/**
* Return an access token.
*
* @throws \RuntimeException
* @return string|null
*/
public function getAccessToken()
{
$accessToken = $this->getAccessTokenFromPersistence();
$grandType = $this->configuration->getGrantType();
if (null !== $accessToken) {
if ($grandType !== $this->storage->get(self::GRAND_TYPE_KEY, null)) {
throw new \RuntimeException('grand_type switching not supported');
}
return $accessToken;
}
if ('password' === $grandType) {
$response = $this->requestAccessToken();
} else {
throw new \RuntimeException('invalid grand_type configured');
}
if (null === $response || 200 != $response->getStatusCode()) {
return null;
}
return $this->setAccessTokenToPersistence($response);
}
