package day12

func FastRunGeneration(plants []byte, rules map[string]byte, rootIndex int) ([]byte, int) {
	newGen := make([]byte, len(plants), len(plants)+4)

	for i := 0; i < len(plants); i++ {
		newGen[i] = rules[getKey(plants, i)]
	}

	result1 := rules[getKey(plants, -2)]
	result2 := rules[getKey(plants, -1)]
	if result1 == '#' || result2 == '#' {
		newGen = append([]byte{result1, result2}, newGen...)
		rootIndex += 2
	}

	result1 = rules[getKey(plants, len(plants))]
	result2 = rules[getKey(plants, len(plants)+1)]
	if result1 == '#' || result2 == '#' {
		newGen = append(newGen, result1, result2)
	}

	return newGen, rootIndex
}

func getKey(plants []byte, i int) string {
	if i < 2 {
		key := ""
		for j := 0; j < 2-i; j++ {
			key += "."
		}
		key += string(plants[0 : i+2])
		return key
	}

	if i > len(plants)-2 {
		key := string(plants[i-2 : len(plants)-1])
		for j := 0; j < len(plants)-1-i; j++ {
			key += "."
		}
		key += string(plants[0 : i+2])
		return key
	}

	return string(plants[i-2 : i+2])
}

func FastSumPlants(plants []byte, rootIndex int) int {
	sum := 0
	for index, value := range plants {
		if value == '#' {
			sum += index - rootIndex
		}
	}
	return sum
}