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Java Lookahead Parser Generator. Generator produces LALR(k) parsers. Grammar rules are entered using annotations. Rule annotation can be attached to reducer method, which keeps rule and it's action together.

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/*
 * Copyright (C) 2013 Timo Vesalainen
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */

package org.vesalainen.parser.util;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayDeque;
import java.util.Deque;

/**
 * DelayedExecutor queues calls to proxy methods so that they are actually 
 * invoked when execute method is called. Only method with void return type
 * are delayed. Other methods are invoked normally.
 * @author Timo Vesalainen
 * @param 
 */
public class DelayedExecutor implements InvocationHandler
{
    private T proxy;
    private Deque queue = new ArrayDeque<>();
    
    public DelayedExecutor(Class intf)
    {
        proxy = (T) Proxy.newProxyInstance(DelayedExecutor.class.getClassLoader(), new Class[] {intf}, this);
    }

    public T getProxy()
    {
        return proxy;
    }
    
    public void append(DelayedExecutor target)
    {
        queue.addAll(target.queue);
    }
    /**
     * Executes delayed invocations
     * @param target
     * @throws Throwable From one of the called methods.
     */
    public void execute(T target) throws Throwable
    {
        try
        {
            for (Invokation invokation : queue)
            {
                invokation.invoke(target);
            }
        }
        catch (InvocationTargetException ex)
        {
            throw ex.getCause();
        }
        catch (ReflectiveOperationException ex)
        {
            throw new RuntimeException(ex);
        }
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
    {
        if (void.class.equals(method.getReturnType()))
        {
            queue.add(new Invokation(method, args));
            return null;
        }
        else
        {
            return method.invoke(proxy, args);
        }
    }
    
    public class Invokation
    {
        private Method method;
        private Object[] args;

        public Invokation(Method method, Object[] args)
        {
            this.method = method;
            this.args = args;
        }
        
        public void invoke(T proxy) throws ReflectiveOperationException
        {
            method.invoke(proxy, args);
        }
    }
}