MailgunSender.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using FluentEmail.Core;
using FluentEmail.Core.Interfaces;
using FluentEmail.Core.Models;
using FluentEmail.Mailgun.HttpHelpers;

namespace FluentEmail.Mailgun
{
    public class MailgunSender : ISender
    {
        private readonly string _apiKey;
        private readonly string _domainName;
        private HttpClient _httpClient;

        public MailgunSender(string domainName, string apiKey, MailGunRegion mailGunRegion = MailGunRegion.USA)
        {
            _domainName = domainName;
            _apiKey = apiKey;
            string url = string.Empty;
            switch(mailGunRegion)
            {
                case MailGunRegion.USA:
                    url = $"https://api.mailgun.net/v3/{_domainName}/";
                    break;
                case MailGunRegion.EU:
                    url = $"https://api.eu.mailgun.net/v3/{_domainName}/";
                    break;

                default:
                    throw new ArgumentException($"'{mailGunRegion}' is not a valid value for {nameof(mailGunRegion)}");
            }
            _httpClient = new HttpClient
            {
                BaseAddress = new Uri(url)
            };

            _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(Encoding.ASCII.GetBytes($"api:{_apiKey}")));
        }

        public SendResponse Send(IFluentEmail email, CancellationToken? token = null)
        {
            return SendAsync(email, token).GetAwaiter().GetResult();
        }

        public async Task<SendResponse> SendAsync(IFluentEmail email, CancellationToken? token = null)
        {
            var parameters = new List<KeyValuePair<string, string>>();

            parameters.Add(new KeyValuePair<string, string>("from", $"{email.Data.FromAddress.Name} <{email.Data.FromAddress.EmailAddress}>"));
            email.Data.ToAddresses.ForEach(x => {
                parameters.Add(new KeyValuePair<string, string>("to", $"{x.Name} <{x.EmailAddress}>"));
            });
            email.Data.CcAddresses.ForEach(x => {
                parameters.Add(new KeyValuePair<string, string>("cc", $"{x.Name} <{x.EmailAddress}>"));
            });
            email.Data.BccAddresses.ForEach(x => {
                parameters.Add(new KeyValuePair<string, string>("bcc", $"{x.Name} <{x.EmailAddress}>"));
            });
            email.Data.ReplyToAddresses.ForEach(x => {
                parameters.Add(new KeyValuePair<string, string>("h:Reply-To", $"{x.Name} <{x.EmailAddress}>"));
            });
            parameters.Add(new KeyValuePair<string, string>("subject", email.Data.Subject));

            parameters.Add(new KeyValuePair<string, string>(email.Data.IsHtml ? "html" : "text", email.Data.Body));

            if (!string.IsNullOrEmpty(email.Data.PlaintextAlternativeBody))
            {
                parameters.Add(new KeyValuePair<string, string>("text", email.Data.PlaintextAlternativeBody));
            }

            email.Data.Tags.ForEach(x =>
            {
                parameters.Add(new KeyValuePair<string, string>("o:tag", x));
            });

            foreach (var emailHeader in email.Data.Headers)
            {
                var key = emailHeader.Key;
                if (!key.StartsWith("h:"))
                {
                    key = "h:" + emailHeader.Key;
                }

                parameters.Add(new KeyValuePair<string, string>(key, emailHeader.Value));
            }

            var files = new List<HttpFile>();
            email.Data.Attachments.ForEach(x =>
            {
                string param;

                if (x.IsInline)
                    param = "inline";
                else
                    param = "attachment";

                files.Add(new HttpFile
                {
                    ParameterName = param,
                    Data = x.Data,
                    Filename = x.Filename,
                    ContentType = x.ContentType
                });
            });

            var response = await _httpClient.PostMultipart<MailgunResponse>("messages", parameters, files).ConfigureAwait(false);

            var result = new SendResponse {MessageId = response.Data?.Id};
            if (!response.Success)
            {
                result.ErrorMessages.AddRange(response.Errors.Select(x => x.ErrorMessage));
                return result;
            }

            return result;
        }
    }
}