prima metà html kotlin 2022

#!/usr/bin/env kotlin

sealed interface Element {
    sealed interface Tag<out C : Element> : Element {

        val children: List<C>
        val attributes: List<Attribute>

        interface Unique<out C : Element> : Tag<C>
        interface Repeatable<out C : Element> : Tag<C>
    }
    data class Text(val content: String) : Element
}

interface Attribute {
    val key: String
    val value: String
}

typealias Tag<C> = Element.Tag<C>
typealias UniqueTag<C> = Element.Tag.Unique<C>
typealias Text = Element.Text

abstract class AbstractTag<C : Element> : Tag<C> {
    protected var actualChildren: List<C> = emptyList()
    final override val children: List<C> get() = actualChildren
    final override val attributes: List<Attribute> = emptyList()
}

class Title(title: String) : UniqueTag<Text> {
    override val children: List<Text> = listOf(Text(title))
    override val attributes: List<Attribute> = emptyList()
}
class Head() : AbstractTag<Tag<Element>>(), UniqueTag<Tag<Element>> {
    fun title(produceTitle: () -> String): Head = apply { actualChildren += Title(produceTitle()) }
}
class Body() : AbstractTag<Element>(), UniqueTag<Element> { }

class HTML() : AbstractTag<Element>(), UniqueTag<Element> {
    fun head(configuration: Head.() -> Head): Head = Head().apply { configuration() }
    fun body(configuration: Body.() -> Body): Body = Body().apply { configuration() }
}

fun html(configuration: HTML.() -> Unit): HTML = HTML().apply { configuration() }

val result = html {
    head {
        title { "Ciao" }
    }
}

println(result)