// Singleton class that keeps a list of the names of different SpaceObject
// classes, e.g., sun, ship, missile...
//
// The non-abstract SpaceObject classes should include a declaration like
// the following:
//
//	static String className = SpaceObjectRegistry.add("sun", new SpaceSun());
//
// SpaceObject subtypes whose objects require initialization must define
// a static member function to (1) allocate an instance, (2) do the required
// initialization, and (3) pass class's identifying name and the instance to
// SpaceObjectRegistry.add().

package SpaceWar;

import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import java.util.Dictionary;

class SpaceObjectRegistry {

	static Hashtable registry;

	// Initialize the registry, if it has not already been initialized.

	private static void initialize() {
		if (registry == null) {
			registry = new Hashtable();
		}
	}

	// Add a SpaceObject to the registry.  Returns null if the
	// registry already contains a SpaceObject of that name, and
	// leaves the old object in the registry.

	public static void put(String name, SpaceObject obj) {
		SpaceObjectRegistry.initialize();
		if (registry.containsKey(name)) {
			return;
		}
		registry.put(name, obj);
		return;
	}

	// Return an enumeration of the currently-registered SpaceObject
	// names.

	public static Enumeration names() {
		SpaceObjectRegistry.initialize();
		return (registry.keys());
	}

	// Return a new uninitialized SpaceObject of the type corresponding
	// to the specified name.  Return null if there is no object of the
	// specified name.

	static SpaceObject clone(String name) {
		SpaceObject so;

		SpaceObjectRegistry.initialize();
		so = (SpaceObject)registry.get(name);
		if (so == null) {
			return (null);
		}
		so = so.cloneMe();
		return (so);
	}
	
	// Return a new initialized SpaceObject of the type corresponding
	// to the specified name.  Return null if there is no object of the
	// specified name.
	
	static SpaceObject clone(String name,
							 int x, int y,
							 double initialAngle,
							 Color initialBodyColor,
							 Color initialTrimColor) {
		SpaceObject so;
		
		so = clone(name);
		if (so == null) {
			return (null);
		}
		so.setPosition(new Point2D.Double((double)x, (double)y));
		so.setAngle(initialAngle);
		so.setBodyColor(initialBodyColor);
		so.setTrimColor(initialTrimColor);
		return (so);
	}

	// Clone the named object in the registry.  Java will throw an
	// exception if the object is not a ControlledSpaceObject.  Return
	// null if there is no object of the specified name.

	static ControlledObject cloneControlled(String name) {
		return ((ControlledObject)SpaceObjectRegistry.clone(name));
	}

	// Disable creation of SpaceObjectRegistry objects.

	private SpaceObjectRegistry() {
	}
}