(Swift 3,4,5...) Payeezy HMAC Computation

Demonstrates how to calculate the HMAC for a Payeezy REST request.

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let crypt = CkoCrypt2()!
    let prng = CkoPrng()!
    var success: Bool

    // An API key such as y6pWAJNyJyjGv66IsVuWnklkKUPFbb0a
    var apiKey: String? = "my_api_key"
    // An API secret such as 86fbae7030253af3cd15faef2a1f4b67353e41fb6799f576b5093ae52901e6f7
    var apiSecret: String? = "my_api_secret"
    // A token such as fdoa-a480ce8951daa73262734cf102641994c1e55e7cdf4c02b6
    var token: String? = "my_merchant_token"

    // The nonce is a random number (bytes), something like "6057786719490086000"
    var nonce: String? = prng.genRandom(8, encoding: "decimal")
    print("nonce = \(nonce!)")

    let dtNow = CkoDateTime()!
    dtNow.setFromCurrentSystemTime()
    let sbTimestamp = CkoStringBuilder()!
    // Get the epoch timestamp in seconds
    sbTimestamp.append(dtNow.getAsUnixTimeStr(false))
    // Change it to milliseconds
    sbTimestamp.append("000")
    // The timestamp is a number similar to this: 1546011905000 (which is a timestamp taken on 28-Dec-2018).
    var timestamp: String? = sbTimestamp.getAsString()
    print("timestamp = \(timestamp!)")

    // Generate the following JSON request body:
    // 	{
    // 	  "merchant_ref": "Astonishing-Sale",
    // 	  "transaction_type": "authorize",
    // 	  "method": "token",
    // 	  "amount": "200",
    // 	  "currency_code": "USD",
    // 	  "token": {
    // 	    "token_type": "FDToken",
    // 	    "token_data": {
    // 	      "type": "visa",
    // 	      "value": "2537446225198291",
    // 	      "cardholder_name": "JohnSmith",
    // 	      "exp_date": "1030",
    // 	      "special_payment": "B"
    // 	    }
    // 	  }
    // 	}

    let json = CkoJsonObject()!
    json.update("merchant_ref", value: "Astonishing-Sale")
    json.update("transaction_type", value: "authorize")
    json.update("method", value: "token")
    json.update("amount", value: "200")
    json.update("currency_code", value: "USD")
    json.update("token.token_type", value: "FDToken")
    json.update("token.token_data.type", value: "visa")
    json.update("token.token_data.value", value: "2537446225198291")
    json.update("token.token_data.cardholder_name", value: "JohnSmith")
    json.update("token.token_data.exp_date", value: "1030")
    json.update("token.token_data.special_payment", value: "B")

    // string hashData = apiKey + nonce + timestamp + token + jsonString;
    let sbHmacData = CkoStringBuilder()!
    sbHmacData.append(apiKey)
    sbHmacData.append(nonce)
    sbHmacData.append(timestamp)
    sbHmacData.append(token)
    sbHmacData.append(json.emit())

    // HMAC the data to produce a hex string.
    crypt.encodingMode = "hexlower"
    crypt.macAlgorithm = "hmac"
    crypt.setMacKeyString(apiSecret)
    crypt.hashAlgorithm = "sha256"
    crypt.charset = "utf-8"
    var hexHash: String? = crypt.macStringENC(sbHmacData.getAsString())

    // Now base64 encode the hex string:
    let sbBase64Hash = CkoStringBuilder()!
    sbBase64Hash.append(hexHash)
    sbBase64Hash.encode("base64", charset: "utf-8")

    print("This is the Authorization header to be sent with the payeezy request:")
    print("Authorization: \(sbBase64Hash.getAsString()!)")

}