Add SMTP email sender

OrderProcessing.EmailWorker/Configuration/EmailOptions.cs

@@ -0,0 +1,23 @@
+namespace OrderProcessing.EmailWorker.Configuration;
+
+public sealed class EmailOptions
+{
+    public const string SectionName = "Email";
+
+    public bool UseSmtp { get; set; }
+
+    public string Host { get; set; } = "smtp.gmail.com";
+
+    public int Port { get; set; } = 587;
+
+    public SmtpSecurityMode SecurityMode { get; set; } = SmtpSecurityMode.StartTls;
+
+    public string UserName { get; set; } = string.Empty;
+
+    public string Password { get; set; } = string.Empty;
+
+    public string FromAddress { get; set; } = string.Empty;
+
+    public string FromName { get; set; } =
+        "Order Processing Platform";
+}

OrderProcessing.EmailWorker/Configuration/SmtpSecurityMode.cs

@@ -0,0 +1,7 @@
+namespace OrderProcessing.EmailWorker.Configuration;
+
+public enum SmtpSecurityMode
+{
+    StartTls,
+    SslOnConnect
+}

OrderProcessing.EmailWorker/Emailing/SmtpEmailSender.cs

@@ -0,0 +1,65 @@
+using MailKit.Net.Smtp;
+using MailKit.Security;
+using Microsoft.Extensions.Options;
+using MimeKit;
+using OrderProcessing.EmailWorker.Configuration;
+
+namespace OrderProcessing.EmailWorker.Emailing;
+
+public sealed class SmtpEmailSender : IEmailSender
+{
+    private readonly EmailOptions _options;
+    private readonly ILogger<SmtpEmailSender> _logger;
+
+    public SmtpEmailSender(IOptions<EmailOptions> options, ILogger<SmtpEmailSender> logger)
+    {
+        _options = options.Value;
+        _logger = logger;
+    }
+
+    public async Task SendAsync(EmailMessage message, CancellationToken cancellationToken)
+    {
+        var mimeMessage = new MimeMessage();
+
+        mimeMessage.From.Add(new MailboxAddress(_options.FromName, _options.FromAddress));
+
+        mimeMessage.To.Add(MailboxAddress.Parse(message.Recipient));
+
+        mimeMessage.Subject = message.Subject;
+
+        mimeMessage.Body = new TextPart("plain")
+        {
+            Text = message.Body
+        };
+
+        using var smtpClient = new MailKit.Net.Smtp.SmtpClient();
+
+        var socketOptions = GetSecureSocketOptions();
+
+        await smtpClient.ConnectAsync(_options.Host, _options.Port, socketOptions, cancellationToken);
+
+        await smtpClient.AuthenticateAsync(_options.UserName, _options.Password, cancellationToken);
+
+        await smtpClient.SendAsync(mimeMessage, cancellationToken);
+
+        await smtpClient.DisconnectAsync(quit: true, cancellationToken);
+
+        _logger.LogInformation(
+            "Email sent successfully to {Recipient} " +
+            "with subject {Subject}",
+            message.Recipient,
+            message.Subject);
+    }
+
+    private SecureSocketOptions GetSecureSocketOptions()
+    {
+        return _options.SecurityMode switch
+        {
+            SmtpSecurityMode.StartTls => SecureSocketOptions.StartTls,
+
+            SmtpSecurityMode.SslOnConnect => SecureSocketOptions.SslOnConnect,
+
+            _ => throw new InvalidOperationException($"Unsupported SMTP security mode '{_options.SecurityMode}'.")
+        };
+    }
+}

OrderProcessing.EmailWorker/OrderProcessing.EmailWorker.csproj

@@ -8,12 +8,14 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="MailKit" Version="4.17.0" />
     <PackageReference Include="Microsoft.EntityFrameworkCore" Version="10.0.9" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="10.0.9">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="10.0.9" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.UserSecrets" Version="10.0.10" />
     <PackageReference Include="Microsoft.Extensions.Hosting" Version="10.0.9" />
     <PackageReference Include="RabbitMQ.Client" Version="7.2.2" />
   </ItemGroup>

OrderProcessing.EmailWorker/Program.cs

@@ -54,8 +54,32 @@
         "RabbitMQ prefetch count must be greater than zero.")
     .ValidateOnStart();
 
+builder.Services
+    .AddOptions<EmailOptions>()
+    .Bind(builder.Configuration.GetSection(EmailOptions.SectionName))
+    .Validate(
+        options => !options.UseSmtp ||!string.IsNullOrWhiteSpace(options.Host), "SMTP host is required.")
+    .Validate(
+        options => !options.UseSmtp || options.Port > 0, "SMTP port must be greater than zero.")
+    .Validate(
+        options => !options.UseSmtp || !string.IsNullOrWhiteSpace(options.UserName), "SMTP username is required.")
+    .Validate(
+        options => !options.UseSmtp || !string.IsNullOrWhiteSpace(options.Password), "SMTP password is required.")
+    .Validate(
+        options => !options.UseSmtp || !string.IsNullOrWhiteSpace(options.FromAddress), "SMTP from address is required.")
+    .ValidateOnStart();
+
+
+var useSmtp = builder.Configuration.GetSection(EmailOptions.SectionName).GetValue<bool>(nameof(EmailOptions.UseSmtp));
 
-builder.Services.AddSingleton<IEmailSender, LoggingEmailSender>();
+if (useSmtp)
+{
+    builder.Services.AddSingleton<IEmailSender, SmtpEmailSender>();
+}
+else
+{
+    builder.Services.AddSingleton<IEmailSender, LoggingEmailSender>();
+}
 
 builder.Services.AddScoped<OrderEventEmailHandler>();
 

OrderProcessing.EmailWorker/appsettings.Development.json

@@ -4,5 +4,8 @@
       "Default": "Information",
       "Microsoft.Hosting.Lifetime": "Information"
     }
+  },
+  "Email": {
+    "UseSmtp": true
   }
 }

OrderProcessing.EmailWorker/appsettings.json

@@ -23,6 +23,16 @@
     "NetworkRecoveryIntervalSeconds": 5,
     "PrefetchCount": 1
   },
+  "Email": {
+    "UseSmtp": false,
+    "Host": "smtp.gmail.com",
+    "Port": 587,
+    "SecurityMode": "StartTls",
+    "UserName": "",
+    "Password": "",
+    "FromAddress": "",
+    "FromName": "Order Processing Platform"
+  },
   "ConnectionStrings": {
     "EmailWorkerConnection": "Server=(localdb)\\mssqllocaldb;Database=OrderProcessingDb;Trusted_Connection=True;TrustServerCertificate=True;"
   }