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 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, ServiceDescriptor[] aProvided, 
			ServiceDescriptor[] aRequired) { 
		_name = aName; 
		_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; 
	}

	@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, ServiceRegistry aRegistry, Service[] aRequiredServices) {
		LOG.info("Initializing '" + aContext + "." + _name + "' with " + Arrays.asList(aRequiredServices));
		doStart(aContext + "." + getName(), aRegistry, 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 aRegistry Registry to which the subsystem must register its services. 
	 * @param aRequiredServices Services that are already running
	 * from other subsystems that may be used. 
	 */
	protected abstract void doStart(String aContext, ServiceRegistry aRegistry, 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, Service aService) { 
		LOG.info(aContext + ": service '" + aService + "' started.");
		_running.put(aService.getDescriptor(), aService);
	}

	@Override
	public Service[] getRunningServices() {
		return _running.values().toArray(new Service[0]);
	}
	
	@Override
	public String toString() {
		return _name; 
	}

}