/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * 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.
 */
package org.apache.catalina.filters;

import java.io.IOException;

import jakarta.servlet.FilterChain;
import jakarta.servlet.GenericFilter;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import org.apache.tomcat.util.res.StringManager;

/**
 * Filter that attempts to force MS WebDAV clients connecting on port 80 to use a WebDAV client that actually works.
 * Other workarounds that might help include:
 * <ul>
 * <li>Specifying the port, even if it is port 80, when trying to connect.</li>
 * <li>Cancelling the first authentication dialog box and then trying to reconnect.</li>
 * </ul>
 * Generally each different version of the MS client has a different set of problems.
 * <p>
 * TODO: Update this filter to recognise specific MS clients and apply the appropriate workarounds for that particular
 * client
 * <p>
 * As a filter, this is configured in web.xml like any other Filter. You usually want to map this filter to whatever
 * your WebDAV servlet is mapped to.
 * <p>
 * In addition to the issues fixed by this Filter, the following issues have also been observed that cannot be fixed by
 * this filter. Where possible the filter will add an message to the logs.
 * <p>
 * XP x64 SP2 (MiniRedir Version 3790)
 * <ul>
 * <li>Only connects to port 80</li>
 * <li>Unknown issue means it doesn't work</li>
 * </ul>
 */
public class WebdavFixFilter extends GenericFilter {

    private static final long serialVersionUID = 1L;
    protected static final StringManager sm = StringManager.getManager(WebdavFixFilter.class);

    /* Start string for all versions */
    private static final String UA_MINIDIR_START = "Microsoft-WebDAV-MiniRedir";
    /* XP 32-bit SP3 */
    private static final String UA_MINIDIR_5_1_2600 = "Microsoft-WebDAV-MiniRedir/5.1.2600";

    /* XP 64-bit SP2 */
    private static final String UA_MINIDIR_5_2_3790 = "Microsoft-WebDAV-MiniRedir/5.2.3790";

    /**
     * Check for the broken MS WebDAV client and if detected issue a re-direct that hopefully will cause the non-broken
     * client to be used.
     */
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {
            chain.doFilter(request, response);
            return;
        }
        HttpServletRequest httpRequest = ((HttpServletRequest) request);
        HttpServletResponse httpResponse = ((HttpServletResponse) response);
        String ua = httpRequest.getHeader("User-Agent");

        if (ua == null || ua.length() == 0 || !ua.startsWith(UA_MINIDIR_START)) {
            // No UA or starts with non MS value
            // Hope everything just works...
            chain.doFilter(request, response);
        } else if (ua.startsWith(UA_MINIDIR_5_1_2600)) {
            // XP 32-bit SP3 - needs redirect with explicit port
            httpResponse.sendRedirect(buildRedirect(httpRequest));
        } else if (ua.startsWith(UA_MINIDIR_5_2_3790)) {
            // XP 64-bit SP2
            if (!httpRequest.getContextPath().isEmpty()) {
                getServletContext().log(sm.getString("webDavFilter.xpRootContext"));
            }
            // Namespace issue maybe
            // see http://greenbytes.de/tech/webdav/webdav-redirector-list.html
            getServletContext().log(sm.getString("webDavFilter.xpProblem"));

            chain.doFilter(request, response);
        } else {
            // Don't know which MS client it is - try the redirect with an
            // explicit port in the hope that it moves the client to a different
            // WebDAV implementation that works
            httpResponse.sendRedirect(buildRedirect(httpRequest));
        }
    }

    private String buildRedirect(HttpServletRequest request) {
        StringBuilder location = new StringBuilder(request.getRequestURL().length());
        location.append(request.getScheme());
        location.append("://");
        location.append(request.getServerName());
        location.append(':');
        // If we include the port, even if it is 80, then MS clients will use
        // a WebDAV client that works rather than the MiniRedir that has
        // problems with BASIC authentication
        location.append(request.getServerPort());
        location.append(request.getRequestURI());
        return location.toString();
    }

}
