/**
 *                                                                            
 * Copyright (c) 2011, 2016 - Loetz GmbH&Co.KG (69115 Heidelberg, Germany)
 *                                                                            
 * All rights reserved. This program and the accompanying materials           
 * are made available under the terms of the Eclipse Public License 2.0        
 * which accompanies this distribution, and is available at                  
 * https://www.eclipse.org/legal/epl-2.0/                                 
 *                                 
 * SPDX-License-Identifier: EPL-2.0                                 
 *                                                                            
 * Contributors:   
 * Christophe Loetz (Loetz GmbH&Co.KG) - initial implementation 
 */
package org.eclipse.osbp.authentication.vaadin;

import com.google.inject.Provider;
import com.vaadin.server.VaadinSession;

import org.apache.shiro.subject.Subject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Use this instead of using {@link org.apache.shiro.SecurityUtils#getSubject()} directly, to ensure that the Subject instance remains
 * consistent for the duration of a Vaadin Session.
 * 
 * depends on ideas of David Sowerby
 */
public class SubjectProvider implements Provider<Subject> {
    
    /** The log. */
    private static Logger log = LoggerFactory.getLogger(SubjectProvider.class);
    
    /** The session provider. */
    private final VaadinSessionProvider sessionProvider;

	/**
	 * Instantiates a new subject provider.
	 *
	 * @param sessionProvider the session provider
	 */
	public SubjectProvider(VaadinSessionProvider sessionProvider) {
        super();
        this.sessionProvider = sessionProvider;
    }

    /* (non-Javadoc)
     * @see com.google.inject.Provider#get()
     */
    @Override
    public synchronized Subject get() {
        Subject subject = null;
        try {
            VaadinSession session = sessionProvider.get();
            subject = session.getAttribute(Subject.class);
            if (subject == null) {
                log.debug("VaadinSession is valid, but does not have a stored Subject, creating a new Subject");
                subject = new Subject.Builder().buildSubject();
                log.debug("storing Subject instance in VaadinSession");
                session.setAttribute(Subject.class, subject);
            }
            return subject;

        } catch (IllegalStateException ise) {
            // this may happen in background threads which are not using a session, or during testing
            log.debug("There is no VaadinSession, creating a new Subject");
            subject = new Subject.Builder().buildSubject();
            return subject;
        }
    }
}