/*
 * Copyright 2011 Federal Chancellery Austria and
 * Graz University of Technology
 * 
 * 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 at.gv.util;

import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Enumeration;

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import at.gv.util.ex.InternalErrorException;

/**
 * Class providing several utility methods for the Servlet API.
 * 
 * @author <a href="mailto:Arne.Tauber@egiz.gv.at">Arne Tauber</a>
 * 
 */
public class WebAppUtil {

	private static Logger log = LoggerFactory.getLogger(WebAppUtil.class);

	public static void sendHTTPRedirect(HttpServletResponse response, String redirectURL) {
		response.setContentLength(0);
		response.setContentType("text/html");
		response.setHeader("Location", redirectURL);
		response.setStatus(HttpServletResponse.SC_FOUND);
	}
	
	public static void disableBrowserCacheForResponse(HttpServletResponse response) {
		log.debug("Disabling browser cache for HttpServletResponse.");
		response.setHeader("Cache-Control", "no-cache,no-store,max-age=0");
		response.setHeader("Pragma", "no-cache");
		response.setDateHeader("Expires", 1);
	}

	public static String getBaseURLUnSecure(HttpServletRequest request) {
		String url = getBaseURL(request);
		if (url.startsWith("https")) {
			return "http" + url.substring(5);
		}
		return url;
	}

	public static String getBaseURL(HttpServletRequest request) {
		StringBuffer buffer = new StringBuffer(getServerURL(request));

		// add context path if available
		String contextPath = request.getContextPath();
		if (MiscUtil.isNotEmpty(contextPath)) {
			buffer.append(contextPath).append("/");
		}

		return buffer.toString();
	}

	public static String getServerURL(HttpServletRequest request) {
		StringBuffer buffer = new StringBuffer();

		// get protocol
		String protocol = request.getScheme();
		buffer.append(protocol).append("://");

		// server name
		buffer.append(request.getServerName());

		// add port if necessary
		int port = request.getServerPort();
		if ((protocol.equals("http") && port != 80)
		    || (protocol.equals("https") && port != 443)) {
			buffer.append(':');
			buffer.append(port);
		}

		return buffer.toString();
	}

	public static String getRequestURLWithParameters(HttpServletRequest request) {
		return getRequestURLWithParameters(request, false);
	}

	public static String getRequestURLWithParameters(HttpServletRequest request,
	    boolean includeRequestParameters) {
		StringBuffer buffer = request.getRequestURL();
		if (includeRequestParameters) {
			Enumeration paramEnum = request.getParameterNames();
			if (paramEnum.hasMoreElements()) {
				buffer.append("?");
				while (paramEnum.hasMoreElements()) {
					String param = (String) paramEnum.nextElement();
					try {
						buffer.append(URLEncoder.encode(param, "UTF-8"));
						if (!MiscUtil.isEmpty(request.getParameter(param))) {
							buffer.append("=").append(
							    URLEncoder.encode(request.getParameter(param), "UTF-8"));
						}

					} catch (UnsupportedEncodingException e) {
						// should never happen as far as the java installation is ok
						throw new InternalErrorException(e);
					}
					if (paramEnum.hasMoreElements()) {
						buffer.append("&");
					}
				}
			}
		} else {
			String queryString = request.getQueryString();
			if (MiscUtil.isNotEmpty(queryString)) {
				buffer.append("?").append(queryString);
			}
		}
		String requestURL = buffer.toString();
		log.debug("Returning request url "
		    + (includeRequestParameters ? "including request parameters" : "")
		    + " \"" + requestURL + "\".");
		return requestURL;
	}

	public static boolean isFullQualifiedURL(String url) {
		MiscUtil.assertNotNull(url, "URL");
		try {
			new URL(url);
			return true;
		} catch (MalformedURLException e) {
			return false;
		}
	}

}