/*
 * Copyright 2002-2015 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 org.springframework.security.web.context.support;

import java.util.Enumeration;
import javax.servlet.ServletContext;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

/**
 * Spring Security extension to Spring's {@link WebApplicationContextUtils}.
 *
 * @author Rob Winch
 */
public abstract class SecurityWebApplicationContextUtils extends WebApplicationContextUtils {

	/**
	 * Find a unique {@code WebApplicationContext} for this web app: either the
	 * root web app context (preferred) or a unique {@code WebApplicationContext}
	 * among the registered {@code ServletContext} attributes (typically coming
	 * from a single {@code DispatcherServlet} in the current web application).
	 * <p>Note that {@code DispatcherServlet}'s exposure of its context can be
	 * controlled through its {@code publishContext} property, which is {@code true}
	 * by default but can be selectively switched to only publish a single context
	 * despite multiple {@code DispatcherServlet} registrations in the web app.
	 * @param servletContext ServletContext to find the web application context for
	 * @return the desired WebApplicationContext for this web app
	 * @see #getWebApplicationContext(ServletContext)
	 * @see ServletContext#getAttributeNames()
	 * @throws IllegalStateException if no WebApplicationContext can be found
	 */
	public static WebApplicationContext findRequiredWebApplicationContext(ServletContext servletContext) {
		WebApplicationContext wac = _findWebApplicationContext(servletContext);
		if (wac == null) {
			throw new IllegalStateException("No WebApplicationContext found: no ContextLoaderListener registered?");
		}
		return wac;
	}

	/**
	 * Copy of {@link #findWebApplicationContext(ServletContext)} for compatibility with spring framework 4.1.x.
	 * @see #findWebApplicationContext(ServletContext)
	 */
	private static WebApplicationContext _findWebApplicationContext(ServletContext sc) {
		WebApplicationContext wac = getWebApplicationContext(sc);
		if (wac == null) {
			Enumeration<String> attrNames = sc.getAttributeNames();
			while (attrNames.hasMoreElements()) {
				String attrName = attrNames.nextElement();
				Object attrValue = sc.getAttribute(attrName);
				if (attrValue instanceof WebApplicationContext) {
					if (wac != null) {
						throw new IllegalStateException("No unique WebApplicationContext found: more than one " +
								"DispatcherServlet registered with publishContext=true?");
					}
					wac = (WebApplicationContext) attrValue;
				}
			}
		}
		return wac;
	}
}
