/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain. Use, modify, and
 * redistribute this code in any way without acknowledgement.
 */

package java.util.concurrent;

import java.util.*;

/**
 * Provides default implementation of {@link ExecutorService}
 * execution methods. This class implements the <tt>submit</tt>,
 * <tt>invokeAny</tt> and <tt>invokeAll</tt> methods using the default
 * {@link FutureTask} class provided in this package.  For example,
 * the the implementation of <tt>submit(Runnable)</tt> creates an
 * associated <tt>FutureTask</tt> that is executed and
 * returned. Subclasses overriding these methods to use different
 * {@link Future} implementations should do so consistently for each
 * of these methods.
 *
 * @since 1.5
 * @author Doug Lea
 */
public abstract class AbstractExecutorService implements ExecutorService {

    public Future<?> submit(Runnable task) {
        FutureTask<Object> ftask = new FutureTask<Object>(task, null);
        execute(ftask);
        return ftask;
    }

    public <T> Future<T> submit(Callable<T> task) {
        FutureTask<T> ftask = new FutureTask<T>(task);
        execute(ftask);
        return ftask;
    }

    // any/all methods, each a little bit different than the other


    public <T> T invokeAny(Collection<Callable<T>> tasks)
        throws InterruptedException, ExecutionException {
        if (tasks == null)
            throw new NullPointerException();
        int n = tasks.size();
        if (n == 0)
            throw new IllegalArgumentException();
        List<Future<T>> futures= new ArrayList<Future<T>>(n);
        ExecutorCompletionService<T> ecs = 
            new ExecutorCompletionService<T>(this);
        try {
            for (Callable<T> t : tasks) 
                futures.add(ecs.submit(t));
            ExecutionException ee = null;
            RuntimeException re = null;
            while (n-- > 0) {
                Future<T> f = ecs.take();
                try {
                    return f.get();
                } catch(ExecutionException eex) {
                    ee = eex;
                } catch(RuntimeException rex) {
                    re = rex;
                }
            }    
            if (ee != null)
                throw ee;
            if (re != null)
                throw new ExecutionException(re);
            throw new ExecutionException();
        } finally {
            for (Future<T> f : futures) 
                f.cancel(true);
        }
    }

    public <T> T invokeAny(Collection<Callable<T>> tasks, 
                           long timeout, TimeUnit unit) 
        throws InterruptedException, ExecutionException, TimeoutException {
        if (tasks == null || unit == null)
            throw new NullPointerException();
        long nanos = unit.toNanos(timeout);
        int n = tasks.size();
        if (n == 0)
            throw new IllegalArgumentException();
        List<Future<T>> futures= new ArrayList<Future<T>>(n);
        ExecutorCompletionService<T> ecs = 
            new ExecutorCompletionService<T>(this);
        try {
            for (Callable<T> t : tasks) 
                futures.add(ecs.submit(t));
            ExecutionException ee = null;
            RuntimeException re = null;
            long lastTime = System.nanoTime();
            while (n-- > 0) {
                Future<T> f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
                if (f == null)
                    throw new TimeoutException();
                try {
                    return f.get();
                } catch(ExecutionException eex) {
                    ee = eex;
                } catch(RuntimeException rex) {
                    re = rex;
                }
                long now = System.nanoTime();
                nanos -= now - lastTime;
                lastTime = now;
            }    
            if (ee != null)
                throw ee;
            if (re != null)
                throw new ExecutionException(re);
            throw new ExecutionException();
        } finally {
            for (Future<T> f : futures) 
                f.cancel(true);
        }
    }

    public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks)
        throws InterruptedException {
        if (tasks == null)
            throw new NullPointerException();
        List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
        boolean done = false;
        try {
            for (Callable<T> t : tasks) {
                FutureTask<T> f = new FutureTask<T>(t);
                futures.add(f);
                execute(f);
            }
            for (Future<T> f : futures) {
                if (!f.isDone()) {
                    try { 
                        f.get(); 
                    } catch(CancellationException ignore) {
                    } catch(ExecutionException ignore) {
                    }
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (Future<T> f : futures) 
                    f.cancel(true);
        }
    }

    public <T> List<Future<T>> invokeAll(Collection<Callable<T>> tasks, 
                                         long timeout, TimeUnit unit) 
        throws InterruptedException {
        if (tasks == null || unit == null)
            throw new NullPointerException();
        long nanos = unit.toNanos(timeout);
        List<Future<T>> futures = new ArrayList<Future<T>>(tasks.size());
        boolean done = false;
        try {
            for (Callable<T> t : tasks) {
                FutureTask<T> f = new FutureTask<T>(t);
                futures.add(f);
                execute(f);
            }
            long lastTime = System.nanoTime();
            for (Future<T> f : futures) {
                if (!f.isDone()) {
                    if (nanos < 0) 
                        return futures; 
                    try { 
                        f.get(nanos, TimeUnit.NANOSECONDS); 
                    } catch(CancellationException ignore) {
                    } catch(ExecutionException ignore) {
                    } catch(TimeoutException toe) {
                        return futures;
                    }
                    long now = System.nanoTime();
                    nanos -= now - lastTime;
                    lastTime = now;
                }
            }
            done = true;
            return futures;
        } finally {
            if (!done)
                for (Future<T> f : futures) 
                    f.cancel(true);
        }
    }

}