# async-cron-scheduler

Runtime-agnostic async task scheduler with cron expression support

- **Lightweight**: Minimal dependencies because it does not rely on a runtime.
- **Efficient**: Tickless design with no reference counters.
- **Runtime-Agnostic**: Bring your own runtime. No runtime dependencies.
- **Async**: A single future drives the entire scheduler service.
- **Task Scheduling**: Schedule multiple jobs with varying timeframes between them.
- **Cron Expressions**: Standardized format for scheduling syntax.

## Demo

```rs
use chrono::offset::Local;
use async_cron_scheduler::*;
use smol::Timer;
use std::time::Duration;

smol::block_on(async move {
    // Creates a scheduler based on the Local timezone. Note that the `sched_service`
    // contains the background job as a future for the caller to decide how to await
    // it. When the scheduler is dropped, the scheduler service will exit as well.
    let (mut scheduler, sched_service) = Scheduler::<Local>::launch(Timer::after);

    // Creates a job which executes every 1 seconds.
    let job = Job::cron("1/1 * * * * *").unwrap();
    let fizz_id = scheduler.insert(job, |id| println!("Fizz")).await;

    // Creates a job which executes every 3 seconds.
    let job = Job::cron("1/3 * * * * *").unwrap();
    let buzz_id = scheduler.insert(job, |id| println!("Buzz")).await;

    // Creates a job which executes every 5 seconds.
    let job = Job::cron("1/5 * * * * *").unwrap();
    let bazz_id = scheduler.insert(job, |id| println!("Bazz")).await;

    // A future which gradually drops jobs from the scheduler.
    let dropper = async move {
        Timer::after(Duration::from_secs(7)).await;
        scheduler.remove(fizz_id).await;
        println!("Fizz gone");
        Timer::after(Duration::from_secs(5)).await;
        scheduler.remove(buzz_id).await;
        println!("Buzz gone");
        Timer::after(Duration::from_secs(1)).await;
        scheduler.remove(bazz_id).await;
        println!("Bazz gone");

        // `scheduler` is dropped here, which causes the sched_service to end.
    };

    // Poll the dropper and scheduler service concurrently until both return.
    futures::future::join(sched_service, dropper).await;
});
```

## License

Licensed under the [Mozilla Public License 2.0](https://choosealicense.com/licenses/mpl-2.0/).

### Contribution

Any contribution intentionally submitted for inclusion in the work by you shall be licensed under the Mozilla Public License 2.0 (MPL-2.0).