254 lines
11 KiB
Markdown
254 lines
11 KiB
Markdown
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---
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title: "Building a Telegram bot in Rust: a journey through Songlify"
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description: An adventure through Rust and Telegram
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tags:
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- blog
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- tech
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- rust
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- telegram
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- songlify
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date: 2022-01-02T15:32:00+02:00
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---
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Some time passed since the last article I wrote there. A lot of stuff happened
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meanwhile, especially with COVID, but here we are again. While busy dealing with
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the mess of real life tasks, three months ago I started to write a little bot
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for Telegram in Rust. It is a simple one, but I consider the journey interesting
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and worth of writing it down. If I add new features worth mentioning I will
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start a series about it, maybe.
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## Telegram bots
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Telegram bots are not something new to me and nowdays are pretty much easy to
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make, so I consider them like a gym where to try out new technologies and
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experiment with stuff. I wrote plentiful of them, some of those are open source
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like for example https://github.com/Augugrumi/TorreArchimedeBot (which is now
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broken 😭) that was useful when going to University, because it scraped the
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university free room web page and from there it was able to tell you which rooms
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where without any lessons and for how much time, allowing you to easily find a
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place where to study with your mates (yep, we didn't like library too much).
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{{< figure src="/content/songlify/telegramscreen.png" alt=`A screenshot of
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TorreArchimedeBot in action.` caption=`A screenshot of TorreArchimedeBot in
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action.` >}}
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Also another one bot worthy of mention is
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https://github.com/Polpetta/RedditToTelegram, that allowed our D&D group to
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receive push notifications of our private Subreddit in our Telegram group.
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As you can see, all of these bots are quite simple, but they have the added
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value of teaching you some new programming concepts, technologies or frameworks
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that can be later applied in something that can be more production environment.
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## Rust
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I started to approach Rust many years ago (I do not remember exactly when).
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First interaction with it was quite interesting to say at least: there were way
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less compiler features (for example now the compiler is able to understand
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object lifetime at compile time most of the time alone, without specifying them)
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that made it a... _not-so-pleasant programming experience_. It had potential
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thought, so by following Rust news I picked it up last year again, noticing that
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now it has improved a lot and it is more pleasant to write. Meanwhile, also
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JetBrains developed a good support for IntelliJ, so now it is even possible to
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debug and perform every operation directly from your IDE UI.
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## Making the two worlds collide: Rust + Telegram
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One of the features I wanted to learn this time regarding Rust was the
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asynchronous support it offers. Rust started to have `async` support with
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[Tokio](https://tokio.rs/) framework, and recently the Rust team started to
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build the asynchronous functionality inside Rust itself. Even if in the first
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steps, it looks promising and the idea of a low-level language, without GC, with
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automatic memory management and so much safety having asynchronous support is
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exciting to me! 🥳 So the only option left, at this point, was to start messing
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around with it. I started by picking up one of the many frameworks that provides
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a layer for the Telegram APIs, [Teloxide](https://github.com/teloxide/teloxide).
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In particular, as you can see from its _README_, one of the examples starts by
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using `#[tokio:main]` macro:
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```rust
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use teloxide::prelude::*;
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#[tokio::main]
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async fn main() {
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teloxide::enable_logging!();
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log::info!("Starting dices_bot...");
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let bot = Bot::from_env().auto_send();
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teloxide::repl(bot, |message| async move {
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message.answer_dice().await?;
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respond(())
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})
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.await;
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}
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```
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This was the reason I picked it up, given that it looked the most promising by
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the time I started the project.
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### Building _Songlify_
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So, after choosing what was going to use to build the bot, I needed a _reason_
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to build it.
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With my friends we usually share a lot of songs (via Spotify links), so I tought
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it was a good idea to build a bot around it. I integrated a Spotify API library
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in it and started hacking up a bot.
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> ⚠ Note that at the time of writing I have just notice the library I use for
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> talking with Spotify, [aspotify](https://crates.io/crates/aspotify) has been
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> deprecated in favour of [rspotify](https://crates.io/crates/rspotify)
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The first bot version was something very simple, and it was a single-file
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program with nothing very fancy (I have written it in a night):
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```rust
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use crate::SpotifyURL::Track;
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use aspotify::{Client, ClientCredentials};
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use teloxide::prelude::*;
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enum SpotifyURL {
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Track(String),
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}
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fn get_spotify_entry(url: &str) -> Option<SpotifyURL> {
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if url.contains("https://open.spotify.com/track/") {
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let track_id = url.rsplit('/').next().and_then(|x| x.split('?').next());
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return match track_id {
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Some(id) => Some(SpotifyURL::Track(id.to_string())),
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None => None,
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};
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}
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return None;
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}
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struct TrackInfo {
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name: String,
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artist: Vec<String>,
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}
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async fn get_spotify_track(spotify: Box<Client>, id: &String) -> Option<TrackInfo> {
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match spotify.tracks().get_track(id.as_str(), None).await {
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Ok(track) => Some(TrackInfo {
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name: track.data.name,
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artist: track.data.artists.iter().map(|x| x.name.clone()).collect(),
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}),
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Err(_e) => None,
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}
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}
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#[tokio::main]
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async fn main() {
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teloxide::enable_logging!();
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log::info!("Starting Songlify...");
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let bot = Bot::from_env().auto_send();
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teloxide::repl(bot, |message| async move {
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let spotify_creds =
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ClientCredentials::from_env().expect("CLIENT_ID and CLIENT_SECRET not found.");
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let spotify_client = Box::new(Client::new(spotify_creds));
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log::info!("Connected to Spotify");
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let text = message.update.text().and_then(get_spotify_entry);
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match text {
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Some(spotify) => match spotify {
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Track(id) => {
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let track_info = get_spotify_track(spotify_client, &id).await;
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match track_info {
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Some(info) => {
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let reply = format!(
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"Track information:\n\
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Track name: {}\n\
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Artists: {}",
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info.name,
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info.artist.join(", ")
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);
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Some(message.reply_to(reply).await?)
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}
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None => None,
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}
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}
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},
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None => None,
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};
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respond(())
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})
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.await;
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log::info!("Exiting...");
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}
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```
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As you can see, basically every time a request arrived to the bot, login to
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Spotify was performed and track information and name retrieved from there. Of
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course this was only the beginning. Now the bot supports albums and playlists
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too, with the possibility to go through each song in the playlist and collect
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general information such as how many artists are in that playlist, how many
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songs and other little information like that. If you see the [bot
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repository](https://git.poldebra.me/polpetta/Songlify) you can see now that
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Spotify functions live in a separate module.
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#### Packaging and distribution
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The obvious choice for a software like that was to incorporate it into a OCI
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image. I wrote a very simple Dockerfile that, once the program was built, took
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the artifact and using the [multi-stage Docker build
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functionality](https://docs.docker.com/develop/develop-images/multistage-build/)
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and put it into a separate container, in order to avoid having build
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dependencies inside the final image. I used the images distributed by the
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[Distroless project](gcr.io/distroless/) (you can find the source on their
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[Github repository](https://github.com/GoogleContainerTools/distroless)) in
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order to obtain the smallest possible image. The final result?
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```
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λ ~/Desktop/git/songlify/ docker images
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REPOSITORY TAG IMAGE ID CREATED SIZE
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test/test latest 8ac7a7018719 5 seconds ago 34MB
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<none> <none> 4bc7fb0699e0 12 seconds ago 1.53GB
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rust 1.56.1-slim-bullseye d3e070c5ffa7 6 weeks ago 667MB
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gcr.io/distroless/base latest-amd64 24787c1cd2e4 52 years ago 20.2MB
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```
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A part from the 52 years old image pulled from `gcr`, you can see that
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`test/test` (actually Songlify) is only of **34MB**. Not much if you consider
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that inside that image there are shared dynamic libraries to make the executable
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able to run, which by default weights 20MB. A plus of these images is that they
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do not run as root user and they do not have any shell of bash integrated,
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making a possible surface attack smaller (not that Docker is secure anyway...).
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I upload the images on Docker Hub, where you can find them here
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https://hub.docker.com/r/polpetta/songlify
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Finally, to run the bot I use a very simple docker-compose definition, that can
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be found in my [server-dotfiles
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repository](https://git.poldebra.me/polpetta/server-dotfiles/src/commit/7e7e1780b2db45f475510c49bf1a2f9e76c4c166/songlify/docker-compose.yml).
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This allows me to easily upgrade the bot by just changing the version and
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running `docker-compose up -d`.
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#### Plans for the future
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Currently I work on the bot only when I feel like I wanna add something. An
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interesting feature to add could be to insert a persistence layer (using a
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database for instance) and add various stats (which is the most shared song? Who
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_is that guy_ that shares the most songs in a group?). Persistence can be
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achieved quite easily by using [Diesel](https://diesel.rs/), an ORM compatible
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with various databases.
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Another cool feature could be to add the _inline bot_ functionality, where you
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can search for songs directly in Spotify. Since I currently have a domain
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available for that I could set it up for receive web-hook notifications, instead
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of performing polling like the bot is currently doing (one requisite for inline
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bots is indeed to receive web-hooks). There are platforms like Heroku where you
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could make the bot run, but currently I prefer to use my box since it gives me
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more flexibility. Experimenting with Heroku could lead to cool results though
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😏.
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Finally, link translation could be something very useful. I have a friend that
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does not use Spotify but prefers to listen to music via YouTube. So an
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interesting feature would be, given a Spotify link, to "convert" it into a
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YouTube link and, of course, _vice-versa_. This could lead to translate
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playlists and albums too into YouTube-based playlists, which of course could be
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very useful if you are trying to avoid the infamous _vendor lock-in_, in this
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case being stuck with Spotify because all you music collection, saved songs, etc
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is there.
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