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package com.sun.grizzly.arp;

import com.sun.grizzly.http.ProcessorTask;
import com.sun.grizzly.http.Task;
import com.sun.grizzly.util.DataStructures;
import java.util.ArrayList;
import java.util.Queue;
import java.util.concurrent.ExecutorService;

/**
 * Default implementation of {@link AsyncHandler}. This class handle 
 * the aysnchronous execution of a {@link ProcessorTask}. The request
 * processing is executed by doing:
 *
 * (1) Wrap the {@link ProcessorTask} using an instance of 
 *     {@link AsyncTask}
 * (2) Execute the {@link AsyncTask} using the wrapped
 *     {@link ProcessorTask} {@link ExecutorService}
 * (3) If the {@link AsyncTask} has been interrupted but ready
 *     to be removed from the interrupted queue, remove it and execute the
 *     remaining operations.
 *
 * @author Jeanfrancois Arcand
 */
public class DefaultAsyncHandler implements AsyncHandler{
    
    /**
     * Cache instance of {@link AsyncTask}
     */
    private final Queue asyncProcessors =
            DataStructures.getCLQinstance(AsyncTask.class);
    
               
    
    /**
     * The {@link AsyncFilter} to execute asynchronous operations on 
     * a {@link ProcessorTask}.
     */
    private final ArrayList asyncFilters =
            new ArrayList();   
    
    
    // ------------------------------------------------- Constructor --------//
    
    
    public DefaultAsyncHandler() {
    }
    
    
    /**
     * Create an instance of {@link AsyncTask}
     */
    private AsyncTask newAsyncProcessorTask(){
        AsyncTask asyncTask = new AsyncProcessorTask();
        asyncTask.setAsyncExecutor(newAsyncExecutor(asyncTask));  
        return asyncTask;
    }
    
    
    /**
     * Create an instance of {@link DefaultAsyncExecutor}
     */    
    protected AsyncExecutor newAsyncExecutor(AsyncTask asyncTask){        
        AsyncExecutor asyncExecutor = new DefaultAsyncExecutor();
        asyncExecutor.setAsyncTask(asyncTask);
        asyncExecutor.setAsyncHandler(this);
            
        for (AsyncFilter l : asyncFilters){
            asyncExecutor.addAsyncFilter(l);
        }
        return asyncExecutor;
    }
    
    
    /**
     * Return an instance of {@link AsyncTask}, which is 
     * configured and ready to be executed.
     */
    private AsyncTask getAsyncProcessorTask(){
        AsyncTask asyncTask = asyncProcessors.poll();
        if ( asyncTask == null) {
            asyncTask = newAsyncProcessorTask();
        } else {
            asyncTask.recycle();
        }
        return asyncTask;
    }
    
    
    // ---------------------------------------------------- Interface -------//
    
    
    /**
     * Handle an instance of a {@link Task}. This method is invoked
     * first by a {@link ProcessorTask}, which delegate its execution to 
     * this handler. This method will uses an {@link AsyncTask} to start 
     * the execution of the defined {@link AsyncFilter}.
     */
    public void handle(Task task){        
        if (task instanceof ProcessorTask){
            AsyncTask apt = getAsyncProcessorTask();
            apt.setThreadPool(task.getThreadPool());
            apt.setSelectorThread(task.getSelectorThread());
            apt.getAsyncExecutor().setProcessorTask((ProcessorTask)task);
            apt.execute(null);
        } else {
            task.execute();
        }
    }
    

    /**
     * Return th {@link Task} to the pool
     */
    public void returnTask(AsyncTask asyncTask){
        asyncProcessors.offer(asyncTask);
    }
    

    /**
     * Add an {@link AsyncFilter}
     */
    public void addAsyncFilter(AsyncFilter asyncFilter) {
        asyncFilters.add(asyncFilter);
    }

    
    /**
     * Remove an {@link AsyncFilter}
     */
    public boolean removeAsyncFilter(AsyncFilter asyncFilter) {
        return asyncFilters.remove(asyncFilter);
    }
}