Command

A pure, functional, typesafe command line parser.

Import

Gradle

repositories {
    mavenCentral()
}

dependencies {
    implementation 'io.typst:command-bukkit:2.1.0'
}

Maven

<dependency>
    <groupId>io.typst</groupId>
    <artifactId>command-bukkit</artifactId>
    <version>0.8.0</version>
</dependency>

Usage

// core/src/test/../CommandTest.java
// MyCommand = AddItem | RemoveItem | OpenItemList | ReloadCommand
Command<MyCommand> command = Command.mapping(
        pair("item", Command.mapping(
                pair("open", Command.present(new OpenItemList())),
                // intArg: Argument<Integer>
                // strArg: Argument<String>
                // AddItem::new = (Integer, String) -> AddItem
                pair("add", Command.argument(AddItem::new, intArg, strArg)),
                pair("remove", Command.argument(RemoveItem::new, intArg))
        )),
        pair("reload", Command.present(new ReloadCommand()))
);
// parsing
String[] args = new String[] {"item", "add", "0", "NAME"};
MyCommand algebra = Command.parseO(args, command).orElse(null);
// execution, check with if-instanceof.
// assumes `MyCommand` is sealed, treat like Enum.
// therefore, this is a valid type casting (not unsafe).
if (algebra instanceof MyCommand.AddItem) {
    MyCommand.AddItem addItem = (MyCommand.AddItem) algebra;
    println(String.format("Adding item %s, %s!", addItem.getIndex(), addItem.getName()));
} else if (algebra instanceof MyCommand.RemoveItem) {
    MyCommand.RemoveItem removeItem = (MyCommand.RemoveItem) algebra;
    println(String.format("Removing item %s", removeItem.getIndex()));
}

FAQ

Why not just execute?

Command<Void> node = Command.mapping(
  pair("foo", Command.argument(integer -> {
    GlobalVariables.someVar = integer;
    System.out.println("Input is: " + integer); // here to break purity
    return null;
  }, intArg))
)

1. Lines too long

If you inline command implementation into the node declaration, it will easily to be ugly and hard to maintain.

2. Concurrent

You can't run Command.parse without synchronization, because it mutates global variable.

3. Type safety

Loose type safety even in typed programming language, you don't know what command is parsed.

4. Testing

Hard to test what it printed.

5. Reusability

Can't run the command implementation without parsing the command arguments.