/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  The ASF licenses this file to You
 * 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.  For additional information regarding
 * copyright in this work, please see the NOTICE file in the top level
 * directory of this distribution.
 */

package org.apache.roller.weblogger.ui.core.filters;

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 org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.roller.weblogger.config.WebloggerRuntimeConfig;

/**
 * A special initialization filter which ensures that we have an opportunity to
 * extract a few pieces of information about the environment we are running in
 * when the first request is sent.
 * 
 * @web.filter name="InitFilter"
 */
public class InitFilter implements Filter {

    private static Log log = LogFactory.getLog(InitFilter.class);

    private boolean initialized = false;

    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {

        if (!initialized) {

            // first request, lets do our initialization
            HttpServletRequest request = (HttpServletRequest) req;
            // HttpServletResponse response = (HttpServletResponse) res;

            // determine absolute and relative url paths to the app
            String relPath = request.getContextPath();
            String absPath = this.getAbsoluteUrl(request);

            // set them in our config
            WebloggerRuntimeConfig.setAbsoluteContextURL(absPath);
            WebloggerRuntimeConfig.setRelativeContextURL(relPath);

            if (log.isDebugEnabled()) {
                log.debug("relPath = " + relPath);
                log.debug("absPath = " + absPath);
            }

            this.initialized = true;
        }

        chain.doFilter(req, res);
    }

    private String getAbsoluteUrl(HttpServletRequest request) {
        return getAbsoluteUrl(request.isSecure(),
                request.getServerName(), request.getContextPath(),
                request.getRequestURI(), request.getRequestURL().toString());
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    @Override
    public void destroy() {
    }

    protected static String getAbsoluteUrl(boolean secure, String serverName, String contextPath, String requestURI, String requestURL){

        String url = null;

        String fullUrl = null;

        if (!secure) {
            fullUrl = requestURL;
        } else {
            fullUrl = "http://" + serverName + contextPath;
        }

        // if the uri is only "/" then we are basically done
        if ("/".equals(requestURI)) {
            if (log.isDebugEnabled()) {
                log.debug("requestURI is only '/'. fullUrl: " + fullUrl);
            }
            return removeTrailingSlash(fullUrl);
        }

        // find first "/" starting after hostname is specified
        int index = fullUrl.indexOf('/',
                fullUrl.indexOf(serverName));

        if (index != -1) {
            // extract just the part leading up to uri
            url = fullUrl.substring(0, index);
        } else {
            url = fullUrl.trim();
        }

        // then just add on the context path
        url += contextPath;

        // make certain that we don't end with a /
        return removeTrailingSlash(url);
    }

    protected static String removeTrailingSlash(String url) {
        if (url.endsWith("/")) {
            return url.substring(0, url.length() - 1);
        }
        return url;
    }
}