waku-org/go-waku

package noise

import (
    "crypto/ed25519"
    "encoding/base64"
    "errors"
    "strings"
)

type QR struct {
    applicationName    string
    applicationVersion string
    shardID            string
    ephemeralPublicKey ed25519.PublicKey
    committedStaticKey []byte
}

func NewQR(applicationName, applicationVersion, shardID string, ephemeralKey ed25519.PublicKey, committedStaticKey []byte) QR {
    return QR{
        applicationName:    applicationName,
        applicationVersion: applicationVersion,
        shardID:            shardID,
        ephemeralPublicKey: ephemeralKey,
        committedStaticKey: committedStaticKey,
    }
}

// Serializes input parameters to a base64 string for exposure through QR code (used by WakuPairing)
func (qr QR) String() string {
    return base64.URLEncoding.EncodeToString([]byte(qr.applicationName)) + ":" +
        base64.URLEncoding.EncodeToString([]byte(qr.applicationVersion)) + ":" +
        base64.URLEncoding.EncodeToString([]byte(qr.shardID)) + ":" +
        base64.URLEncoding.EncodeToString(qr.ephemeralPublicKey) + ":" +
        base64.URLEncoding.EncodeToString(qr.committedStaticKey[:])
}

func (qr QR) Bytes() []byte {
    return []byte(qr.String())
}

func decodeBase64String(inputValue string) ([]byte, error) {
    enc := base64.StdEncoding
    if strings.ContainsAny(inputValue, "-_") {
        enc = base64.URLEncoding
    }
    if len(inputValue)%4 != 0 {
        enc = enc.WithPadding(base64.NoPadding)
    }

    return enc.DecodeString(inputValue)
}

// StringToQR deserializes input string in base64 to the corresponding (applicationName, applicationVersion, shardId, ephemeralKey, committedStaticKey)
func StringToQR(qrString string) (QR, error) {
    values := strings.Split(qrString, ":")
    if len(values) != 5 {
        return QR{}, errors.New("invalid qr string")
    }

    applicationName, err := decodeBase64String(values[0])
    if err != nil {
        return QR{}, err
    }

    applicationVersion, err := decodeBase64String(values[1])
    if err != nil {
        return QR{}, err
    }

    shardID, err := decodeBase64String(values[2])
    if err != nil {
        return QR{}, err
    }

    ephemeralKey, err := decodeBase64String(values[3])
    if err != nil {
        return QR{}, err
    }

    committedStaticKey, err := decodeBase64String(values[4])
    if err != nil {
        return QR{}, err
    }

    return QR{
        applicationName:    string(applicationName),
        applicationVersion: string(applicationVersion),
        shardID:            string(shardID),
        ephemeralPublicKey: ephemeralKey,
        committedStaticKey: committedStaticKey,
    }, nil
}