Add Algorithm and Digits methods (#74)

* Add Algorithm and Digits methods

This commit adds two new methods that expose the Algorithm
and the Digits parameters from the Key URL.

This is useful for users of the GenerateCustomCode methods.

Signed-off-by: Dominik Schulz <dominik.schulz@gauner.org>

* Make Digits return Digits not unit64

Signed-off-by: Dominik Schulz <dominik.schulz@gauner.org>

otp.go

@@ -18,9 +18,6 @@
 package otp
 
 import (
-	"github.com/boombuler/barcode"
-	"github.com/boombuler/barcode/qr"
-
 	"crypto/md5"
 	"crypto/sha1"
 	"crypto/sha256"
@@ -30,8 +27,11 @@ import (
 	"hash"
 	"image"
 	"net/url"
-	"strings"
 	"strconv"
+	"strings"
+
+	"github.com/boombuler/barcode"
+	"github.com/boombuler/barcode/qr"
 )
 
 // Error when attempting to convert the secret from base32 to raw bytes.
@@ -61,7 +61,6 @@ func NewKeyFromURL(orig string) (*Key, error) {
 	s := strings.TrimSpace(orig)
 
 	u, err := url.Parse(s)
-
 	if err != nil {
 		return nil, err
 	}
@@ -81,7 +80,6 @@ func (k *Key) String() string {
 // to enroll a user's TOTP/HOTP key.
 func (k *Key) Image(width int, height int) (image.Image, error) {
 	b, err := qr.Encode(k.orig, qr.M, qr.Auto)
-
 	if err != nil {
 		return nil, err
 	}
@@ -146,11 +144,45 @@ func (k *Key) Period() uint64 {
 	if u, err := strconv.ParseUint(q.Get("period"), 10, 64); err == nil {
 		return u
 	}
-	
+
 	// If no period is defined 30 seconds is the default per (rfc6238)
 	return 30
 }
 
+// Digits returns a tiny int representing the number of OTP digits.
+func (k *Key) Digits() Digits {
+	q := k.url.Query()
+
+	if u, err := strconv.ParseUint(q.Get("digits"), 10, 64); err == nil {
+		switch u {
+		case 8:
+			return DigitsEight
+		default:
+			return DigitsSix
+		}
+	}
+
+	// Six is the most common value.
+	return DigitsSix
+}
+
+// Algorithm returns the algorithm used or the default (SHA1).
+func (k *Key) Algorithm() Algorithm {
+	q := k.url.Query()
+
+	a := strings.ToLower(q.Get("algorithm"))
+	switch a {
+	case "md5":
+		return AlgorithmMD5
+	case "sha256":
+		return AlgorithmSHA256
+	case "sha512":
+		return AlgorithmSHA512
+	default:
+		return AlgorithmSHA1
+	}
+}
+
 // URL returns the OTP URL as a string
 func (k *Key) URL() string {
 	return k.url.String()

otp_test.go

@@ -18,18 +18,20 @@
 package otp
 
 import (
-	"github.com/stretchr/testify/require"
-
 	"testing"
+
+	"github.com/stretchr/testify/require"
 )
 
 func TestKeyAllThere(t *testing.T) {
-	k, err := NewKeyFromURL(`otpauth://totp/Example:alice@google.com?secret=JBSWY3DPEHPK3PXP&issuer=Example`)
+	k, err := NewKeyFromURL(`otpauth://totp/Example:alice@google.com?secret=JBSWY3DPEHPK3PXP&issuer=Example&algorithm=sha256&digits=8`)
 	require.NoError(t, err, "failed to parse url")
 	require.Equal(t, "totp", k.Type(), "Extracting Type")
 	require.Equal(t, "Example", k.Issuer(), "Extracting Issuer")
 	require.Equal(t, "alice@google.com", k.AccountName(), "Extracting Account Name")
 	require.Equal(t, "JBSWY3DPEHPK3PXP", k.Secret(), "Extracting Secret")
+	require.Equal(t, AlgorithmSHA256, k.Algorithm())
+	require.Equal(t, DigitsEight, k.Digits())
 }
 
 func TestKeyIssuerOnlyInPath(t *testing.T) {