Code cleanup

Core/Service/EntityFormatter.cs

@@ -0,0 +1,83 @@
+#nullable enable
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Telegram.Bot.Types;
+using Telegram.Bot.Types.Enums;
+
+namespace Kruzya.TelegramBot.Core.Service;
+
+internal class EntityFormatter
+{
+    private static readonly Dictionary<MessageEntityType, string> HtmlMap = new()
+    {
+        { MessageEntityType.Bold, "<b>{0}</b>" },
+        { MessageEntityType.Code, "<code>{0}</code>" },
+        { MessageEntityType.Italic, "<i>{0}</i>" },
+        { MessageEntityType.TextMention, "<a href=\"tg://user?id={1}\">{0}</a>" },
+        { MessageEntityType.Pre, "<pre>{0}</pre>" },
+        { MessageEntityType.Underline, "<u>{0}</u>" },
+        { MessageEntityType.TextLink, "<a href=\"{1}\">{0}</a>" }
+    };
+
+    private static readonly Dictionary<MessageEntityType, string> MarkdownMap = new()
+    {
+        { MessageEntityType.Bold, "*{0}*" },
+        { MessageEntityType.Code, "```{0}```" },
+        { MessageEntityType.Italic, "_{0}_" },
+        { MessageEntityType.TextMention, "[{0}](tg://user?id={1})" },
+        { MessageEntityType.Pre, "```{0}```" },
+        { MessageEntityType.Underline, "__{0}__" },
+        { MessageEntityType.TextLink, "[{0}]({1})" }
+    };
+
+    /// <summary>
+    /// Performs the formatting a text representation of message from <see cref="Message"/> entity with 
+    /// </summary>
+    /// <param name="msg"></param>
+    /// <param name="parseMode"></param>
+    /// <returns></returns>
+    public string? FormatMessage(Message msg, ParseMode parseMode = ParseMode.Html)
+    {
+        var text = "";
+        var entities = msg.Entities;
+
+        if (entities != null)
+        {
+            // Suppress the warning about possibility using empty ref (CS8602).
+            text = msg.Text!;
+
+            // TODO: Currently, this algo don't support inherited entities. This need thinking.
+            foreach (var entity in entities.Reverse())
+            {
+                var entityText = text.Substring(entity.Offset, entity.Length);
+
+                text = text.Replace(entityText, FormatEntity(entity, entityText, parseMode));
+            }            
+        }
+
+        return text;
+    }
+
+    public string FormatEntity(MessageEntity entity, string text, ParseMode parseMode)
+    {
+        var dict = parseMode switch
+        {
+            ParseMode.Html => HtmlMap,
+            ParseMode.Markdown => MarkdownMap,
+            ParseMode.MarkdownV2 => MarkdownMap,
+            _ => throw new Exception("Unsupported parse mode")
+        };
+
+        var arg = entity.Type switch
+        {
+            MessageEntityType.TextMention => entity.User!.Id.ToString(),
+            MessageEntityType.TextLink => entity.Url!,
+            _ => ""
+        };
+
+        return dict[entity.Type].Replace("{0}", text)
+            .Replace("{1}", arg);
+    }
+}