RenewableSpotifyApi wrapper class

/**
 * {@code RenewableSpotifyApi} is the wrapper over spotify rest api.
 */
public class RenewableSpotifyApi implements Supplier<Api> {
    private final Api               api;
    private       ClientCredentials clientCredentials;
    private       Instant           timeOfReceipt;

    public RenewableSpotifyApi(Config config) {
        this.api = Api.builder()
            .clientId(config.getString("spotify.client.id"))
            .clientSecret(config.getString("spotify.client.secret"))
            .build();
    }

    synchronized public Api get() {
        if (clientCredentials == null) {
            renewCredentials();
        } else {
            final long passedTime = (Instant.now().toEpochMilli() - timeOfReceipt.toEpochMilli()) / 1000;
            final int expiresIn = clientCredentials.getExpiresIn();
            if (passedTime >= expiresIn) {
                renewCredentials();
            }
        }
        return api;
    }

    private void renewCredentials() {
        try {
            clientCredentials = api.clientCredentialsGrant().build().get();
            timeOfReceipt = Instant.now();
            api.setAccessToken(clientCredentials.getAccessToken());
        } catch (IOException | WebApiException e) {
            throw new RuntimeException(e);
        }
    }
}