Command Design Pattern

CommandPatternExample.kt

class CommandPatternExample {
    companion object {
        @JvmStatic
        fun main(args: Array<String>) {
            val remoteControl: BaseRemoteControl = RemoteControl()
            println("-----Testing onButtonPressed on RemoteControl for Car-----")
            val car = Car()
            val carMoveCommand: Command = CarMoveCommand(car)
            remoteControl.onButtonPressed(carMoveCommand)
            println("-----Testing offButtonPressed on RemoteControl for Car-----")
            val carStopCommand: Command = CarStopCommand(car)
            remoteControl.offButtonPressed(carStopCommand)
            println("-----Testing undoButtonPressed() on RemoteControl for Car-----")
            remoteControl.undoButtonPressed()
            println("-----Testing onButtonPressed on RemoteControl for RotatingTop-----")
            val top = RotatingTop()
            val topRotateCommand: Command = TopRotateCommand(top)
            remoteControl.onButtonPressed(topRotateCommand)
            println("-----Testing offButtonPressed on RemoteControl for RotatingTop-----")
            val topStopRotateCommand: Command = TopStopRotateCommand(top)
            remoteControl.offButtonPressed(topStopRotateCommand)
            println("-----Testing undoButtonPressed on RemoteControl for RotatingTop-----")
            remoteControl.undoButtonPressed()
        }
    }
}

/**
 * Base for Remote Control System.
 * [execute] to execute some operation.
 * [undo] to undo recent operation.
 */
interface Command {
    fun execute()
    fun undo()
}

/**
 * Car class with some basic features [move] and [stop].
 */
class Car {
    fun move() = println("Car is moving")
    fun stop() = println("Car has stopped")
}

/**
 * RotatingTop class with some basic features [startRotating] and [stopRotating].
 */
class RotatingTop {
    fun startRotating() = println("Top has start rotating")
    fun stopRotating() = println("Top has stopped rotating")
}

/**
 * Concrete class of [Command], implement (Car move and stop) the operations for [execute] and [undo].
 *
 * @param car [Car] object.
 */
class CarMoveCommand(private val car: Car) : Command {
    override fun execute() {
        println("CarMoveCommand.execute(): Invoking move() on Car")
        car.move()
    }

    override fun undo() {
        println("CarMoveCommand.undo():  Undoing previous action->Invoking stop() on Car")
        car.stop()
    }
}

/**
 * Concrete class of [Command], implement (Car stop and move) the operations for [execute] and [undo].
 *
 * @param car [Car] object.
 */
class CarStopCommand(private val car: Car) : Command {
    override fun execute() {
        println("CarStopCommand.execute(): Invoking stop() on Car")
        car.stop()
    }

    override fun undo() {
        println("CarStopCommand.undo(): Undoing previous action-> Invoking move() on Car")
        car.move()
    }
}

/**
 * Concrete class of [Command], implement (Rotating start or stop) the operations for [execute] and [undo].
 *
 * @param rotatingTop [RotatingTop] object.
 */
class TopRotateCommand(private var rotatingTop: RotatingTop) : Command {
    override fun execute() {
        println("TopRotateCommand.execute(): Invoking startRotating() on RotatingTop")
        rotatingTop.startRotating()
    }

    override fun undo() {
        println("TopRotateCommand.undo(): Undoing previous action->Invoking stopRotating() on RotatingTop")
        rotatingTop.stopRotating()
    }
}

/**
 * Concrete class of [Command], implement (Rotating stop or start) the operations for [execute] and [undo].
 *
 * @param rotatingTop [RotatingTop] object.
 */
class TopStopRotateCommand(private var rotatingTop: RotatingTop) : Command {
    override fun execute() {
        println("TopStopRotateCommand.execute(): Invoking stopRotating() on RotatingTop")
        rotatingTop.stopRotating()
    }

    override fun undo() {
        println("TopStopRotateCommand.undo(): Undoing previous action->Invoking startRotating() on RotatingTop")
        rotatingTop.startRotating()
    }
}

/**
 * Base Remote Control features.
 */
interface BaseRemoteControl {
    fun onButtonPressed(onCommand: Command)

    fun offButtonPressed(offCommand: Command)

    fun undoButtonPressed()
}

/**
 * Implementation of [BaseRemoteControl].
 */
class RemoteControl : BaseRemoteControl {
    private var onCommand: Command? = null
    private var offCommand: Command? = null
    private var undoCommand: Command? = null
    override fun onButtonPressed(onCommand: Command) {
        this.onCommand = onCommand
        onCommand.execute()
        undoCommand = onCommand
    }

    override fun offButtonPressed(offCommand: Command) {
        this.offCommand = offCommand
        offCommand.execute()
        undoCommand = offCommand
    }

    override fun undoButtonPressed() {
        undoCommand?.undo()
    }
}