Arakne / Araknemu

 * This file is part of Araknemu.

 *

 * Araknemu is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * Araknemu is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with Araknemu.  If not, see <https://www.gnu.org/licenses/>.

 *

 * Copyright (c) 2017-2022 Vincent Quatrevieux

 */

package fr.quatrevieux.araknemu.util;

import java.util.ArrayList;

import java.util.List;

import java.util.concurrent.AbstractExecutorService;

import java.util.concurrent.Callable;

import java.util.concurrent.Executors;

import java.util.concurrent.ScheduledExecutorService;

import java.util.concurrent.ScheduledFuture;

import java.util.concurrent.TimeUnit;

/**

 * Replacement of {@link Executors} class for create {@link ScheduledExecutorService} instances

 *

 * By default, this factory will only forward calls to {@link Executors} for create executors.

 * A testing mode can be enabled using {@link ExecutorFactory#enableTestingMode()} which allows direct execution,

 * and keep tracking of all created instances for perform a shutdown when calling {@link ExecutorFactory#resetTestingExecutor()}

 */

public final class ExecutorFactory {

    private static boolean testing = false;

    private static boolean directExecution = true;

    private static final List<TestingExecutor> testingExecutors = new ArrayList<>();

    /**

     * Disable constructor

     */

    private ExecutorFactory() { }

    /**

     * Create a single thread executor service

     * If testing mode is enabled, a TestingExecutor is returned

     *

     * @see Executors#newSingleThreadScheduledExecutor()

     */

    public static ScheduledExecutorService createSingleThread() {

        if (testing) {

            return createTestingExecutor();

        }

        return Executors.newSingleThreadScheduledExecutor();

    }

    /**

     * Create an executor service with the requested amount of threads in the pool

     * If testing mode is enabled, a TestingExecutor is returned

     *

     * @see Executors#newScheduledThreadPool(int)

     */

    public static ScheduledExecutorService create(int corePoolSize) {

        if (testing) {

            return createTestingExecutor();

        }

        return Executors.newScheduledThreadPool(corePoolSize);

    }

    /**

     * Enable testing mode

     *

     * In testing mode all created executors instance are kept to perform shutdown on reset

     * Also all created executor will support direct execution (i.e. submitted tasks will be executed by the current thread)

     *

     * If testing mode is enabled, {@link ExecutorFactory#resetTestingExecutor()} should be called after tests

     * for free created threads

     *

     * /!\ This method must not be called on production environment

     *

     * @see ExecutorFactory#resetTestingExecutor() For reset all created executors

     * @see ExecutorFactory#enableDirectExecution() For enable direct execution (default mode)

     * @see ExecutorFactory#disableDirectExecution() For disable direct execution

     */

    public static void enableTestingMode() {

        testing = true;

        directExecution = true;

    }

    /**

     * Disable testing mode

     *

     * @see ExecutorFactory#enableTestingMode() For enable it

     */

    public static void disableTestingMode() {

        resetTestingExecutor();

        testing = false;

    }

    /**

     * Shutdown all created executors

     *

     * This method must be called after tests execution to free threads and memory

     * This method is also enabled the direct execution mode

     *

     * Note: this method as no effects if testing mode is disabled

     */

    public static void resetTestingExecutor() {

        for (TestingExecutor executor : testingExecutors) {

            try {

                executor.shutdownNow();

            } catch (RuntimeException e) {

                // Ignore

            }

        }

        testingExecutors.clear();

        directExecution = true;

    }

    /**

     * Enable direct execution of task

     * This is the default mode on testing mode.

     *

     * When enabled, all actions submitted using {@link java.util.concurrent.ExecutorService#execute(Runnable)}

     * or {@link java.util.concurrent.ExecutorService#submit(Runnable)} will be executed on the current thread

     * instead of the internal executor one.

     *

     * This mode has no impact on scheduled tasks, which will be executed asynchronously.

     *

     * Note: this method as no effects if testing mode is disabled

     *

     * @see ExecutorFactory#disableDirectExecution() For disable this mode

     */

    public static void enableDirectExecution() {

        directExecution = true;

    }

    /**

     * Disable direct execution of task

     *

     * After this method call, all calls to created executors will be executed asynchronously.

     *

     * Note: this method as no effects if testing mode is disabled

     *

     * @see ExecutorFactory#enableDirectExecution() For re-enabled this mode

     */

    public static void disableDirectExecution() {

        directExecution = false;

    }

    private static ScheduledExecutorService createTestingExecutor() {

        final TestingExecutor executor = new TestingExecutor();

        testingExecutors.add(executor);

        return executor;

    }

    /**

     * Implementation of ScheduledExecutorService allowing direct execution

     * All calls are forwarded to a real executor service

     */

    private static class TestingExecutor extends AbstractExecutorService implements ScheduledExecutorService {

        private final ScheduledExecutorService inner = Executors.newSingleThreadScheduledExecutor((r) -> {

            final Thread thread = new Thread(r);

            thread.setName("Testing");

            return thread;

        });

        @Override

        public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {

            return inner.schedule(command, delay, unit);

        }

        @Override

        public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) {

            return inner.schedule(callable, delay, unit);

        }

        @Override

        public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) {

            return inner.scheduleAtFixedRate(command, initialDelay, period, unit);

        }

        @Override

        public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) {

            return inner.scheduleWithFixedDelay(command, initialDelay, delay, unit);

        }

        @Override

        public void shutdown() {

            inner.shutdown();

        }

        @Override

        public List<Runnable> shutdownNow() {

            return inner.shutdownNow();

        }

        @Override

        public boolean isTerminated() {

            return inner.isTerminated();

        }

        @Override

        public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {

            return inner.awaitTermination(timeout, unit);

        }

        @Override

        public void execute(Runnable runnable) {

            if (directExecution) {

                runnable.run();

            } else {

                inner.execute(runnable);

            }

        }

    }

}