main.go

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

var digitLength = 7
var digitWidth = 5

func main() {
	fmt.Println(os.Args)
	if len(os.Args) != 2 && len(os.Args) != 4 {
		log.Println("Need only one input number")
		log.Println(os.Args)
		os.Exit(1)
	}
	symbolFlag := flag.Bool("symbol", false, "set custom symbol for the art")
	flag.Parse()
	var symbol, number string
	if *symbolFlag {

		number = os.Args[3]
		symbol = os.Args[2]
	}
	if _, err := strconv.ParseUint(number, 10, 64); err != nil {
		log.Println("Input argument is integer non-convertible: ", err.Error())
		os.Exit(1)
	}

	digs := prepareDigits(symbol)

	sb := strings.Builder{}
	for i := 0; i < 7; i++ {
		for _, num := range number {
			sb.WriteString(digs[int(num-48)][i] + " ")
		}
		if i != digitLength-1 {

			sb.WriteByte('\n')
		}
	}
	asteriskBorder := strings.Repeat("*", len(number)*(digitWidth+1)-1)

	fmt.Printf("%s\n%s\n%s", asteriskBorder, sb.String(), asteriskBorder)
}

func prepareDigits(symbol string) map[int][]string {

	artNumbers := strings.Trim(digits, "\n")

	numbers := make(map[int][]string)

	for i, digit := range strings.Split(artNumbers, "\n\n") {
		for _, digitString := range strings.Split(digit, "\n") {

			numbers[i] = append(numbers[i], fmt.Sprintf("%-5s", digitString))

		}

	}

	return numbers

}