }
+}