// The version of Heroku ping-pong-bot, which uses a webhook to receive updates
// from Telegram, instead of long polling.

use teloxide::{dispatching::update_listeners, prelude::*};

use std::{convert::Infallible, env, net::SocketAddr, sync::Arc};
use tokio::sync::mpsc;
use warp::Filter;

use reqwest::StatusCode;

#[tokio::main]
async fn main() {
    run().await;
}

async fn handle_rejection(
    error: warp::Rejection,
) -> Result<impl warp::Reply, Infallible> {
    log::error!("Cannot process the request due to: {:?}", error);
    Ok(StatusCode::INTERNAL_SERVER_ERROR)
}

pub async fn webhook<'a>(
    bot: Arc<Bot>,
) -> impl update_listeners::UpdateListener<Infallible> {
    // Heroku defines auto defines a port value
    let teloxide_token = env::var("TELOXIDE_TOKEN")
        .expect("TELOXIDE_TOKEN env variable missing");
    let port: u16 = env::var("PORT")
        .expect("PORT env variable missing")
        .parse()
        .expect("PORT value to be integer");
    // Heroku host example .: "heroku-ping-pong-bot.herokuapp.com"
    let host = env::var("HOST").expect("have HOST env variable");
    let path = format!("bot{}", teloxide_token);
    let url = format!("https://{}/{}", host, path);

    bot.set_webhook(url).send().await.expect("Cannot setup a webhook");

    let (tx, rx) = mpsc::unbounded_channel();

    let server = warp::post()
        .and(warp::path(path))
        .and(warp::body::json())
        .map(move |json: serde_json::Value| {
            let try_parse = match serde_json::from_str(&json.to_string()) {
                Ok(update) => Ok(update),
                Err(error) => {
                    log::error!(
                        "Cannot parse an update.\nError: {:?}\nValue: {}\n\
                       This is a bug in teloxide, please open an issue here: \
                       https://github.com/teloxide/teloxide/issues.",
                        error,
                        json
                    );
                    Err(error)
                }
            };
            if let Ok(update) = try_parse {
                tx.send(Ok(update))
                    .expect("Cannot send an incoming update from the webhook")
            }

            StatusCode::OK
        })
        .recover(handle_rejection);

    let serve = warp::serve(server);

    let address = format!("0.0.0.0:{}", port);
    tokio::spawn(serve.run(address.parse::<SocketAddr>().unwrap()));
    rx
}

async fn run() {
    teloxide::enable_logging!();
    log::info!("Starting heroku_ping_pong_bot!");

    let bot = Bot::from_env();

    Dispatcher::new(Arc::clone(&bot))
        .messages_handler(|rx: DispatcherHandlerRx<Message>| {
            rx.for_each(|message| async move {
                message.answer_str("pong").await.log_on_error().await;
            })
        })
        .dispatch_with_listener(
            webhook(bot).await,
            LoggingErrorHandler::with_custom_text(
                "An error from the update listener",
            ),
        )
        .await;
}