mod models {
    use serde::{Deserialize, Serialize};
    use tokio_pg_mapper_derive::PostgresMapper;

    #[derive(Deserialize, PostgresMapper, Serialize)]
    #[pg_mapper(table = "users")] // singular 'user' is a keyword..
    pub struct User {
        pub email: String,
        pub first_name: String,
        pub last_name: String,
        pub username: String,
    }
}

mod errors {
    use actix_web::{HttpResponse, ResponseError};
    use deadpool_postgres::PoolError;
    use derive_more::{Display, From};
    use tokio_pg_mapper::Error as PGMError;
    use tokio_postgres::error::Error as PGError;

    #[derive(Display, From, Debug)]
    pub enum MyError {
        NotFound,
        PGError(PGError),
        PGMError(PGMError),
        PoolError(PoolError),
    }
    impl std::error::Error for MyError {}

    impl ResponseError for MyError {
        fn error_response(&self) -> HttpResponse {
            match *self {
                MyError::NotFound => HttpResponse::NotFound().finish(),
                _ => HttpResponse::InternalServerError().finish(),
            }
        }
    }
}

mod db {
    use crate::{errors::MyError, models::User};
    use deadpool_postgres::Client;
    use tokio_pg_mapper::FromTokioPostgresRow;

    pub async fn add_user(client: &Client, user_info: User) -> Result<User, MyError> {
        let _stmt = include_str!("../sql/add_user.sql");
        let _stmt = _stmt.replace("$table_fields", &User::sql_table_fields());
        let stmt = client.prepare(&_stmt).await.unwrap();

        client
            .query(
                &stmt,
                &[
                    &user_info.email,
                    &user_info.first_name,
                    &user_info.last_name,
                    &user_info.username,
                ],
            )
            .await?
            .iter()
            .map(|row| User::from_row_ref(row).unwrap())
            .collect::<Vec<User>>()
            .pop()
            .ok_or(MyError::NotFound) // more applicable for SELECTs
    }
}

mod handlers {
    use crate::{db, errors::MyError, models::User};
    use actix_web::{web, Error, HttpResponse};
    use deadpool_postgres::{Client, Pool};

    pub async fn add_user(
        user: web::Json<User>,
        db_pool: web::Data<Pool>,
    ) -> Result<HttpResponse, Error> {
        let user_info: User = user.into_inner();

        let client: Client =
            db_pool.get().await.map_err(|err| MyError::PoolError(err))?;

        let new_user = db::add_user(&client, user_info).await?;

        Ok(HttpResponse::Ok().json(new_user))
    }
}

use actix_web::{web, App, HttpServer};
use deadpool_postgres::{Manager, Pool};
use handlers::add_user;
use tokio_postgres::{Config, NoTls};

#[actix_rt::main]
async fn main() -> std::io::Result<()> {
    const SERVER_ADDR: &str = "127.0.0.1:8080";

    let pg_config = "postgres://test_user:testing@127.0.0.1:5432/testing_db"
        .parse::<Config>()
        .unwrap();

    let pool = Pool::new(
        Manager::new(pg_config, NoTls),
        16, // # of connections in pool
    );

    let server = HttpServer::new(move || {
        App::new()
            .data(pool.clone())
            .service(web::resource("/users").route(web::post().to(add_user)))
    })
    .bind(SERVER_ADDR)?
    .run();
    println!("Server running at http://{}/", SERVER_ADDR);

    server.await
}