hrynco-notification-service/HrynCo.NotificationService.Services/EmailChannels/Send/SendEmailHandler.cs

using System.Net;
using System.Net.Mail;
using HrynCo.NotificationService.DAL.Abstract;
using HrynCo.NotificationService.DAL.Abstract.Providers;
using HrynCo.NotificationService.DAL.Abstract.Repositories;
using HrynCo.NotificationService.Services.Core;
using HrynCo.NotificationService.Services.Logging;
using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;

namespace HrynCo.NotificationService.Services.EmailChannels.Send;

internal sealed class SendEmailHandler
    : RequestHandler<SendEmailCommand, ServiceResult<Core.Unit>>
{
    private readonly IEmailChannelRepository _channels;
    private readonly IEmailChannelUsageRepository _usage;

    public SendEmailHandler(
        IContextualSerilogLogger<SendEmailCommand> logger,
        IUnitOfWork unitOfWork,
        IEmailChannelRepository channels,
        IEmailChannelUsageRepository usage)
        : base(logger, unitOfWork)
    {
        _channels = channels;
        _usage = usage;
    }

    protected override async Task<ServiceResult<Core.Unit>> DoOnHandle(
        SendEmailCommand request, CancellationToken cancellationToken)
    {
        var channel = await _channels.GetByIdAsync(request.ChannelId, cancellationToken);
        if (channel is null)
            return Failure<Core.Unit>($"Channel '{request.ChannelId}' not found.");

        if (channel.Settings is not SmtpChannelSettings smtp)
            return Failure<Core.Unit>($"Channel type '{channel.EmailChannelType}' is not supported for sending.");

        try
        {
            using var client = new SmtpClient(smtp.Host, smtp.Port)
            {
                EnableSsl = smtp.UseSsl,
                Credentials = string.IsNullOrWhiteSpace(smtp.Username)
                    ? null
                    : new NetworkCredential(smtp.Username, smtp.Password)
            };

            using var mail = new MailMessage
            {
                From = new MailAddress(smtp.FromEmail, smtp.FromName),
                Subject = request.Subject,
                Body = request.HtmlBody,
                IsBodyHtml = true
            };

            if (!string.IsNullOrWhiteSpace(request.TextBody))
            {
                var plain = AlternateView.CreateAlternateViewFromString(request.TextBody, null, "text/plain");
                mail.AlternateViews.Add(plain);
            }

            mail.To.Add(new MailAddress(request.RecipientEmail, request.RecipientName));

            await client.SendMailAsync(mail, cancellationToken);
        }
        catch (Exception ex)
        {
            Logger.Error(ex, "SMTP send failed for channel {ChannelId}", request.ChannelId);
            return Failure<Core.Unit>(ex.Message);
        }

        await _usage.IncrementUsageAsync(
            request.ChannelId,
            DateOnly.FromDateTime(DateTime.UtcNow),
            cancellationToken);

        return Success(Unit.Value);
    }
}