use std::{env, sync::Arc, thread};

use r2d2_mysql::{
    mysql::{prelude::*, Opts, OptsBuilder},
    r2d2, MySqlConnectionManager,
};

fn main() {
    let url = env::var("DATABASE_URL").unwrap();
    let opts = Opts::from_url(&url).unwrap();
    let builder = OptsBuilder::from_opts(opts);
    let manager = MySqlConnectionManager::new(builder);
    let pool = Arc::new(r2d2::Pool::builder().max_size(4).build(manager).unwrap());

    let mut tasks = vec![];

    for _ in 0..3 {
        let pool = pool.clone();
        let th = thread::spawn(move || {
            let mut conn = pool.get().expect("error getting connection from pool");

            let _ = conn
                .query("SELECT version()")
                .map(|rows: Vec<String>| rows.is_empty())
                .expect("error executing query");
        });

        tasks.push(th);
    }

    for th in tasks {
        let _ = th.join();
    }
}