added MarkdownToEntities

EXAMPLES.md

@@ -15,11 +15,12 @@ Remember that these are just simple example codes that you should adjust to your
 ```csharp
 using var client = new WTelegram.Client(Environment.GetEnvironmentVariable);
 await client.LoginUserIfNeeded();
-var resolved = await client.Contacts_ResolveUsername("username");
+var resolved = await client.Contacts_ResolveUsername("username"); // without the @
 await client.SendMessageAsync(resolved, "Hello!");
 ```
 *Note: This also works if the @username points to a chat, but you must join the chat before posting there.
 You can check `resolved` properties to ensure it's a user or a chat. If the username is invalid/unused, the API call raises an exception.*
+
 ### Send a message to someone by phone number
 ```csharp
 using var client = new WTelegram.Client(Environment.GetEnvironmentVariable);
@@ -30,6 +31,16 @@ if (contacts.imported.Length > 0)
 ```
 *Note: To prevent spam, Telegram may restrict your ability to add new phone numbers.*
 
+### Send a Markdown message to ourself (Saved Messages)
+```csharp
+using var client = new WTelegram.Client(Environment.GetEnvironmentVariable);
+await client.LoginUserIfNeeded();
+var text = "Hello __dear *friend*__!\nEnjoy this `userbot` written with [WTelegramClient](https://github.com/wiz0u/WTelegramClient)";
+var entities = client.MarkdownToEntities(ref text);
+await client.SendMessageAsync(InputPeer.Self, text, entities: entities);
+```
+See [MarkdownV2 formatting style](https://core.telegram.org/bots/api/#markdownv2-style) for details.
+
 ### List all chats (groups/channels) the user is in and send a message to one
 ```csharp
 using var client = new WTelegram.Client(Environment.GetEnvironmentVariable);

src/Encryption.cs

@@ -436,7 +436,7 @@ j4WcDuXc2CTHgH8gFTNhp/Y8/SpDOhvn9QIDAQAB
 
 #if !NETCOREAPP2_0_OR_GREATER
 		// adapted from https://github.com/dotnet/aspnetcore/blob/main/src/DataProtection/Cryptography.KeyDerivation/src/PBKDF2/ManagedPbkdf2Provider.cs
-		public static byte[] PBKDF2_SHA512(byte[] password, byte[] salt, int iterationCount, int numBytesRequested)
+		private static byte[] PBKDF2_SHA512(byte[] password, byte[] salt, int iterationCount, int numBytesRequested)
 		{
 			// PBKDF2 is defined in NIST SP800-132, Sec. 5.3: http://csrc.nist.gov/publications/nistpubs/800-132/nist-sp800-132.pdf
 			byte[] retVal = new byte[numBytesRequested];

src/Helpers.TL.cs

@@ -353,4 +353,93 @@ namespace TL
 			return sb.Append('}').ToString();
 		}
 	}
+
+	public static class Helpers
+	{
+		public static MessageEntity[] MarkdownToEntities(this WTelegram.Client client, ref string text)
+		{
+			var entities = new List<MessageEntity>();
+			var sb = new StringBuilder(text);
+			for (int offset = 0; offset < sb.Length;)
+			{
+				switch (sb[offset])
+				{
+					case '\\': sb.Remove(offset++, 1); break;
+					case '*':
+						ProcessEntity<MessageEntityBold>();
+						break;
+					case '_':
+						if (offset + 1 < sb.Length && sb[offset + 1] == '_')
+						{
+							sb.Remove(offset, 1);
+							ProcessEntity<MessageEntityUnderline>();
+						}
+						else
+							ProcessEntity<MessageEntityItalic>();
+						break;
+					case '~':
+						ProcessEntity<MessageEntityStrike>();
+						break;
+					case '`':
+						if (offset + 2 < sb.Length && sb[offset + 1] == '`' && sb[offset + 2] == '`')
+						{
+							int header = 3;
+							if (entities.FindLast(e => e.length == 0) is MessageEntityPre pre)
+								pre.length = offset - pre.offset;
+							else
+							{
+								while (offset + header < sb.Length && !char.IsWhiteSpace(sb[offset + header]))
+									header++;
+								entities.Add(new MessageEntityPre { offset = offset, language = sb.ToString(offset + 3, header - 3) });
+							}
+							sb.Remove(offset, header);
+						}
+						else
+							ProcessEntity<MessageEntityCode>();
+						break;
+					case '[':
+						entities.Add(new MessageEntityTextUrl { offset = offset });
+						sb.Remove(offset, 1);
+						break;
+					case ']':
+						if (offset + 1 < sb.Length && sb[offset + 1] == '(' && entities.FindLast(e => e.length == 0) is MessageEntityTextUrl textUrl)
+						{
+							textUrl.length = offset - textUrl.offset;
+							sb.Remove(offset, 2);
+						}
+						else
+							offset++;
+						break;
+					case ')':
+						var lastIndex = entities.FindLastIndex(e => e.length == 0 || e is MessageEntityTextUrl { url: null });
+						MessageEntity entity;
+						if (lastIndex >= 0 && (entity = entities[lastIndex]).length != 0)
+						{
+							var urlStart = entity.offset + entity.length;
+							var urlLength = offset - urlStart;
+							var url = sb.ToString(urlStart, urlLength);
+							sb.Remove(urlStart, urlLength + 1);
+							offset = urlStart;
+							if (url.StartsWith("tg://user?id=") && long.TryParse(url[13..], out var user_id) && client.GetAccessHashFor<User>(user_id) is long hash && hash != 0)
+								entities[lastIndex] = new InputMessageEntityMentionName { offset = entity.offset, length = entity.length, user_id = new InputUser { user_id = user_id, access_hash = hash } };
+							else
+								((MessageEntityTextUrl)entity).url = url;
+						}
+						break;
+					default: offset++; break;
+				}
+
+				void ProcessEntity<T>() where T : MessageEntity, new()
+				{
+					if (entities.LastOrDefault(e => e.length == 0) is T prevEntity)
+						prevEntity.length = offset - prevEntity.offset;
+					else
+						entities.Add(new T { offset = offset });
+					sb.Remove(offset, 1);
+				}
+			}
+			text = sb.ToString();
+			return entities.Count == 0 ? null : entities.ToArray();
+		}
+	}
 }