/*
    *  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.util.LinkedList;
  import java.util.Queue;
  
  import org.apache.mina.core.buffer.IoBuffer;
  import org.apache.mina.core.filterchain.IoFilter.NextFilter;
  import org.apache.mina.core.future.DefaultWriteFuture;
  import org.apache.mina.core.future.WriteFuture;
  import org.apache.mina.core.session.IoSession;
  import org.apache.mina.core.write.DefaultWriteRequest;
  import org.apache.mina.core.write.WriteRequest;
  import org.apache.mina.proxy.filter.ProxyFilter;
  import org.apache.mina.proxy.filter.ProxyHandshakeIoBuffer;
  import org.apache.mina.proxy.session.ProxyIoSession;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * AbstractProxyLogicHandler.java - Helper class to handle proxy handshaking logic. Derived classes 
   * implement proxy type specific logic.
   * <p>
   * Based upon SSLHandler from mina-filter-ssl.
   * 
   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
   * @since MINA 2.0.0-M3
   */
  public abstract class AbstractProxyLogicHandler implements ProxyLogicHandler {
  
      private final static Logger LOGGER = LoggerFactory.getLogger(AbstractProxyLogicHandler.class);
  
      /**
       * Object that contains all the proxy authentication session informations.
       */
      private ProxyIoSession proxyIoSession;
  
      /**
       * Queue of write events which occurred before the proxy handshake had completed.
       */
      private Queue<Event> writeRequestQueue = null;
  
      /**
       * Has the handshake been completed.
       */
      private boolean handshakeComplete = false;
  
      /**
       * Creates a new {@link AbstractProxyLogicHandler}.
       * 
       * @param proxyIoSession {@link ProxyIoSession} in use.
       */
      public AbstractProxyLogicHandler(ProxyIoSession proxyIoSession) {
          this.proxyIoSession = proxyIoSession;
      }
  
      /**
       * @return the proxy filter {@link ProxyFilter}.
       */
      protected ProxyFilter getProxyFilter() {
          return proxyIoSession.getProxyFilter();
      }
  
      /**
       * @return the session.
       */
      protected IoSession getSession() {
          return proxyIoSession.getSession();
      }
  
      /**
       * @return the {@link ProxyIoSession} object.
       */
      public ProxyIoSession getProxyIoSession() {
          return proxyIoSession;
      }
  
      /**
       * Writes data to the proxy server.
       * 
       * @param nextFilter the next filter
      * @param data Data buffer to be written.
      * @return A Future for the write operation
      */
     protected WriteFuture writeData(final NextFilter nextFilter, final IoBuffer data) {
         // write net data
         ProxyHandshakeIoBuffer writeBuffer = new ProxyHandshakeIoBuffer(data);
 
         LOGGER.debug("   session write: {}", writeBuffer);
 
         WriteFuture writeFuture = new DefaultWriteFuture(getSession());
         getProxyFilter().writeData(nextFilter, getSession(), new DefaultWriteRequest(writeBuffer, writeFuture), true);
 
         return writeFuture;
     }
 
     /**
      * @return <tt>true</tt> if handshaking is complete and
      * data can be sent through the proxy.
      */
     public boolean isHandshakeComplete() {
         synchronized (this) {
             return handshakeComplete;
         }
     }
 
     /**
      * Signals that the handshake has finished.
      */
     protected final void setHandshakeComplete() {
         synchronized (this) {
             handshakeComplete = true;
         }
 
         ProxyIoSession proxyIoSession = getProxyIoSession();
         proxyIoSession.getConnector().fireConnected(proxyIoSession.getSession()).awaitUninterruptibly();
 
         LOGGER.debug("  handshake completed");
 
         // Connected OK
         try {
             proxyIoSession.getEventQueue().flushPendingSessionEvents();
             flushPendingWriteRequests();
         } catch (Exception ex) {
             LOGGER.error("Unable to flush pending write requests", ex);
         }
     }
 
     /**
      * Send any write requests which were queued whilst waiting for handshaking to complete.
      * 
      * @throws Exception If we can't flush the pending write requests
      */
     protected synchronized void flushPendingWriteRequests() throws Exception {
         LOGGER.debug(" flushPendingWriteRequests()");
 
         if (writeRequestQueue == null) {
             return;
         }
 
         Event scheduledWrite;
         while ((scheduledWrite = writeRequestQueue.poll()) != null) {
             LOGGER.debug(" Flushing buffered write request: {}", scheduledWrite.data);
 
             getProxyFilter().filterWrite(scheduledWrite.nextFilter, getSession(), (WriteRequest) scheduledWrite.data);
         }
 
         // Free queue
         writeRequestQueue = null;
     }
 
     /**
      * Enqueue a message to be written once handshaking is complete.
      */
     public synchronized void enqueueWriteRequest(final NextFilter nextFilter, final WriteRequest writeRequest) {
         if (writeRequestQueue == null) {
             writeRequestQueue = new LinkedList<Event>();
         }
 
         writeRequestQueue.offer(new Event(nextFilter, writeRequest));
     }
 
     /**
      * Closes the session.
      * 
      * @param message the error message
      * @param t the exception which caused the session closing
      */
     protected void closeSession(final String message, final Throwable t) {
         if (t != null) {
             LOGGER.error(message, t);
             proxyIoSession.setAuthenticationFailed(true);
         } else {
             LOGGER.error(message);
         }
 
         getSession().closeNow();
     }
 
     /**
      * Closes the session.
      * 
      * @param message the error message
      */
     protected void closeSession(final String message) {
         closeSession(message, null);
     }
 
     /**
      * Event wrapper class for enqueued events.
      */
     private final static class Event {
         private final NextFilter nextFilter;
 
         private final Object data;
 
         Event(final NextFilter nextFilter, final Object data) {
             this.nextFilter = nextFilter;
             this.data = data;
         }
     }
 }