//! Helpers shared between harness modules and tests.

use std::future::Future;
use std::net::{Ipv4Addr, SocketAddr, TcpListener};
use std::time::{Duration, Instant};

/// Pick a free TCP port by binding to `127.0.0.1:0` and immediately releasing.
///
/// There is a small race: another process may grab the port between drop and
/// the child re-binding, but for local single-user test runs it's negligible.
pub fn free_port() -> u16 {
    let l = TcpListener::bind(SocketAddr::from((Ipv4Addr::LOCALHOST, 0))).expect("bind :0");
    l.local_addr().expect("local_addr").port()
}

/// Poll `cond` every 50ms until it returns `true` or `timeout` elapses.
/// Panics on timeout with `label`.
pub async fn wait_for_async<F, Fut>(label: &str, timeout: Duration, mut cond: F)
where
    F: FnMut() -> Fut,
    Fut: Future<Output = bool>,
{
    let deadline = Instant::now() + timeout;
    while Instant::now() < deadline {
        if cond().await {
            return;
        }
        tokio::time::sleep(Duration::from_millis(50)).await;
    }
    panic!("timed out after {timeout:?} waiting for: {label}");
}