//==============================================================================
// Registry.java
//==============================================================================

package sample.resource;

import java.util.Map;
import java.util.HashMap;

/**
* Responsibilities:<ul>
* <li>provides access to the registered resources.</li>
* </ul><p></p>
* 
* @author Copyright 2003 Nikolas S. Boyd.
*/
public class Registry {


/** Contains the registered resources. */
private Map contents;

/** Maintains the resource registry. */
private Registrar registrar;

/** Manages the resource backing store. */
private StorageManager manager;


/**
* Returns the resouce named (resourceName).
* @param resourceName identifies a registered resource.
* @return null if no such resource exists.
*/
public Resource 
getResourceNamed(String resourceName) {
	if (resourceName == null) return null;
	return (Resource) this.contents.get(resourceName);
}

/**
* Returns the registered resource names.
*/
public String[] 
getResourceNames() {
	String[] empty = {};
	return (String[]) this.contents.keySet().toArray(empty);
}

/**
* Stores the registered resources in the backing store.
*/
public void storeResources() {
	this.manager.storeResources(this);
}


/**
* Constructs a new Registry.
*/
protected Registry() {
	this.contents = this.createContents();
	this.registrar = this.createRegistrar();
	this.accept(this.createStorageManager());
	this.registerShutdownHook();
}

/**
* Accepts the (storageManager) for resource loading.
* @param storageManager loads the configured resources.
*/
protected void 
accept(StorageManager storageManager) {
	this.manager = storageManager;
	storageManager.loadResources(registrar);
}

/**
* Returns a new contents map.
*/
protected Map createContents() {
	return new HashMap();
}

/**
* Returns a new registrar.
*/
protected Registrar createRegistrar() {
	return new Registrar();
}

/**
* Returns a new storage manager.
*/
protected StorageManager createStorageManager() {
	return new StorageManager();
}

/**
* Registers a shutdown hook.
*/
protected void registerShutdownHook() {
	Runtime.getRuntime()
		.addShutdownHook(this.createShutdownHook());
}

/**
* Returns a new shutdown hook.
*/
protected Thread createShutdownHook() {
	return new Thread() {
		public void run() {
			manager.storeResources(Registry.this);
		}
	};
}


/**
* Responsibilities:<ul>
* <li>maintains the resource registry.</li>
* </ul><p></p>
* 
* @author Copyright 2003 Nikolas S. Boyd.
*/
protected class Registrar {

/**
* Registers the supplied (resource).
* @param resource identifies a resource to be registered.
*/
public void 
register(Resource resource) {
	contents.put(resource.getName(), resource);
}

} // Registrar


} // ResourceRegistry