package main

import (
	"io"
	"log"
	"os"
	"strconv"
	"strings"
)

const (
	AGES = 9
)

func main() {
	if err := myMain(); err != nil {
		log.Println(err)
	}
}

func myMain() error {
	// parse input.txt
	lanterns, err := parseInput("input.txt")
	if err != nil {
		return err
	}

	log.Println(solveFirst(lanterns, 80))
	log.Println(solveFirst(lanterns, 256))

	return nil
}

func solveFirst(lf []int, days int) int {
	age := lanternage(lf)

	for i := 0; i < days; i++ {
		new := age[0]
		age[0] = age[1]
		age[1] = age[2]
		age[2] = age[3]
		age[3] = age[4]
		age[4] = age[5]
		age[5] = age[6]
		age[6] = age[7] + new
		age[7] = age[8]
		age[8] = new
	}

	return sum(age)
}

func sum(in [AGES]int) int {
	var sum int
	for _, item := range in {
		sum += item
	}
	return sum
}

func lanternage(lf []int) [AGES]int {
	var ret [AGES]int
	for _, fish := range lf {
		ret[fish] += 1
	}
	return ret
}

func parseInput(fileName string) ([]int, error) {
	var ret []int
	fd, err := os.Open(fileName)
	if err != nil {
		return ret, err
	}
	defer fd.Close()

	input, err := io.ReadAll(fd)
	if err != nil {
		return nil, err
	}

	instr := strings.Split(strings.TrimSuffix(string(input), "\n"), ",")
	for _, elem := range instr {
		tmp, err := strconv.Atoi(elem)
		if err != nil {
			return nil, err
		}
		ret = append(ret, tmp)
	}

	return ret, nil
}