/**
 * Copyright 2007-2016, Kaazing Corporation. All rights reserved.
 *
 * 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 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 static final 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 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() + ").");
        }
    }
}
