mesa-fab-approval/MesaFabApproval.API/Services/SmtpService.cs

using System.Net.Mail;

using MesaFabApproval.API.Clients;
using MesaFabApproval.Models;

using Microsoft.IdentityModel.Tokens;

namespace MesaFabApproval.API.Services;

public interface ISmtpService {
    Task<bool> SendEmail(IEnumerable<MailAddress> recipients, IEnumerable<MailAddress> ccRecipients, string subject, string body);
}

public class SmtpService : ISmtpService {
    private readonly ILogger<SmtpService> _logger;
    private readonly ISmtpClientWrapper _smtpClient;
    private readonly bool _shouldSendEmail;

    public SmtpService(ILogger<SmtpService> logger, ISmtpClientWrapper smtpClient, AppSettings appSettings) {
        _logger = logger ??
            throw new ArgumentNullException("ILogger not injected");
        _smtpClient = smtpClient ??
            throw new ArgumentNullException("SmtpClient not injected");
        _shouldSendEmail = appSettings.ShouldSendEmail;
    }

    public async Task<bool> SendEmail(IEnumerable<MailAddress> recipients,
                                      IEnumerable<MailAddress> ccRecipients,
                                      string subject,
                                      string body) {
        if (recipients.IsNullOrEmpty()) throw new ArgumentNullException("recipients cannot be null or empty!");
        if (ccRecipients is null) throw new ArgumentNullException("ccRecipients cannot be null!");
        if (subject.IsNullOrEmpty()) throw new ArgumentNullException("subject cannot be null or empty!");
        if (body.IsNullOrEmpty()) throw new ArgumentNullException("body cannot be null or empty!");

        return await Task.Run(() => {
            int maxRetries = 3;
            int backoffSeconds = 30;

            bool messageWasSent = false;

            try {
                if (_shouldSendEmail) {
                    int remainingRetries = maxRetries;
                    while (!messageWasSent && remainingRetries > 0) {
                        try {
                            Task.Delay((maxRetries - remainingRetries--) * backoffSeconds * 1000);

                            _logger.LogInformation($"Attempting to send notification. Remaining retries: {remainingRetries}");

                            MailMessage msg = new MailMessage();
                            msg.IsBodyHtml = true;
                            msg.From = new MailAddress("MesaFabApproval@infineon.com", "Mesa Fab Approval");
                            msg.Sender = new MailAddress("MesaFabApproval@infineon.com", "Mesa Fab Approval");
                            foreach (MailAddress recipient in recipients) msg.To.Add(recipient);
                            msg.Bcc.Add("chase.tucker@infineon.com");
                            foreach (MailAddress ccRecipient in ccRecipients) msg.CC.Add(ccRecipient);
                            msg.Subject = subject;
                            msg.Body = body;

                            _smtpClient.Send(msg);

                            messageWasSent = true;
                        } catch (Exception ex) {
                            _logger.LogError($"Message not sent successfully. Exception: {ex.Message}");
                        }
                    }
                } else {
                    _logger.LogInformation("Not sending email per local configuration");
                    messageWasSent = true;
                }
            } catch (Exception ex) {
                _logger.LogError($"An exception occurred when attempting to send notification. Exception: {ex.Message}");
            }

            return messageWasSent;
        });
    }
}