fun getAppSignature(context: Context) = context.packageManager.getPackageInfo(context.packageName, PackageManager.GET_SIGNATURES)
        .signatures.mapNotNull { hash(context.packageName, it.toCharsString()) }.firstOrNull()

private fun hash(packageName: String, signature: String) = try {
    val messageDigest = MessageDigest.getInstance("SHA-256")
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
        messageDigest.update("$packageName $signature".toByteArray(StandardCharsets.UTF_8))
    }
    var hashSignature = messageDigest.digest()
    hashSignature = Arrays.copyOfRange(hashSignature, 0, 9)
    var base64Hash = Base64.encodeToString(hashSignature, Base64.NO_PADDING or Base64.NO_WRAP)
    base64Hash = base64Hash.substring(0, 11)
    base64Hash
} catch (e: NoSuchAlgorithmException) {
    null
}