Copyright (c) 2005, 2015 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
    James Blackburn (Broadcom Corp.) - ongoing development
    Lars Vogel  - Bug 473427
/*******************************************************************************
 * Copyright (c) 2005, 2015 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
 *     James Blackburn (Broadcom Corp.) - ongoing development
 *     Lars Vogel <Lars.Vogel@vogella.com> - Bug 473427
 *******************************************************************************/
package org.eclipse.core.internal.resources.mapping;

import java.util.HashMap;
import java.util.Map;
import org.eclipse.core.internal.utils.Policy;
import org.eclipse.core.resources.ResourcesPlugin;
import org.eclipse.core.resources.mapping.IModelProviderDescriptor;
import org.eclipse.core.resources.mapping.ModelProvider;
import org.eclipse.core.runtime.*;

public class ModelProviderManager {

	private static Map<String, IModelProviderDescriptor> descriptors;
	private static ModelProviderManager instance;

	public synchronized static ModelProviderManager getDefault() {
		if (instance == null) {
			instance = new ModelProviderManager();
		}
		return instance;
	}

	private void detectCycles() {
		// TODO Auto-generated method stub

	}

	public IModelProviderDescriptor getDescriptor(String id) {
		lazyInitialize();
		return descriptors.get(id);
	}

	public IModelProviderDescriptor[] getDescriptors() {
		lazyInitialize();
		return descriptors.values().toArray(new IModelProviderDescriptor[descriptors.size()]);
	}

	public ModelProvider getModelProvider(String modelProviderId) throws CoreException {
		IModelProviderDescriptor desc = getDescriptor(modelProviderId);
		if (desc == null)
			return null;
		return desc.getModelProvider();
	}

	protected void lazyInitialize() {
		if (descriptors != null)
			return;
		IExtensionPoint point = Platform.getExtensionRegistry().getExtensionPoint(ResourcesPlugin.PI_RESOURCES, ResourcesPlugin.PT_MODEL_PROVIDERS);
		IExtension[] extensions = point.getExtensions();
		descriptors = new HashMap<>(extensions.length * 2 + 1);
		for (IExtension extension : extensions) {
			IModelProviderDescriptor desc = null;
			try {
				desc = new ModelProviderDescriptor(extension);
			} catch (CoreException e) {
				Policy.log(e);
			}
			if (desc != null)
				descriptors.put(desc.getId(), desc);
		}
		//do cycle detection now so it only has to be done once
		//cycle detection on a graph subset is a pain
		detectCycles();
	}

}