Implemented email notifications

Author: brokenthorn

.editorconfig

@@ -1,6 +1,6 @@
 root = true
 
-[*.{cs,vb}]
+[*.*]
 tab_width = 2
 indent_size = 2
 indent_style = space

.gitignore

@@ -1,3 +1,6 @@
+# appsettings.json file used only during Development
+/appsettings.Development.json
+
 # Files created by app during run time:
 /*.log.txt
 /*.log.csv

Constants.cs

@@ -1,19 +1,19 @@
-namespace bt_sql_backup_service
+namespace BtSqlBackupService
 {
   public static class Constants
   {
     /// <summary>
-    /// Windows service name. Needs to be unique per system.
+    ///   Windows service name. Needs to be unique per system.
     /// </summary>
     public const string serviceName = "bt_sql_backup_service";
 
     /// <summary>
-    /// Windows service display name.
+    ///   Windows service display name.
     /// </summary>
     public const string displayName = "SQL Backup Service";
 
     /// <summary>
-    /// Windows service description field.
+    ///   Windows service description field.
     /// </summary>
     public const string description = "BrokenThorn's SQL Backup Service";
   }

Entities/Commands.cs

@@ -0,0 +1,53 @@
+namespace BtSqlBackupService.Entities
+{
+  /// <summary>
+  ///   A SQL command entity.
+  /// </summary>
+  /// <remarks>
+  ///   This entity holds information about a SQL command script, a Cron schedule
+  ///   and SQL Server connection string representing the server on which the
+  ///   command should be executed.
+  /// </remarks>
+  public class SqlCommandEntity
+  {
+    /// <summary>
+    ///   A short name for this command.
+    /// </summary>
+    /// <value></value>
+    public string Name { get; set; }
+
+    /// <summary>
+    ///   A description of what this command is or does.
+    /// </summary>
+    public string Description { get; set; }
+
+    /// <summary>
+    ///   Connection string for the SQL server that the command will be executed on.
+    /// </summary>
+    public string ConnectionString { get; set; }
+
+    /// <summary>
+    ///   SQL command to execute.
+    /// </summary>
+    public string SqlCommand { get; set; }
+
+    /// <summary>
+    ///   The number of seconds to wait before terminating the attempt to execute
+    ///   the SqlCommand and returning an error.
+    /// </summary>
+    /// <value>Timeout in seconds</value>
+    public int CommandTimeout { get; set; }
+
+    /// <summary>
+    ///   Schedule in cron syntax style.
+    /// </summary>
+    public string Cron { get; set; }
+
+    /// <summary>
+    ///   An email address or comma separated list of email addresses to send
+    ///   notifications to.
+    /// </summary>
+    /// <value></value>
+    public string NotifyEmails { get; set; }
+  }
+}

Entities/SmtpClientSettings.cs

@@ -0,0 +1,16 @@
+namespace BtSqlBackupService.Entities
+{
+  /// <summary>
+  ///   Settings for the SMTP mail client.
+  /// </summary>
+  public class SmtpClientSettings
+  {
+    public string Server { get; set; }
+    public int Port { get; set; }
+    public string SenderName { get; set; }
+    public string SenderEmail { get; set; }
+    public string Username { get; set; }
+    public string Password { get; set; }
+    public string AdminEmail { get; set; }
+  }
+}

Mailer.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Threading.Tasks;
+using BtSqlBackupService.Entities;
+using MailKit.Net.Smtp;
+using Microsoft.Extensions.Logging;
+using MimeKit;
+
+namespace BtSqlBackupService
+{
+  /// <summary>
+  ///   A simple electronic mail sender.
+  /// </summary>
+  public class Mailer
+  {
+    private readonly ILogger _logger;
+    private readonly SmtpClientSettings _smtpClientSettings;
+
+    public Mailer(SmtpClientSettings smtpClientSettings, ILogger logger)
+    {
+      _smtpClientSettings = smtpClientSettings;
+      _logger = logger;
+    }
+
+    /// <summary>
+    ///   Sends an email message with an HTML body.
+    /// </summary>
+    /// <param name="toEmailAddress">The email address of the receiver</param>
+    /// <param name="subject">The email's subject</param>
+    /// <param name="body">The HTML or text body of the emial</param>
+    /// <returns>A task for the completion of the command.</returns>
+    /// <exception cref="InvalidOperationException">
+    ///   Thrown when the underlying implementation throws any errors.
+    /// </exception>
+    public async Task SendEmailAsync(string toEmailAddress, string subject,
+      string body)
+    {
+      try
+      {
+        _logger.LogInformation(
+          $"Sending email to {toEmailAddress}, subject '{subject}'.");
+
+        var message = new MimeMessage();
+
+        message.Sender = new MailboxAddress(_smtpClientSettings.SenderName,
+          _smtpClientSettings.SenderEmail);
+
+        foreach (var address in toEmailAddress.Split(';'))
+        {
+          message.To.Add(MailboxAddress.Parse(address));
+        }
+
+        message.Subject = subject;
+        message.Body = new TextPart("html") {Text = body};
+
+        using (var client = new SmtpClient())
+        {
+          client.ServerCertificateValidationCallback = (s, c, h, e) => true;
+
+          await client.ConnectAsync(_smtpClientSettings.Server,
+            _smtpClientSettings.Port);
+          await client.AuthenticateAsync(_smtpClientSettings.Username,
+            _smtpClientSettings.Password);
+          await client.SendAsync(message);
+          await client.DisconnectAsync(true);
+          
+          _logger.LogInformation(
+            $"Email sent to {toEmailAddress}, subject '{subject}'.");
+        }
+      }
+      catch (Exception e)
+      {
+        _logger.LogError(
+          $"Failed to send email to {toEmailAddress}: {e.Message}");
+      }
+    }
+  }
+}