Print QR codes in the terminal

main.go

package main

import (
	"fmt"
	"net/url"
	"os"

	qrcode "github.com/skip2/go-qrcode"
)

func main() {
	if len(os.Args) < 4 {
		fmt.Println(`
Usage:
	qr "$TITLE" "$USERNAME" "$SECRET"
`)
		os.Exit(1)
	}

	issuer := uriEncode(os.Args[1])
	username := uriEncode(os.Args[2])
	secret := uriEncode(os.Args[3])

	qr := fmt.Sprintf("otpauth://totp/%s:%s?secret=%s&issuer=%s", issuer, username, secret, issuer)

	q, err := qrcode.New(qr, qrcode.Medium)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

	bitmap := q.Bitmap()
	for i := 0; i < len(bitmap); i += 2 {
		for j := 0; j < len(bitmap[i]); j++ {
			var top, bottom bool
			top = bitmap[i][j]
			if i+1 < len(bitmap) {
				bottom = bitmap[i+1][j]
			}
			switch {
			case !top && !bottom:
				fmt.Print(" ")
			case !top && bottom:
				fmt.Print("▄")
			case top && !bottom:
				fmt.Print("▀")
			case top && bottom:
				fmt.Print("█")
			}
		}
		fmt.Print("\n")
	}
}

func uriEncode(s string) string {
	return (&url.URL{Path: s}).String()
}