use rocket::{get, routes};

pub fn rocket() -> rocket::Rocket<rocket::Build> {
    rocket::build().mount("/", routes![metrics,])
}

#[get("/metrics")]
fn metrics() -> Result<String, ServerError> {
    Ok(
        prometheus::TextEncoder::new()
            .encode_to_string(&prometheus::default_registry().gather())?,
    )
}

enum ServerError {
    Prometheus,
}

impl From<prometheus::Error> for ServerError {
    fn from(_: prometheus::Error) -> Self {
        Self::Prometheus
    }
}

impl<'a> rocket::response::Responder<'a, 'a> for ServerError {
    fn respond_to(self, _: &'a rocket::Request<'_>) -> rocket::response::Result<'a> {
        Err(match self {
            ServerError::Prometheus => rocket::http::Status::InternalServerError,
        })
    }
}