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//! The [`Bot`] struct and server setup.

use crate::{core::Core, request::CallbackAPIRequest};
use rocket::{
    config::{Config, Environment},
    http::Status,
    State,
};
use rocket_contrib::json::Json;
use rvk::APIClient;
use std::sync::{Arc, Mutex};

/// The string `ok` which needs to be sent in response to every Callback API
/// request.
const VK_OK: &'static str = "ok";

/// [`Bot`] represents a chat bot, and hands received requests to [`Core`].
#[derive(Debug, Clone)]
pub struct Bot {
    api: Arc<Mutex<APIClient>>,
    confirmation_token: String,
    group_id: i32,
    secret: String,
    port: u16,
    core: Core,
}

impl Bot {
    /// Creates a new [`Bot`].
    #[must_use = "the bot does nothing unless started via `.start()`"]
    pub fn new(
        vk_token: &str,
        confirmation_token: &str,
        group_id: i32,
        secret: &str,
        port: u16,
        core: Core,
    ) -> Self {
        Self {
            api: Arc::new(Mutex::new(APIClient::new(vk_token.into()))),
            confirmation_token: confirmation_token.into(),
            group_id,
            secret: secret.into(),
            port,
            core,
        }
    }

    /// Alias for `self.core.handle(req, self.api())`.
    pub fn handle(&self, req: &CallbackAPIRequest) {
        self.core.handle(req, self.api());
    }

    /// Starts this [`Bot`], consuming `self`.
    ///
    /// # Panics
    /// - if Rocket was not able to launch.
    pub fn start(self) -> ! {
        info!("starting bot...");

        let err = rocket::custom(
            Config::build(Environment::Production)
                .address("0.0.0.0")
                .port(self.port)
                .unwrap(),
        )
        .mount("/", routes![post, get])
        .manage(self)
        .launch();

        panic!("{}", err);
    }

    /// Returns the [`rvk::APIClient`] stored in this [`Bot`].
    pub fn api(&self) -> Arc<Mutex<APIClient>> {
        Arc::clone(&self.api)
    }

    /// Returns the confirmation token stored in this [`Bot`].
    pub fn confirmation_token(&self) -> &String {
        &self.confirmation_token
    }

    /// Returns the group ID stored in this [`Bot`].
    pub fn group_id(&self) -> i32 {
        self.group_id
    }

    /// Returns the secret stored in this [`Bot`].
    pub fn secret(&self) -> &String {
        &self.secret
    }
}

/// Handles `GET` requests by returning
/// [`rocket::http::Status::MethodNotAllowed`].
#[get("/")]
fn get() -> Status {
    debug!("received a GET request");
    Status::MethodNotAllowed
}

/// Handles `POST` requests by first checking that secret and group ID are
/// correct, and then responds with either confirmation token (if that is what
/// was requested) or [`VK_OK`] in the other case.
#[post("/", format = "json", data = "<data>")]
fn post(data: Json<CallbackAPIRequest>, state: State<Bot>) -> Result<String, Status> {
    let bot = &*state;

    match &data {
        x if x.secret() != bot.secret() => {
            debug!("received a POST request with invalid `secret`");
            Err(Status::Forbidden)
        }
        x if x.group_id() != bot.group_id() => {
            debug!("received a POST request with invalid `group_id`");
            Err(Status::Forbidden)
        }
        x if x.r#type() == "confirmation" => {
            debug!("responded with confirmation token");
            Ok(bot.confirmation_token().clone())
        }
        _ => {
            bot.handle(&data);
            Ok(VK_OK.into())
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn get_returns_405() {
        assert_eq!(get(), Status::MethodNotAllowed);
    }

    fn post_test(secret: &str, group_id: i32, event: &str) -> Result<String, Status> {
        let rocket = rocket::ignite().manage(Bot::new(
            "vk_token",
            "confirmation_token",
            1,
            "secret",
            12345,
            Default::default(),
        ));

        post(
            Json(CallbackAPIRequest::new(
                secret,
                group_id,
                event,
                Default::default(),
            )),
            State::from(&rocket).unwrap(),
        )
    }

    #[test]
    fn post_invalid_secret_returns_403() {
        assert_eq!(post_test("wrong_secret", 1, ""), Err(Status::Forbidden));
    }

    #[test]
    fn post_invalid_group_id_returns_403() {
        assert_eq!(post_test("secret", 1337, ""), Err(Status::Forbidden));
    }

    #[test]
    fn post_confirmation_returns_confirmation_token() {
        assert_eq!(
            post_test("secret", 1, "confirmation"),
            Ok("confirmation_token".to_string())
        );
    }
}