# Reactive Programming for Bevy

This library provides sophisticated [reactive programming](https://en.wikipedia.org/wiki/Reactive_programming) for the [bevy](https://bevyengine.org/) ECS. In addition to supporting one-shot chains of async operations, it can support reusable workflows with parallel branches, synchronization, races, and cycles. These workflows can be hierarchical, so a workflow can be used as a building block by other workflows.

![sense-think-act workflow](assets/figures/sense-think-act_workflow.svg)

# Why use bevy impulse?

There are several different categories of problems that bevy impulse sets out to solve. If any one of these use-cases is relevant to you, it's worth considering bevy impulse as a solution:

* Coordinating **async activities** (e.g. filesystem i/o, network i/o, or long-running calculations) with regular bevy systems
* Calling **one-shot systems** on an ad hoc basis, where the systems require an input value and produce an output value that you need to use
* Defining a **procedure** to be followed by your application or by an agent or pipeline within your application
* Designing a complex **state machine** that gradually switches between different modes or behaviors while interacting with the world
* Managing many **parallel threads** of activities that need to be synchronized or raced against each other

# Helpful Links

 * [Introduction to workflows](https://docs.google.com/presentation/d/1_vJTyFKOB1T0ylCbp1jG72tn8AXYQOKgTGh9En9si-w/edit?usp=sharing)
 * [Bevy Engine](https://bevyengine.org/)
 * [Bevy Cheat Book](https://bevy-cheatbook.github.io/)
 * [Rust Book](https://doc.rust-lang.org/stable/book/)

# Experimenting

### Install Rust

Follow [official guidelines](https://www.rust-lang.org/tools/install) to install the Rust language.

### Get source code

```
$ git clone https://github.com/open-rmf/bevy_impulse
```

### Build

To build the library simply go to the root directory of the repo and run

```
$ cargo build
```

### Test

The library's tests can be run with

```
$ cargo test
```

### View Documentation

Like most Rust projects, the library documentation is written into the source code and can be built and viewed with

```
$ cargo doc --open
```

After the first release of the library, the documentation will be hosted on docs.rs. We will update this README with a link to that documentation once it is ready.