// <recommend-two>
use actix_web::{
    error, get,
    http::{header::ContentType, StatusCode},
    App, HttpResponse, HttpServer,
};
use derive_more::{Display, Error};

#[derive(Debug, Display, Error)]
enum UserError {
    #[display(fmt = "An internal error occurred. Please try again later.")]
    InternalError,
}

impl error::ResponseError for UserError {
    fn error_response(&self) -> HttpResponse {
        HttpResponse::build(self.status_code())
            .insert_header(ContentType::html())
            .body(self.to_string())
    }

    fn status_code(&self) -> StatusCode {
        match *self {
            UserError::InternalError => StatusCode::INTERNAL_SERVER_ERROR,
        }
    }
}

#[get("/")]
async fn index() -> Result<&'static str, UserError> {
    do_thing_that_fails().map_err(|_e| UserError::InternalError)?;
    Ok("success!")
}
// </recommend-two>

fn do_thing_that_fails() -> Result<(), std::io::Error> {
    Err(std::io::Error::new(std::io::ErrorKind::Other, "some error"))
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| App::new().service(index))
        .bind(("127.0.0.1", 8080))?
        .run()
        .await
}