/**************************************************************
 * 
 * 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 com.sun.star.lib.uno.environments.remote;

import com.sun.star.lang.DisposedException;

/**
 * The <code>JobQueue</code> implements a queue for jobs.
 * For every jobs thread id exists a job queue which is registered
 * at the <code>ThreadPool</code>.
 * A JobQueue is splitted in a sync job queue and an async job queue.
 * The sync job queue is the registerd queue, it delegates async jobs
 * (put by <code>putjob</code>) into the async queue, which is only 
 * known by the sync queue.
 * <p>
 * @version 	$Revision: 1.19 $ $ $Date: 2008-04-11 11:21:18 $
 * @author 	    Kay Ramme
 * @see         com.sun.star.lib.uno.environments.remote.ThreadPool
 * @see         com.sun.star.lib.uno.environments.remote.Job
 * @see         com.sun.star.lib.uno.environments.remote.ThreadId
 * @since       UDK1.0
 */
public class JobQueue {
	/**
	 * When set to true, enables various debugging output.
	 */
	private static final boolean DEBUG = false;

	protected Job _head;                 // the head of the job list
	protected Job _tail;                 // the tail of the job list

	protected ThreadId  _threadId;       // the thread id of the queue
	protected int       _ref_count = 0;  // the stack deepness
	protected boolean   _createThread;   // create a worker thread, if needed
	protected boolean   _createThread_now;   // create a worker thread, if needed
	protected Thread    _worker_thread;  // the thread that does the jobs

	protected Object    _disposeId; // the active dispose id
	protected Object    _doDispose = null;
	protected Throwable _throwable;

	protected JobQueue  _async_jobQueue; // chaining job qeueus for asyncs
	protected JobQueue  _sync_jobQueue;  // chaining job qeueus for syncs

	protected boolean _active = false;

	protected JavaThreadPoolFactory _javaThreadPoolFactory;

	/**
	 * A thread for dispatching jobs
	 */
	class JobDispatcher extends Thread {
		Object _disposeId;

		JobDispatcher(Object disposeId) {
			if(DEBUG) System.err.println("JobQueue$JobDispatcher.<init>:" + _threadId);

			_disposeId = disposeId;
		}

		ThreadId getThreadId() {
			return _threadId;
		}

		public void run() {
			if(DEBUG) System.err.println("ThreadPool$JobDispatcher.run: " + Thread.currentThread());
		
			try {
  				enter(2000, _disposeId);
			}
			catch(Throwable throwable) {
				if(_head != null || _active) { // there was a job in progress, so give a stack
					System.err.println(getClass().getName() + " - exception occurred:" + throwable);
					throwable.printStackTrace(System.err);
				}
			}
			finally {
				release();
			}

			if(DEBUG) System.err.println("##### " + getClass().getName() + ".run - exit:" + _threadId);

//  			try {
//  				Object object = new Object();
//  				synchronized(object) {
//  					object.wait();
//  				}
//  			}
//  			catch(InterruptedException interruptedException) {
//  			}
		}
	}


	/**
	 * Constructs a async job queue with the given thread id
	 * which belongs to the given sync job queue.
	 * <p>
	 * @param threadId         the thread id
	 * @param sync_jobQueue    the sync queue this async queue belongs to
	 * @see                    com.sun.star.lib.uno.environments.remote.ThreadID
	 */
	JobQueue(JavaThreadPoolFactory javaThreadPoolFactory, ThreadId threadId) {
		_javaThreadPoolFactory = javaThreadPoolFactory;
        _threadId = ThreadId.createFresh();

		_sync_jobQueue    = javaThreadPoolFactory.getJobQueue(threadId);
		if(_sync_jobQueue == null) {
			_sync_jobQueue = new JobQueue(javaThreadPoolFactory, threadId, true);
			_sync_jobQueue.acquire();
		}

		_sync_jobQueue._async_jobQueue = this;

		_createThread     = true;
		_createThread_now = true;

		acquire();

		if(DEBUG) System.err.println("##### " + getClass().getName() + " - init:" +  _threadId);
	}

	/**
	 * Constructs a sync job queue with the given thread id and the given thread.
	 * <p>
	 * @param threadId        the thread id
	 * @param createThread    if true, the queue creates a worker thread if needed
	 * @see             com.sun.star.lib.uno.environments.remote.ThreadID
	 */
	JobQueue(JavaThreadPoolFactory javaThreadPoolFactory, ThreadId threadId, boolean createThread){ 
		_javaThreadPoolFactory   = javaThreadPoolFactory;
		_threadId         = threadId;
		_createThread     = createThread;
		_createThread_now = createThread;

		if(DEBUG) System.err.println("##### " + getClass().getName() + " - init:" +  _threadId + " " + createThread);
	}

	/**
	 * Gives the thread id of this queue
	 * <p>
	 * @return  the thread id
	 * @see     com.sun.star.lib.uno.environments.remote.ThreadID
	 */
	ThreadId getThreadId() {
		return _threadId;
	}

	synchronized void acquire() {
        // add only synchronous queues .
		if(_ref_count <= 0 && _sync_jobQueue == null ) 
			_javaThreadPoolFactory.addJobQueue(this);

		++ _ref_count;
	}

	synchronized void release() {
		-- _ref_count;

		if(_ref_count <= 0) {
            // only synchronous queues needs to be removed .
            if( _sync_jobQueue == null ) 
                _javaThreadPoolFactory.removeJobQueue(this);


			if(_sync_jobQueue != null) {
				_sync_jobQueue._async_jobQueue = null;
				_sync_jobQueue.release();
			}
		}
	}

	/**
	 * Removes a job from the queue.
	 * <p>
	 * @return a job or null if timed out
	 * @param  waitTime        the maximum amount of time to wait for a job 
	 */
	private Job removeJob(int waitTime) {
		if(DEBUG) System.err.println("##### " + getClass().getName() + ".removeJob:" + _head + " " + _threadId);

		Job job = null;
		synchronized (this) {
			// wait max. waitTime time for a job to enter the queue
			boolean waited = false;
			while(_head == null && (waitTime == 0 || !waited)) {
				if(_doDispose == _disposeId) {
					_doDispose = null;
					throw (DisposedException)
                        new DisposedException().initCause(_throwable);
				}

				// notify sync queues
				notifyAll();

				try {
					// wait for new job
					wait(waitTime);
				}
				catch(InterruptedException interruptedException) {
  					throw new com.sun.star.uno.RuntimeException(getClass().getName() + ".removeJob - unexpected:" + interruptedException);
				}
				
				// signal that we have already waited once
				waited = true;
			}


			if(_head != null) {
				Job current = _head;
				_head    = _head._next;
				
				if(_head == null)
					_tail = null;
				
				job = current;
				_active = true;
			}
		}

		// always wait for asynchron jobqueue to be finished !
		if(job != null && _async_jobQueue != null) {
			synchronized(_async_jobQueue) { 
				// wait for async queue to be empty and last job to be done
				while(_async_jobQueue._active || _async_jobQueue._head != null) {
					if(DEBUG) System.err.println("waiting for async:" + _async_jobQueue._head + " " +  _async_jobQueue._worker_thread);

					if(_doDispose == _disposeId) {
						_doDispose = null;
						throw (DisposedException)
                            new DisposedException().initCause(_throwable);
					}

					try {
						_async_jobQueue.wait();
					}
					catch(InterruptedException interruptedException) {
						throw new com.sun.star.uno.RuntimeException(getClass().getName() + ".removeJob - unexpected:" + interruptedException);
					}
				}
			}
		}

		return job;
	}

	/**
	 * Puts a job into the queue.
	 * <p>
	 * @param  job        the job
	 * @param  disposeId  a dispose id
	 */
	synchronized void putJob(Job job, Object disposeId) {
		if(DEBUG) System.err.println("##### " + getClass().getName() + ".putJob todoes: " + " job:" + job);
		
		if(_tail != null) 
			_tail._next = job;
		else
			_head = job;
		
		_tail = job;

		if(_worker_thread == null && _createThread && _createThread_now) { // if there is no thread, which dispatches and if shall create one, create one

			acquire();

			_createThread_now = false;
			new JobDispatcher(disposeId).start();
		}

		// always notify possible waiters
		notifyAll();
	}

	/**
	 * Enters the job queue.
	 * <p>
	 * @return the result of the final job (reply)
	 * @param  disposeId  a dispose id
	 */
	Object enter(Object disposeId) throws Throwable {
		return enter(0, disposeId); // wait infinitly
	}

	/**
	 * Enters the job queue.
	 * <p>
	 * @return the result of the final job (reply)
	 * @param  waitTime   the maximum amount of time to wait for a job (0 means wait infinitly)
	 * @param  disposeId  a dispose id
	 */
	Object enter(int waitTime, Object disposeId) throws Throwable {
		if(DEBUG) System.err.println("#####" + getClass().getName() + ".enter: " + _threadId);

		boolean quit = false;

		Object hold_disposeId = _disposeId;
		_disposeId = disposeId;

		Object result = null;

		Thread hold_worker_thread = _worker_thread;
		_worker_thread = Thread.currentThread();

		while(!quit) {
			Job job = null;
			
			try {
				job = removeJob(waitTime);
				
				if(job != null) {
					try {
						result = job.execute();
					}
					finally {
						_active = false;
					}

					if (!job.isRequest()) {
						job.dispose();

						quit = true;
					}

					job = null;
				}
				else
					quit = true;

				
			}
			finally { // ensure that this queue becomes disposed, if necessary
				if(DEBUG) System.err.println("##### " + getClass().getName() + ".enter leaving: " + _threadId + " " + _worker_thread + " " + hold_worker_thread + " " + result);

				synchronized(this) {
					if(job != null || (quit && _head == null)) {
						_worker_thread = hold_worker_thread;

						_createThread_now = true;
					
						_disposeId = hold_disposeId;

						if(_sync_jobQueue != null)
							notifyAll(); // notify waiters (e.g. this is an asyncQueue and there is a sync waiting)
					}
					else
						quit = false;

				}
			}
		}

		return result;
	}

	/**
	 * If the given disposeId is registered,
	 * interrups the worker thread.
	 * <p>
	 * @param disposeId    the dispose id
	 */
	synchronized void dispose(Object disposeId, Throwable throwable) {
		if(_sync_jobQueue == null) { // dispose only sync queues
			_doDispose = disposeId;
			_throwable = throwable;
			
			// get thread out of wait and let it throw the throwable
			if(DEBUG) System.err.println(getClass().getName() + ".dispose - notifying thread");
			
			notifyAll();
		}
	}
}