/* Copyright 2017 Google Inc.
 *
 * 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.

 *  2019.12.15-Changed method releaseExecutor
 *                  Huawei Technologies Co., Ltd.
 *
 */
package com.huawei.push.messaging;

import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;


/** Default ThreadManager implementations used by the HCM SDK */
public class HuaweiThreadManager {

    public static final ThreadManager DEFAULT_THREAD_MANAGER = new DefaultThreadManager();

    /**
     * An abstract ThreadManager implementation that uses the same executor service
     * across all active apps. The executor service is initialized when the first app is initialized,
     * and terminated when the last app is deleted. This class is thread safe.
     */
    abstract static class GlobalThreadManager extends ThreadManager {
        private final Object lock = new Object();
        private final Set<String> apps = new HashSet<>();
        private ExecutorService executorService;

        @Override
        protected ExecutorService getExecutor(HuaweiApp app) {
            synchronized (lock) {
                if (executorService == null) {
                    executorService = doInit();
                }
                apps.add(app.getOption().getCredential().getAppId());
                return executorService;
            }
        }

        @Override
        protected void releaseExecutor(HuaweiApp app, ExecutorService executor) {
            synchronized (lock) {
                String appId = app.getOption().getCredential().getAppId();
                if (apps.remove(appId) && apps.isEmpty()) {
                    doCleanup(executorService);
                    executorService = null;
                }
            }
        }

        /**
         * Initializes the executor service. Called when the first application is initialized.
         */
        protected abstract ExecutorService doInit();

        /**
         * Cleans up the executor service. Called when the last application is deleted.
         */
        protected abstract void doCleanup(ExecutorService executorService);
    }

    private static class DefaultThreadManager extends GlobalThreadManager {

        @Override
        protected ExecutorService doInit() {
            ThreadFactory threadFactory = HuaweiScheduledExecutor.getThreadFactoryWithName(getThreadFactory(), "huawei-default-%d");
            return Executors.newCachedThreadPool(threadFactory);
        }

        @Override
        protected void doCleanup(ExecutorService executorService) {
            executorService.shutdown();
        }

        @Override
        protected ThreadFactory getThreadFactory() {
            return Executors.defaultThreadFactory();
        }
    }
}