Copyright (c) 2005, 2013 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2005, 2013 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.osgi.internal.loader.buddy;

import java.io.IOException;
import java.net.URL;
import java.util.*;
import org.eclipse.osgi.container.ModuleCapability;
import org.eclipse.osgi.container.ModuleWiring;
import org.eclipse.osgi.container.namespaces.EquinoxModuleDataNamespace;
import org.eclipse.osgi.internal.loader.BundleLoader;

Registered policy is an implementation of a buddy policy. 
It is responsible for looking up a class in the bundles (registrant) that declare interest in the bundle that require the buddy loading.
Note that the registrants must have a direct dependency on the bundle needing buddy.
/**
 *Registered policy is an implementation of a buddy policy. 
 * It is responsible for looking up a class in the bundles (registrant) that declare interest in the bundle that require the buddy loading.
 * Note that the registrants must have a direct dependency on the bundle needing buddy.
 */
public class RegisteredPolicy extends DependentPolicy {

	public RegisteredPolicy(BundleLoader requester) {
		super(requester);

		//Filter the dependents;
		if (allDependents == null)
			return;

		String requesterName = requester.getWiring().getRevision().getSymbolicName();
		for (Iterator<ModuleWiring> iter = allDependents.iterator(); iter.hasNext();) {
			ModuleWiring wiring = iter.next();
			List<ModuleCapability> moduleDatas = wiring.getRevision().getModuleCapabilities(EquinoxModuleDataNamespace.MODULE_DATA_NAMESPACE);
			@SuppressWarnings("unchecked")
			List<String> registeredList = (List<String>) (moduleDatas.isEmpty() ? null : moduleDatas.get(0).getAttributes().get(EquinoxModuleDataNamespace.CAPABILITY_BUDDY_REGISTERED));
			if (registeredList == null || registeredList.isEmpty()) {
				iter.remove();
			} else {
				boolean contributes = false;
				for (String registeredName : registeredList) {
					if (registeredName.equals(requesterName)) {
						contributes = true;
						break;
					}
				}
				if (!contributes) {
					iter.remove();
				}
			}
		}

		//After the filtering, if nothing is left then null out the variable for optimization
		if (allDependents.size() == 0)
			allDependents = null;
	}

	@Override
	public Class<?> loadClass(String name) {
		if (allDependents == null)
			return null;

		Class<?> result = null;
		int size = allDependents.size();
		for (int i = 0; i < size && result == null; i++) {
			ModuleWiring searchWiring = allDependents.get(i);
			BundleLoader searchLoader = (BundleLoader) searchWiring.getModuleLoader();
			if (searchLoader != null) {
				try {
					result = searchLoader.findClass(name);
				} catch (ClassNotFoundException e) {
					//Nothing to do, just keep looking
					continue;
				}
			}
		}
		return result;
	}

	@Override
	public URL loadResource(String name) {
		if (allDependents == null)
			return null;

		URL result = null;
		int size = allDependents.size();
		for (int i = 0; i < size && result == null; i++) {
			ModuleWiring searchWiring = allDependents.get(i);
			BundleLoader searchLoader = (BundleLoader) searchWiring.getModuleLoader();
			if (searchLoader != null) {
				result = searchLoader.findResource(name);
			}
		}
		return result;
	}

	@Override
	public Enumeration<URL> loadResources(String name) {
		if (allDependents == null)
			return null;

		Enumeration<URL> results = null;
		int size = allDependents.size();
		for (int i = 0; i < size; i++) {
			try {
				ModuleWiring searchWiring = allDependents.get(i);
				BundleLoader searchLoader = (BundleLoader) searchWiring.getModuleLoader();
				if (searchLoader != null) {
					results = BundleLoader.compoundEnumerations(results, searchLoader.findResources(name));
				}
			} catch (IOException e) {
				//Ignore and keep looking
			}
		}
		return results;
	}
}