added /start message handling

Services/HandleStartMessage.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+using JsonFlatFileDataStore;
+using Microsoft.Extensions.Logging;
+using mstdnCats.Models;
+using Telegram.Bot;
+using Telegram.Bot.Types;
+using Telegram.Bot.Types.Enums;
+using Telegram.Bot.Types.ReplyMarkups;
+
+namespace CatsOfMastodonBot.Services
+{
+    public class HandleStartMessage
+    {
+        public static async Task HandleStartMessageAsync(Message message, TelegramBotClient _bot, IDocumentCollection<Post> _db, ILogger<MastodonBot>? logger)
+        {
+            // choose all media attachments that are approved
+            var mediaAttachmentsToSelect = _db.AsQueryable().Where(p => p.MediaAttachments.Any(m => m.Approved == true)).ToList();
+            // select random approved media attachment
+            var selectedMediaAttachment = mediaAttachmentsToSelect[new Random().Next(mediaAttachmentsToSelect.Count)];
+            // send media attachment
+            await _bot.SendPhotoAsync(message.Chat.Id, selectedMediaAttachment.MediaAttachments.FirstOrDefault(m => m.Approved == true).Url,
+            caption: $"<a href=\"" + selectedMediaAttachment.Url + "\">" + $"Here is your cat!" + "</br>" + "View on Mastodon 🐈" + " </a>", parseMode: ParseMode.Html
+                        , replyMarkup: new InlineKeyboardMarkup().AddButton(InlineKeyboardButton.WithUrl("Join channel 😺", selectedMediaAttachment.Url))
+                        .AddNewRow()
+                        .AddButton(InlineKeyboardButton.WithCallbackData("Send me another one!", $"new_random")));
+
+
+        }
+    }
+}