Refactor TimeBasedOtp to be a wrapper around CounterBasedOtp.

1 files changed, 4 insertions, 38 deletions

diff --git a/OATH.Net/TimeBasedOtp.cs b/OATH.Net/TimeBasedOtp.cs
index 3fea09c..61e41c4 100644
--- a/OATH.Net/TimeBasedOtp.cs
+++ b/OATH.Net/TimeBasedOtp.cs
@@ -14,33 +14,16 @@ namespace OathNet
 
     public class TimeBasedOtp
     {
-        private static int[] digits = new int[]
-        { 
-            1,        // 0
-            10,       // 1
-            100,      // 2
-            1000,     // 3
-            10000,    // 4
-            100000,   // 5
-            1000000,  // 6
-            10000000, // 7
-            100000000 // 8
-        };
-
-        private byte[] secretKey;
-
-        private int otpLength;
+        private CounterBasedOtp counterOtp;
 
         public TimeBasedOtp(byte[] secretKey, int otpLength)
         {
-            this.secretKey = secretKey;
-            this.otpLength = otpLength;
+            this.counterOtp = new CounterBasedOtp(secretKey, otpLength);
         }
 
         public TimeBasedOtp(string secretKeyHex, int otpLength)
         {
-            this.secretKey = secretKeyHex.HexStringToByteArray();
-            this.otpLength = otpLength;
+            this.counterOtp = new CounterBasedOtp(secretKeyHex, otpLength);
         }
 
         public string ComputeOtp(DateTime time)
@@ -48,25 +31,8 @@ namespace OathNet
             var unixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
             var span = time.ToUniversalTime() - unixEpoch;
             var steps = (int)(span.TotalSeconds / 30);
-            var stepString = steps.ToString("X16");
-
-            var counter = stepString.HexStringToByteArray();
-
-            var hmac = new HMACSHA1(this.secretKey);
-            var hash = hmac.ComputeHash(counter);
-
-            int offset = hash[hash.Length - 1] & 0xF;
-
-            int binary = ((hash[offset] & 0x7F) << 24) |
-                         ((hash[offset + 1] & 0xFF) << 16) |
-                         ((hash[offset + 2] & 0xFF) << 8) |
-                         (hash[offset + 3] & 0xFF);
-
-            var otp = binary % TimeBasedOtp.digits[this.otpLength];
-
-            var result = otp.ToString("D" + this.otpLength.ToString());
 
-            return result;
+            return this.counterOtp.ComputeOtp(steps);
         }
     }
 }