Expose method to get string value to TOTP #28

CHANGELOG.md

@@ -4,6 +4,9 @@
   - `shake128generator`
   - `shake256generator`
 - Generalize the random seed list generation to support web
+- Expose methods to get padded string value from TOTP:
+  - `valueString`
+  - `streamString`
 
 # 1.19.1
 

example/otpauth_parser.dart

@@ -183,9 +183,8 @@ void main(List<String> args) {
   for (int i = 0; i < uris.length; ++i) {
     print(uris[i]);
     var totp = parse(uris[i]) as TOTP;
-    totp.stream.listen((e) {
+    totp.streamString.listen((otp) {
       if (i == 0) print("\nTime: ${DateTime.now()}\n ${'-' * 40}");
-      var otp = e.toString().padLeft(totp.digits, '0');
       var left = otp.substring(0, totp.digits ~/ 2);
       var right = otp.substring(totp.digits ~/ 2);
       var joined = '$left $right';

lib/src/core/otpauth.dart

@@ -21,6 +21,10 @@ abstract class OTPAuth {
     this.issuer,
   }) : assert(digits >= 4 && digits <= 15);
 
-  /// Generates the OTP value
+  /// Generates the next OTP value
   int value();
+
+  /// Returns the next OTP value as string
+  @pragma('vm:prefer-inline')
+  String valueString() => value().toString().padLeft(digits, '0');
 }

lib/src/totp.dart

@@ -63,9 +63,14 @@ class TOTP extends HOTP {
     };
   }
 
-  /// A broadcast stream that reports new OTP on every [period] interval
+  /// A broadcast stream that reports new OTP value on every [period] interval
   Stream<int> get stream => _controller.stream;
 
+  /// A broadcast stream that reports new OTP value as string on every [period]
+  /// interval
+  Stream<String> get streamString =>
+      _controller.stream.map((e) => e.toString().padLeft(digits, '0'));
+
   /// The current time in milliseconds since EPOCH with adjusted delta shift
   int get currentTime => DateTime.now().millisecondsSinceEpoch + _timeDelta;