/*
 * Copyright 2009-2010 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.batch.admin.web.interceptor;

import java.util.Collection;
import java.util.Date;
import java.util.HashSet;
import java.util.LinkedHashSet;

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

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.ui.ModelMap;
import org.springframework.validation.BindException;
import org.springframework.validation.Errors;
import org.springframework.validation.ObjectError;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import org.springframework.web.util.WebUtils;

/**
 * Interceptor that looks for an extension on the request path and adds it to the view name if it matches a list
 * provided. This can be used to do simple content negotiation based on request path extensions, as is usual with
 * browsers (the view that is finally resolved could have a different content type than the original request).
 * 
 * @author Dave Syer
 * 
 */
public class ContentTypeInterceptor extends HandlerInterceptorAdapter implements BeanFactoryAware {

	private Collection<String> extensions = new HashSet<String>();

	private BeanFactory beanFactory;

	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
		this.beanFactory = beanFactory;
	}

	/**
	 * A collection of extensions to append to view names.
	 * 
	 * @param extensions the extensions (e.g. [rss, xml, atom])
	 */
	public void setExtensions(Collection<String> extensions) {
		this.extensions = new LinkedHashSet<String>(extensions);
	}

	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

		String scheme = request.getScheme();
		StringBuffer url = new StringBuffer(scheme + "://");
		url.append(request.getServerName());
		int port = request.getServerPort();
		if ((scheme.equals("http") && port != 80) || (scheme.equals("https") && port != 443)) {
			url.append(":" + port);
		}

		request.setAttribute("baseUrl", url.toString());
		request.setAttribute("currentTime", new Date());

		return true;

	}

	/**
	 * Compare the extension of the request path (if there is one) with the set provided, and if it matches then add the
	 * same extension to the view name, if it is not already present.
	 * 
	 * @see HandlerInterceptorAdapter#postHandle(HttpServletRequest, HttpServletResponse, Object, ModelAndView)
	 */
	@Override
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
			ModelAndView modelAndView) throws Exception {

		if (modelAndView == null) {
			return;
		}

		String pathInfo = request.getPathInfo();
		String path = pathInfo==null ? "" : WebUtils.extractFullFilenameFromUrlPath(pathInfo);
		if (!path.contains(".")) {
			return;
		}
		String extension = path.substring(path.lastIndexOf(".") + 1);

		exposeErrors(modelAndView.getModelMap());

		if (extensions.contains(extension)) {

			if (modelAndView.isReference()) {

				String viewName = modelAndView.getViewName();
				if (viewName.contains(".")) {
					viewName = viewName.substring(0, path.lastIndexOf("."));
				}

				String newViewName = viewName + "." + extension;
				if (beanFactory == null || beanFactory.containsBean(newViewName)) {
					// Adding a suffix only makes sense for bean name resolution
					modelAndView.setViewName(newViewName);
				}

			}

		}

	}

	private void exposeErrors(ModelMap modelMap) {
		if (modelMap.containsAttribute("errors")) {
			return;
		}
		BindException errors = new BindException(new Object(), "target");
		boolean hasErrors = false;
		for (Object value : modelMap.values()) {
			if (value instanceof Errors) {
				for (ObjectError error : ((Errors) value).getGlobalErrors()) {
					errors.addError(error);
					hasErrors = true;
				}
			}
		}
		if (hasErrors) {
			modelMap.addAttribute("errors", errors);
		}
	}
}