/*
    *  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 a request 
   * to the appropriate authentication mechanism logic handler.
   * 
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   * @since MINA 2.0.0-M3
   */
  public class HttpSmartProxyHandler extends AbstractHttpLogicHandler {
      private static final 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;
  
      /**
       * Creates a new HttpSmartProxyHandler instance
       * 
       * @param proxyIoSession The Prowxy IoSession
       */
      public HttpSmartProxyHandler(final ProxyIoSession proxyIoSession) {
          super(proxyIoSession);
      }
  
      /**
       * Performs the handshake processing.
       * 
       * @param nextFilter the next filter
       */
      @Override
      public void doHandshake(final NextFilter nextFilter) throws ProxyAuthException {
          logger.debug(" doHandshake()");
  
          if (authHandler != null) {
              authHandler.doHandshake(nextFilter);
          } else {
              if (requestSent) {
                  // Safety check
                  throw new ProxyAuthException("Authentication request already sent");
              }
  
              logger.debug("  sending HTTP request");
  
              // Compute request headers
              HttpProxyRequest./../../../org/apache/mina/proxy/handlers/http/HttpProxyRequest.html#HttpProxyRequest">HttpProxyRequest req = (HttpProxyRequest) getProxyIoSession().getRequest();
              Map<String, List<String>> headers = req.getHeaders() != null ? req.getHeaders()
                      : new HashMap<String, List<String>>();
  
              AbstractAuthLogicHandler.addKeepAliveHeaders(headers);
              req.setHeaders(headers);
  
              // Write request to the proxy
              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.
       * 
      * @param response the proxy response
      */
     private void autoSelectAuthHandler(final HttpProxyResponse response) throws ProxyAuthException {
         // Get the Proxy-Authenticate header
         List<String> values = response.getHeaders().get("Proxy-Authenticate");
         ProxyIoSession proxyIoSession = getProxyIoSession();
 
         if (values == null || values.isEmpty()) {
             authHandler = HttpAuthenticationMethods.NO_AUTH.getNewHandler(proxyIoSession);
 
         } else if (getProxyIoSession().getPreferedOrder() == null) {
             // No preference order set for auth mechanisms
             int method = -1;
 
             // Test which auth mechanism to use. First found is the first used
             // that's why we test in a decreasing security quality order.
             for (String proxyAuthHeader : values) {
                 proxyAuthHeader = proxyAuthHeader.toLowerCase();
 
                 if (proxyAuthHeader.contains("ntlm")) {
                     method = HttpAuthenticationMethods.NTLM.getId();
                     break;
                 } else if (proxyAuthHeader.contains("digest") && method != HttpAuthenticationMethods.NTLM.getId()) {
                     method = HttpAuthenticationMethods.DIGEST.getId();
                 } else if (proxyAuthHeader.contains("basic") && method == -1) {
                     method = HttpAuthenticationMethods.BASIC.getId();
                 }
             }
 
             if (method != -1) {
                 try {
                     authHandler = HttpAuthenticationMethods.getNewHandler(method, proxyIoSession);
                 } catch (Exception ex) {
                     logger.debug("Following exception occured:", ex);
                 }
             }
 
             if (authHandler == null) {
                 authHandler = HttpAuthenticationMethods.NO_AUTH.getNewHandler(proxyIoSession);
             }
 
         } else {
             for (HttpAuthenticationMethods method : proxyIoSession.getPreferedOrder()) {
                 if (authHandler != null) {
                     break;
                 }
 
                 if (method == HttpAuthenticationMethods.NO_AUTH) {
                     authHandler = HttpAuthenticationMethods.NO_AUTH.getNewHandler(proxyIoSession);
                     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(proxyIoSession);
                             break;
                         } else if (proxyAuthHeader.contains("digest") && method == HttpAuthenticationMethods.DIGEST) {
                             authHandler = HttpAuthenticationMethods.DIGEST.getNewHandler(proxyIoSession);
                             break;
                         } else if (proxyAuthHeader.contains("ntlm") && method == HttpAuthenticationMethods.NTLM) {
                             authHandler = HttpAuthenticationMethods.NTLM.getNewHandler(proxyIoSession);
                             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 proxy 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("Error: unexpected response code " + response.getStatusLine()
                     + " received from proxy.");
         }
     }
 }