/// <summary>Each message sent to Realex should have a hash, attached. For a message using the remote
/// interface this is generated using the This is generated from the TIMESTAMP, MERCHANT_ID,
/// ORDER_ID, AMOUNT, and CURRENCY fields concatenated together with "." in between each field.
/// This confirms the message comes
/// from the client and
/// Generate a hash, required for all messages sent to IPS to prove it was not tampered with.
/// <p>
/// Hashing takes a string as input, and produce a fixed size number (160 bits for SHA-1 which
/// this implementation uses). This number is a hash of the input, and a small change in the
/// input results in a substantial change in the output. The functions are thought to be secure
/// in the sense that it requires an enormous amount of computing power and time to find a string
/// that hashes to the same value. In others words, there's no way to decrypt a secure hash.
/// Given the larger key size, this implementation uses SHA-1 which we prefer that you, but Realex
/// has retained compatibilty with MD5 hashing for compatibility with older systems.
/// <p>
/// <p>
/// To construct the hash for the remote interface follow this procedure:
///
/// To construct the hash for the remote interface follow this procedure:
/// Form a string by concatenating the above fields with a period ('.') in the following order
/// <p>
/// (TIMESTAMP.MERCHANT_ID.ORDER_ID.AMOUNT.CURRENCY)
/// <p>
/// Like so (where a field is empty an empty string "" is used):
/// <p>
/// (20120926112654.thestore.ORD453-11.29900.EUR)
/// <p>
/// Get the hash of this string (SHA-1 shown below).
/// <p>
/// (b3d51ca21db725f9c7f13f8aca9e0e2ec2f32502)
/// <p>
/// Create a new string by concatenating this string and your shared secret using a period.
/// <p>
/// (b3d51ca21db725f9c7f13f8aca9e0e2ec2f32502.mysecret )
/// <p>
/// Get the hash of this value. This is the value that you send to Realex Payments.
/// <p>
/// (3c3cac74f2b783598b99af6e43246529346d95d1)
///
/// This method takes the pre-built string of concatenated fields and the secret and returns the
/// SHA-1 hash to be placed in the request sent to Realex.
///
/// @param toHash
/// @param secret
/// @return the hash as a hex string
/// </summary>
/// <param name="toHash"></param>
/// <param name="secret"></param>
///<returns>string</returns>
public static string GenerateHash(string toHash, string secret = null, ShaHashType shaType = ShaHashType.SHA1)
{
if (toHash == null)
{
return(toHash);
}
string toHashFirstPass = shaType == ShaHashType.SHA1 ? DigestUtils.Sha1Hex(toHash, shaType) : DigestUtils.ShaHex(toHash, shaType);
if (secret != null)
{
string toHashSecondPass = new StringBuilder(toHashFirstPass).Append(".").Append(secret).ToString();
return(shaType == ShaHashType.SHA1 ? DigestUtils.Sha1Hex(toHashSecondPass, shaType): DigestUtils.ShaHex(toHashSecondPass, shaType));
}
return(toHashFirstPass);
}