SendGrid email provider and service

Author: rxtur

Blogifier.sln

@@ -33,6 +33,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "docs", "docs", "{6015AFDB-9
 		docs\MySQL.md = docs\MySQL.md
 		docs\Notifications.md = docs\Notifications.md
 		docs\Security.md = docs\Security.md
+		docs\SendGrid.md = docs\SendGrid.md
 		docs\SqlServer.md = docs\SqlServer.md
 		docs\Themes.md = docs\Themes.md
 		docs\VideoAudio.md = docs\VideoAudio.md

docs/SendGrid.md

@@ -0,0 +1,27 @@
+Blogifier uses [SendGrid](https://sendgrid.com/) as email provider. It is one of the cloud 
+email providers recommended for ASP.NET Core. It is free for under 100 daily emails and has 
+paid options if someone needs more.
+
+### SendGrid API
+To use SendGrid, blogger would need to sign up for service and get 
+[API key](https://sendgrid.com/solutions/email-api/). Once you have API key, all that
+required is to update `appsettings.json`: 
+
+```cmd
+{
+  "Blogifier": {
+    "SendGridApiKey": "YOUR-SENDGRID-API-KEY",
+    "SendGridEmailFrom": "admin@blog.com",
+    "SendGridEmailFromName": "Blog admin"
+  }
+}
+```
+
+Currently, SendGrid only used by Newsletter widget. When guest subscribles to the blog via Newsletter,
+every time new post gets published, Blogifier goes over list of subscribers and sends notification
+about new publicatoin to every subscriber.
+
+### Why not SMTP?
+Plain SMTP client routes calls to actual SMTP email server, like Gmail or HotMail.
+Unfortunately, most SMTP providers and hosters block 3rd party email traffic. 
+Cloud providers have limitations, but much more reliable.

src/App/Pages/Admin/Posts/Edit.cshtml.cs

@@ -4,6 +4,8 @@
 using Core.Services;
 using Microsoft.AspNetCore.Mvc;
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 
 namespace App.Pages.Admin.Posts
@@ -16,11 +18,13 @@ public class EditModel : AdminPageModel
 
         IDataService _db;
         INotificationService _ns;
+        ISendGridService _sg;
 
-        public EditModel(IDataService db, INotificationService ns)
+        public EditModel(IDataService db, INotificationService ns, ISendGridService sg)
         {
             _db = db;
             _ns = ns;
+            _sg = sg;
         }
 
         public async Task OnGetAsync(int id)
@@ -83,6 +87,12 @@ public async Task<IActionResult> OnPostAsync()
                     PostItem = item;
                     Message = Resources.Saved;
 
+                    if(PostItem.Status == SaveStatus.Publishing)
+                    {
+                        List<string> emails = _db.Newsletters.All().Select(n => n.Email).ToList();
+                        await _sg.SendNewsletters(PostItem, emails);
+                    }
+
                     return Redirect($"~/admin/posts/edit?id={PostItem.Id}");
                 }
             }

src/App/app.db

@@ -1,19 +1,13 @@
 {
-  "Foo": "foo",
   "Blogifier": {
     "DbProvider": "SQLite",
     "ConnString": "DataSource=app.db",
-    "Title": "Blog title",
-    "Description": "Short description of the blog",
-    "Cover": "data/admin/cover-desk.jpg",
-    "Logo": "lib/img/logo-white.png",
-    "Avatar": "lib/img/avatar.jpg",
-    "Theme": "Standard",
-    "BlogThemes": null,
-    "ItemsPerPage": 10,
-    "UseDescInPostList": true,
     "ImportTypes": "zip,7z,xml,pdf,doc,docx,xls,xlsx,mp3,avi",
     "ImageExtensions": "png,jpg,gif,bmp,tiff",
+    "Avatar": "lib/img/avatar.jpg",
+    "SendGridApiKey": "YOUR-SENDGRID-API-KEY",
+    "SendGridEmailFrom": "admin@blog.com",
+    "SendGridEmailFromName": "Blog admin",
     "DemoMode": false
   }
 }

src/App/appsettings.json

@@ -14,6 +14,7 @@
     <PackageReference Include="Microsoft.SyndicationFeed.ReaderWriter" Version="1.0.2" />
     <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="2.1.2" />
     <PackageReference Include="ReverseMarkdown" Version="2.0.0" />
+    <PackageReference Include="Sendgrid" Version="9.10.0" />
   </ItemGroup>
 
 </Project>

src/Core/Core.csproj

@@ -37,6 +37,7 @@ public static IServiceCollection AddAppServices(this IServiceCollection services
             services.AddTransient<IImportService, ImportService>();
             services.AddTransient<INotificationService, NotificationService>();
             services.AddTransient<IWebService, WebService>();
+            services.AddTransient<ISendGridService, SendGridService>();
 
             services.AddTransient<UserManager<AppUser>>();
 

src/Core/Extensions/ServiceCollectionExtensions.cs

@@ -0,0 +1,75 @@
+using Core.Data;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+using SendGrid;
+using SendGrid.Helpers.Mail;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Core.Services
+{
+    public interface ISendGridService
+    {
+        Task SendNewsletters(PostItem postItem, List<string> emails);
+        Task SendEmail(string to, string subject, string content);
+    }
+
+    public class SendGridService : ISendGridService
+    {
+        private readonly IConfiguration _config;
+        private readonly ILogger _logger;
+
+        public SendGridService(IConfiguration config, ILogger<SendGridService> logger)
+        {
+            _config = config;
+            _logger = logger;
+        }
+
+        public async Task SendNewsletters(PostItem postItem, List<string> emails)
+        {
+            foreach (var email in emails)
+            {
+                var subject = "Newsletter: " + postItem.Title;
+                var htmlContent = postItem.Description;
+
+                await SendEmail(email, subject, htmlContent);
+            }
+        }
+
+        public async Task SendEmail(string to, string subject, string content)
+        {
+            var section = _config.GetSection("Blogifier");
+
+            if(section != null)
+            {
+                var apiKey = section.GetValue<string>("SendGridApiKey");
+
+                if (!string.IsNullOrEmpty(apiKey))
+                {
+                    try
+                    {
+                        var client = new SendGridClient(apiKey);
+
+                        var fromEmail = section.GetValue<string>("SendGridEmailFrom") ?? "admin@blog.com";
+                        var fromName = section.GetValue<string>("SendGridEmailFromName") ?? "Blog admin";
+                        var from = new EmailAddress(fromEmail, fromName);
+
+                        var msg = MailHelper.CreateSingleEmail(from, new EmailAddress(to), subject, content.StripHtml(), content);
+                        var response = await client.SendEmailAsync(msg);
+
+                        if(response.StatusCode == System.Net.HttpStatusCode.Unauthorized)
+                        {
+                            _logger.LogError("SendGrid service returned 'Unauthorized' - please verfiy SendGrid API key in configuration file");
+                        }
+                    }
+                    catch (System.Exception ex)
+                    {
+                        _logger.LogError(ex.Message);
+                    }
+                }
+                
+            }
+            await Task.CompletedTask;
+        }
+    }
+}