write to Buffer from Retroft interceptor

write to Buffer from Retroft interceptor

    @Throws(IOException::class)
    override fun intercept(chain: Interceptor.Chain): Response {

        val firebaseToken = Utils.getFirebaseToken(context)
        val originalRequest: Request = chain.request()
        var newRequest = originalRequest.newBuilder()
            .addHeader("content-type", "application/json;charset=UTF-8")
            .addHeader("accept", "application/json")
            .addHeader("api-version", "1.0")
            .addHeader("authorization", "Bearer $firebaseToken")
            .addHeader("DEVICEOS", "Android " + versionCodeName + ", API Level: " + Build.VERSION.SDK_INT)
            .addHeader("APPVERSION", BuildConfig.VERSION_NAME + " " + BuildConfig.VERSION_CODE)
            .addHeader("APPLANG", Locale.getDefault().language)
            .build()

        if (newRequest.url.toString() == BuildConfig.API_ADDRESS + "api/transacoes.php" || newRequest.url.toString() == BuildConfig.API_ADDRESS + "api/transacoes_log.php") {
            var signature: String? = ""
            if (newRequest.body != null) {
                val buffer = Buffer()
                newRequest.body?.writeTo(buffer)
                signature = generateHashWithHmac256(
                    Base64.encodeToString(
                        buffer.readString(StandardCharsets.UTF_8).toByteArray(), Base64.NO_WRAP
                    )
                )
            }
            newRequest = newRequest.newBuilder()
                .addHeader("X-Biip-Signature", signature ?: "")
                .build()
        }

        val response = chain.proceed(newRequest)
        return response
    }