fun main() {
    val input = readInput("Day05")
    println(Day05.part1(input))
    println(Day05.part2(input))
}

data class Move(val size: Int, val from: Int, val to: Int)


class Day05 {
    companion object {

        fun part1(input: List<String>): String {
            val (initial, rawActions) = input.partitionOnElement("")

            val numberOfStacks = initial.maxOf { it.length } / 3
            val stacks: List<ArrayDeque<Char>> = (1..numberOfStacks).toList().map { ArrayDeque<Char>(initial.size * 2) }
            val initialReversed = initial.dropLast(1).reversed()
            for (level in initialReversed) {
                for (i in 1..numberOfStacks) {
                    val value = level.getOrNull((4 * i) - 3)
                    if (value != null && value != ' ') {
                        stacks[i - 1].addLast(value)
                    }
                }
            }

            val actions = rawActions.map { it.split("move ", " from ", " to ").subList(1, 4).map { v -> v.toInt() } }
                .map { (size, from, to) -> Move(size, from, to) }


            for (action in actions) {
                for (i in 0 until action.size) {
                    stacks[action.to - 1].addLast(stacks[action.from - 1].removeLast())
                }
            }

            return stacks.mapNotNull { it.removeLastOrNull() }.joinToString("")
        }

        fun part2(input: List<String>): String {
            val (initial, rawActions) = input.partitionOnElement("")

            val numberOfStacks = initial.maxOf { it.length } / 3
            val stacks: MutableList<ArrayDeque<Char>> =
                (1..numberOfStacks).toList().map { ArrayDeque<Char>(initial.size * 2) }.toMutableList()
            val initialReversed = initial.dropLast(1).reversed()
            for (level in initialReversed) {
                for (i in 1..numberOfStacks) {
                    val value = level.getOrNull((4 * i) - 3)
                    if (value != null && value != ' ') {
                        stacks[i - 1].addLast(value)
                    }
                }
            }

            val actions = rawActions.map { it.split("move ", " from ", " to ").subList(1, 4).map { v -> v.toInt() } }
                .map { (size, from, to) -> Move(size, from, to) }


            for (action in actions) {
                val splitPoint = stacks[action.from - 1].size - action.size
                val newFrom = stacks[action.from - 1].subList(0, splitPoint)
                val swap = stacks[action.from - 1].subList(splitPoint, stacks[action.from - 1].size)

                stacks[action.from - 1] = ArrayDeque(newFrom)
                stacks[action.to - 1].addAll(swap)
            }

            return stacks.mapNotNull { it.removeLastOrNull() }.joinToString("")
        }

    }
}
