using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.OpenSsl;
using Org.BouncyCastle.Security;
using RestEase;

namespace ePaymentsApiConsoleApp
{
    /// <summary>
    /// The example shows how to send request to ePayments api using signing by .pem certificate
    /// </summary>
    public class Program
    {
        // Init constants        

        // KeyId
        private const string KeyId = "KeyId";
        
        // .pem extension certificate file path
        private const string Pem = "PemCertificateFilePath.pem";
        
        // ePayments api url
        private const string Api = "https://api.sandbox.epayments.com/";

        /// <summary>
        /// Main method
        /// </summary>
        /// <param name="args"></param>
        /// <returns></returns>
        static async Task Main(string[] args)
        {
            await FetchTransactions();
            await FetchUserAsync();
        }

        /// <summary>
        /// Example request
        /// The method returns Transaction list using signing by a .pem certificate
        /// In case if body is not empty, api.Signature field should take the signature of body request by .pem certificate
        /// </summary>
        /// <returns></returns>
        public static async Task FetchTransactions()
        {
            var transactionListRequest = new TransactionListRequest()
            {
                From = 1, Take = 10
            };

            var body = JsonConvert.SerializeObject(transactionListRequest);
            
            var api = RestClient.For<IApi>(Api);
            api.Signature = SignBy(body, Pem);
            api.KeyId = KeyId;
            api.UserAgent = $".net {Environment.Version}";
            var transactions = await api.FetchTransactions(transactionListRequest);
        }

        /// <summary>
        /// Example request
        /// The method returns user information using signing by a .pem certificate
        /// In case if body is empty, api.Signature field should take the signature of request url by .pem certificate 
        /// </summary>
        /// <returns></returns>
        public static async Task FetchUserAsync()
        {
            var api = RestClient.For<IApi>(Api);
            api.Signature = SignBy($"{Api}v1/user", Pem);
            api.KeyId = KeyId;
            var user = await api.FetchUserAsync();
        }


        /// <summary>
        /// Make a sign of the message by .pem certificate
        /// </summary>
        /// <returns></returns>
        private static string SignBy(string message, string pem)
        {
            var pr = new PemReader(new StringReader(File.ReadAllText(pem)));
            var keyPair = (AsymmetricCipherKeyPair)pr.ReadObject();
            var rsaParams = DotNetUtilities.ToRSAParameters((RsaPrivateCrtKeyParameters)keyPair.Private);

            using(var csp = new RSACryptoServiceProvider())
            {
                csp.ImportParameters(rsaParams);
                var bytes = Encoding.UTF8.GetBytes(message);
                var inArray = csp.SignData(bytes, (object) CryptoConfig.MapNameToOID("SHA512"));
                return Convert.ToBase64String(inArray);
            }
        }
    }
    
    /// <summary>
    /// Api interface for RestClient
    /// </summary>
    public interface IApi
    {
        [Header("user-agent")]
        string UserAgent { get; set; }
        
        [Header("X-Signature")]
        string Signature { get; set; }
        
        [Header("X-Key-Id")]
        string KeyId { get; set; }
        
        [Get("v1/user")]
        Task<dynamic> FetchUserAsync();

        [Post("v3/Transactions")]
        Task<TransactionResponse> FetchTransactions([Body] TransactionListRequest request);
    }

    /// <summary>
    /// TrasactionResponse model
    /// </summary>
    public class TransactionResponse
    {
        public TransactionItem[] Transactions { get; set; }
        
        public class TransactionItem
        {
            public string OperationId { get; set; }
            
            // ...
        }
    }
    
    /// <summary>
    /// TransactionListRequest model
    /// </summary>
    public class TransactionListRequest 
    {
        public int Take { get; set; }
        public int From { get; set; }
       
        // ...
    }

}