r/org.eclipse.statet.r.apps/src/org/eclipse/statet/r/apps/ui/AppRegistry.java

/*=============================================================================#
 # Copyright (c) 2017, 2019 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.r.apps.ui;

import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import org.eclipse.statet.jcommons.collections.CopyOnWriteIdentityListSet;
import org.eclipse.statet.jcommons.lang.NonNullByDefault;
import org.eclipse.statet.jcommons.lang.Nullable;
import org.eclipse.statet.jcommons.ts.core.Tool;


@NonNullByDefault
public class AppRegistry {
	
	
	public static final byte APP_STARTED=                   1;
	public static final byte APP_STOPPED=                   2;
	
	
	public static class AppStateEvent extends RApp.AppEvent {
		
		
		private final byte type;
		
		private final URL id;
		
		
		public AppStateEvent(final byte type, final URL id, final RApp app) {
			super(app);
			this.type= type;
			this.id= id;
		}
		
		
		public byte getType() {
			return this.type;
		}
		
		public URL getId() {
			return this.id;
		}
		
	}
	
	public static interface Listener {
		
		
		void onAppStateChanged(AppStateEvent event);
		
	}
	
	
	private static class AppEntry {
		
		
		private final URL id;
		
		private RApp app;
		private boolean isRunning;
		
		
		public AppEntry(final URL id) {
			this.id= id;
		}
		
	}
	
	
	private static final AppRegistry INSTANCE= new AppRegistry();
	
	public static AppRegistry getInstance() {
		return INSTANCE;
	}
	
	
	private final Map<URL, AppEntry> sessions= new HashMap<>();
	
	private final CopyOnWriteIdentityListSet<Listener> listeners= new CopyOnWriteIdentityListSet<>();
	
	
	public AppRegistry() {
	}
	
	
	public void addListener(final Listener listener) {
		this.listeners.add(listener);
	}
	
	public void removeListener(final Listener listener) {
		this.listeners.remove(listener);
	}
	
	private void notifyListeners(final AppStateEvent event) {
		for (final Listener listener : this.listeners) {
			listener.onAppStateChanged(event);
		}
	}
	
	
	public synchronized void onAppStarted(final URL id, final RApp app) {
		final AppEntry entry= this.sessions.computeIfAbsent(id, AppEntry::new);
		
		if (entry.isRunning) {
			notifyListeners(new AppStateEvent(APP_STOPPED, id, entry.app));
		}
		
		entry.app= app;
		entry.isRunning= true;
		notifyListeners(new AppStateEvent(APP_STARTED, id, app));
	}
	
	public synchronized void onAppStopped(final URL id, final RApp app) {
		final AppEntry entry= this.sessions.get(id);
		if (entry != null && entry.app == app) {
			entry.isRunning= false;
			notifyListeners(new AppStateEvent(APP_STOPPED, id, app));
		}
	}
	
	public synchronized @Nullable RApp getApp(final URL id) {
		final AppEntry entry= this.sessions.get(id);
		return (entry != null) ? entry.app : null;
	}
	
	public synchronized @Nullable RApp getApp(final Tool tool) {
		for (final AppEntry entry : this.sessions.values()) {
			if (entry.isRunning && entry.app.getTool() == tool) {
				return entry.app;
			}
		}
		return null;
	}
	
}