btcpayserver/BTCPayServer/Payments/Changelly/Changelly.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using BTCPayServer.Payments.Changelly.Models;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using SshNet.Security.Cryptography;

namespace BTCPayServer.Payments.Changelly
{
    public class Changelly
    {
        private readonly string _apisecret;
        private readonly bool _showFiat;
        private readonly HttpClient _httpClient;

        public Changelly(IHttpClientFactory httpClientFactory,  string apiKey, string apiSecret, string apiUrl, bool showFiat = true)
        {
            _apisecret = apiSecret;
            _showFiat = showFiat;
            _httpClient = httpClientFactory.CreateClient();
            _httpClient.BaseAddress = new Uri(apiUrl);
            _httpClient.DefaultRequestHeaders.Add("api-key", apiKey);
        }


        private static string ToHexString(byte[] array)
        {
            var hex = new StringBuilder(array.Length * 2);
            foreach (var b in array)
            {
                hex.AppendFormat("{0:x2}", b);
            }

            return hex.ToString();
        }

        private async Task<ChangellyResponse<T>> PostToApi<T>(string message)
        {
                var hmac = new HMACSHA512(Encoding.UTF8.GetBytes(_apisecret));
                var hashMessage = hmac.ComputeHash(Encoding.UTF8.GetBytes(message));
                var sign = ToHexString(hashMessage);

                var request = new HttpRequestMessage(HttpMethod.Post, "");
                request.Headers.Add("sign", sign);
                request.Content = new StringContent(message, Encoding.UTF8, "application/json");

                var result = await _httpClient.SendAsync(request);

                if (!result.IsSuccessStatusCode)
                    throw new ChangellyException(result.ReasonPhrase);
                var content =
                    await result.Content.ReadAsStringAsync();
                return JObject.Parse(content).ToObject<ChangellyResponse<T>>();
            
        }

        public virtual async Task<IEnumerable<CurrencyFull>> GetCurrenciesFull()
        {
                const string message = @"{
		            ""jsonrpc"": ""2.0"",
		            ""id"": 1,
		            ""method"": ""getCurrenciesFull"",
		            ""params"": []
			    }";

                var result = await PostToApi<IEnumerable<CurrencyFull>>(message);
                var appendedResult = _showFiat
                    ? result.Result.Concat(new[]
                    {
                        new CurrencyFull()
                        {
                            Enable = true,
                            Name = "EUR",
                            FullName = "Euro",
                            PayInConfirmations = 0,
                            ImageLink = "https://changelly.com/api/coins/eur.png"
                        },
                        new CurrencyFull()
                        {
                            Enable = true,
                            Name = "USD",
                            FullName = "US Dollar",
                            PayInConfirmations = 0,
                            ImageLink = "https://changelly.com/api/coins/usd.png"
                        }
                    })
                    : result.Result;
            return appendedResult;
        }

        public virtual async Task<decimal> GetExchangeAmount(string fromCurrency,
            string toCurrency,
            decimal amount)
        {
                var message =
                    $"{{\"id\": \"test\",\"jsonrpc\": \"2.0\",\"method\": \"getExchangeAmount\",\"params\":{{\"from\": \"{fromCurrency}\",\"to\": \"{toCurrency}\",\"amount\": \"{amount}\"}}}}";

                var result = await PostToApi<string>(message);

            return Convert.ToDecimal(result.Result);
        }
    }
}