How can I make the bot send a welcome message to a member joining a group?

[CrawKatt]

I managed to make a welcome message for my bot but I had two problems that I have not been able to solve.

1. the bot cannot link new users that do not have @username (I don't know if it is possible to mention users without username through the bot).
2. when I promote a user to administrator or change his permissions, the bot sends a welcome message mentioning the administrator who promoted the user.

I leave the code below (it's a bit messy but I'll polish it when I can solve the problems):

use crate::commands::*;
pub mod database;
pub mod commands;
pub mod utils;
pub mod buttons;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {

    // Initialize the logging environment for Teloxide
    pretty_env_logger::init();
    log::info!("Iniciando Bot...");

    // Load environment variables from a .env file
    dotenv().ok();

    // Connect to the database
    //conectar().await.expect("Error al conectar con la Base de Datos");

    // Load the init message from a txt file
    let init_message = include_str!("init_message.txt");

    // Print a message to the console to indicate that the bot has started
    println!("{init_message}\n");

    let bot = teloxide::Bot::from_env().parse_mode(MarkdownV2);
    let handler = dptree::entry().inspect(|u:Update| {
        println!("{u:#?}");
    })
        .branch(Update::filter_message().endpoint(message_handler))
        .branch(Update::filter_callback_query().endpoint(callback_handler))
        .branch(Update::filter_message().branch(Message::filter_new_chat_members().endpoint(chat_member_handler)))
        //.branch(Update::filter_chat_member().endpoint(chat_member_handler))
        .branch(Update::filter_inline_query().endpoint(inline_query_handler));

    Dispatcher::builder(bot.clone(), handler)
        .enable_ctrlc_handler()
        .build()
        .dispatch()
        .await;

    Ok(())
}

async fn chat_member_handler(bot:Bot, chat_member:ChatMemberUpdated, test_member: Update) -> Result<(), Box<dyn Error + Send + Sync>> {
    let telegram_group_name = chat_member.chat.title().unwrap_or("");

    println!("{:#?}", test_member);

    let first_name = chat_member.clone().from.first_name;

    let username = if let Some(name) = chat_member.from.username {
        name
    } else if first_name == chat_member.from.first_name {
        first_name.clone()
    } else {
        return Err("Error: Username or first name not found".into());
    };

    let member = bot.get_chat_member(chat_member.chat.id, chat_member.new_chat_member.user.id).await?;
    let member_status = member.status();

    if let ChatMemberStatus::Left = member_status {

        if username == first_name {
            bot.send_message(chat_member.chat.id, format!("Hasta pronto {username}!"))
                .parse_mode(ParseMode::Html)
                .await?;
        } else {
            bot.send_message(chat_member.chat.id, format!("Hasta pronto @{username}!"))
                .parse_mode(ParseMode::Html)
                .await?;
        }

    } else if username == first_name {
        bot.send_message(chat_member.chat.id, format!("Bienvenido a {telegram_group_name} {username}!"))
            .parse_mode(ParseMode::Html)
            .await?;
    } else {
        bot.send_message(chat_member.chat.id, format!("Bienvenido a {telegram_group_name} @{username}!"))
            .parse_mode(ParseMode::Html)
            .await?;
    }

    Ok(())
}

Is there any clue or advice you can give me please. Thank you very much in advance.

PD: I will leave the link to my bot repository just in case https://github.com/CrawKatt/TeloxBeta/tree/experimental

[WaffleLapkin]

Re 1.: you can use something like user.mention().unwrap_or_else(|| html::user_mention(user.id, user.full_name())), see the code for details on how this works (you can also use user.url() to get that tg:// url).

Re 2.: You can do something like .filter(|m: ChatMemberUpdated| m.old_chat_member.kind.is_left() && m.new_chat_member.kind.is_present()) (please check the details of is_left and is_present docs, as those are a bit tricky).

Hope that helps.

[WaffleLapkin]

I'm not sure where did you take bot.new_chat_member from, new_chat_member (and similarly for old) is a field of ChatMemberUpdated.

Also I'm not sure I understood, did you figure it out in the end?...

[CrawKatt]

ahhh I get it, I was confused. I thought the old_chat_member/new_chat_member method was for my bot variable instead of my chat_member variable. I think I understand what to do

[CrawKatt]

I have made a breakthrough, the bot now no longer mentions the admin if you promote a user, but the welcome message is still triggered when there is a promotion to admin. I think I am now understanding the use of kind.

This is what I have so far in my function:

async fn chat_member_handler(bot:Bot, chat_member:ChatMemberUpdated) -> MemberResult {
    let telegram_group_name = chat_member.chat.title().unwrap_or("");

    let first_name = chat_member.new_chat_member.user.first_name.clone();
    let username = chat_member.new_chat_member.user.username.unwrap_or(first_name.clone());
    println!("{:#?}", username);

    let member_status = chat_member.new_chat_member.kind.is_present();
    if !member_status {

        if username == first_name {
            bot.send_message(chat_member.chat.id, format!("Hasta pronto {username}!"))
                .parse_mode(ParseMode::Html)
                .await?;
        } else {
            bot.send_message(chat_member.chat.id, format!("Hasta pronto @{username}!"))
                .parse_mode(ParseMode::Html)
                .await?;
        }

    } else if username == first_name {
        bot.send_message(chat_member.chat.id, format!("Bienvenido a {telegram_group_name} {username}!"))
            .parse_mode(ParseMode::Html)
            .await?;
    } else {
        bot.send_message(chat_member.chat.id, format!("Bienvenido a {telegram_group_name} @{username}!"))
            .parse_mode(ParseMode::Html)
            .await?;
    }

    Ok(())
}

[CrawKatt]

I found the solution

1. regarding the problem with the user mention. I tried with the unwrap_or solution but I had an error about expecting an i64 but I found a UserId, which did not allow me to compile. After searching I ended up finding a solution from StackOverflow where they used a Telegram link and that's when it occurred to me to use the user_id inside a format with the tag.

2. regarding the welcome message bug, the .filter() method solution worked. The problem I had was that I was applying the method backwards, which caused the method to have no effect. Thank you very much for the advice, it was very useful and I learned a lot of new things.

I leave the code of my solution for those who have the same problem.

Welcome Function

async fn chat_member_welcome(bot:Bot, chat_member:ChatMemberUpdated) -> MemberResult {
    let telegram_group_name = chat_member.chat.title().unwrap_or("");
    let first_name = chat_member.old_chat_member.user.first_name.clone();
    let user_id = chat_member.old_chat_member.user.id;
    let username = chat_member.old_chat_member.user.username.unwrap_or(first_name.clone());
    let username = format!("<a href=\"tg://user?id={user_id}\">{username}</a>");

    bot.send_message(chat_member.chat.id, format!("bienvenido a {telegram_group_name} {username}!"))
        .parse_mode(ParseMode::Html)
        .await?;

    Ok(())
}

Goodbye Function

async fn chat_member_goodbye(bot:Bot, chat_member:ChatMemberUpdated) -> MemberResult {
    let first_name = chat_member.old_chat_member.user.first_name;
    let username = chat_member.old_chat_member.user.username.unwrap_or(first_name.clone());
    let user_id = chat_member.old_chat_member.user.id;
    let username = format!("<a href=\"tg://user?id={user_id}\">{username}</a>");

    bot.send_message(chat_member.chat.id, format!("Hasta pronto {username}!"))
        .parse_mode(ParseMode::Html)
        .await?;

    Ok(())
}

handler

let handler = dptree::entry()
    .inspect(|u: Update| {
        println!("{u:#?}");
    })
    .branch(Update::filter_message().endpoint(message_handler))
    .branch(Update::filter_callback_query().endpoint(callback_handler))
    .branch(Update::filter_inline_query().endpoint(inline_query_handler))
    .branch(
        Update::filter_chat_member() // filter method before endpoint
            .filter(|m: ChatMemberUpdated| {
                m.old_chat_member.kind.is_left() && m.new_chat_member.kind.is_present()
            })
            .endpoint(chat_member_welcome),
    )
    .branch(
        Update::filter_chat_member() // filter method before endpoint
            .filter(|m: ChatMemberUpdated| {
                m.new_chat_member.kind.is_left() && m.old_chat_member.kind.is_present()
            })
            .endpoint(chat_member_goodbye),
    );

[WaffleLapkin]

regarding the problem with the user mention. I tried with the unwrap_or solution but I had an error about expecting an i64 but I found a UserId, which did not allow me to compile.

You can easily convert UserId -> i64 via the chat id:

let x: UserId = ...;

let ChatId(y) = ChatId::from(x);
// y is i64

The inverse is a bit more tricky and maybe we should provide nicer APIs, but you can simply cast ig:

fn chat_id_as_user_id(c: ChatId) -> Option<UserId> {
    c.is_user().then(|c| User(c.0 as u64))
}

---

Also, you don't need .kind when checking member status:

-                m.old_chat_member.kind.is_left() && m.new_chat_member.kind.is_present()
+                m.old_chat_member.is_left() && m.new_chat_member.is_present()

This is because ChatMember has those methods via deref.

---

And for the love of satan, please, use rustfmt/format on save/whatever before posting code here. I've formatted your handler code using playground and it became 10 times as readable (this would also help you catch the ordering bug).