package main

import (
	"fmt"
	"os"
	"regexp"
	"strconv"
)

var mul_re *regexp.Regexp = regexp.MustCompile(`mul\(([0-9]+),([0-9]+)\)`)

func check(e error) {
	if e != nil {
		panic(e)
	}
}

func handle_muls(input string) int {
	total := 0

	matches := mul_re.FindAllStringSubmatch(input, -1)
	for _, match := range matches {
		first, err := strconv.Atoi(match[1])
		check(err)
		second, err := strconv.Atoi(match[2])
		check(err)

		total += first * second
	}
	return total
}

func next(matches [][]int, start int) [][]int {
	for i, match := range matches {
		if match[0] > start {
			return matches[i:]
		}
	}
	return nil
}

func main() {
	instructions, err := os.ReadFile("./three.txt")
	check(err)

	str_instructions := string(instructions)

	// Find all mul instructions
	fmt.Println(handle_muls(str_instructions))

	// Handle disables and enables
	total := 0
	enable_re := regexp.MustCompile(`do\(\)`)
	disable_re := regexp.MustCompile(`don't\(\)`)
	dos := enable_re.FindAllStringIndex(str_instructions, -1)
	donts := disable_re.FindAllStringIndex(str_instructions, -1)

	enabled := true
	done := false

	start_i := 0
	end_i := 0

	for !done {
		if enabled {
			donts = next(donts, start_i)
			if donts == nil {
				total += handle_muls(str_instructions[start_i:])
				done = true
			} else {
				end_i = donts[0][0]
				total += handle_muls(str_instructions[start_i : end_i+1])
				enabled = false
			}
		} else {
			dos = next(dos, end_i)
			if dos == nil {
				done = true
			} else {
				start_i = dos[0][1]
				enabled = true
			}
		}
	}
	fmt.Println(dos)
	fmt.Println(donts)
	fmt.Println(total)
}