package com.howgoodiwas.util;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

/**
 * Servlet filter which disables URL-encoded session identifiers.
 * 
 * <pre>
 * Copyright (c) 2006, Craig Condit. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS &quot;AS IS&quot;
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Modified by Devon Hillard (devon@digitalsanctuary.com) to only filter for GoogleBot, 
 * not for users without cookies enabled.
 * </pre>
 */
@SuppressWarnings("deprecation")
public class DisableUrlSessionFilter implements Filter {

    /**
     * The string to look for in the User-Agent header to identify the GoogleBot.
     */
    private static final String GOOGLEBOT_AGENT_STRING = "googlebot";

    /**
     * The request header with the User-Agent information in it.
     */
    private static final String USER_AGENT_HEADER_NAME = "User-Agent";

    /**
     * Filters requests to disable URL-based session identifiers.
     * 
     * @param pRequest
     *                the request
     * @param pResponse
     *                the response
     * @param pChain
     *                the chain
     * 
     * @throws IOException
     *                 Signals that an I/O exception has occurred.
     * @throws ServletException
     *                 the servlet exception
     */
    public void doFilter(final ServletRequest pRequest, final ServletResponse pResponse, final FilterChain pChain)
	    throws IOException, ServletException {
	// skip non-http requests
	if (!(pRequest instanceof HttpServletRequest)) {
	    pChain.doFilter(pRequest, pResponse);
	    return;
	}

	HttpServletRequest httpRequest = (HttpServletRequest) pRequest;
	HttpServletResponse httpResponse = (HttpServletResponse) pResponse;

	boolean isGoogleBot = false;

	if (httpRequest != null) {
	    String userAgent = httpRequest.getHeader(USER_AGENT_HEADER_NAME);
	    if (StringUtils.isNotBlank(userAgent)) {
		if (userAgent.toLowerCase().indexOf(GOOGLEBOT_AGENT_STRING) > -1) {
		    isGoogleBot = true;
		}
	    }
	}

	if (isGoogleBot) {
	    // wrap response to remove URL encoding
	    HttpServletResponseWrapper wrappedResponse = new HttpServletResponseWrapper(httpResponse) {
		@Override
		public String encodeRedirectUrl(final String url) {
		    return url;
		}

		@Override
		public String encodeRedirectURL(final String url) {
		    return url;
		}

		@Override
		public String encodeUrl(final String url) {
		    return url;
		}

		@Override
		public String encodeURL(final String url) {
		    return url;
		}
	    };

	    // process next request in chain
	    pChain.doFilter(pRequest, wrappedResponse);
	} else {
	    pChain.doFilter(pRequest, pResponse);
	}
    }

    /**
     * Unused.
     * 
     * @param pConfig
     *                the config
     * 
     * @throws ServletException
     *                 the servlet exception
     */
    public void init(final FilterConfig pConfig) throws ServletException {
    }

    /**
     * Unused.
     */
    public void destroy() {
    }
}