/*
    *  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;
  
  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.session.ProxyIoSession;
  import org.apache.mina.proxy.utils.StringUtilities;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * HttpSmartProxyHandler.java - HTTP proxy handler that automatically handles forwarding request 
   * to the appropriate authentication mechanism logic handler.
   * 
   * @author The Apache MINA Project (dev@mina.apache.org)
   * @version $Rev: 685703 $, $Date: 2008-08-14 00:14:47 +0200 (Thu, 14 Aug 2008) $
   * @since MINA 2.0.0-M3
   */
  public class HttpSmartProxyHandler extends AbstractHttpLogicHandler {
      private final static Logger logger = LoggerFactory
              .getLogger(HttpSmartProxyHandler.class);
  
      /**
       * Has the HTTP proxy request been sent ?
       */
      private boolean requestSent = false;
  
      /**
       * The automatically selected http authentication logic handler. 
       */
      private AbstractAuthLogicHandler authHandler;
  
      public HttpSmartProxyHandler(final ProxyIoSession proxyIoSession) {
          super(proxyIoSession);
      }
  
      /**
       * Perform any handshaking processing.
       */
      public void doHandshake(final NextFilter nextFilter)
              throws ProxyAuthException {
          logger.debug(" doHandshake()");
  
          if (authHandler != null) {
              authHandler.doHandshake(nextFilter);
          } else {
              if (requestSent) {
                  throw new ProxyAuthException(
                          "Authentication request already sent");
              }
  
              logger.debug("  sending HTTP request");
  
              // Send request
              HttpProxyRequest req = (HttpProxyRequest) getProxyIoSession()
                      .getRequest();
              Map<String, List<String>> headers = req.getHeaders() != null ? req
                      .getHeaders() : new HashMap<String, List<String>>();
  
              StringUtilities.addValueToHeader(headers, "Keep-Alive",
                      HttpProxyConstants.DEFAULT_KEEP_ALIVE_TIME, true);
              StringUtilities.addValueToHeader(headers, "Proxy-Connection",
                      "keep-Alive", true);
              req.setHeaders(headers);
  
              writeRequest(nextFilter, req);
              requestSent = true;
          }
      }
  
      /**
       * Automatic selection of the authentication algorithm. If <code>preferedOrder</code> is set then
       * algorithms are selected from the list order otherwise the algorithm tries to select the most 
       * secured algorithm available first.
       */
      private void autoSelectAuthHandler(final HttpProxyResponse response)
              throws ProxyAuthException {
         // Get the Proxy-Authenticate header
         List<String> values = response.getHeaders().get("Proxy-Authenticate");
 
         if (values == null || values.size() == 0) {
             authHandler = HttpAuthenticationMethods.NO_AUTH
                     .getNewHandler(getProxyIoSession());
 
         } else if (getProxyIoSession().getPreferedOrder() == null) {
             for (String proxyAuthHeader : values) {
                 proxyAuthHeader = proxyAuthHeader.toLowerCase();
 
                 try {
                     // Test which auth mechanism to use. First found is the first used that's why we test
                     // in a decreasing security quality order.
                     if (proxyAuthHeader.contains("ntlm")) {
                         authHandler = HttpAuthenticationMethods.NTLM
                                 .getNewHandler(getProxyIoSession());
                         break;
                     } else if (proxyAuthHeader.contains("digest")) {
                         authHandler = HttpAuthenticationMethods.DIGEST
                                 .getNewHandler(getProxyIoSession());
                         break;
                     } else if (proxyAuthHeader.contains("basic")) {
                         authHandler = HttpAuthenticationMethods.BASIC
                                 .getNewHandler(getProxyIoSession());
                         break;
                     }
                 } catch (Exception ex) {
                     logger.debug("Following exception occured:", ex);
                 }
             }
 
             if (authHandler == null) {
                 authHandler = HttpAuthenticationMethods.NO_AUTH
                         .getNewHandler(getProxyIoSession());
             }
 
         } else {
             for (HttpAuthenticationMethods method : getProxyIoSession()
                     .getPreferedOrder()) {
                 if (authHandler != null) {
                     break;
                 }
 
                 if (method == HttpAuthenticationMethods.NO_AUTH) {
                     authHandler = HttpAuthenticationMethods.NO_AUTH
                             .getNewHandler(getProxyIoSession());
                     break;
                 }
 
                 for (String proxyAuthHeader : values) {
                     proxyAuthHeader = proxyAuthHeader.toLowerCase();
 
                     try {
                         // test which auth mechanism to use
                         if (proxyAuthHeader.contains("basic")
                                 && method == HttpAuthenticationMethods.BASIC) {
                             authHandler = HttpAuthenticationMethods.BASIC
                                     .getNewHandler(getProxyIoSession());
                             break;
                         } else if (proxyAuthHeader.contains("digest")
                                 && method == HttpAuthenticationMethods.DIGEST) {
                             authHandler = HttpAuthenticationMethods.DIGEST
                                     .getNewHandler(getProxyIoSession());
                             break;
                         } else if (proxyAuthHeader.contains("ntlm")
                                 && method == HttpAuthenticationMethods.NTLM) {
                             authHandler = HttpAuthenticationMethods.NTLM
                                     .getNewHandler(getProxyIoSession());
                             break;
                         }
                     } catch (Exception ex) {
                         logger.debug("Following exception occured:", ex);
                     }
                 }
             }
 
         }
 
         if (authHandler == null) {
             throw new ProxyAuthException(
                     "Unknown authentication mechanism(s): " + values);
         }
     }
 
     /**
      * Handle a HTTP response from the proxy server.
      * 
      * @param response The response.
      */
     @Override
     public void handleResponse(final HttpProxyResponse response)
             throws ProxyAuthException {
         if (!isHandshakeComplete()
                 && ("close".equalsIgnoreCase(StringUtilities
                         .getSingleValuedHeader(response.getHeaders(),
                                 "Proxy-Connection")) || "close"
                         .equalsIgnoreCase(StringUtilities
                                 .getSingleValuedHeader(response.getHeaders(),
                                         "Connection")))) {
             getProxyIoSession().setReconnectionNeeded(true);
         }
 
         if (response.getStatusCode() == 407) {
             if (authHandler == null) {
                 autoSelectAuthHandler(response);
             }
             authHandler.handleResponse(response);
         } else {
             throw new ProxyAuthException("Received error response code ("
                     + response.getStatusLine() + ").");
         }
     }
 }