package day19

import (
	"math"
	"tools"
)

func getNextIndex(m map[int]int, start, max int) int {
	index := start
	for {
		index++
		if index > max {
			index = 0
		}
		if _, ok := m[index]; ok {
			return index
		}
	}
}

func Part1(puzzle tools.AoCPuzzle) interface{} {
	elfCount := puzzle.GetInputInt()
	elfs := make(map[int]int)
	for i := 0; i < elfCount; i++ {
		elfs[i] = 1
	}

	index := 0
	for len(elfs) > 1 {
		nextIndex := getNextIndex(elfs, index, elfCount)
		delete(elfs, nextIndex)
		index = getNextIndex(elfs, nextIndex, elfCount)
	}

	return index + 1
}

func Part2(puzzle tools.AoCPuzzle) interface{} {
	elfCount := puzzle.GetInputInt()
	var elfs []int
	for i := 0; i < elfCount; i++ {
		elfs = append(elfs, i+1)
	}

	// Future optimization path?
	// 0..4; 0 eliminates 2 (index + floor(half), 1 eliminates 4 (1 + half(len)), 3 eliminates 1 (index + floor(half))
	// eliminate (1:?)2:1:2:1:...until len(2) (start with 1 for equal lens and 2 for unequal lens)
	for len(elfs) > 1 {
		half := int(math.Floor(float64(len(elfs) / 2)))
		elfs = append(elfs, elfs[0])
		elfs = append(elfs[1:half], elfs[half+1:]...)
	}

	return elfs[0]
}