matrix-rust-bot/src/main.rs

use std::{env, process::exit};

use matrix_sdk::{
    config::SyncSettings,
    room::Room,
    ruma::events::room::{
        member::StrippedRoomMemberEvent,
        message::{MessageType, OriginalSyncRoomMessageEvent, RoomMessageEventContent},
    },
    Client,
};
use tokio::time::{sleep, Duration};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    tracing_subscriber::fmt::init();

    // parse the command line for homeserver, username and password
    let (homeserver_url, username, password) =
        match (env::args().nth(1), env::args().nth(2), env::args().nth(3)) {
            (Some(a), Some(b), Some(c)) => (a, b, c),
            _ => {
                eprintln!(
                    "Usage: {} <homeserver_url> <username> <password>",
                    env::args().next().unwrap()
                );
                // exist if missing
                exit(1)
            }
        };

    // our actual runner
    login_and_sync(homeserver_url, &username, &password).await?;
    Ok(())
}

// The core sync loop we have running.
async fn login_and_sync(
    homeserver_url: String,
    username: &str,
    password: &str,
) -> anyhow::Result<()> {
    // First, we set up the client.

    // Note that when encryption is enabled, you should use a persistent store to be
    // able to restore the session with a working encryption setup.
    // See the `persist_session` example.
    let client = Client::builder()
        // We use the convenient client builder to set our custom homeserver URL on it.
        .homeserver_url(homeserver_url)
        .build()
        .await?;

    // Then let's log that client in
    client
        .matrix_auth()
        .login_username(username, password)
        .initial_device_display_name("getting started bot")
        .await?;

    // It worked!
    println!("logged in as {username}");

    // Now, we want our client to react to invites. Invites sent us stripped member
    // state events so we want to react to them. We add the event handler before
    // the sync, so this happens also for older messages. All rooms we've
    // already entered won't have stripped states anymore and thus won't fire
    client.add_event_handler(on_stripped_state_member);

    // An initial sync to set up state and so our bot doesn't respond to old
    // messages. If the `StateStore` finds saved state in the location given the
    // initial sync will be skipped in favor of loading state from the store
    let sync_token = client.sync_once(SyncSettings::default()).await.unwrap().next_batch;

    // now that we've synced, let's attach a handler for incoming room messages, so
    // we can react on it
    client.add_event_handler(on_room_message);

    // since we called `sync_once` before we entered our sync loop we must pass
    // that sync token to `sync`
    let settings = SyncSettings::default().token(sync_token);
    // this keeps state from the server streaming in to the bot via the
    // EventHandler trait
    client.sync(settings).await?; // this essentially loops until we kill the bot

    Ok(())
}

// Whenever we see a new stripped room member event, we've asked our client to
// call this function. So what exactly are we doing then?
async fn on_stripped_state_member(
    room_member: StrippedRoomMemberEvent,
    client: Client,
    room: Room,
) {
    if room_member.state_key != client.user_id().unwrap() {
        // the invite we've seen isn't for us, but for someone else. ignore
        return;
    }

    // looks like the room is an invited room, let's attempt to join then
    if let Room::Invited(room) = room {
        // The event handlers are called before the next sync begins, but
        // methods that change the state of a room (joining, leaving a room)
        // wait for the sync to return the new room state so we need to spawn
        // a new task for them.
        tokio::spawn(async move {
            println!("Autojoining room {}", room.room_id());
            let mut delay = 2;

            while let Err(err) = room.accept_invitation().await {
                // retry autojoin due to synapse sending invites, before the
                // invited user can join for more information see
                // https://github.com/matrix-org/synapse/issues/4345
                eprintln!("Failed to join room {} ({err:?}), retrying in {delay}s", room.room_id());

                sleep(Duration::from_secs(delay)).await;
                delay *= 2;

                if delay > 3600 {
                    eprintln!("Can't join room {} ({err:?})", room.room_id());
                    break;
                }
            }
            println!("Successfully joined room {}", room.room_id());
        });
    }
}

// This fn is called whenever we see a new room message event. You notice that
// the difference between this and the other function that we've given to the
// handler lies only in their input parameters. However, that is enough for the
// rust-sdk to figure out which one to call one and only do so, when
// the parameters are available.
async fn on_room_message(event: OriginalSyncRoomMessageEvent, room: Room) {
    // First, we need to unpack the message: We only want messages from rooms we are
    // still in and that are regular text messages - ignoring everything else.
    let Room::Joined(room) = room else { return };
    let MessageType::Text(text_content) = event.content.msgtype else { return };

    // here comes the actual "logic": when the bot see's a `!party` in the message,
    // it responds
    if text_content.body.contains("!party") {
        let content = RoomMessageEventContent::text_plain("🎉🎊🥳 let's PARTY!! 🥳🎊🎉");

        println!("sending");

        // send our message to the room we found the "!party" command in
        // the last parameter is an optional transaction id which we don't
        // care about.
        room.send(content, None).await.unwrap();

        println!("message sent");
    }
}