Copyright (c) 2016-present, RxJava Contributors.
Licensed 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.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * Licensed 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 io.reactivex.internal.schedulers;

import java.util.*;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicReference;

Manages the creating of ScheduledExecutorServices and sets up purging.
/**
 * Manages the creating of ScheduledExecutorServices and sets up purging.
 */
public final class SchedulerPoolFactory {
    
Utility class. /** Utility class. */
    private SchedulerPoolFactory() {
        throw new IllegalStateException("No instances!");
    }

    static final String PURGE_ENABLED_KEY = "rx2.purge-enabled";

    
Indicates the periodic purging of the ScheduledExecutorService is enabled.
/**
     * Indicates the periodic purging of the ScheduledExecutorService is enabled.
     */
    public static final boolean PURGE_ENABLED;

    static final String PURGE_PERIOD_SECONDS_KEY = "rx2.purge-period-seconds";

    
Indicates the purge period of the ScheduledExecutorServices created by create().
/**
     * Indicates the purge period of the ScheduledExecutorServices created by create().
     */
    public static final int PURGE_PERIOD_SECONDS;

    static final AtomicReference<ScheduledExecutorService> PURGE_THREAD =
            new AtomicReference<ScheduledExecutorService>();

    // Upcast to the Map interface here to avoid 8.x compatibility issues.
    // See http://stackoverflow.com/a/32955708/61158
    static final Map<ScheduledThreadPoolExecutor, Object> POOLS =
            new ConcurrentHashMap<ScheduledThreadPoolExecutor, Object>();

    
Starts the purge thread if not already started.
/**
     * Starts the purge thread if not already started.
     */
    public static void start() {
        tryStart(PURGE_ENABLED);
    }

    static void tryStart(boolean purgeEnabled) {
        if (purgeEnabled) {
            for (;;) {
                ScheduledExecutorService curr = PURGE_THREAD.get();
                if (curr != null) {
                    return;
                }
                ScheduledExecutorService next = Executors.newScheduledThreadPool(1, new RxThreadFactory("RxSchedulerPurge"));
                if (PURGE_THREAD.compareAndSet(curr, next)) {

                    next.scheduleAtFixedRate(new ScheduledTask(), PURGE_PERIOD_SECONDS, PURGE_PERIOD_SECONDS, TimeUnit.SECONDS);

                    return;
                } else {
                    next.shutdownNow();
                }
            }
        }
    }

    
Stops the purge thread.
/**
     * Stops the purge thread.
     */
    public static void shutdown() {
        ScheduledExecutorService exec = PURGE_THREAD.getAndSet(null);
        if (exec != null) {
            exec.shutdownNow();
        }
        POOLS.clear();
    }

    static {
        Properties properties = System.getProperties();

        PurgeProperties pp = new PurgeProperties();
        pp.load(properties);

        PURGE_ENABLED = pp.purgeEnable;
        PURGE_PERIOD_SECONDS = pp.purgePeriod;

        start();
    }

    static final class PurgeProperties {

        boolean purgeEnable;

        int purgePeriod;

        void load(Properties properties) {
            if (properties.containsKey(PURGE_ENABLED_KEY)) {
                purgeEnable = Boolean.parseBoolean(properties.getProperty(PURGE_ENABLED_KEY));
            } else {
                purgeEnable = true;
            }

            if (purgeEnable && properties.containsKey(PURGE_PERIOD_SECONDS_KEY)) {
                try {
                    purgePeriod = Integer.parseInt(properties.getProperty(PURGE_PERIOD_SECONDS_KEY));
                } catch (NumberFormatException ex) {
                    purgePeriod = 1;
                }
            } else {
                purgePeriod = 1;
            }
        }
    }

    
Creates a ScheduledExecutorService with the given factory.
Params:
factory – the thread factory
Returns:
the ScheduledExecutorService/**
     * Creates a ScheduledExecutorService with the given factory.
     * @param factory the thread factory
     * @return the ScheduledExecutorService
     */
    public static ScheduledExecutorService create(ThreadFactory factory) {
        final ScheduledExecutorService exec = Executors.newScheduledThreadPool(1, factory);
        tryPutIntoPool(PURGE_ENABLED, exec);
        return exec;
    }

    static void tryPutIntoPool(boolean purgeEnabled, ScheduledExecutorService exec) {
        if (purgeEnabled && exec instanceof ScheduledThreadPoolExecutor) {
            ScheduledThreadPoolExecutor e = (ScheduledThreadPoolExecutor) exec;
            POOLS.put(e, exec);
        }
    }

    static final class ScheduledTask implements Runnable {
        @Override
        public void run() {
            for (ScheduledThreadPoolExecutor e : new ArrayList<ScheduledThreadPoolExecutor>(POOLS.keySet())) {
                if (e.isShutdown()) {
                    POOLS.remove(e);
                } else {
                    e.purge();
                }
            }
        }
    }
}