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 package com.sun.grizzly;

 import com.sun.grizzly.filter.ReadFilter;

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.HashSet;

 import java.util.List;

 import java.util.logging.Level;

 /**

  * Default ProtocolChain implementation.

  *

  * @author Jeanfrancois Arcand

  */

 public class DefaultProtocolChain implements ProtocolChain {

     public enum Phase {EXECUTE, POST_EXECUTE};

     /**

      * The list of ProtocolFilter this chain will invoke.

      */

     protected List<ProtocolFilter> protocolFilters;

     /**

      * The list of {@link EventHandler}s, which will be notified about this

      * {@link ProtocolChain} events

      */

     protected Collection<EventHandler> eventHandlers;

     /**

      * <tt>true</tt> if a pipelined execution is required. A pipelined execution

      * occurs when a ProtocolFilter implementation set the 

      * ProtocolFilter.READ_SUCCESS as an attribute to a Context. When this 

      * attribute is present, the ProtocolChain will not release the current

      * running Thread and will re-execute all its ProtocolFilter. 

      */

     protected boolean continousExecution = true;

     public DefaultProtocolChain() {

         protocolFilters = new ArrayList<ProtocolFilter>();

         eventHandlers = new HashSet<EventHandler>();

     }

     /**

      * Execute this ProtocolChain.

      * @param ctx {@link Context}

      * @throws java.lang.Exception 

      */

     public void execute(Context ctx) throws Exception {

         execute(ctx,0);

     }

     /**

      * Execute this ProtocolChain.

      * @param ctx {@link Context}

      * @param firstFilter The first filter to be invoked.

      * @throws java.lang.Exception 

      */

     public void execute(Context ctx, int firstFilter) throws Exception {

         if (protocolFilters.size() != 0){

             boolean reinvokeChain = true;

             while (reinvokeChain){

                 int currentPosition = executeProtocolFilter(ctx,firstFilter);

                 reinvokeChain = postExecuteProtocolFilter(currentPosition, ctx);

             }

         }

     }    

     /**

      * Execute the ProtocolFilter.execute method. If a ProtocolFilter.execute

      * return false, avoid invoking the next ProtocolFilter.

      * @param ctx {@link Context}

      * @return position of next {@link ProtocolFilter} to exexute

      */

     protected int executeProtocolFilter(Context ctx) {

         return executeProtocolFilter(ctx,0);

     }

     /**

      * Execute the ProtocolFilter.execute method. If a ProtocolFilter.execute

      * return false, avoid invoking the next ProtocolFilter.

      * @param ctx {@link Context}

      * @param firstFilter The first filter position to be invoked. 

      * @return position of next {@link ProtocolFilter} to exexute

      */

     protected int executeProtocolFilter(Context ctx, int firstFilter) {

         boolean invokeNext;

         int size = protocolFilters.size();

         int currentPosition = 0;

         ProtocolFilter protocolFilter = null;

         for (int i=firstFilter; i < size; i++) {

             try {

                 protocolFilter = protocolFilters.get(i);

                 invokeNext = protocolFilter.execute(ctx);

             } catch (Exception ex){

                 invokeNext = false;

                 i--;

                 Controller.logger().log(Level.SEVERE,

                         "ProtocolChain exception",ex);

                 notifyException(Phase.EXECUTE, protocolFilter, ex);

             }

             currentPosition = i;

             if ( !invokeNext ) break;

         }

         return currentPosition;

     }

     /**

      * Execute the ProtocolFilter.postExcute.

      * @param currentPosition position in list of {@link ProtocolFilter}s

      * @param ctx {@link Context}

      * @return false, always false

      */

     protected boolean postExecuteProtocolFilter(int currentPosition,Context ctx) {

         boolean invokeNext = true;

         ProtocolFilter tmpHandler = null;

         boolean reinvokeChain = false;

         for (int i = currentPosition; i > -1; i--){

             try{

                 tmpHandler = protocolFilters.get(i);

                 invokeNext = tmpHandler.postExecute(ctx);                 

             } catch (Exception ex){

                 Controller.logger().log(Level.SEVERE,

                         "ProtocolChain exception",ex);

                 notifyException(Phase.POST_EXECUTE, tmpHandler, ex);

             }

             if ( !invokeNext ) {

                break;

             }

         }

         if (continousExecution 

             && currentPosition == protocolFilters.size() -1

             && (Boolean)ctx.removeAttribute(ProtocolFilter.SUCCESSFUL_READ) 

                 == Boolean.TRUE) {

             reinvokeChain = true;    

         } 

         return reinvokeChain;

     }

     /**

      * Remove a ProtocolFilter.

      * @param theFilter the ProtocolFilter to remove

      * @return removed ProtocolFilter

      */

     public boolean removeFilter(ProtocolFilter theFilter) {

         return protocolFilters.remove(theFilter);

     }

     /**

      * Add the {@link ProtocolFilter} to this {@link ProtocolChain}

      * @param protocolFilter to add

      * @return 

      */

     public boolean addFilter(ProtocolFilter protocolFilter) {

         return protocolFilters.add(protocolFilter);

     }

     /**

      * Insert a ProtocolFilter at position pos.

      * @param pos 

      * @param protocolFilter 

      */

     public void addFilter(int pos, ProtocolFilter protocolFilter){

         protocolFilters.add(pos,protocolFilter);

     }

     /**

      *Insert a ProtocolFilter at position pos.

      * @param pos - position in this ProtocolChain

      * @param protocolFilter - {@link ProtocolFilter} to insert

      * @return {@link ProtocolFilter} that was set

      */

     public ProtocolFilter setProtocolFilter(int pos,

             ProtocolFilter protocolFilter) {

         return protocolFilters.set(pos,protocolFilter);

     }

     /**

      * Set to <tt>true</tt> if the current {@link Pipeline} can 

      * re-execute its ProtocolFilter(s) after a successful execution. Enabling

      * this property is useful for protocol that needs to support pipelined

      * message requests as the ProtocolFilter are automatically re-executed, 

      * avoiding the overhead of releasing the current Thread, registering 

      * back the SelectionKey to the SelectorHandler and waiting for a new

      * NIO event. 

      * 

      * Some protocols (like http) can get the http headers in one

      * SocketChannel.read, parse the message and then get the next http message 

      * on the second SocketChannel.read(). Not having to release the Thread

      * and re-execute the ProtocolFilter greatly improve performance.

      * @param continousExecution true to enable continuous execution.

      *        (default is false).

      */

     public void setContinuousExecution(boolean continousExecution){

         this.continousExecution = continousExecution;

         for (ProtocolFilter filter : protocolFilters){

             if (filter instanceof ReadFilter){

                 ((ReadFilter)filter).setContinuousExecution(continousExecution);

                 break;

             }

         }

     }

     /**

      * Return <tt>true</tt> if the current {@link Pipeline} can 

      * re-execute its ProtocolFilter after a successful execution. 

      */    

     public boolean isContinuousExecution(){

         return continousExecution;

     }

     /**

      * Add the {@link EventHandler}

      * @param eventHandler 

      * @return true, if {@link EventHandler} was added, false otherwise

      */

     public boolean addEventHandler(EventHandler eventHandler) {

         return eventHandlers.add(eventHandler);

     }

     /**

      * Remove the {@link EventHandler}.

      * @param eventHandler the <code>ProtocolFilter<code> to remove

      * @return true, if {@link EventHandler} was removed, false otherwise

      */

     public boolean removeEventHandler(EventHandler eventHandler) {

         return eventHandlers.remove(eventHandler);

     }

     /**

      * Notifies all {@link EventHandler}s about exception, which occured

      * @param phase execution <code>Phase</code>, where exception occured

      * @param filter {@link ProtocolFilter}, where exception occured

      * @param throwable actual exception

      */

     protected void notifyException(Phase phase, ProtocolFilter filter, 

             Throwable throwable) {

         for(EventHandler eventHandler : eventHandlers) {

             try {

                 eventHandler.onException(phase, filter, throwable);

             } catch(Exception e) {

                 Controller.logger().log(Level.SEVERE,

                         "ProtocolChain notifyException exception", e);

             }

         }

     }

     /**

      * Interface, which introduces handler, which will be notified about event,

      * happened on {@link ProtocolChain}

      */

     public interface EventHandler {

         public void onException(Phase phase, ProtocolFilter filter, 

                 Throwable throwable);

     }

 }