/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package samples.gae.security;

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.appengine.api.users.User;
import com.google.appengine.api.users.UserServiceFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.security.authentication.AuthenticationDetailsSource;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.web.authentication.AuthenticationFailureHandler;
import org.springframework.security.web.authentication.SimpleUrlAuthenticationFailureHandler;
import org.springframework.security.web.authentication.WebAuthenticationDetails;
import org.springframework.security.web.authentication.WebAuthenticationDetailsSource;
import org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationToken;
import org.springframework.util.Assert;
import org.springframework.web.filter.GenericFilterBean;
import samples.gae.users.GaeUser;

/**
 * @author Luke Taylor
 */
public class GaeAuthenticationFilter extends GenericFilterBean {
	private static final String REGISTRATION_URL = "/register.htm";

	private final Logger logger = LoggerFactory.getLogger(getClass());

	private final AuthenticationDetailsSource<HttpServletRequest, WebAuthenticationDetails> ads = new WebAuthenticationDetailsSource();
	private AuthenticationManager authenticationManager;
	private AuthenticationFailureHandler failureHandler = new SimpleUrlAuthenticationFailureHandler();

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		Authentication authentication = SecurityContextHolder.getContext()
				.getAuthentication();
		User googleUser = UserServiceFactory.getUserService().getCurrentUser();

		if (authentication != null
				&& !loggedInUserMatchesGaeUser(authentication, googleUser)) {
			SecurityContextHolder.clearContext();
			authentication = null;
			((HttpServletRequest) request).getSession().invalidate();
		}

		if (authentication == null) {
			if (googleUser != null) {
				logger.debug("Currently logged on to GAE as user " + googleUser);
				logger.debug("Authenticating to Spring Security");
				// User has returned after authenticating via GAE. Need to authenticate
				// through Spring Security.
				PreAuthenticatedAuthenticationToken token = new PreAuthenticatedAuthenticationToken(
						googleUser, null);
				token.setDetails(ads.buildDetails((HttpServletRequest) request));

				try {
					authentication = authenticationManager.authenticate(token);
					SecurityContextHolder.getContext().setAuthentication(authentication);

					if (authentication.getAuthorities().contains(AppRole.NEW_USER)) {
						logger.debug("New user authenticated. Redirecting to registration page");
						((HttpServletResponse) response).sendRedirect(REGISTRATION_URL);

						return;
					}

				}
				catch (AuthenticationException e) {
					failureHandler.onAuthenticationFailure((HttpServletRequest) request,
							(HttpServletResponse) response, e);

					return;
				}
			}
		}

		chain.doFilter(request, response);
	}

	private boolean loggedInUserMatchesGaeUser(Authentication authentication,
			User googleUser) {
		assert authentication != null;

		if (googleUser == null) {
			// User has logged out of GAE but is still logged into application
			return false;
		}

		GaeUser gaeUser = (GaeUser) authentication.getPrincipal();

		if (!gaeUser.getEmail().equals(googleUser.getEmail())) {
			return false;
		}

		return true;

	}

	@Override
	public void afterPropertiesSet() throws ServletException {
		Assert.notNull(authenticationManager, "AuthenticationManager must be set");
	}

	public void setAuthenticationManager(AuthenticationManager authenticationManager) {
		this.authenticationManager = authenticationManager;
	}

	public void setFailureHandler(AuthenticationFailureHandler failureHandler) {
		this.failureHandler = failureHandler;
	}
}
