package day02

import (
	"math"
	"strconv"
	"strings"
)

// Very messy and not my finest work but not too bad for 6am

func parseInput(input string) [][2]int {
	var ranges [][2]int
	lines := strings.Split(strings.TrimSpace(input), ",")
	for _, part := range lines {
		if part == "" {
			continue
		}
		ab := strings.Split(part, "-")
		if len(ab) != 2 {
			continue
		}

		a, _ := strconv.Atoi(ab[0])
		b, _ := strconv.Atoi(ab[1])
		ranges = append(ranges, [2]int{a, b})
	}
	return ranges
}

func divisors(n int) []int {
	out := make([]int, 0)
	for i := 1; i <= n; i++ {
		if n%i == 0 {
			out = append(out, i)
		}
	}
	return out
}

func Part1(input string) int {
	ranges := parseInput(input)
	invalidSum := 0

	for _, r := range ranges {
		low, high := r[0], r[1]

		minLen := len(strconv.Itoa(low))
		maxLen := len(strconv.Itoa(high))

		for digits := minLen; digits <= maxLen; digits++ {
			if digits%2 != 0 {
				continue
			}

			half := digits / 2
			start := int(math.Pow(10, float64(half-1)))
			end := int(math.Pow(10, float64(half)))

			for first := start; first < end; first++ {
				s := strconv.Itoa(first)
				selected, _ := strconv.Atoi(s + s)

				if selected < low {
					continue
				}
				if selected > high {
					break
				}

				invalidSum += selected
			}
		}
	}

	return invalidSum
}

func Part2(input string) int {
	ranges := parseInput(input)
	total := 0

	for _, r := range ranges {
		low, high := r[0], r[1]
		seen := make(map[int]bool)

		minLen := len(strconv.Itoa(low))
		maxLen := len(strconv.Itoa(high))

		for d := minLen; d <= maxLen; d++ {
			for _, L := range divisors(d) {
				k := d / L
				if k < 2 {
					continue
				}
				start := int(math.Pow(10, float64(L-1)))
				end := int(math.Pow(10, float64(L)))

				for base := start; base < end; base++ {
					s := strings.Repeat(strconv.Itoa(base), k)
					selected, _ := strconv.Atoi(s)

					if selected < low {
						continue
					}
					if selected > high {
						break
					}

					if !seen[selected] {
						seen[selected] = true
						total += selected
					}
				}
			}
		}
	}

	return total
}