org.eclipse.blockchain.core/src/org/eclipse/blockchain/core/events/BlockchainEnvironmentChangedTrigger.java

/*******************************************************************************
 * Copyright (c) 2020 RBEI and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v. 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     Adhith Gopal - Initial API and Implementation
 *******************************************************************************/
package org.eclipse.blockchain.core.events;

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

/**
 * Environment changed Trigger
 */
public class BlockchainEnvironmentChangedTrigger {

	private final List<IBlockchainEnvironmentChangedListener> observers = new ArrayList<>();
	private static BlockchainEnvironmentChangedTrigger instance;

	protected BlockchainEnvironmentChangedTrigger() {
	}

	/**
	 * @return - An instance of BlockchainEnvironmentChangedTrigger
	 */
	public static BlockchainEnvironmentChangedTrigger getInstance() {
		if (null == instance) {
			instance = new BlockchainEnvironmentChangedTrigger();
		}
		return instance;
	}

	/**
	 * Method used to add blockchain environment changed listener's to the list
	 * of listener's
	 *
	 * @param observer
	 *            - The listener to be added.
	 */
	public void addBlockchainEnvironmentChangedListener(
			final IBlockchainEnvironmentChangedListener observer) {
		getInstance().observers.add(observer);
	}

	protected void triggerEnvironmentChange(final String newEnvironment) {
		notifyListeners(new BlockchainEnvironmentChangedEvent(newEnvironment));
	}

	private void notifyListeners(
			final IBlockchainEnvironmentChangedEvent event) {
		getInstance().observers
				.forEach(o -> o.blockchainEnvironmentChanged(event));
	}
}