/*

   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 org.apache.batik.util;

import java.util.ArrayList;
import java.util.List;
import java.util.Iterator;
import java.util.Collections;
import java.util.Random;

/**
 * The purpose of this class is to invoke a series of runnables as
 * closely to synchronously as possible.  It does this by starting 
 * a thread for each one, getting the threads into there run method,
 * then quickly running through (in random order) and notifying each
 * thread.
 */
public class ThreadPounder {
    List runnables;
    Object [] threads;
    Object lock = new Object();

    public ThreadPounder(List runnables)  
        throws InterruptedException {
        this(runnables, new Random(1234));
    }

    public ThreadPounder(List runnables, Random rand) 
        throws InterruptedException {
        this.runnables = new ArrayList(runnables);
        Collections.shuffle(this.runnables, rand);
        threads = new Object[this.runnables.size()];
        int i=0;
        Iterator iter= this.runnables.iterator();
        synchronized (lock) {
            while (iter.hasNext()) {
                Thread t = new SyncThread((Runnable)iter.next());
                t.start();
                lock.wait();
                threads[i] = t;
                i++;
            }
        }
    }

    public void start() {
        synchronized(this) {
            this.notifyAll();
        }

    }

    class SyncThread extends Thread {
        Runnable toRun;
        public long runTime;
        public SyncThread(Runnable toRun) {
            this.toRun = toRun;
        }

        public void run() {
            try {
                synchronized (ThreadPounder.this) {
                    synchronized (lock) {
                        // Let pounder know I'm ready to go
                        lock.notify();
                    }
                    // Wait for pounder to wake me up.
                    ThreadPounder.this.wait();
                }
                toRun.run();
            } catch (InterruptedException ie) {
            }
        }
    }

    public static void main(String [] str) { 
        List l = new ArrayList(20);
        for (int i=0; i<20; i++) {
            final int x = i;
            l.add(new Runnable() {
                    public void run() {
                        System.out.println("Thread " + x);
                    }
                });
        }

        try { 
            ThreadPounder tp = new ThreadPounder(l);
            System.out.println("Starting:" );
            tp.start();
            System.out.println("All Started:" );
        } catch (InterruptedException ie) {
            ie.printStackTrace();
        }
    }
}
