/* 
 * Copyright 2004-2005 OpenSymphony 
 * 
 * Licensed 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.
 * 
 */

/*
 * Previously Copyright (c) 2001-2004 James House
 */
package org.quartz.simpl;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.quartz.SchedulerConfigException;
import org.quartz.spi.ThreadPool;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * <p>
 * This is class is a simple implementation of a thread pool, based on the
 * <code>{@link org.quartz.spi.ThreadPool}</code> interface.
 * </p>
 * 
 * <p>
 * <CODE>Runnable</CODE> objects are sent to the pool with the <code>{@link #runInThread(Runnable)}</code>
 * method, which blocks until a <code>Thread</code> becomes available.
 * </p>
 * 
 * <p>
 * The pool has a fixed number of <code>Thread</code>s, and does not grow or
 * shrink based on demand.
 * </p>
 * 
 * @author James House
 * @author Juergen Donnerstag
 */
public class SimpleThreadPool implements ThreadPool {

    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Data members.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    private int count = -1;

    private int prio = Thread.NORM_PRIORITY;

    private boolean isShutdown = false;
    private boolean handoffPending = false;

    private boolean inheritLoader = false;

    private boolean inheritGroup = true;

    private boolean makeThreadsDaemons = false;

    private ThreadGroup threadGroup;

    private final Object nextRunnableLock = new Object();

    private List workers;
    private LinkedList availWorkers = new LinkedList();
    private LinkedList busyWorkers = new LinkedList();

    private String threadNamePrefix = "SimpleThreadPoolWorker";

    private final Log log = LogFactory.getLog(getClass());

    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Constructors.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    /**
     * <p>
     * Create a new (unconfigured) <code>SimpleThreadPool</code>.
     * </p>
     * 
     * @see #setThreadCount(int)
     * @see #setThreadPriority(int)
     */
    public SimpleThreadPool() {
    }

    /**
     * <p>
     * Create a new <code>SimpleThreadPool</code> with the specified number
     * of <code>Thread</code> s that have the given priority.
     * </p>
     * 
     * @param threadCount
     *          the number of worker <code>Threads</code> in the pool, must
     *          be > 0.
     * @param threadPriority
     *          the thread priority for the worker threads.
     * 
     * @see java.lang.Thread
     */
    public SimpleThreadPool(int threadCount, int threadPriority) {
        setThreadCount(threadCount);
        setThreadPriority(threadPriority);
    }

    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Interface.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    public Log getLog() {
        return log;
    }

    public int getPoolSize() {
        return getThreadCount();
    }

    /**
     * <p>
     * Set the number of worker threads in the pool - has no effect after
     * <code>initialize()</code> has been called.
     * </p>
     */
    public void setThreadCount(int count) {
        this.count = count;
    }

    /**
     * <p>
     * Get the number of worker threads in the pool.
     * </p>
     */
    public int getThreadCount() {
        return count;
    }

    /**
     * <p>
     * Set the thread priority of worker threads in the pool - has no effect
     * after <code>initialize()</code> has been called.
     * </p>
     */
    public void setThreadPriority(int prio) {
        this.prio = prio;
    }

    /**
     * <p>
     * Get the thread priority of worker threads in the pool.
     * </p>
     */
    public int getThreadPriority() {
        return prio;
    }

    public void setThreadNamePrefix(String prfx) {
        this.threadNamePrefix = prfx;
    }

    public String getThreadNamePrefix() {
        return threadNamePrefix;
    }

    /**
     * @return Returns the
     *         threadsInheritContextClassLoaderOfInitializingThread.
     */
    public boolean isThreadsInheritContextClassLoaderOfInitializingThread() {
        return inheritLoader;
    }

    /**
     * @param inheritLoader
     *          The threadsInheritContextClassLoaderOfInitializingThread to
     *          set.
     */
    public void setThreadsInheritContextClassLoaderOfInitializingThread(
            boolean inheritLoader) {
        this.inheritLoader = inheritLoader;
    }

    public boolean isThreadsInheritGroupOfInitializingThread() {
        return inheritGroup;
    }

    public void setThreadsInheritGroupOfInitializingThread(
            boolean inheritGroup) {
        this.inheritGroup = inheritGroup;
    }


    /**
     * @return Returns the value of makeThreadsDaemons.
     */
    public boolean isMakeThreadsDaemons() {
        return makeThreadsDaemons;
    }

    /**
     * @param makeThreadsDaemons
     *          The value of makeThreadsDaemons to set.
     */
    public void setMakeThreadsDaemons(boolean makeThreadsDaemons) {
        this.makeThreadsDaemons = makeThreadsDaemons;
    }

    public void initialize() throws SchedulerConfigException {

        if (count <= 0) {
            throw new SchedulerConfigException(
                    "Thread count must be > 0");
        }
        if (prio <= 0 || prio > 9) {
            throw new SchedulerConfigException(
                    "Thread priority must be > 0 and <= 9");
        }

        if(isThreadsInheritGroupOfInitializingThread()) {
            threadGroup = Thread.currentThread().getThreadGroup();
        } else {
            // follow the threadGroup tree to the root thread group.
            threadGroup = Thread.currentThread().getThreadGroup();
            ThreadGroup parent = threadGroup;
            while ( !parent.getName().equals("main") ) {
                threadGroup = parent;
                parent = threadGroup.getParent();
            }
            threadGroup = new ThreadGroup(parent, "SimpleThreadPool");
            if (isMakeThreadsDaemons()) {
                threadGroup.setDaemon(true);
            }
        }


        if (isThreadsInheritContextClassLoaderOfInitializingThread()) {
            getLog().info(
                    "Job execution threads will use class loader of thread: "
                            + Thread.currentThread().getName());
        }

        // create the worker threads and start them
        Iterator workerThreads = createWorkerThreads(count).iterator();
        while(workerThreads.hasNext()) {
            WorkerThread wt = (WorkerThread) workerThreads.next();
            wt.start();
            availWorkers.add(wt);
        }
    }

    protected List createWorkerThreads(int count) {
        workers = new LinkedList();
        for (int i = 1; i<= count; ++i) {
            WorkerThread wt = new WorkerThread(this, threadGroup,
                getThreadNamePrefix() + "-" + i,
                getThreadPriority(),
                isMakeThreadsDaemons());
            if (isThreadsInheritContextClassLoaderOfInitializingThread()) {
                wt.setContextClassLoader(Thread.currentThread()
                        .getContextClassLoader());
            }
            workers.add(wt);
        }

        return workers;
    }

    /**