Copyright (c) 2004, 2013 IBM Corporation and others. All rights reserved.
This program and the accompanying materials are made available under the
terms of the Eclipse Public License 2.0 which accompanies this distribution,
t https://www.eclipse.org/legal/epl-2.0/
t
t SPDX-License-Identifier: EPL-2.0
Contributors:
	IBM - Initial API and implementation
	Oracle - Fix for bug 408506
/*******************************************************************************
 * Copyright (c) 2004, 2013 IBM Corporation and others. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which accompanies this distribution,
t https://www.eclipse.org/legal/epl-2.0/
t
t SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 * 	IBM - Initial API and implementation
 * 	Oracle - Fix for bug 408506
 ******************************************************************************/
package org.eclipse.core.internal.adapter;

import java.util.ArrayList;
import org.eclipse.core.internal.registry.Handle;
import org.eclipse.core.internal.registry.RegistryMessages;
import org.eclipse.core.internal.runtime.IAdapterFactoryExt;
import org.eclipse.core.internal.runtime.RuntimeLog;
import org.eclipse.core.runtime.*;
import org.eclipse.osgi.util.NLS;

Instances of this class represent adapter factories that have been
contributed via the adapters extension point. The concrete factory is not
loaded until the factory's plugin is loaded, AND until the factory is
requested to supply an adapter.
/**
 * Instances of this class represent adapter factories that have been
 * contributed via the adapters extension point. The concrete factory is not
 * loaded until the factory's plugin is loaded, AND until the factory is
 * requested to supply an adapter.
 */
class AdapterFactoryProxy implements IAdapterFactory, IAdapterFactoryExt {
	private IConfigurationElement element;
	
The real factory. Null until the factory is loaded.
/**
	 * The real factory. Null until the factory is loaded.
	 */
	private IAdapterFactory factory;
	private boolean factoryLoaded = false;
	
Store Id of the declaring extension. We might need it in case
the owner goes away (in this case element becomes invalid).
/**
	 * Store Id of the declaring extension. We might need it in case
	 * the owner goes away (in this case element becomes invalid).
	 */
	private String ownerId;

	private int internalOwnerID = -1;

	
Creates a new factory proxy based on the given configuration element.
Returns the new proxy, or null if the element could not be created.
/**
	 * Creates a new factory proxy based on the given configuration element.
	 * Returns the new proxy, or null if the element could not be created.
	 */
	public static AdapterFactoryProxy createProxy(IConfigurationElement element) {
		AdapterFactoryProxy result = new AdapterFactoryProxy();
		result.element = element;
		IExtension extension = element.getDeclaringExtension();
		result.ownerId = extension.getUniqueIdentifier();
		if (extension instanceof Handle)
			result.internalOwnerID = ((Handle) extension).getId();
		if ("factory".equals(element.getName())) //$NON-NLS-1$
			return result;
		result.logError();
		return null;
	}

	public boolean originatesFrom(IExtension extension) {
		String id = extension.getUniqueIdentifier();
		if (id != null) // match by public ID declared in XML
			return id.equals(ownerId);

		if (!(extension instanceof Handle))
			return false; // should never happen

		return (internalOwnerID == ((Handle) extension).getId());
	}

	String getAdaptableType() {
		//cannot return null because it can cause startup failure
		String result = element.getAttribute("adaptableType"); //$NON-NLS-1$
		if (result != null)
			return result;
		logError();
		return ""; //$NON-NLS-1$
	}

	@Override
	public <T> T getAdapter(Object adaptableObject, Class<T> adapterType) {
		if (!factoryLoaded)
			loadFactory(false);
		return factory == null ? null : factory.getAdapter(adaptableObject, adapterType);
	}

	@Override
	public Class<?>[] getAdapterList() {
		if (!factoryLoaded)
			loadFactory(false);
		return factory == null ? null : factory.getAdapterList();
	}

	@Override
	public String[] getAdapterNames() {
		IConfigurationElement[] children = element.getChildren();
		ArrayList<String> adapters = new ArrayList<>(children.length);
		for (IConfigurationElement child : children) {
			//ignore unknown children for forward compatibility
			if ("adapter".equals(child.getName())) {//$NON-NLS-1$
				String type = child.getAttribute("type"); //$NON-NLS-1$
				if (type != null)
					adapters.add(type);
			}
		}
		if (adapters.isEmpty())
			logError();
		return adapters.toArray(new String[adapters.size()]);
	}

	IExtension getExtension() {
		return element.getDeclaringExtension();
	}

	
Loads the real adapter factory, but only if its associated plug-in is
already loaded. Returns the real factory if it was successfully loaded.
Params:
force – if true the plugin providing the
factory will be loaded if necessary, otherwise no plugin activations
will occur./**
	 * Loads the real adapter factory, but only if its associated plug-in is
	 * already loaded. Returns the real factory if it was successfully loaded.
	 * @param force if <code>true</code> the plugin providing the
	 * factory will be loaded if necessary, otherwise no plugin activations
	 * will occur.
	 */
	@Override
	public synchronized IAdapterFactory loadFactory(boolean force) {
		if (factory != null || factoryLoaded)
			return factory;
		String contributorName = element.getContributor().getName();
		boolean isActive;
		// Different VMs have different degrees of "laziness" for the class loading.
		// To make sure that VM won't try to load EquinoxUtils before getting into
		// this try-catch block, the fully qualified name is used (removing entry for
		// the EquinoxUtils from the import list).
		try {
			isActive = org.eclipse.core.internal.registry.osgi.EquinoxUtils.isActive(contributorName);
		} catch (NoClassDefFoundError noClass) {
			// This block will only be triggered if VM loads classes in a very "eager" way.
			isActive = true;
		}
		if (!force && !isActive)
			return null;
		try {
			factory = (IAdapterFactory) element.createExecutableExtension("class"); //$NON-NLS-1$
		} catch (CoreException e) {
			String msg = NLS.bind(RegistryMessages.adapters_cantInstansiate, getAdaptableType(), element.getContributor().getName());
			RuntimeLog.log(new Status(IStatus.ERROR, RegistryMessages.OWNER_NAME, 0, msg, e));
		} finally {
			//set to true to prevent repeated attempts to load a broken factory
			factoryLoaded = true;
		}
		return factory;
	}

	
The factory extension was malformed. Log an appropriate exception
/**
	 * The factory extension was malformed. Log an appropriate exception
	 */
	private void logError() {
		String msg = NLS.bind(RegistryMessages.adapters_badAdapterFactory, element.getContributor().getName());
		RuntimeLog.log(new Status(IStatus.ERROR, RegistryMessages.OWNER_NAME, 0, msg, null));
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append("AdapterFactoryProxy [contributor: "); //$NON-NLS-1$
		sb.append(element.getContributor());
		sb.append(", adaptableType: "); //$NON-NLS-1$
		sb.append(getAdaptableType());
		if (factory != null) {
			sb.append(", factory: "); //$NON-NLS-1$
			sb.append(factory);
		}
		sb.append("]"); //$NON-NLS-1$
		return sb.toString();
	}
}