class Movable : Item {

    var speed = 8

    var movement : Movement = null

    fun movement() : Movement = movement

    override fun end() {
        if (movement != null && movement.toSquare.entrant == this) {
            movement.toSquare.entrant = null
            movement = null
        }
        super.end()
    }

    override fun isAlternate() : boolean = false

    override fun isMoving() : boolean = movement != null

    fun move( direction : int ) {
        moveDelta( Item.getDeltaX( direction ), Item.getDeltaY( direction ), speed )
    }
    fun move( direction : int, speed : int ) {
        moveDelta( Item.getDeltaX( direction ), Item.getDeltaY( direction ), speed )
    }


    fun moveEast() {
        moveDelta( 1, 0, speed )
    }

    fun moveNorth() {
        moveDelta( 0, 1, speed )
    }

    fun moveWest() {
        moveDelta( -1, 0, speed )
    }

    fun moveSouth() {
        moveDelta( 0, -1, speed )
    }


    fun moveDelta( dx : int, dy : int ) {
        moveDelta( dx, dy, speed )
    }

    // Items can optionally have an animation while moving.
    // If so, the animation acts in parallel with the Movement
    fun createAnimation( direction : int ) : Action = null

    fun moveDelta( dx : int , dy : int , speed : int ) {
        val movement = Movement( this, dx, dy, speed )
        val animation = createAnimation( Item.getDirection( dx, dy ) )
        if (animation == null) {
            replaceAction( movement )
        } else {
            replaceAction( animation.whilst( movement ) )
        }
        act()
    }


    override fun lookEast() : LookedAt = lookDelta( 1, 0, speed)

    override fun lookWest() : LookedAt = lookDelta( -1, 0, speed )

    override fun lookNorth() : LookedAt = lookDelta( 0, 1, speed )

    override fun lookSouth() : LookedAt = lookDelta( 0, -1, speed )

    override fun look( direction : int ) : LookedAt = look( direction, speed )

    override fun lookDelta( dx : int, dy : int ) : LookedAt = lookDelta( dx, dy, speed )


    fun moved( movement : Movement ) {
        replaceAction( createAction() )
    }

}