package de.skyrising.aoc2021.day21

import de.skyrising.aoc.*
import it.unimi.dsi.fastutil.objects.Object2LongLinkedOpenHashMap

val test = TestInput("""
    Player 1 starting position: 4
    Player 2 starting position: 8
""")

@PuzzleName("<NAME>")
fun PuzzleInput.part1(): Any {
    var (p1, p2) = parseInput(this)
    val dice = Dice()
    var score1 = 0
    var score2 = 0
    var rolls = 0
    while (score2 < 1000) {
        p1 = move(p1, dice.next() + dice.next() + dice.next())
        rolls += 3
        score1 += p1
        if (score1 >= 1000) break
        p2 = move(p2, dice.next() + dice.next() + dice.next())
        rolls += 3
        score2 += p2
    }
    return minOf(score1, score2) * rolls
}

fun PuzzleInput.part2(): Any {
    val (i1, i2) = parseInput(this)
    var wins1 = 0L
    var wins2 = 0L
    val universes = Object2LongLinkedOpenHashMap<Universe>()
    universes[Universe(i1, i2, 0, 0)] = 1L
    while (universes.isNotEmpty()) {
        val (universe, count) = universes.object2LongEntrySet().first()
        universes.removeLong(universe)
        val (p1, p2, score1, score2) = universe
        for (d11 in 1..3) for (d12 in 1..3) for (d13 in 1..3) {
            val p12 = move(p1, d11 + d12 + d13)
            val score12 = score1 + p12
            if (score12 >= 21) {
                wins1 += count
                continue
            }
            for (d21 in 1..3) for (d22 in 1..3) for (d23 in 1..3) {
                val p22 = move(p2, d21 + d22 + d23)
                val score22 = score2 + p22
                if (score22 >= 21) {
                    wins2 += count
                    continue
                }
                val newUniverse = Universe(p12, p22, score12, score22)
                universes[newUniverse] = universes.getLong(newUniverse) + count
            }
        }
    }
    return maxOf(wins1, wins2)
}

private fun move(p: Int, amount: Int) = (p + amount - 1) % 10 + 1

data class Universe(val p1: Int, val p2: Int, val score1: Int, val score2: Int)

data class Dice(var next: Int = 1) {
    fun next(): Int {
        val r = next
        next++
        if (next > 1000) next = 1
        return r
    }
}

private fun parseInput(input: PuzzleInput) = Pair(input.lines[0].ints().getInt(1), input.lines[1].ints().getInt(1))