using System;

using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Numerics;

namespace SampleSoftCert
{
    class Program
    {

        // Helper method to convert a hexadecimal string to a byte array
        private static byte[] HexStringToByteArray(string hex)
        {
            int length = hex.Length;
            byte[] bytes = new byte[length / 2];
            for (int i = 0; i < length; i += 2)
            {
                bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
            }
            return bytes;
        }

        static void Main(string[] args)
        {

            String PIN = "12345678";
            String softcertFile = "D:\\DEVELOPMENT\\DEV-WORKSPACE\\SampleSoftCert\\sample-co.p12";
            String dataToSign = "<xml>e-invoice data</xml>";

            // Load the .p12 file into an X509Certificate2 object
            X509Certificate2 certificate = new X509Certificate2(softcertFile, PIN);

            // Check if the certificate has a private key
            if (!certificate.HasPrivateKey)
            {
                Console.WriteLine("Certificate does not have a private key.");
                return;
            }

            // Get the private key from the certificate
            RSA privateKey = certificate.GetRSAPrivateKey();
            Console.WriteLine(certificate.Issuer);
            Console.WriteLine(certificate.SerialNumber);
            // Export the certificate to a byte array
            byte[] certBytes = certificate.Export(X509ContentType.Cert);

            // Convert the byte array to a Base64 string
            string certBase64 = Convert.ToBase64String(certBytes);

            // Display the Base64 encoded certificate
            Console.WriteLine("Base64 Encoded Certificate:");
            Console.WriteLine(certBase64);

            // Get the serial number as a hexadecimal string
            string serialNumberHex = certificate.SerialNumber;

            // Convert the hexadecimal string to a byte array
            byte[] serialNumberBytes = HexStringToByteArray(serialNumberHex);

            // Reverse the byte array to match the little-endian format
            Array.Reverse(serialNumberBytes);

            // Convert the byte array to a BigInteger
            BigInteger serialNumberBigInt = new BigInteger(serialNumberBytes);

            // Display the serial number as an integer
            Console.WriteLine("Serial Number (BigInteger): " + serialNumberBigInt);

            // Initialize the signature object
            using (RSA rsa = privateKey)
            {
                // Create an instance of the SHA256 hash algorithm
                using (SHA256 sha256 = SHA256.Create())
                {
                    // Compute the hash of the data
                    byte[] hash = sha256.ComputeHash(System.Text.Encoding.UTF8.GetBytes(dataToSign));

                    // Create an RSA signature formatter
                    RSAPKCS1SignatureFormatter rsaFormatter = new RSAPKCS1SignatureFormatter(rsa);
                    rsaFormatter.SetHashAlgorithm("SHA256");

                    // Create the signature
                    byte[] signature = rsaFormatter.CreateSignature(hash);

                    // Convert the signature to a base64 string for display
                    string signatureBase64 = Convert.ToBase64String(signature);

                    Console.WriteLine("Signature: " + signatureBase64);
                }
            }
        }
    }
}