New: Telegram notifications

Closes #1355

src/NzbDrone.Core/Notifications/Telegram/TelegramService.cs

@@ -0,0 +1,72 @@
+using System;
+using System.Net;
+using FluentValidation.Results;
+using NLog;
+using NzbDrone.Common.Extensions;
+using NzbDrone.Common.Serializer;
+using RestSharp;
+using NzbDrone.Core.Rest;
+
+namespace NzbDrone.Core.Notifications.Telegram
+{
+    public interface ITelegramProxy
+    {
+        void SendNotification(string title, string message, TelegramSettings settings);
+        ValidationFailure Test(TelegramSettings settings);
+    }
+
+    public class TelegramProxy : ITelegramProxy
+    {
+        private readonly Logger _logger;
+        private const string URL = "https://api.telegram.org";
+
+        public TelegramProxy(Logger logger)
+        {
+            _logger = logger;
+        }
+
+        public void SendNotification(string title, string message, TelegramSettings settings)
+        {
+            //Format text to add the title before and bold using markdown
+            var text = $"*{title}*\n{message}";
+            var client = RestClientFactory.BuildClient(URL);
+            var request = new RestRequest("bot{token}/sendmessage", Method.POST);
+
+            request.AddUrlSegment("token", settings.BotToken);
+            request.AddParameter("chat_id", settings.ChatId);
+            request.AddParameter("parse_mode", "Markdown");
+            request.AddParameter("text", text);
+
+            client.ExecuteAndValidate(request);
+        }
+
+        public ValidationFailure Test(TelegramSettings settings)
+        {
+            try
+            {
+                const string title = "Test Notification";
+                const string body = "This is a test message from Sonarr";
+
+                SendNotification(title, body, settings);
+            }
+            catch (Exception ex)
+            {
+                _logger.Error(ex, "Unable to send test message: " + ex.Message);
+
+                var restException = ex as RestException;
+
+                if (restException != null && restException.Response.StatusCode == HttpStatusCode.BadRequest)
+                {
+                    var error = Json.Deserialize<TelegramError>(restException.Response.Content);
+                    var property = error.Description.ContainsIgnoreCase("chat not found") ? "ChatId" : "BotToken";
+
+                    return new ValidationFailure(property, error.Description);
+                }
+
+                return new ValidationFailure("BotToken", "Unable to send test message");
+            }
+
+            return null;
+        }
+    }
+}