package adventofcode.y2018

import adventofcode.io.AdventSolution

fun main() = repeat(10){Day14.solve()}

object Day14 : AdventSolution(2018, 14, "Chocolate Charts") {

    override fun solvePartOne(input: String): String {
        val targetSize = input.toInt() + 10
        return generateRecipes { it.size == targetSize }
                .takeLast(10)
                .joinToString("")
    }


    override fun solvePartTwo(input: String): Int {
        val target = input.map { it - '0' }
        val recipes = generateRecipes { it.endMatches(target) }
        return recipes.size - target.size
    }

    private fun generateRecipes(stop: (List<Int>) -> Boolean): MutableList<Int> {
        val recipes = mutableListOf(3, 7)
        var e1 = 0
        var e2 = 1
        while (true) {
            var score = recipes[e1] + recipes[e2]
            if (score >= 10) {
                recipes += 1
                if (stop(recipes)) return recipes
                score -= 10
            }

            recipes += score
            if (stop(recipes)) return recipes

            e1 = (e1 + recipes[e1] + 1)
            while (e1 >= recipes.size) e1 -= recipes.size
            e2 = (e2 + recipes[e2] + 1)
            while (e2 >= recipes.size) e2 -= recipes.size
        }
    }

    //faster version of takeLast(end.size)==end
    private fun List<Int>.endMatches(end: List<Int>) =
            this.size >= end.size && end.indices.all { end[it] == this[size - end.size + it] }
}
