package ch.ranil.aoc.aoc2022

import ch.ranil.aoc.AbstractDay
import org.junit.jupiter.api.Test
import kotlin.test.assertEquals

object Day05 : AbstractDay() {
    @Test
    fun tests() {
        assertEquals("CMZ", compute1(testInput))
        assertEquals("VJSFHWGFT", compute1(puzzleInput))

        assertEquals("MCD", compute2(testInput))
        assertEquals("LCTQFBVZV", compute2(puzzleInput))
    }

    private fun compute1(input: List<String>): String {
        val (stacks, moves) = input.parse()

        moves.forEach {
            applyMove(it, stacks)
        }

        return stacks.readAnswer()
    }

    private fun compute2(input: List<String>): String {
        val (stacks, moves) = input.parse()

        moves.forEach {
            applyMove2(it, stacks)
        }

        return stacks.readAnswer()
    }

    private fun applyMove(move: String, stacks: Stacks) {
        val (count, from, to) = move.parse()
        repeat(count) {
            val toMove = stacks[from].removeLast()
            stacks[to].addLast(toMove)
        }
    }

    private fun applyMove2(move: String, stacks: Stacks) {
        val (count, from, to) = move.parse()
        stacks[from]
            .takeLast(count)
            .forEach {
                stacks[from].removeLast()
                stacks[to].addLast(it)
            }
    }

    private fun String.parse(): Move {
        val parts = split(" ")
        return Move(
            count = parts[1].toInt(),
            from = parts[3].toInt() - 1,
            to = parts[5].toInt() - 1,
        )
    }

    private fun List<String>.parse(): Pair<Stacks, List<String>> {
        val stackData = this.takeWhile { it.isNotBlank() }

        val numberOfStacks = stackData
            .last()
            .split(" ")
            .last { it.isNotBlank() }
            .toInt()

        val stacks = List(numberOfStacks) { ArrayDeque<Char>() }
        stackData
            .dropLast(1)
            .reversed()
            .forEach {
                it.putOnStacks(stacks)
            }

        val moves = this.drop(stackData.size + 1)

        return stacks to moves
    }

    private fun String.putOnStacks(stacks: Stacks) {
        val charArray = this.toCharArray()
        for (i in stacks.indices) {
            val idx = 4 * i + 1
            val char = charArray.elementAtOrNull(idx) ?: ' '
            if (char != ' ') stacks[i].add(char)
        }
    }

    private fun Stacks.readAnswer(): String {
        return map { it.last() }
            .joinToString("")
    }

    private data class Move(val count: Int, val from: Int, val to: Int)

}

private typealias Stacks = List<ArrayDeque<Char>>
