novaloop.paymoapi/src/Extensions/HttpClientExtensions.cs

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

namespace Novaloop.PaymoApi.Extensions
{
    internal static class HttpClientExtensions
    {
        internal static void SetApiKeyHeader(this HttpClient client, string apiKey)
        {
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Base64Encode($"{apiKey}:random"));
        }

        internal static async Task<HttpResponseMessage> PatchAsync(this HttpClient client, string uri, HttpContent content)
        {
            var method = new HttpMethod("PATCH");
            if (client.BaseAddress is null)
            {
                throw new ArgumentException("Can not handle 'BaseAddress' null value configuration.");
            }

            var request = new HttpRequestMessage(method, new Uri(CombineBaseUrlWithSegment(client.BaseAddress.ToString(), uri))) {Content = content};
            return await client.SendAsync(request);
        }

        private static string CombineBaseUrlWithSegment(string uri1, string uri2)
        {
            return $"{uri1.TrimEnd('/')}/{uri2.TrimStart('/')}";
        }

        private static string Base64Encode(string plainText)
        {
            return Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(plainText));
        }
    }
}