Implement mail service with configuration and settings management

FoodsharingSiegen.Server/Service/MailService.cs

@@ -0,0 +1,57 @@
+using System.Threading.Tasks;
+using FoodsharingSiegen.Contracts.Model;
+using MailKit.Net.Smtp;
+using MailKit.Security;
+using Microsoft.Extensions.Options;
+using MimeKit;
+using MimeKit.Text;
+
+namespace FoodsharingSiegen.Server.Service
+{
+    /// <summary>
+    /// Default implementation of <see cref="IMailService"/> which sends emails via SMTP using MailKit.
+    /// </summary>
+    public class MailService : IMailService
+    {
+        private readonly MailSettings _mailSettings;
+        private readonly TermSettings _termSettings;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MailService"/> class.
+        /// </summary>
+        /// <param name="appSettings">The configured application settings injected by DI, containing the <see cref="MailSettings"/>.</param>
+        public MailService(IOptions<AppSettings> appSettings)
+        {
+            _mailSettings = appSettings.Value.Mail;
+            _termSettings = appSettings.Value.Terms;
+        }
+
+        /// <inheritdoc/>
+        public async Task SendEmailAsync(string toEmail, string subject, string htmlBody)
+        {
+            var email = new MimeMessage();
+            email.From.Add(new MailboxAddress(_termSettings.Title, _mailSettings.FromAddress));
+            email.To.Add(MailboxAddress.Parse(toEmail));
+            email.Subject = subject;
+            
+            var textPart = new TextPart(TextFormat.Html) 
+            { 
+                Text = htmlBody 
+            };
+            email.Body = textPart;
+
+            using var smtp = new SmtpClient();
+            var secureOptions = _mailSettings.UseSsl ? SecureSocketOptions.StartTls : SecureSocketOptions.Auto;
+            
+            await smtp.ConnectAsync(_mailSettings.Host, _mailSettings.Port, secureOptions);
+            
+            if (!string.IsNullOrWhiteSpace(_mailSettings.Username))
+            {
+                await smtp.AuthenticateAsync(_mailSettings.Username, _mailSettings.Password);
+            }
+            
+            await smtp.SendAsync(email);
+            await smtp.DisconnectAsync(true);
+        }
+    }
+}