after.java

public class CommandGenerateStructure extends SimpleCommand
{
    public CommandGenerateStructure()
    {
        super(RCConfig.commandPrefix + "gen");
        permitFor(2);
    }

    @Override
    public Expect<?> expect()
    {
        return RCExpect.expectRC()
                .structure()
                .surfacePos("x", "z")
                .named("gen")
                .next(params -> new RCParameters(params).rc().genericStructure().tryGet()
                        .map(structure -> structure.generationTypes(GenerationType.class).stream().map(GenerationType::id))
                ).optionalU("generation type id")
    }

    @Override
    @ParametersAreNonnullByDefault
    public void execute(MinecraftServer server, ICommandSender sender, String[] args) throws CommandException
    {
        RCParameters parameters = RCParameters.of(args, expect()::declare);

        String structureID = parameters.get().first().require();
        Structure<?> structure = parameters.rc().structure().require();
        GenerationType generationType = parameters.rc("gen").generationType(structure).require();
        BlockSurfacePos pos = parameters.surfacePos("x", "z", sender.getPosition(), false).require();

        Placer placer = generationType.placer();

        StructureGenerator<?> generator = new StructureGenerator<>(structure).world(sender.getWorld()).generationInfo(generationType)
                .structureID(structureID).randomPosition(pos, placer).fromCenter(true);

        Optional<StructureBoundingBox> boundingBox = generator.boundingBox();
        if (!boundingBox.isPresent())
            throw ServerTranslations.commandException("commands.strucGen.noPlace");

        if (structure instanceof GenericStructure && world == sender.getEntityWorld())
        {
            GenericStructure genericStructureInfo = (GenericStructure) structure;

            BlockPos lowerCoord = StructureBoundingBoxes.min(boundingBox.get());

            OperationRegistry.queueOperation(new OperationGenerateStructure(genericStructureInfo, generationType.id(), lowerCoord, false)
                    .withStructureID(structureID).prepare(world), sender);
        }
        else
        {
            if (generator.generate() == null)
                throw ServerTranslations.commandException("commands.strucGen.noPlace");
        }
    }
}