/*
 *  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.mina.proxy.handlers.http.ntlm;

import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.mina.core.filterchain.IoFilter.NextFilter;
import org.apache.mina.proxy.ProxyAuthException;
import org.apache.mina.proxy.handlers.http.AbstractAuthLogicHandler;
import org.apache.mina.proxy.handlers.http.HttpProxyConstants;
import org.apache.mina.proxy.handlers.http.HttpProxyRequest;
import org.apache.mina.proxy.handlers.http.HttpProxyResponse;
import org.apache.mina.proxy.session.ProxyIoSession;
import org.apache.mina.proxy.utils.StringUtilities;
import org.apache.mina.util.Base64;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * HttpNTLMAuthLogicHandler.java - HTTP NTLM authentication mechanism logic handler.
 * 
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 * @since MINA 2.0.0-M3
 */
public class HttpNTLMAuthLogicHandler extends AbstractAuthLogicHandler {

    private final static Logger LOGGER = LoggerFactory.getLogger(HttpNTLMAuthLogicHandler.class);

    /**
     * The challenge provided by the server.
     */
    private byte[] challengePacket = null;

    /**
     * {@inheritDoc}
     */
    public HttpNTLMAuthLogicHandler(final ProxyIoSession proxyIoSession) throws ProxyAuthException {
        super(proxyIoSession);

        ((HttpProxyRequest) request).checkRequiredProperties(HttpProxyConstants.USER_PROPERTY,
                HttpProxyConstants.PWD_PROPERTY, HttpProxyConstants.DOMAIN_PROPERTY,
                HttpProxyConstants.WORKSTATION_PROPERTY);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void doHandshake(NextFilter nextFilter) throws ProxyAuthException {
        LOGGER.debug(" doHandshake()");

        if (step > 0 && challengePacket == null) {
            throw new IllegalStateException("NTLM Challenge packet not received");
        }

        HttpProxyRequest req = (HttpProxyRequest) request;
        Map<String, List<String>> headers = req.getHeaders() != null ? req.getHeaders()
                : new HashMap<String, List<String>>();

        String domain = req.getProperties().get(HttpProxyConstants.DOMAIN_PROPERTY);
        String workstation = req.getProperties().get(HttpProxyConstants.WORKSTATION_PROPERTY);

        if (step > 0) {
            LOGGER.debug("  sending NTLM challenge response");

            byte[] challenge = NTLMUtilities.extractChallengeFromType2Message(challengePacket);
            int serverFlags = NTLMUtilities.extractFlagsFromType2Message(challengePacket);

            String username = req.getProperties().get(HttpProxyConstants.USER_PROPERTY);
            String password = req.getProperties().get(HttpProxyConstants.PWD_PROPERTY);

            byte[] authenticationPacket = NTLMUtilities.createType3Message(username, password, challenge, domain,
                    workstation, serverFlags, null);

            StringUtilities.addValueToHeader(headers, "Proxy-Authorization",
                    "NTLM " + new String(Base64.encodeBase64(authenticationPacket)), true);

        } else {
            LOGGER.debug("  sending NTLM negotiation packet");

            byte[] negotiationPacket = NTLMUtilities.createType1Message(workstation, domain, null, null);
            StringUtilities.addValueToHeader(headers, "Proxy-Authorization",
                    "NTLM " + new String(Base64.encodeBase64(negotiationPacket)), true);
        }

        addKeepAliveHeaders(headers);
        req.setHeaders(headers);

        writeRequest(nextFilter, req);
        step++;
    }

    /**
     * Returns the value of the NTLM Proxy-Authenticate header.
     * 
     * @param response the proxy response
     */
    private String getNTLMHeader(final HttpProxyResponse response) {
        List<String> values = response.getHeaders().get("Proxy-Authenticate");

        for (String s : values) {
            if (s.startsWith("NTLM")) {
                return s;
            }
        }

        return null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void handleResponse(final HttpProxyResponse response) throws ProxyAuthException {
        if (step == 0) {
            String challengeResponse = getNTLMHeader(response);
            step = 1;

            if (challengeResponse == null || challengeResponse.length() < 5) {
                // Nothing to handle at this step. 
                // Just need to send a reply type 1 message in doHandshake().
                return;
            }

            // else there was no step 0 so continue to step 1.
        }

        if (step == 1) {
            // Header should look like :
            // Proxy-Authenticate: NTLM still_some_more_stuff
            String challengeResponse = getNTLMHeader(response);

            if (challengeResponse == null || challengeResponse.length() < 5) {
                throw new ProxyAuthException("Unexpected error while reading server challenge !");
            }

            try {
                challengePacket = Base64.decodeBase64(challengeResponse.substring(5).getBytes(
                        proxyIoSession.getCharsetName()));
            } catch (IOException e) {
                throw new ProxyAuthException("Unable to decode the base64 encoded NTLM challenge", e);
            }
            step = 2;
        } else {
            throw new ProxyAuthException("Received unexpected response code (" + response.getStatusLine() + ").");
        }
    }
}
