package org.wamblee.system;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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 AbstractSubSystem implements SubSystem {

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

	private String _name;
	private ServiceRegistry _registry; 
	private List<ServiceDescriptor> _provided;
	private List<ServiceDescriptor> _required;
	private Map<ServiceDescriptor, Service> _running;
	
	/**
	 * Constructs the subsystem.
	 * 
	 * @param aRegistry
	 *            Registry of services.
	 * @param aName
	 *            Name of the system.
	 * @param aProvided
	 *            Provided services.
	 * @param aRequired
	 *            Required services.
	 */
	protected AbstractSubSystem(String aName, ServiceRegistry aRegistry, ServiceDescriptor[] aProvided,
			ServiceDescriptor[] aRequired) {
		_name = aName;
		_registry = aRegistry; 
		_provided = new ArrayList<ServiceDescriptor>();
		_provided.addAll(Arrays.asList(aProvided));
		_required = new ArrayList<ServiceDescriptor>();
		_required.addAll(Arrays.asList(aRequired));
		_running = new HashMap<ServiceDescriptor, Service>();
	}

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

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

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

	@Override
	public final Service[] start(String aContext,
			Service[] aRequiredServices) {
		LOG.info("Initializing '" + aContext + "." + _name + "' with "
				+ Arrays.asList(aRequiredServices));
		doStart(aContext + "." + getName(), aRequiredServices);
		return _running.values().toArray(new Service[0]);
	}

	/**
	 * Must be implemented for initializing the subsystem. The implementation
	 * must call {@link #addService(Service)} for each service that is started.
	 *  
	 * @param aRequiredServices
	 *            Services that are already running from other subsystems that
	 *            may be used.
	 */
	protected abstract void doStart(String aContext,
			Service[] aRequiredServices);

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

	@Override
	public Service[] getRunningServices() {
		return _running.values().toArray(new Service[0]);
	}
	
	@Override
	public void stop() {
		doStop(); 	
		for (Service svc: _running.values()) { 
			getRegistry().remove(svc);
		}
	}
	
	protected abstract void doStop(); 

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

}