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/*
 * Copyright (c) 2008, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.grizzly.impl;

import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import org.glassfish.grizzly.Cacheable;
import org.glassfish.grizzly.CompletionHandler;
import org.glassfish.grizzly.ThreadCache;

/**
 * {@link Future} implementation with the specific unmodifiable result.
 *
 * @see Future
 *
 * @author Alexey Stashok
 */
public final class ReadyFutureImpl implements FutureImpl {
    private static final ThreadCache.CachedTypeIndex CACHE_IDX = ThreadCache.obtainIndex(ReadyFutureImpl.class, 4);

    /**
     * Construct cancelled {@link Future}.
     */
    public static  ReadyFutureImpl create() {
        final ReadyFutureImpl future = takeFromCache();
        if (future != null) {
            future.isCancelled = true;
            return future;
        }

        return new ReadyFutureImpl<>();
    }

    /**
     * Construct {@link Future} with the result.
     */
    public static  ReadyFutureImpl create(R result) {
        final ReadyFutureImpl future = takeFromCache();
        if (future != null) {
            future.result = result;
            return future;
        }

        return new ReadyFutureImpl<>(result);
    }

    /**
     * Construct failed {@link Future}.
     */
    public static  ReadyFutureImpl create(Throwable failure) {
        final ReadyFutureImpl future = takeFromCache();
        if (future != null) {
            future.failure = failure;
            return future;
        }

        return new ReadyFutureImpl<>(failure);
    }

    @SuppressWarnings("unchecked")
    private static  ReadyFutureImpl takeFromCache() {
        return ThreadCache.takeFromCache(CACHE_IDX);
    }

    protected R result;
    private Throwable failure;
    private boolean isCancelled;

    /**
     * Construct cancelled {@link Future}.
     */
    private ReadyFutureImpl() {
        this(null, null, true);
    }

    /**
     * Construct {@link Future} with the result.
     */
    private ReadyFutureImpl(R result) {
        this(result, null, false);
    }

    /**
     * Construct failed {@link Future}.
     */
    private ReadyFutureImpl(Throwable failure) {
        this(null, failure, false);
    }

    private ReadyFutureImpl(R result, Throwable failure, boolean isCancelled) {
        this.result = result;
        this.failure = failure;
        this.isCancelled = isCancelled;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void addCompletionHandler(final CompletionHandler completionHandler) {
        if (isCancelled) {
            completionHandler.cancelled();
        } else if (failure != null) {
            completionHandler.failed(failure);
        } else {
            completionHandler.completed(result);
        }
    }

    /**
     * Get current result value without any blocking.
     *
     * @return current result value without any blocking.
     */
    @Override
    public R getResult() {
        return result;
    }

    /**
     * Should not be called for ReadyFutureImpl
     */
    public void setResult(R result) {
        throw new IllegalStateException("Can not be reset on ReadyFutureImpl");
    }

    /**
     * Do nothing.
     *
     * @return cancel state, which was set during construction.
     */
    @Override
    public boolean cancel(boolean mayInterruptIfRunning) {
        return isCancelled;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isCancelled() {
        return isCancelled;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isDone() {
        return true;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public R get() throws InterruptedException, ExecutionException {
        if (isCancelled) {
            throw new CancellationException();
        } else if (failure != null) {
            throw new ExecutionException(failure);
        }

        return result;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public R get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
        if (isCancelled) {
            throw new CancellationException();
        } else if (failure != null) {
            throw new ExecutionException(failure);
        } else if (result != null) {
            return result;
        } else {
            throw new TimeoutException();
        }
    }

    /**
     * Should not be called for ReadyFutureImpl
     */
    @Override
    public void failure(Throwable failure) {
        throw new IllegalStateException("Can not be reset on ReadyFutureImpl");
    }

    @Override
    public void result(R result) {
        throw new IllegalStateException("Can not be reset on ReadyFutureImpl");
    }

    private void reset() {
        result = null;
        failure = null;
        isCancelled = false;
    }

    @Override
    public void markForRecycle(boolean recycleResult) {
        recycle(recycleResult);
    }

    @Override
    public void recycle() {
        recycle(false);
    }

    @Override
    public void recycle(boolean recycleResult) {
        if (recycleResult && result != null && result instanceof Cacheable) {
            ((Cacheable) result).recycle();
        }

        reset();
        ThreadCache.putToCache(CACHE_IDX, this);
    }
}