.gitignore

@@ -9,3 +9,4 @@ hugo.darwin
 hugo.linux
 
 node_modules/
+.hugo_build.lock

content/english/posts/songlify-1.md

@@ -0,0 +1,255 @@
+---
+title: "Building a Telegram bot in Rust: a journey through Songlify"
+description: An adventure through Rust and Telegram
+tags:
+- blog
+- tech
+- rust
+- telegram
+- songlify
+date: 2022-01-05T17:01:00+02:00
+---
+
+Some time passed since the last article I wrote there. A lot of stuff happened
+meanwhile, especially with COVID, but here we are again. While busy dealing with
+the mess of real life tasks, three months ago I started to write a little bot
+for Telegram in Rust. It is a simple one, but I consider the journey interesting
+and worth of writing it down. If I add new features worth mentioning I will
+start a series about it, maybe.
+
+## Telegram bots
+
+Telegram bots are not something new to me and nowadays are pretty much easy to
+make, so I consider them like a gym where to try out new technologies and
+experiment with stuff. I wrote plentiful of them, some of those are open source
+like for example <https://github.com/Augugrumi/TorreArchimedeBot> (which is
+currently broken 😭) that was useful when going to University, because it
+scraped the university free room web page and from there it was able to tell you
+which rooms where without any lessons and for how much time, allowing you to
+easily find a place where to study with your mates (yep, we didn't like library
+too much).
+
+{{< figure src="/content/songlify/telegramscreen.png" alt=`A screenshot of
+TorreArchimedeBot in action.` caption=`A screenshot of TorreArchimedeBot in
+action.` >}}
+
+Also another one bot worthy of mention is
+<https://github.com/Polpetta/RedditToTelegram>, that allowed our D&D group to
+receive push notifications of our private Subreddit in our Telegram group.
+
+As you can see, all of these bots are quite simple, but they have the added
+value of teaching you some new programming concepts, technologies or frameworks
+that can be later applied in something that can be more production environment.
+
+## Rust
+
+I started to approach Rust many years ago (I do not remember exactly when).
+First interaction with it was quite interesting to say at least: there were way
+less compiler features (for example now the compiler is able to understand
+object lifetime at compile time most of the time alone, without specifying them)
+that made it a... _not-so-pleasant programming experience_. It had potential
+thought, so by following Rust news I picked it up last year again, noticing that
+now it has improved a lot and it is more pleasant to write. Meanwhile, also
+JetBrains developed a good support for IntelliJ, so now it is even possible to
+debug and perform every operation directly from your IDE UI.
+
+## Making the two worlds collide: Rust + Telegram
+
+One of the features I wanted to learn this time regarding Rust was the
+asynchronous support it offers. Rust started to have `async` support with
+[Tokio](https://tokio.rs/) framework, and recently the Rust team started to
+build the asynchronous functionality inside Rust itself. Even if in the first
+steps, it looks promising and the idea of a low-level language, without GC, with
+automatic memory management and so much safety having asynchronous support is
+exciting to me! 🥳 So the only option left, at this point, was to start messing
+around with it. I started by picking up one of the many frameworks that provides
+a layer for the Telegram APIs, [Teloxide](https://github.com/teloxide/teloxide).
+In particular, as you can see from its _README_, one of the examples starts by
+using `#[tokio:main]` macro:
+
+```rust
+use teloxide::prelude::*;
+
+#[tokio::main]
+async fn main() {
+    teloxide::enable_logging!();
+    log::info!("Starting dices_bot...");
+
+    let bot = Bot::from_env().auto_send();
+
+    teloxide::repl(bot, |message| async move {
+        message.answer_dice().await?;
+        respond(())
+    })
+    .await;
+}
+```
+
+This was the reason I picked it up, given that it looked the most promising by
+the time I started the project.
+
+### Building _Songlify_
+
+So, after choosing what was going to use to build the bot, I needed a _reason_
+to build it.
+
+With my friends we usually share a lot of songs (via Spotify links), so I
+thought it was a good idea to build a bot around it. I integrated a Spotify API
+library in it and started hacking up a bot.
+
+> ⚠ Note that at the time of writing I have just noticed that the library I use
+> for speaking with Spotify, [aspotify](https://crates.io/crates/aspotify) has
+> been deprecated in favour of [rspotify](https://crates.io/crates/rspotify)
+
+The first bot version was something very simple, and it was a single-file
+program with nothing very fancy (I have written it in a night):
+
+```rust
+use crate::SpotifyURL::Track;
+use aspotify::{Client, ClientCredentials};
+use teloxide::prelude::*;
+
+enum SpotifyURL {
+    Track(String),
+}
+
+fn get_spotify_entry(url: &str) -> Option<SpotifyURL> {
+    if url.contains("https://open.spotify.com/track/") {
+        let track_id = url.rsplit('/').next().and_then(|x| x.split('?').next());
+        return match track_id {
+            Some(id) => Some(SpotifyURL::Track(id.to_string())),
+            None => None,
+        };
+    }
+    return None;
+}
+
+struct TrackInfo {
+    name: String,
+    artist: Vec<String>,
+}
+
+async fn get_spotify_track(spotify: Box<Client>, id: &String) -> Option<TrackInfo> {
+    match spotify.tracks().get_track(id.as_str(), None).await {
+        Ok(track) => Some(TrackInfo {
+            name: track.data.name,
+            artist: track.data.artists.iter().map(|x| x.name.clone()).collect(),
+        }),
+        Err(_e) => None,
+    }
+}
+
+#[tokio::main]
+async fn main() {
+    teloxide::enable_logging!();
+    log::info!("Starting Songlify...");
+
+    let bot = Bot::from_env().auto_send();
+    teloxide::repl(bot, |message| async move {
+        let spotify_creds =
+            ClientCredentials::from_env().expect("CLIENT_ID and CLIENT_SECRET not found.");
+        let spotify_client = Box::new(Client::new(spotify_creds));
+
+        log::info!("Connected to Spotify");
+        let text = message.update.text().and_then(get_spotify_entry);
+        match text {
+            Some(spotify) => match spotify {
+                Track(id) => {
+                    let track_info = get_spotify_track(spotify_client, &id).await;
+                    match track_info {
+                        Some(info) => {
+                            let reply = format!(
+                                "Track information:\n\
+                                Track name: {}\n\
+                                Artists: {}",
+                                info.name,
+                                info.artist.join(", ")
+                            );
+                            Some(message.reply_to(reply).await?)
+                        }
+                        None => None,
+                    }
+                }
+            },
+            None => None,
+        };
+        respond(())
+    })
+    .await;
+
+    log::info!("Exiting...");
+}
+```
+
+As you can see, basically every time a request arrived to the bot, login to
+Spotify was performed and track information and name retrieved from there. Of
+course this was only the beginning (also you can "appreciate" the number of
+nested blocks there...). Now the bot supports albums and playlists too, with the
+possibility to go through each song in the playlist and collect general
+information such as how many artists are in that playlist, how many songs and
+other little information like that. If you see the [bot
+repository](https://git.poldebra.me/polpetta/Songlify) you can see now that
+Spotify functions live in a separate module.
+
+#### Packaging and distribution
+
+The obvious choice for a software like that was to incorporate it into a OCI
+image. I wrote a very simple Dockerfile that, once the program was built, took
+the artifact and using the [multi-stage Docker build
+functionality](https://docs.docker.com/develop/develop-images/multistage-build/)
+and put it into a separate container, in order to avoid having build
+dependencies inside the final image. I used the images distributed by the
+[Distroless project](gcr.io/distroless/) (you can find the source on their
+[Github repository](https://github.com/GoogleContainerTools/distroless)) in
+order to obtain the smallest possible image. The final result?
+
+```txt
+λ ~/Desktop/git/songlify/ docker images
+REPOSITORY               TAG                    IMAGE ID       CREATED          SIZE
+test/test                latest                 8ac7a7018719   5 seconds ago    34MB
+<none>                   <none>                 4bc7fb0699e0   12 seconds ago   1.53GB
+rust                     1.56.1-slim-bullseye   d3e070c5ffa7   6 weeks ago      667MB
+gcr.io/distroless/base   latest-amd64           24787c1cd2e4   52 years ago     20.2MB
+```
+
+A part from the 52 years old image pulled from `gcr`, you can see that
+`test/test` (actually Songlify) is only of **34MB**. Not much if you consider
+that inside that image there are shared dynamic libraries to make the executable
+able to run, which by default weights 20MB. A plus of these images is that they
+do not run as root user and they do not have any shell of bash integrated,
+making a possible surface attack smaller (not that Docker is secure anyway...).
+I upload the images on Docker Hub, where you can find them here
+<https://hub.docker.com/r/polpetta/songlify>
+
+Finally, to run the bot I use a very simple docker-compose definition, that can
+be found in my [server-dotfiles
+repository](https://git.poldebra.me/polpetta/server-dotfiles/src/commit/7e7e1780b2db45f475510c49bf1a2f9e76c4c166/songlify/docker-compose.yml).
+This allows me to easily upgrade the bot by just changing the version and
+running `docker-compose up -d`.
+
+#### Plans for the future
+
+Currently I work on the bot only when I feel like I wanna add something. An
+interesting feature to add could be to insert a persistence layer (using a
+database for instance) and add various stats (which is the most shared song? Who
+_is that guy_ that shares the most songs in a group?). Persistence can be
+achieved quite easily by using [Diesel](https://diesel.rs/), an ORM compatible
+with various databases.
+
+Another cool feature could be to add the _inline bot_ functionality, where you
+can search for songs directly in Spotify. Since I currently have a domain
+available for that I could set it up for receive web-hook notifications, instead
+of performing polling like the bot is currently doing (one requisite for inline
+bots is indeed to receive web-hooks). There are platforms like Heroku where you
+could make the bot run, but currently I prefer to use my box since it gives me
+more flexibility. Experimenting with Heroku could lead to cool results though
+😏.
+
+Finally, link translation could be something very useful. I have a friend that
+does not use Spotify but prefers to listen to music via YouTube. So an
+interesting feature would be, given a Spotify link, to "convert" it into a
+YouTube link and, of course, _vice-versa_. This could lead to translate
+playlists and albums too into YouTube-based playlists, which of course could be
+very useful if you are trying to avoid the infamous _vendor lock-in_, in this
+case being stuck with Spotify because all you music collection, saved songs, etc
+is there.

tools/dictionary.en.pws

@@ -35,4 +35,46 @@ Terraform
 dojo
 Gitea
 orchestrators
-md
+md
+Spotify
+spotify
+ORM
+Songlify
+dotfiles
+txt
+amd
+cd
+gcr
+OCI
+songlify
+TorreArchimedeBot
+Subreddit
+JetBrains
+IntelliJ
+UI
+async
+GC
+README
+tokio
+teloxide
+fn
+env
+repl
+telegramscreen
+SpotifyURL
+aspotify
+ClientCredentials
+enum
+url
+str
+TrackInfo
+Ok
+TrackInfo
+Dockerfile
+Distroless
+bc
+fb
+ffa
+struct
+Vec
+creds