//! Run with
//!
//! ```not_rust
//! cargo run -p example-tokio-postgres
//! ```

use axum::{
    extract::{FromRef, FromRequestParts, State},
    http::{request::Parts, StatusCode},
    routing::get,
    Router,
};
use bb8::{Pool, PooledConnection};
use bb8_postgres::PostgresConnectionManager;
use tokio_postgres::NoTls;
use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};

#[tokio::main]
async fn main() {
    tracing_subscriber::registry()
        .with(
            tracing_subscriber::EnvFilter::try_from_default_env()
                .unwrap_or_else(|_| format!("{}=debug", env!("CARGO_CRATE_NAME")).into()),
        )
        .with(tracing_subscriber::fmt::layer())
        .init();

    // set up connection pool
    let manager =
        PostgresConnectionManager::new_from_stringlike("host=localhost user=postgres", NoTls)
            .unwrap();
    let pool = Pool::builder().build(manager).await.unwrap();

    // build our application with some routes
    let app = Router::new()
        .route(
            "/",
            get(using_connection_pool_extractor).post(using_connection_extractor),
        )
        .with_state(pool);

    // run it
    let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
        .await
        .unwrap();
    tracing::debug!("listening on {}", listener.local_addr().unwrap());
    axum::serve(listener, app).await;
}

type ConnectionPool = Pool<PostgresConnectionManager<NoTls>>;

async fn using_connection_pool_extractor(
    State(pool): State<ConnectionPool>,
) -> Result<String, (StatusCode, String)> {
    let conn = pool.get().await.map_err(internal_error)?;

    let row = conn
        .query_one("select 1 + 1", &[])
        .await
        .map_err(internal_error)?;
    let two: i32 = row.try_get(0).map_err(internal_error)?;

    Ok(two.to_string())
}

// we can also write a custom extractor that grabs a connection from the pool
// which setup is appropriate depends on your application
struct DatabaseConnection(PooledConnection<'static, PostgresConnectionManager<NoTls>>);

impl<S> FromRequestParts<S> for DatabaseConnection
where
    ConnectionPool: FromRef<S>,
    S: Send + Sync,
{
    type Rejection = (StatusCode, String);

    async fn from_request_parts(_parts: &mut Parts, state: &S) -> Result<Self, Self::Rejection> {
        let pool = ConnectionPool::from_ref(state);

        let conn = pool.get_owned().await.map_err(internal_error)?;

        Ok(Self(conn))
    }
}

async fn using_connection_extractor(
    DatabaseConnection(conn): DatabaseConnection,
) -> Result<String, (StatusCode, String)> {
    let row = conn
        .query_one("select 1 + 1", &[])
        .await
        .map_err(internal_error)?;
    let two: i32 = row.try_get(0).map_err(internal_error)?;

    Ok(two.to_string())
}

/// Utility function for mapping any error into a `500 Internal Server Error`
/// response.
fn internal_error<E>(err: E) -> (StatusCode, String)
where
    E: std::error::Error,
{
    (StatusCode::INTERNAL_SERVER_ERROR, err.to_string())
}