pencelab

inline fun panel(init: (@ShapeDsl Panel).() -> Unit): Panel {
    return Panel().apply { init() }
}

inline fun Panel.square(init: SquareBuilder.() -> Unit): Square {
    return SquareBuilder().apply { init() }.build().also { this.addShape(it) }
}

inline fun Panel.triangle(init: TriangleBuilder.() -> Unit): Triangle {
    return TriangleBuilder().apply { init() }.build().also { this.addShape(it) }

pencelab

panel {
    square {
        lines = 8
        char = 'd'

        this@panel.triangle {
            lines = 10
            char = 'x'
        }
    }

pencelab

@ShapeDsl
abstract class ShapeBuilder {

    private companion object {
        const val DEFAULT_CHAR = '*'
    }

    var char = DEFAULT_CHAR
    var lines = 0

pencelab

inline fun Panel.square(init: SquareBuilder.() -> Unit): Square {
    return SquareBuilder().apply { init() }.build().also { this.addShape(it) }
}

pencelab

@ShapeDsl
class SquareBuilder: ShapeBuilder() {
    override fun build() = Square(lines, char)
}

pencelab

inline fun panel(init: (@ShapeDsl Panel).() -> Unit): Panel {
    return Panel().apply { init() }
}

inline fun Panel.square(init: (@ShapeDsl SquareBuilder).() -> Unit): Square {
    return SquareBuilder().apply { init() }.build().also { this.addShape(it) }
}

pencelab

@DslMarker
@Target(AnnotationTarget.CLASS, AnnotationTarget.TYPE)
annotation class ShapeDsl

pencelab

panel {
    square {
        lines = 8
        char = 'd'
        
        square {
            lines = 5
            char = 'o'
            
            triangle {

pencelab

inline fun panel(init: Panel.() -> Unit): Panel {
    return Panel().apply { init() }
}

inline fun Panel.square(init: SquareBuilder.() -> Unit): Square {
    return SquareBuilder().apply { init() }.build().also { this.addShape(it) }
}

inline fun Panel.triangle(init: TriangleBuilder.() -> Unit): Triangle {
    return TriangleBuilder().apply { init() }.build().also { this.addShape(it) }

pencelab

operator fun Shape.plus(shape: Shape): ComposedShape = this union shape

operator fun Shape.minus(shape: Shape): ComposedShape = this intersection shape