# Regorus Java

**Regorus** is

  - *Rego*-*Rus(t)*  - A fast, light-weight [Rego](https://www.openpolicyagent.org/docs/latest/policy-language/)
   interpreter written in Rust.
  - *Rigorous* - A rigorous enforcer of well-defined Rego semantics.

See main [Regorus page](https://github.com/microsoft/regorus) for more details about the project.

## Usage

Regorus Java is published to Maven Central with native libraries for the following:

- 64-bit Linux (kernel 3.2+, glibc 2.17+)
- ARM64 Linux (kernel 4.1, glibc 2.17+)
- 64-bit macOS (10.12+, Sierra+)
- ARM64 macOS (11.0+, Big Sur+)
- 64-bit MSVC (Windows 7+)

If you need to run it in a different OS or an architecture you need to manually [build it](#Building).

If you're on one of the supported platforms, you can just pull prebuilt JAR from Maven Central by declaring a dependency on `com.microsoft.regorus:regorus-java`.

With [Maven](https://maven.apache.org/):
```xml
<dependencies>
    <dependency>
        <groupId>com.microsoft.regorus</groupId>
        <artifactId>regorus-java</artifactId>
        <version>0.0.1</version>
    </dependency>
</dependencies>
```

With [Gradle](https://gradle.org/):
```kotlin
// build.gradle.kts
implementation("com.microsoft.regorus:regorus-java:0.0.1")
```

Afterwards you can use it as follows:

```java
import com.microsoft.regorus.Engine;

public class Test {
    public static void main(String[] args) {
        try (Engine engine = new Engine()) {
            engine.addPolicy(
                "hello.rego",
                "package test\nmessage = concat(\", \", [input.message, data.message])"
            );
            engine.addDataJson("{\"message\":\"World!\"}");
            engine.setInputJson("{\"message\":\"Hello\"}");
            String resJson = engine.evalQuery("data.test.message");

            System.out.println(resJson);
        }
    }
}
```

And you can see the following output once you run it:
```shell
{"result":[{"expressions":[{"value":"Hello, World!","text":"data.test.message","location":{"row":1,"col":1}}]}]}
```

## Building

In order to build Regorus Java for a target platform, you need to install Rust target
for that target platform first:

```bash
$ rustup target add aarch64-apple-darwin
```

Afterwards, you can build native library for that target using:
```bash
$ cargo build --release --target aarch64-apple-darwin
```

You will then have a native library at `../../target/aarch64-apple-darwin/release/libregorus_java.dylib` depending on your target.

You can then build a JAR from source using:
```bash
$ mvn package
```

And you will have a JAR at `./target/regorus-java-0.0.1.jar`.

You need to make sure both of the artifacts in Java's classpath.
For example with `java` CLI:
```bash
$ java -Djava.library.path=../../target/aarch64-apple-darwin/release/ -cp target/regorus-java-0.0.1.jar Test.java
```