/**
 * Copyright (c) 2023, WSO2 LLC. (https://www.wso2.com).
 *
 * WSO2 LLC. licenses this file to you 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 com.wso2.openbanking.accelerator.service.activator.internal;

import com.wso2.openbanking.accelerator.service.activator.OBServiceObserver;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

/**
 * ServiceObservable.
 * <p>
 * Maintains one-to-many dependency with OBServiceObservers in such a way that whenever ServiceActivator
 * OSGI bundle changes its status to ACTIVE, the dependents get notified
 */
public class ServiceObservable {

    private static volatile ServiceObservable instance;
    private final List<OBServiceObserver> obServiceObservers;

    private ServiceObservable() {
        this.obServiceObservers = new ArrayList<>();
    }

    public static ServiceObservable getInstance() {
        if (instance == null) {
            synchronized (ServiceObservable.class) {
                if (instance == null) {
                    instance = new ServiceObservable();
                }
            }
        }
        return instance;
    }

    public synchronized void registerServiceObserver(OBServiceObserver obServiceObserver) {
        this.obServiceObservers.add(obServiceObserver);
    }

    public synchronized void activateAllServiceObservers() {
        this.obServiceObservers.parallelStream()
                .filter(Objects::nonNull)
                .forEach(OBServiceObserver::activate);

        this.obServiceObservers.clear();
    }
}
