/**
* Creates an instance of this class (only once) and returns it
* @return GoogleAuth
*/
public static function getInstance()
{
# Create the instance if it hasn't been created yet
if (!isset(GoogleAuth::$instance)) {
GoogleAuth::$instance = new GoogleAuth();
}
# Set auth access token
# Access token is session is set when user successfully signs in
# using Google and is returned back to the page (the method to catch the code
# that is passed back is in index.php)
GoogleAuth::$auth = HTTPSession::getInstance()->ACCESS_TOKEN;
# If auth code is not empty, it means that user was successfully signed in
# using Google sign in, therefore set the received access token for client
# and authorise using HTTPSession
if (!empty(GoogleAuth::$auth)) {
GoogleAuth::$instance->setToken();
# TODO: First we need to check if session is still valid
# This implementation needs to be finished in the future version,
# since it gets more complex and takes too much time
if (GoogleAuth::$instance->checkIfExpired()) {
echo "Google session expired";
die;
}
# Login the user using provided email
HTTPSession::getInstance()->LoginGoogle(GoogleAuth::$instance->getUserEmail());
}
# Return the new instance or already existing instance
return GoogleAuth::$instance;
}
