A helper class which can generate a URI for google authenticator.

GoogleAuthenticatorUtils.kt

import android.net.Uri

object GoogleAuthenticatorUtils {
    enum class KeyType(val uriKey: String) {
        TIME_BASED("totp"),
        COUNTER_BASED("hotp")
    }
  
    //Based on https://github.com/google/google-authenticator/wiki/Key-Uri-Format

    /**
     * Generate URI with containing the secret keys information:
     * @param type A type which is either time based (totp) or counter based (hotp)
     * @param issuer The issuer parameter is a string value indicating the provider or service this account is associated with, URL-encoded according to [RFC 3986](http://tools.ietf.org/html/rfc3986).
     * @param accountName e.g. the user's email address
     * @param secret The secret parameter is an arbitrary key value encoded in Base32 according to [RFC 3548](http://tools.ietf.org/html/rfc3548). The padding specified in [RFC 3548 section 2.2](https://tools.ietf.org/html/rfc3548#section-2.2) is not required and should be omitted.
     * @param digits The digits parameter may have the values 6 or 8 (unless an [IllegalArgumentException] will be thrown), and determines how long of a one-time passcode to display to the user. The default is 6.
     * @param counterOrPeriod This is counter for counter based keys and period in time based ones. The counter parameter is required when provisioning a key for use with HOTP. It will set the initial counter value. The period parameter defines a period that a TOTP code will be valid for, in seconds. The default value is 30.
     * @return A URI in the following format: `otpauth://TYPE/LABEL?PARAMETERS` For example: `otpauth://totp/Example:[email protected]?secret=JBSWY3DPEHPK3PXP&issuer=Example`
     */
    fun generateGoogleAuthenticatorKeyUri(
        type: KeyType,
        issuer: String,
        accountName: String,
        secret: String,
        digits: Int? = null,
        counterOrPeriod: Int? = null
    ): Uri = Uri.Builder()
        .scheme("otpauth")
        .authority(type.uriKey)
        .appendPath("$issuer:$accountName")
        .appendQueryParameter("secret", secret)
        .appendQueryParameter("issuer", issuer)
        .apply {
            if (digits == null)
                return@apply
            if (digits != 6 && digits != 8)
                throw IllegalArgumentException("Digits param must be 6 or 8. Current value: $digits")
            appendQueryParameter("digits", digits.toString())
        }
        .apply {
            when (type) {
                KeyType.COUNTER_BASED -> {
                    if (counterOrPeriod == null)
                        throw IllegalArgumentException("Counter param is required when key type is counter based.")
                    appendQueryParameter("counter", counterOrPeriod.toString())
                }
                KeyType.TIME_BASED -> {
                    counterOrPeriod?.let { appendQueryParameter("period", it.toString()) }
                }
            }
        }
        .build()
}