class ExchangeServerReminderService : IMailServerReminderService
    {
        readonly Logger logger = LogManager.GetCurrentClassLogger();
        readonly ExchangeService exchangeService;
        readonly IBus bus;
        private readonly string recruitmentGroupEmail;

        public ExchangeServerReminderService(string exchangeAuthUsername,
           string exchangeAuthPassword,
           string autodiscoverUrl,
           string recruitmentGroupEmail,
           IBus bus)
        {
            if (String.IsNullOrWhiteSpace(exchangeAuthUsername))
                throw new ArgumentNullException("exchangeAuthUsername");
            if (String.IsNullOrWhiteSpace(exchangeAuthPassword))
                throw new ArgumentNullException("exchangeAuthPassword");
            if (String.IsNullOrWhiteSpace(autodiscoverUrl))
                throw new ArgumentNullException("autodiscoverUrl");

            if (String.IsNullOrWhiteSpace(recruitmentGroupEmail))
                throw new ArgumentNullException("recruitmentGroupEmail");
            if (bus == null)
                throw new ArgumentNullException("bus");

            this.bus = bus;
            this.recruitmentGroupEmail = recruitmentGroupEmail;
            exchangeService = new ExchangeService(ExchangeVersion.Exchange2013_SP1);
            exchangeService.Credentials = new WebCredentials(exchangeAuthUsername, exchangeAuthPassword);
            exchangeService.AutodiscoverUrl(autodiscoverUrl, url => true);
        }

        public ExchangeServerReminderService(string exchangeAuthUsername,
            string exchangeAuthPassword,
            string recruitmentGroupEmail,
            IBus bus)
        {
            if (String.IsNullOrWhiteSpace(exchangeAuthUsername))
                throw new ArgumentNullException("exchangeAuthUsername");
            if (String.IsNullOrWhiteSpace(exchangeAuthPassword))
                throw new ArgumentNullException("exchangeAuthPassword");

            if (String.IsNullOrWhiteSpace(recruitmentGroupEmail))
                throw new ArgumentNullException("recruitmentGroupEmail");
            if (bus == null)
                throw new ArgumentNullException("bus");

            this.bus = bus;
            this.recruitmentGroupEmail = recruitmentGroupEmail;
            exchangeService = new ExchangeService(ExchangeVersion.Exchange2013_SP1);
            exchangeService.Credentials = new WebCredentials(exchangeAuthUsername, exchangeAuthPassword);
            exchangeService.AutodiscoverUrl(exchangeAuthUsername, url => true);
        }


        public string CreateOrUpdateAppointment(string subject, string body, DateTime startTime, string exchangeServerAppointmentId, DateTime eventDate, DateTime remindAt, IEnumerable<Document> cv)
        {
            if (String.IsNullOrWhiteSpace(subject))
                throw new ArgumentNullException("subject");
            if (String.IsNullOrWhiteSpace(body))
                throw new ArgumentNullException("body");
            if (startTime == default(DateTime))
                throw new ArgumentException("startTime");

            Appointment appointment;
            try
            {
                appointment = Appointment.Bind(exchangeService, exchangeServerAppointmentId);
                appointment.Subject = subject;
                appointment.Resources.Clear();
                appointment.Body = body;
                appointment.Body.BodyType = BodyType.HTML;
                appointment.Start = startTime;
                appointment.End = startTime;
                appointment.ReminderMinutesBeforeStart = (int)(eventDate - remindAt).TotalMinutes;
                appointment.RequiredAttendees.Clear();
                appointment.RequiredAttendees.Add(recruitmentGroupEmail);
                appointment.Attachments.Clear();
                foreach (var attachment in cv)
                {
                    appointment.Attachments.AddFileAttachment(attachment.Name + attachment.Extension, attachment.Content);
                }
                appointment.Update(ConflictResolutionMode.AlwaysOverwrite, SendInvitationsOrCancellationsMode.SendOnlyToAll);
                return appointment.Id.UniqueId;

            }
            catch (Exception e)
            {
                using (var principalContext = new PrincipalContext(ContextType.Domain, Environment.UserDomainName))
                {
                    var up = UserPrincipal.FindByIdentity(principalContext, HttpContext.Current.User.Identity.Name);
                    //appointment not found
                    appointment = new Appointment(exchangeService)
                    {
                        Subject = subject,
                        Body = body
                    };
                    appointment.Body.BodyType = BodyType.HTML;
                    appointment.Start = startTime;
                    appointment.End = startTime;
                    appointment.RequiredAttendees.Add(recruitmentGroupEmail);
                    appointment.ReminderMinutesBeforeStart = (int)(eventDate - remindAt).TotalMinutes;
                    appointment.Importance = Importance.High;
                    foreach (var attachment in cv)
                    {
                        appointment.Attachments.AddFileAttachment(attachment.Name + attachment.Extension, attachment.Content);
                    }

                    appointment.Save(new FolderId(WellKnownFolderName.Calendar, up.EmailAddress), SendInvitationsMode.SendOnlyToAll);

                    return appointment.Id.UniqueId;
                }
            }


        }
    }
}