/*
 * Copyright 2004, 2005, 2006 Acegi Technology Pty Limited
 *
 * 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 org.springframework.security.web.authentication;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.web.AuthenticationEntryPoint;
import org.springframework.security.web.DefaultRedirectStrategy;
import org.springframework.security.web.PortMapper;
import org.springframework.security.web.PortMapperImpl;
import org.springframework.security.web.PortResolver;
import org.springframework.security.web.PortResolverImpl;
import org.springframework.security.web.RedirectStrategy;
import org.springframework.security.web.access.ExceptionTranslationFilter;
import org.springframework.security.web.util.RedirectUrlBuilder;
import org.springframework.security.web.util.UrlUtils;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Used by the {@link ExceptionTranslationFilter} to commence a form login authentication
 * via the {@link UsernamePasswordAuthenticationFilter}.
 * <p>
 * Holds the location of the login form in the {@code loginFormUrl} property, and uses
 * that to build a redirect URL to the login page. Alternatively, an absolute URL can be
 * set in this property and that will be used exclusively.
 * <p>
 * When using a relative URL, you can set the {@code forceHttps} property to true, to
 * force the protocol used for the login form to be {@code HTTPS}, even if the original
 * intercepted request for a resource used the {@code HTTP} protocol. When this happens,
 * after a successful login (via HTTPS), the original resource will still be accessed as
 * HTTP, via the original request URL. For the forced HTTPS feature to work, the
 * {@link PortMapper} is consulted to determine the HTTP:HTTPS pairs. The value of
 * {@code forceHttps} will have no effect if an absolute URL is used.
 *
 * @author Ben Alex
 * @author colin sampaleanu
 * @author Omri Spector
 * @author Luke Taylor
 * @since 3.0
 */
public class LoginUrlAuthenticationEntryPoint implements AuthenticationEntryPoint,
		InitializingBean {
	// ~ Static fields/initializers
	// =====================================================================================

	private static final Log logger = LogFactory
			.getLog(LoginUrlAuthenticationEntryPoint.class);

	// ~ Instance fields
	// ================================================================================================

	private PortMapper portMapper = new PortMapperImpl();

	private PortResolver portResolver = new PortResolverImpl();

	private String loginFormUrl;

	private boolean forceHttps = false;

	private boolean useForward = false;

	private final RedirectStrategy redirectStrategy = new DefaultRedirectStrategy();

	/**
	 *
	 * @param loginFormUrl URL where the login page can be found. Should either be
	 * relative to the web-app context path (include a leading {@code /}) or an absolute
	 * URL.
	 */
	public LoginUrlAuthenticationEntryPoint(String loginFormUrl) {
		Assert.notNull(loginFormUrl, "loginFormUrl cannot be null");
		this.loginFormUrl = loginFormUrl;
	}

	// ~ Methods
	// ========================================================================================================

	public void afterPropertiesSet() throws Exception {
		Assert.isTrue(
				StringUtils.hasText(loginFormUrl)
						&& UrlUtils.isValidRedirectUrl(loginFormUrl),
				"loginFormUrl must be specified and must be a valid redirect URL");
		if (useForward && UrlUtils.isAbsoluteUrl(loginFormUrl)) {
			throw new IllegalArgumentException(
					"useForward must be false if using an absolute loginFormURL");
		}
		Assert.notNull(portMapper, "portMapper must be specified");
		Assert.notNull(portResolver, "portResolver must be specified");
	}

	/**
	 * Allows subclasses to modify the login form URL that should be applicable for a
	 * given request.
	 *
	 * @param request the request
	 * @param response the response
	 * @param exception the exception
	 * @return the URL (cannot be null or empty; defaults to {@link #getLoginFormUrl()})
	 */
	protected String determineUrlToUseForThisRequest(HttpServletRequest request,
			HttpServletResponse response, AuthenticationException exception) {

		return getLoginFormUrl();
	}

	/**
	 * Performs the redirect (or forward) to the login form URL.
	 */
	public void commence(HttpServletRequest request, HttpServletResponse response,
			AuthenticationException authException) throws IOException, ServletException {

		String redirectUrl = null;

		if (useForward) {

			if (forceHttps && "http".equals(request.getScheme())) {
				// First redirect the current request to HTTPS.
				// When that request is received, the forward to the login page will be
				// used.
				redirectUrl = buildHttpsRedirectUrlForRequest(request);
			}

			if (redirectUrl == null) {
				String loginForm = determineUrlToUseForThisRequest(request, response,
						authException);

				if (logger.isDebugEnabled()) {
					logger.debug("Server side forward to: " + loginForm);
				}

				RequestDispatcher dispatcher = request.getRequestDispatcher(loginForm);

				dispatcher.forward(request, response);

				return;
			}
		}
		else {
			// redirect to login page. Use https if forceHttps true

			redirectUrl = buildRedirectUrlToLoginPage(request, response, authException);

		}

		redirectStrategy.sendRedirect(request, response, redirectUrl);
	}

	protected String buildRedirectUrlToLoginPage(HttpServletRequest request,
			HttpServletResponse response, AuthenticationException authException) {

		String loginForm = determineUrlToUseForThisRequest(request, response,
				authException);

		if (UrlUtils.isAbsoluteUrl(loginForm)) {
			return loginForm;
		}

		int serverPort = portResolver.getServerPort(request);
		String scheme = request.getScheme();

		RedirectUrlBuilder urlBuilder = new RedirectUrlBuilder();

		urlBuilder.setScheme(scheme);
		urlBuilder.setServerName(request.getServerName());
		urlBuilder.setPort(serverPort);
		urlBuilder.setContextPath(request.getContextPath());
		urlBuilder.setPathInfo(loginForm);

		if (forceHttps && "http".equals(scheme)) {
			Integer httpsPort = portMapper.lookupHttpsPort(Integer.valueOf(serverPort));

			if (httpsPort != null) {
				// Overwrite scheme and port in the redirect URL
				urlBuilder.setScheme("https");
				urlBuilder.setPort(httpsPort.intValue());
			}
			else {
				logger.warn("Unable to redirect to HTTPS as no port mapping found for HTTP port "
						+ serverPort);
			}
		}

		return urlBuilder.getUrl();
	}

	/**
	 * Builds a URL to redirect the supplied request to HTTPS. Used to redirect the
	 * current request to HTTPS, before doing a forward to the login page.
	 */
	protected String buildHttpsRedirectUrlForRequest(HttpServletRequest request)
			throws IOException, ServletException {

		int serverPort = portResolver.getServerPort(request);
		Integer httpsPort = portMapper.lookupHttpsPort(Integer.valueOf(serverPort));

		if (httpsPort != null) {
			RedirectUrlBuilder urlBuilder = new RedirectUrlBuilder();
			urlBuilder.setScheme("https");
			urlBuilder.setServerName(request.getServerName());
			urlBuilder.setPort(httpsPort.intValue());
			urlBuilder.setContextPath(request.getContextPath());
			urlBuilder.setServletPath(request.getServletPath());
			urlBuilder.setPathInfo(request.getPathInfo());
			urlBuilder.setQuery(request.getQueryString());

			return urlBuilder.getUrl();
		}

		// Fall through to server-side forward with warning message
		logger.warn("Unable to redirect to HTTPS as no port mapping found for HTTP port "
				+ serverPort);

		return null;
	}

	/**
	 * Set to true to force login form access to be via https. If this value is true (the
	 * default is false), and the incoming request for the protected resource which
	 * triggered the interceptor was not already <code>https</code>, then the client will
	 * first be redirected to an https URL, even if <tt>serverSideRedirect</tt> is set to
	 * <tt>true</tt>.
	 */
	public void setForceHttps(boolean forceHttps) {
		this.forceHttps = forceHttps;
	}

	protected boolean isForceHttps() {
		return forceHttps;
	}

	public String getLoginFormUrl() {
		return loginFormUrl;
	}

	public void setPortMapper(PortMapper portMapper) {
		Assert.notNull(portMapper, "portMapper cannot be null");
		this.portMapper = portMapper;
	}

	protected PortMapper getPortMapper() {
		return portMapper;
	}

	public void setPortResolver(PortResolver portResolver) {
		Assert.notNull(portResolver, "portResolver cannot be null");
		this.portResolver = portResolver;
	}

	protected PortResolver getPortResolver() {
		return portResolver;
	}

	/**
	 * Tells if we are to do a forward to the {@code loginFormUrl} using the
	 * {@code RequestDispatcher}, instead of a 302 redirect.
	 *
	 * @param useForward true if a forward to the login page should be used. Must be false
	 * (the default) if {@code loginFormUrl} is set to an absolute value.
	 */
	public void setUseForward(boolean useForward) {
		this.useForward = useForward;
	}

	protected boolean isUseForward() {
		return useForward;
	}
}
