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/*******************************************************************************
 * Copyright (c) 2005, 2021 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.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Map;
import org.eclipse.osgi.container.ModuleContainer;
import org.eclipse.osgi.container.ModuleWire;
import org.eclipse.osgi.container.ModuleWiring;
import org.eclipse.osgi.internal.container.Capabilities;
import org.eclipse.osgi.internal.loader.BundleLoader;
import org.osgi.framework.namespace.HostNamespace;
import org.osgi.framework.namespace.PackageNamespace;
import org.osgi.framework.wiring.BundleCapability;
import org.osgi.framework.wiring.BundleRevision;
import org.osgi.framework.wiring.FrameworkWiring;
import org.osgi.resource.Namespace;

/**
 * Global policy is an implementation of a buddy policy. It is responsible
 * for looking up a class within the global set of exported classes. If multiple
 * version of the same package are exported in the system, the exported package
 * with the highest version will be returned.
 */
public class GlobalPolicy implements IBuddyPolicy {
	private FrameworkWiring frameworkWiring;

	public GlobalPolicy(FrameworkWiring frameworkWiring) {
		this.frameworkWiring = frameworkWiring;
	}

	@Override
	public Class loadClass(String name) {
		return getExportingBundles(BundleLoader.getPackageName(name)) //
				.stream().findFirst().map(b -> b.findClassNoParentNoException(name)).orElse(null);
	}

	@Override
	public URL loadResource(String name) {
		return getExportingBundles(BundleLoader.getResourcePackageName(name)) //
				.stream().findFirst().map(b -> b.findResource(name)).orElse(null);
	}

	@Override
	public Enumeration loadResources(String name) {
		Enumeration results = null;
		Collection exporters = getExportingBundles(name);
		for (BundleLoader exporter : exporters) {
			try {
				results = BundleLoader.compoundEnumerations(results, exporter.findResources(name));
			}catch (IOException e) {
				//ignore IO problems and try next package
			}
		}
		return results;
	}

	private Collection getExportingBundles(String pkgName) {
		Collection result = new ArrayList<>();
		String filter = "(" + PackageNamespace.PACKAGE_NAMESPACE + "=" + pkgName + ")"; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
		Map directives = Collections.singletonMap(Namespace.REQUIREMENT_FILTER_DIRECTIVE, filter);
		Map attributes = Collections.singletonMap(Capabilities.SYNTHETIC_REQUIREMENT, Boolean.TRUE);
		Collection packages = frameworkWiring.findProviders(
				ModuleContainer.createRequirement(PackageNamespace.PACKAGE_NAMESPACE, directives, attributes));
		for (BundleCapability pkg : packages) {
			ModuleWiring wiring = (ModuleWiring) pkg.getRevision().getWiring();
			if (wiring != null) {
				if ((pkg.getRevision().getTypes() & BundleRevision.TYPE_FRAGMENT) != 0) {
					// use the hosts
					if (wiring != null) {
						for (ModuleWire hostWire : wiring.getRequiredModuleWires(HostNamespace.HOST_NAMESPACE)) {
							result.add((BundleLoader) hostWire.getProviderWiring().getModuleLoader());
						}
					}
				} else {
					result.add((BundleLoader) wiring.getModuleLoader());
				}
			}
		}
		return result;
	}
}