/*
    *  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;
  
  import java.net.InetSocketAddress;
  import java.net.SocketAddress;
  import java.util.concurrent.Executor;
  
  import org.apache.mina.core.buffer.IoBuffer;
  import org.apache.mina.core.file.FileRegion;
  import org.apache.mina.core.filterchain.IoFilter;
  import org.apache.mina.core.future.ConnectFuture;
  import org.apache.mina.core.future.DefaultConnectFuture;
  import org.apache.mina.core.future.IoFuture;
  import org.apache.mina.core.service.AbstractIoConnector;
  import org.apache.mina.core.service.DefaultTransportMetadata;
  import org.apache.mina.core.service.IoHandler;
  import org.apache.mina.core.service.TransportMetadata;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.core.session.IoSessionConfig;
  import org.apache.mina.core.session.IoSessionInitializer;
  import org.apache.mina.proxy.filter.ProxyFilter;
  import org.apache.mina.proxy.handlers.socks.SocksProxyRequest;
  import org.apache.mina.proxy.session.ProxyIoSession;
  import org.apache.mina.proxy.session.ProxyIoSessionInitializer;
  import org.apache.mina.transport.socket.DefaultSocketSessionConfig;
  import org.apache.mina.transport.socket.SocketConnector;
  import org.apache.mina.transport.socket.SocketSessionConfig;
  
  /**
   * ProxyConnector.java - Decorator for {@link SocketConnector} to provide proxy support, 
   * as suggested by MINA list discussions.
   * <p>
   * Operates by intercepting connect requests and replacing the endpoint address with the 
   * proxy address, then adding a {@link ProxyFilter} as the first {@link IoFilter} which 
   * performs any necessary handshaking with the proxy before allowing data to flow 
   * normally. During the handshake, any outgoing write requests are buffered.
   * 
   * @see        http://www.nabble.com/Meta-Transport%3A-an-idea-on-implementing-reconnection-and-proxy-td12969001.html
   * @see        http://issues.apache.org/jira/browse/DIRMINA-415
   * 
   * @author The Apache MINA Project (dev@mina.apache.org)
   * @since MINA 2.0.0-M3
   */
  public class ProxyConnector extends AbstractIoConnector {
      private static final TransportMetadata METADATA = new DefaultTransportMetadata(
              "proxy", "proxyconnector", false, true, InetSocketAddress.class,
              SocketSessionConfig.class, IoBuffer.class, FileRegion.class);
  
      /**
       * Wrapped connector to use for outgoing TCP connections.
       */
      private SocketConnector connector = null;
  
      /**
       * Proxy filter instance.
       */
      private final ProxyFilter proxyFilter = new ProxyFilter();
  
      /**
       * The {@link ProxyIoSession} in use.
       */
      private ProxyIoSession proxyIoSession;
  
      /**
       * This future will notify it's listeners when really connected to the target
       */
      private DefaultConnectFuture future;
  
      /**
       * Creates a new proxy connector.
       */
      public ProxyConnector() {
          super(new DefaultSocketSessionConfig(), null);
      }
  
      /**
       * Creates a new proxy connector.
       * 
       * @param connector Connector used to establish proxy connections.
       */
      public ProxyConnector(final SocketConnector connector) {        
         this(connector, new DefaultSocketSessionConfig(), null);
     }
 
     /**
      * Creates a new proxy connector. 
      * @see AbstractIoConnector(IoSessionConfig, Executor).
      */
     public ProxyConnector(final SocketConnector connector, IoSessionConfig config, Executor executor) {
         super(config, executor);
         setConnector(connector);
     }    
     
     /**
      * {@inheritDoc}
      */
     @Override
     public IoSessionConfig getSessionConfig() {
         return connector.getSessionConfig();
     }
 
     /**
      * Returns the {@link ProxyIoSession} linked with this connector.
      */
     public ProxyIoSession getProxyIoSession() {
         return proxyIoSession;
     }
 
     /**
      * Sets the proxy session object of this connector.
      * @param proxyIoSession the configuration of this connector.
      */
     public void setProxyIoSession(ProxyIoSession proxyIoSession) {
         if (proxyIoSession == null) {
             throw new NullPointerException("proxySession object cannot be null");
         }
 
         if (proxyIoSession.getProxyAddress() == null) {
             throw new NullPointerException(
                     "proxySession.proxyAddress cannot be null");
         }
 
         proxyIoSession.setConnector(this);
         setDefaultRemoteAddress(proxyIoSession.getProxyAddress());
         this.proxyIoSession = proxyIoSession;
     }
 
     /**
      * Connects to the specified <code>address</code>.  If communication starts
      * successfully, events are fired to the connector's <code>handler</code>.
      * 
      * @param remoteAddress the remote address to connect to
      * @param localAddress the local address
      * @param sessionInitializer the session initializer
      * @return {@link ConnectFuture} that will tell the result of the connection attempt
      */
     @SuppressWarnings("unchecked")
     @Override
     protected ConnectFuture connect0(
             final SocketAddress remoteAddress,
             final SocketAddress localAddress,
             final IoSessionInitializer<? extends ConnectFuture> sessionInitializer) {
         if (!proxyIoSession.isReconnectionNeeded()) {
             // First connection
             IoHandler handler = getHandler();
             if (!(handler instanceof AbstractProxyIoHandler)) {
                 throw new IllegalArgumentException(
                         "IoHandler must be an instance of AbstractProxyIoHandler");
             }
 
             connector.setHandler(handler);
             future = new DefaultConnectFuture();
         }
 
         ConnectFuture conFuture = connector.connect(proxyIoSession
                 .getProxyAddress(), new ProxyIoSessionInitializer(
                 sessionInitializer, proxyIoSession));
 
         // If proxy does not use reconnection like socks the connector's 
         // future is returned. If we're in the middle of a reconnection
         // then we send back the connector's future which is only used
         // internally while <code>future</code> will be used to notify
         // the user of the connection state.
         if (proxyIoSession.getRequest() instanceof SocksProxyRequest
                 || proxyIoSession.isReconnectionNeeded()) {
             return conFuture;
         }
 
         return future;
     }
 
     /**
      * Cancels the real connection when reconnection is in use.
      */
     public void cancelConnectFuture() {
         future.cancel();
     }
 
     /**
      * Fires the connection event on the real future to notify the client.
      * 
      * @param session the current session
      * @return the future holding the connected session
      */
     protected ConnectFuture fireConnected(final IoSession session) {
         future.setSession(session);
         return future;
     }
 
     /**
      * Get the {@link SocketConnector} to be used for connections
      * to the proxy server.
      */
     public final SocketConnector getConnector() {
         return connector;
     }
 
     /**
      * Sets the {@link SocketConnector} to be used for connections
      * to the proxy server.
      * 
      * @param connector the connector to use
      */
     private final void setConnector(final SocketConnector connector) {
         if (connector == null) {
             throw new NullPointerException("connector cannot be null");
         }
 
         this.connector = connector;
         String className = ProxyFilter.class.getName();
 
         // Removes an old ProxyFilter instance from the chain
         if (connector.getFilterChain().contains(className)) {
             connector.getFilterChain().remove(className);
         }
 
         // Insert the ProxyFilter as the first filter in the filter chain builder        
         connector.getFilterChain().addFirst(className, proxyFilter);
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     protected IoFuture dispose0() throws Exception {
         if (connector != null) {
             connector.dispose();
         }
         return null;
     }
 
     /**
      * {@inheritDoc}
      */
     public TransportMetadata getTransportMetadata() {
         return METADATA;
     }
 }