Add template support for email notifications

src/DNS-BLM.Api/Controllers/DnsBlocklistScanController.cs

@@ -18,7 +18,7 @@ public async Task<string> ScanConfiguredDomains()
 
         if (domains == null) throw new Exception("Domains not found");
 
-        return await mediator.Send(new ScanBlacklistCommand(domains, false));
+        return await mediator.Send(new ScanBlacklistCommand(domains));
     }
 
     // [HttpGet("ScanCustomDomain", Name = "ScanCustomDomain")]

src/DNS-BLM.Application/Commands/ScanBlacklistCommand.cs

@@ -31,15 +31,14 @@ public async Task<string> Handle(ScanBlacklistCommand request, CancellationToken
             var results = messageService.GetResults();
             messageService.Clear();
 
-            if (request.SendMail && results is not null)
+            if (request.SendMail && !string.IsNullOrWhiteSpace(results))
             {
                 await notificationService.Notify("DNS-BLM Scanning Results", results);
             }
             else
             {
                 if (results is null)
                     results = "No blacklisted Domains.";
-                logger.LogInformation("Mail notification skipped as per request");
             }
 
             return results;

src/DNS-BLM.Domain/Configuration/MailConfiguration.cs

@@ -22,4 +22,6 @@ public class MailConfiguration
 
     [Required]
     public bool EnableSsl { get; init; } = true;
+    public string MailTemplate { get; init; } = string.Empty;
+
 }

src/DNS-BLM.Infrastructure/DNS-BLM.Infrastructure.csproj

@@ -8,6 +8,7 @@
     </PropertyGroup>
 
     <ItemGroup>
+      <PackageReference Include="Handlebars.Net" Version="2.1.6" />
       <PackageReference Include="MailKit" Version="4.12.1" />
       <PackageReference Include="Sentry.AspNetCore" Version="5.10.0" />
     </ItemGroup>

src/DNS-BLM.Infrastructure/ModuleRegistry.cs

@@ -15,6 +15,7 @@ public static void AddInfrastructureModule(this IServiceCollection services, App
         services.AddSingleton<INotificationService, MailNotificationService>();
         services.AddScoped<MessageService>();
         services.AddSingleton<RetryService>();
+        services.AddSingleton<TemplateService>();
 
         string? virusTotalApiKey = appConfiguration.ApiCredentials.VirusTotal;
 

src/DNS-BLM.Infrastructure/Services/MessageService.cs

@@ -1,10 +1,12 @@
 using System.Collections.Concurrent;
+using DNS_BLM.Domain.Configuration;
 using DNS_BLM.Infrastructure.Dtos;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
 
 namespace DNS_BLM.Infrastructure.Services;
 
-public class MessageService(ILogger<MessageService> logger)
+public class MessageService(ILogger<MessageService> logger, TemplateService templateService, IOptions<AppConfiguration> appConfiguration)
 {
     private ConcurrentBag<ScanResult> _results = [];
     private HashSet<string> _domains = [];
@@ -34,21 +36,9 @@ public void AddResult(ScanResult result)
         {
             logger.LogDebug($"{result.Domain}: {result.ScannerName} - {result.IsBlacklisted}");
         }
-
-        List<string> allResults = new List<string>();
-        foreach (var domain in _domains)
-        {
-            var domainResults = _results.Where(r => r.Domain == domain && r.IsBlacklisted).ToArray();
-            var result = ArrangeResults(domainResults);
-            if (result == null) continue;
-            allResults.Add(result);
-        }
-
-        var results = string.Join(Environment.NewLine, allResults);
-        if (String.IsNullOrWhiteSpace(results))
-            logger.LogError("No results available to return, despite passing previous checks!");
-        ArgumentException.ThrowIfNullOrWhiteSpace(results, nameof(results));
 
+        var domainResults = _results.Where(r => r.IsBlacklisted).ToArray();
+        var results = templateService.RenderTemplate(domainResults.ToList(), appConfiguration.Value.Mail.MailTemplate);
         return results;
     }
 

src/DNS-BLM.Infrastructure/Services/NotificationServices/MailNotificationService.cs

@@ -31,7 +31,7 @@ public async Task Notify(string subject, string message)
                 mailMessage.Subject = subject;
 
                 var builder = new BodyBuilder ();
-                builder.HtmlBody = message.Replace("\n", "<br/>");
+                builder.HtmlBody = message;
 
                 mailMessage.Body = builder.ToMessageBody();
 

src/DNS-BLM.Infrastructure/Services/TemplateService.cs

@@ -0,0 +1,97 @@
+using System.Collections.Concurrent;
+using DNS_BLM.Infrastructure.Dtos;
+using HandlebarsDotNet;
+using Microsoft.Extensions.Logging;
+
+namespace DNS_BLM.Infrastructure.Services;
+
+public class TemplateService() // ILogger<TemplateService> logger
+{
+    private readonly ConcurrentDictionary<string, HandlebarsTemplate<object, object>> _compiledTemplates = new();
+
+    public string RenderTemplate(List<ScanResult> model, string? template = null)
+    {
+        string defaultTemplate =
+            """
+            <!DOCTYPE html>
+            <html lang="en">
+            <head>
+              <meta charset="UTF-8" />
+              <title>DNS-BLM Results</title>
+            </head>
+            <body style="margin:0; padding:0; background-color:#f4f4f4;">
+              <center>
+                <table width="100%" bgcolor="#f4f4f4" cellpadding="0" cellspacing="0" border="0">
+                  <tr>
+                    <td align="center">
+                      <table width="600" cellpadding="0" cellspacing="0" border="0" bgcolor="#ffffff" style="border:1px solid #ddd;">
+                        <tr>
+                          <td align="center" bgcolor="#004080" style="padding:24px 0 24px 0; color:#ffffff; font-size:24px; font-family:Arial,sans-serif; font-weight:bold;">
+                            DNS-BLM Results
+                          </td>
+                        </tr>
+                        <tr>
+                          <td style="padding:24px 24px 24px 24px;">
+                            <table width="100%" cellpadding="8" cellspacing="0" border="1" style="border-collapse:collapse; border-color:#ddd; font-family:Arial,sans-serif; font-size:14px;">
+                              <thead>
+                                <tr bgcolor="#e6f0ff" style="font-weight:bold;">
+                                  <th align="left" style="border-color:#ddd;">Domain</th>
+                                  <th align="left" style="border-color:#ddd;">Scanner</th>
+                                  <th align="left" style="border-color:#ddd;">Details</th>
+                                </tr>
+                              </thead>
+                              <tbody>
+                                {{#each this}}
+                                  <tr>
+                                    <td style="border-color:#ddd;">{{Domain}}</td>
+                                    <td style="border-color:#ddd;">{{ScannerName}}</td>
+                                    <td style="border-color:#ddd;">
+                                      {{#if ScanResultUrl}}
+                                        <a href="{{ScanResultUrl}}" target="_blank" style="color:#004080; text-decoration:underline;">View Report</a>
+                                      {{else}}
+                                        N/A
+                                      {{/if}}
+                                    </td>
+                                  </tr>
+                                {{/each}}
+                              </tbody>
+                            </table>
+                          </td>
+                        </tr>
+                        <tr>
+                          <td align="center" style="padding:16px 0 16px 0; color:#777; font-size:12px; font-family:Arial,sans-serif; border-top:1px solid #ddd;">
+                            Sent by <a href="https://github.com/Hutch79-Dev/DNS-BLM" target="_blank" style="color:#004080; text-decoration:none;">DNS-BLM</a>
+                          </td>
+                        </tr>
+                      </table>
+                    </td>
+                  </tr>
+                </table>
+              </center>
+            </body>
+            </html>
+            """;
+        try
+        {
+            var usableTemplate = string.IsNullOrWhiteSpace(template) ? defaultTemplate : template;
+            var compiledTemplate = _compiledTemplates.GetOrAdd(
+                (usableTemplate), _ => Handlebars.Compile(usableTemplate));
+
+            var result = compiledTemplate(model);
+            return result;
+        }
+        catch (Exception ex)
+        {
+            throw new InvalidOperationException($"Failed to render template", ex);
+        }
+    }
+
+    /// <summary>
+    /// Deletes all precompiled Templates.
+    /// Only needs to be used if a Template is changed
+    /// </summary>
+    public void ClearCompiledTemplates()
+    {
+        _compiledTemplates.Clear();
+    }
+}