package org.wamblee.system;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Abstract subsystem class making it easy to implement new subsystems.
 */
public abstract class AbstractComponent implements Component {

	private static final Log LOG = LogFactory.getLog(AbstractComponent.class);

	private Status _status; 
	private String _name; 
	private List<ProvidedInterface> _provided;
	private List<RequiredInterface> _required;
	private Set<ProvidedInterface> _running;
	
	/**
	 * Constructs the subsystem.
	 *
	 * @param aName
	 *            Name of the system.
	 * @param aProvided
	 *            Provided services.
	 * @param aRequired
	 *            Required services.
	 */
	protected AbstractComponent(String aName, ProvidedInterface[] aProvided,
			RequiredInterface[] aRequired) {
		_status = Status.NOT_STARTED;
		_name = aName;
		_provided = new ArrayList<ProvidedInterface>();
		_provided.addAll(Arrays.asList(aProvided));
		_required = new ArrayList<RequiredInterface>();
		_required.addAll(Arrays.asList(aRequired));
		_running = new HashSet<ProvidedInterface>();
	}
	
	@Override
	public Status getStatus() {
		return _status; 
	}

	@Override
	public final String getName() {
		return _name;
	}

	@Override
	public final ProvidedInterface[] getProvidedServices() {
		return _provided.toArray(new ProvidedInterface[0]);
	}

	@Override
	public final RequiredInterface[] getRequiredServices() {
		return _required.toArray(new RequiredInterface[0]);
	}

	@Override
	public final void start(String aContext) {
		LOG.info("Initializing '" + aContext + "." + _name + "'");
		doStart(aContext + "." + getName());
		_status = Status.RUNNING;
		if ( _running.size() != _provided.size()) { 
			List<ProvidedInterface> remaining = 
				new ArrayList<ProvidedInterface>(_provided);
			remaining.removeAll(_running);
			throw new SystemAssemblyException(aContext + "." + getName() + ": not all services were started, missing " + remaining);
		}
	}

	/**
	 * Must be implemented for initializing the subsystem. The implementation
	 * must call {@link #addService(Service)} for each service that is started.
	 */
	protected abstract void doStart(String aContext);

	/**
	 * Implementations must call this method to indicate that a new service has
	 * been started.
	 * 
	 * @param aService
	 *            Service.
	 */
	protected final void addService(String aContext,
			ProvidedInterface aDescriptor, Object aService) {
		LOG.info(aContext + ": service '" + aService + "' started.");
		_running.add(aDescriptor);
		aDescriptor.publish(aService);
	}

	@Override
	public ProvidedInterface[] getRunningServices() {
		return _running.toArray(new ProvidedInterface[0]);
	}
	
	@Override
	public void stop() {
		doStop(); 	
		_status = Status.STOPPED;
	}
	
	protected abstract void doStop(); 

	@Override
	public String toString() {
		return _name;
	}

}