zonfig 0.1.0

A small dynamic configuration loader with file watching and hot reload support.
Documentation 
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use std::time::Duration;

use serde::Deserialize;

#[derive(Debug, Deserialize, PartialEq, Eq)]
struct AppConfig {
    host: String,
    port: u16,
}

#[tokio::test]
async fn publishes_valid_updates() {
    let dir = tempfile::tempdir().expect("tempdir");
    let path = dir.path().join("app.toml");

    std::fs::write(&path, "host = \"127.0.0.1\"\nport = 8080\n").expect("write initial");

    let watched = zonfig::watch::<AppConfig>(&path).await.expect("watch");
    let mut reader = watched.subscribe();

    tokio::time::sleep(Duration::from_millis(200)).await;
    std::fs::write(&path, "host = \"0.0.0.0\"\nport = 9090\n").expect("write update");

    let updated = tokio::time::timeout(Duration::from_secs(3), reader.changed())
        .await
        .expect("update timeout")
        .expect("changed");

    assert_eq!(updated.host, "0.0.0.0");
    assert_eq!(updated.port, 9090);
}

#[tokio::test]
async fn calls_change_hooks_after_valid_updates() {
    let dir = tempfile::tempdir().expect("tempdir");
    let path = dir.path().join("app.toml");

    std::fs::write(&path, "host = \"127.0.0.1\"\nport = 8080\n").expect("write initial");

    let watched = zonfig::watch::<AppConfig>(&path).await.expect("watch");
    let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel();

    watched.on_change(move |config| {
        let _ = tx.send(config.port);
    });

    tokio::time::sleep(Duration::from_millis(200)).await;
    std::fs::write(&path, "host = \"0.0.0.0\"\nport = 9090\n").expect("write update");

    let port = tokio::time::timeout(Duration::from_secs(3), rx.recv())
        .await
        .expect("hook timeout")
        .expect("hook event");

    assert_eq!(port, 9090);
}

#[tokio::test]
async fn cooldown_suppresses_burst_updates() {
    let dir = tempfile::tempdir().expect("tempdir");
    let path = dir.path().join("app.toml");

    std::fs::write(&path, "host = \"127.0.0.1\"\nport = 8080\n").expect("write initial");

    let watched = zonfig::watch_with_options::<AppConfig>(
        &path,
        zonfig::WatchOptions::default().with_cooldown(Duration::from_millis(350)),
    )
    .await
    .expect("watch");
    let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel();

    watched.on_change(move |config| {
        let _ = tx.send(config.port);
    });

    tokio::time::sleep(Duration::from_millis(200)).await;
    std::fs::write(&path, "host = \"0.0.0.0\"\nport = 9090\n").expect("write first update");
    tokio::time::sleep(Duration::from_millis(80)).await;
    std::fs::write(&path, "host = \"0.0.0.0\"\nport = 9091\n").expect("write second update");

    let port = tokio::time::timeout(Duration::from_secs(3), rx.recv())
        .await
        .expect("hook timeout")
        .expect("hook event");

    assert_eq!(port, 9090);
    assert!(
        tokio::time::timeout(Duration::from_millis(500), rx.recv())
            .await
            .is_err(),
        "burst updates should trigger one reload"
    );
}

#[tokio::test]
async fn keeps_last_good_value_after_invalid_update() {
    let dir = tempfile::tempdir().expect("tempdir");
    let path = dir.path().join("app.toml");

    std::fs::write(&path, "host = \"127.0.0.1\"\nport = 8080\n").expect("write initial");

    let watched = zonfig::watch::<AppConfig>(&path).await.expect("watch");
    let mut errors = watched.errors();

    tokio::time::sleep(Duration::from_millis(200)).await;
    std::fs::write(&path, "host = \"broken\"\nport = \"not a number\"\n").expect("write invalid");

    let error = tokio::time::timeout(Duration::from_secs(3), errors.recv())
        .await
        .expect("error timeout")
        .expect("error event");

    assert!(matches!(&*error, zonfig::Error::Parse { .. }));
    assert_eq!(watched.get().port, 8080);
}

#[tokio::test]
async fn with_reads_latest_value() {
    let dir = tempfile::tempdir().expect("tempdir");
    let path = dir.path().join("app.toml");

    std::fs::write(&path, "host = \"127.0.0.1\"\nport = 8080\n").expect("write initial");

    let watched = zonfig::watch::<AppConfig>(&path).await.expect("watch");
    let mut reader = watched.clone();

    assert_eq!(watched.with(|config| config.port), 8080);

    tokio::time::sleep(Duration::from_millis(200)).await;
    std::fs::write(&path, "host = \"0.0.0.0\"\nport = 9090\n").expect("write update");

    tokio::time::timeout(Duration::from_secs(3), reader.changed())
        .await
        .expect("update timeout")
        .expect("changed");

    assert_eq!(watched.with(|config| config.port), 9090);
}

#[tokio::test]
async fn calls_error_hooks_after_invalid_updates() {
    let dir = tempfile::tempdir().expect("tempdir");
    let path = dir.path().join("app.toml");

    std::fs::write(&path, "host = \"127.0.0.1\"\nport = 8080\n").expect("write initial");

    let watched = zonfig::watch::<AppConfig>(&path).await.expect("watch");
    let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel();

    watched.on_error(move |error| {
        let _ = tx.send(matches!(&*error, zonfig::Error::Parse { .. }));
    });

    tokio::time::sleep(Duration::from_millis(200)).await;
    std::fs::write(&path, "host = \"broken\"\nport = \"not a number\"\n").expect("write invalid");

    let is_parse_error = tokio::time::timeout(Duration::from_secs(3), rx.recv())
        .await
        .expect("hook timeout")
        .expect("hook event");

    assert!(is_parse_error);
    assert_eq!(watched.get().port, 8080);
}