package main

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

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

func main() {

    dat, err := os.ReadFile("data.txt")
    check(err)
    dat_str := string(dat)
    
    // get all numbers within mul(*,*) using capture groups and do() / don't()
    r := regexp.MustCompile("mul\\(([0-9]{1,3}),([0-9]{1,3})\\)|do\\(\\)|don't\\(\\)")
    matches := r.FindAllStringSubmatch(dat_str, -1)

    acc := 0
    enabled := true

    for _, elem := range matches {
        switch elem[0] {
            case "do()":
                enabled = true
            case "don't()":
                enabled = false
            default:
                if enabled {
                    // convert to numbers
                    num1, err := strconv.Atoi(elem[1])
                    check(err)
                    num2, err := strconv.Atoi(elem[2])
                    check(err)
                        
                    acc += num1 * num2
                }
        }
    }

    fmt.Println(acc)
}