Discussion on: Advent of Code 2019 Solution Megathread - Day 22: Slam Shuffle

import arrow.core.getOrElse
import arrow.core.toOption
import java.nio.file.Files
import java.nio.file.Paths

sealed class ShuffleMethods : (List<Int>) -> List<Int> {
    object DealIntoStack : ShuffleMethods() {
        override fun invoke(p1: List<Int>) = p1.reversed()
    }

    class Cut(val n: Int) : ShuffleMethods() {
        override fun invoke(p1: List<Int>): List<Int> {
            return if (n >= 0) {
                p1.drop(n) + p1.take(n)
            } else {
                p1.takeLast(-1 * n) + p1.dropLast(-1 * n)
            }
        }
    }

    class DealIncrement(val n: Int) : ShuffleMethods() {
        override fun invoke(p1: List<Int>): List<Int> {
            return p1.withIndex().sortedBy { (it.index * n) % p1.size }.map { it.value }
        }
    }

}


val regexIncrement = """deal with increment (\d+)""".toRegex()
const val dealIntoStack = "deal into new stack"
val regexCut = """cut (-?\d+)""".toRegex()


fun String.toShuffleMethod(): ShuffleMethods {
    if (this == dealIntoStack) {
        return ShuffleMethods.DealIntoStack
    }
    return when (val incrementMatch = regexIncrement.matchEntire(this)) {
        null -> {
            val cutMatch = regexCut.matchEntire(this).toOption()
            ShuffleMethods.Cut(cutMatch.getOrElse { throw error("unknown style: $this") }.groupValues[1].toInt())
        }
        else -> ShuffleMethods.DealIncrement(incrementMatch.groupValues[1].toInt())
    }
}


object Day22 {
    private const val FILENAME = "src/main/resources/day22.txt"
    val fileData get() = Files.readAllLines(Paths.get(FILENAME))

    fun part1(input: List<String>, deck: List<Int> = (0 until 10007).toList()): List<Int> {
        val methods = input.map { it.toShuffleMethod() }
        return shuffle(methods, deck)
    }



    private fun shuffle(
        methods: List<ShuffleMethods>,
        deck: List<Int>
    ): List<Int> {
        return methods.fold(deck) { acc, curr -> curr(acc) }
    }

}

fun main() {
    println(Day22.part1(Day22.fileData).withIndex().first { (i, v) -> v == 2019 })
}