ANTOOZA-BACKEND/Infrastructure/Messaging/Email/DirectMailService.cs

using Application.Abstractions.Cache;
using Application.Abstractions.Messaging.Email;
using Application.Features.Config.Get;
using Infrastructure.Persistence;
using SharedKernel;
using MailKit.Net.Smtp;
using MailKit.Security;
using MimeKit;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Infrastructure.Messaging.Email;

/// <summary>
/// SMTP 직접 발송. Admin 단에서만 사용. (API는 QueuedMailService로 큐잉)
/// </summary>
public class DirectMailService : IMailService
{
    private readonly ILogger<DirectMailService> _logger;
    private readonly ICacheService _cache;
    private readonly AppSettings.SmtpSection _smtp;
    private readonly AppDbContext _db;

    // SMTP 정보
    public string Host { get; set; } = default!;
    public int Port { get; set; } = 587;
    public string? User { get; set; }
    public string? Password { get; set; }
    public bool UseStartTls { get; set; } = true;
    public string FromEmail { get; set; } = default!;
    public string FromName { get; set; } = "no-reply";

    public DirectMailService(ILogger<DirectMailService> logger, ICacheService cache, IOptions<AppSettings> options, AppDbContext db)
    {
        _logger = logger;
        _cache = cache;
        _smtp = options.Value.SMTP;
        _db = db;
    }

    public async Task SendAsync(SendData data, CancellationToken ct = default)
    {
        _logger.LogInformation("Sending email to {ToAddress} with subject {Subject}", data.ToAddress, data.Subject);

        // 1. Redis 캐시에서 Config 조회
        var config = await _cache.GetAsync<Response>(CacheKeys.Config, ct);
        if (config is null)
        {
            var entity = await _db.Config.AsNoTracking().OrderByDescending(x => x.ID).FirstOrDefaultAsync();
            if (entity is null)
            {
                Host = _smtp.Host;
                Port = _smtp.Port;
                User = _smtp.User;
                Password = _smtp.Password;
                UseStartTls = _smtp.UseStartTls;
                FromEmail = _smtp.FromEmail;
                FromName = _smtp.FromName;
            }
            else
            {
                Host = entity.Basic.SmtpServer ?? "";
                Port = entity.Basic.SmtpPort ?? 587;
                UseStartTls = entity.Basic.SmtpEnableSSL;
                User = entity.Basic.SmtpUsername;
                Password = entity.Basic.SmtpPassword;
                FromEmail = entity.Basic.FromEmail ?? "";
                FromName = entity.Basic.FromName ?? "";
            }
        }
        else
        {
            Host = config.Basic.SmtpServer ?? _smtp.Host;
            Port = config.Basic.SmtpPort ?? _smtp.Port;
            UseStartTls = config.Basic.SmtpEnableSSL;
            User = config.Basic.SmtpUsername ?? _smtp.User;
            Password = config.Basic.SmtpPassword ?? _smtp.Password;
            FromEmail = config.Basic.FromEmail ?? _smtp.FromEmail;
            FromName = config.Basic.FromName ?? _smtp.FromName;
        }

        // FromEmail 의 도메인을 SMTP HELO/EHLO + Message-Id FQDN 으로 사용한다.
        // - 기본 hostname (예: "prod", "localhost") 으로 HELO 보내면 mail.dpot.dev rspamd 가 milter-reject (5.7.1).
        // - Message-Id 의 host part 가 FQDN 이 아니면 (예: <...@prod>) Gmail 등이 스팸함行 신호로 사용.
        var atIndex = FromEmail.IndexOf('@');
        var fromDomain = atIndex >= 0 && atIndex < FromEmail.Length - 1
            ? FromEmail[(atIndex + 1)..]
            : "dpot.dev";

        var message = new MimeMessage();
        message.From.Add(new MailboxAddress(FromName, FromEmail));
        message.To.Add(MailboxAddress.Parse(data.ToAddress));
        message.Subject = data.Subject;
        message.MessageId = MimeKit.Utils.MimeUtils.GenerateMessageId(fromDomain);

        var body = new BodyBuilder
        {
            HtmlBody = data.MessageHtml,
            TextBody = data.MessageText
        };

        message.Body = body.ToMessageBody();

        using var client = new SmtpClient
        {
            LocalDomain = fromDomain
        };
        var secure = Port == 465 ? SecureSocketOptions.SslOnConnect : UseStartTls ? SecureSocketOptions.StartTls : SecureSocketOptions.Auto;

        await client.ConnectAsync(Host, Port, secure, ct);

        if (!string.IsNullOrWhiteSpace(User))
        {
            await client.AuthenticateAsync(User, Password, ct);
        }

        await client.SendAsync(message, ct);
        await client.DisconnectAsync(true, ct);

        _logger.LogInformation("Email sent to {ToAddress} with subject {Subject}", data.ToAddress, data.Subject);
    }
}