Copyright (c) 2008, 2015 Freescale Semiconductor 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:
    Freescale Semiconductor - initial API and implementation
    IBM Corporation - ongoing development
    James Blackburn (Broadcom Corp.) - ongoing development
    Lars Vogel  - Bug 473427
/*******************************************************************************
 * Copyright (c) 2008, 2015 Freescale Semiconductor 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:
 *     Freescale Semiconductor - initial API and implementation
 *     IBM Corporation - ongoing development
 *     James Blackburn (Broadcom Corp.) - ongoing development
 *     Lars Vogel <Lars.Vogel@vogella.com> - Bug 473427
 *******************************************************************************/
package org.eclipse.core.internal.resources;

import java.util.HashMap;
import java.util.Map;
import org.eclipse.core.internal.utils.Messages;
import org.eclipse.core.internal.utils.Policy;
import org.eclipse.core.resources.IResource;
import org.eclipse.core.resources.ResourcesPlugin;
import org.eclipse.core.resources.variableresolvers.PathVariableResolver;
import org.eclipse.core.runtime.*;
import org.eclipse.osgi.util.NLS;

Repository for all variable providers available through the extension points.
Since:
3.6/**
 * Repository for all variable providers available through the extension points.
 * @since 3.6
 */
public class ProjectVariableProviderManager {

	public static class Descriptor {
		PathVariableResolver provider = null;
		String name = null;
		String value = null;

		public Descriptor(IExtension extension, IConfigurationElement element) throws RuntimeException, CoreException {
			name = element.getAttribute("variable"); //$NON-NLS-1$
			value = element.getAttribute("value"); //$NON-NLS-1$
			try {
				String classAttribute = "class"; //$NON-NLS-1$
				if (element.getAttribute(classAttribute) != null)
					provider = (PathVariableResolver) element.createExecutableExtension(classAttribute);
			} catch (CoreException e) {
				Policy.log(e);
			}
			if (name == null)
				fail(NLS.bind(Messages.mapping_invalidDef, extension.getUniqueIdentifier()));
		}

		protected void fail(String reason) throws CoreException {
			throw new ResourceException(new Status(IStatus.ERROR, ResourcesPlugin.PI_RESOURCES, 1, reason, null));
		}

		public String getName() {
			return name;
		}

		public String getValue(String variable, IResource resource) {
			if (value != null)
				return value;
			return provider.getValue(variable, resource);
		}

		public String[] getVariableNames(String variable, IResource resource) {
			if (provider != null)
				return provider.getVariableNames(variable, resource);
			if (name.equals(variable))
				return new String[] {variable};
			return null;
		}
	}

	private static Map<String, Descriptor> descriptors;
	private static Descriptor[] descriptorsArray;
	private static ProjectVariableProviderManager instance = new ProjectVariableProviderManager();

	public static ProjectVariableProviderManager getDefault() {
		return instance;
	}

	public Descriptor[] getDescriptors() {
		lazyInitialize();
		return descriptorsArray;
	}

	protected void lazyInitialize() {
		if (descriptors != null)
			return;
		IExtensionPoint point = Platform.getExtensionRegistry().getExtensionPoint(ResourcesPlugin.PI_RESOURCES, ResourcesPlugin.PT_VARIABLE_PROVIDERS);
		IExtension[] extensions = point.getExtensions();
		descriptors = new HashMap<>(extensions.length * 2 + 1);
		for (IExtension extension : extensions) {
			IConfigurationElement[] elements = extension.getConfigurationElements();
			int count = elements.length;
			for (int j = 0; j < count; j++) {
				IConfigurationElement element = elements[j];
				String elementName = element.getName();
				if (elementName.equalsIgnoreCase("variableResolver")) { //$NON-NLS-1$
					Descriptor desc = null;
					try {
						desc = new Descriptor(extension, element);
					} catch (CoreException e) {
						Policy.log(e);
					}
					if (desc != null)
						descriptors.put(desc.getName(), desc);
				}
			}
		}
		descriptorsArray = descriptors.values().toArray(new Descriptor[descriptors.size()]);
	}

	public Descriptor findDescriptor(String name) {
		lazyInitialize();
		Descriptor result = descriptors.get(name);
		return result;
	}
}