content: /*******************************************************************************
   * Copyright (c) 2000, 2008 IBM Corporation and others.
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *     IBM Corporation - initial API and implementation
   *******************************************************************************/
  package org.eclipse.wst.jsdt.internal.ui.text.folding;
  
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.eclipse.core.runtime.Assert;
  import org.eclipse.core.runtime.CoreException;
  import org.eclipse.core.runtime.IConfigurationElement;
  import org.eclipse.core.runtime.IExtensionRegistry;
  import org.eclipse.core.runtime.IStatus;
  import org.eclipse.core.runtime.Platform;
  import org.eclipse.core.runtime.Status;
  import org.eclipse.jface.preference.IPreferenceStore;
  import org.eclipse.wst.jsdt.internal.corext.util.Messages;
  import org.eclipse.wst.jsdt.internal.ui.JavaScriptPlugin;
  import org.eclipse.wst.jsdt.ui.PreferenceConstants;
  import org.eclipse.wst.jsdt.ui.text.folding.IJavaFoldingStructureProvider;
  
  
  /**
   * 
   */
  public class JavaFoldingStructureProviderRegistry {
  
  	private static final String EXTENSION_POINT= "foldingStructureProviders"; //$NON-NLS-1$
  
  	/** The map of descriptors, indexed by their identifiers. */
  	private Map fDescriptors;
  
  	/**
  	 * Creates a new instance.
  	 */
  	public JavaFoldingStructureProviderRegistry() {
  	}
  
  	/**
  	 * Returns an array of <code>JavaFoldingStructureProviderDescriptor</code> describing
  	 * all extension to the <code>foldingProviders</code> extension point.
  	 *
  	 * @return the list of extensions to the
  	 *         <code>quickDiffReferenceProvider</code> extension point
  	 */
  	public JavaFoldingStructureProviderDescriptor[] getFoldingProviderDescriptors() {
  		synchronized (this) {
  			ensureRegistered();
  			return (JavaFoldingStructureProviderDescriptor[]) fDescriptors.values().toArray(new JavaFoldingStructureProviderDescriptor[fDescriptors.size()]);
  		}
  	}
  
  	/**
  	 * Returns the folding provider descriptor with identifier <code>id</code> or
  	 * <code>null</code> if no such provider is registered.
  	 *
  	 * @param id the identifier for which a provider is wanted
  	 * @return the corresponding provider descriptor, or <code>null</code> if none can be
  	 *         found
  	 */
  	public JavaFoldingStructureProviderDescriptor getFoldingProviderDescriptor(String id) {
  		synchronized (this) {
  			ensureRegistered();
  			return (JavaFoldingStructureProviderDescriptor) fDescriptors.get(id);
  		}
  	}
  
  	/**
  	 * Instantiates and returns the provider that is currently configured in the
  	 * preferences.
  	 *
  	 * @return the current provider according to the preferences
  	 */
  	public IJavaFoldingStructureProvider getCurrentFoldingProvider() {
  		IPreferenceStore preferenceStore= JavaScriptPlugin.getDefault().getPreferenceStore();
  		String currentProviderId= preferenceStore.getString(PreferenceConstants.EDITOR_FOLDING_PROVIDER);
  		JavaFoldingStructureProviderDescriptor desc= getFoldingProviderDescriptor(currentProviderId);
  		
  		// Fallback to default if extension has gone
  		if (desc == null) {
  			String message= Messages.format(FoldingMessages.JavaFoldingStructureProviderRegistry_warning_providerNotFound_resetToDefault, currentProviderId);
  			JavaScriptPlugin.log(new Status(IStatus.WARNING, JavaScriptPlugin.getPluginId(), IStatus.OK, message, null));
  			
  			String defaultProviderId= preferenceStore.getDefaultString(PreferenceConstants.EDITOR_FOLDING_PROVIDER);
  			
  			desc= getFoldingProviderDescriptor(defaultProviderId);
  			Assert.isNotNull(desc);
  			
  			preferenceStore.setToDefault(PreferenceConstants.EDITOR_FOLDING_PROVIDER);
  		}
  
  		try {
  			return desc.createProvider();
  		} catch (CoreException e) {
  			JavaScriptPlugin.log(e);
  			return null;
  		}
  	}
  
  	/**
  	 * Ensures that the extensions are read and stored in
  	 * <code>fDescriptors</code>.
  	 */
  	private void ensureRegistered() {
  		if (fDescriptors == null)
  			reloadExtensions();
  	}
  
  	/**
  	 * Reads all extensions.
  	 * <p>
  	 * This method can be called more than once in
  	 * order to reload from a changed extension registry.
  	 * </p>
  	 */
  	public void reloadExtensions() {
  		IExtensionRegistry registry= Platform.getExtensionRegistry();
  		Map map= new HashMap();
  
  		IConfigurationElement[] elements= registry.getConfigurationElementsFor(JavaScriptPlugin.getPluginId(), EXTENSION_POINT);
  		for (int i= 0; i < elements.length; i++) {
  			JavaFoldingStructureProviderDescriptor desc= new JavaFoldingStructureProviderDescriptor(elements[i]);
  			map.put(desc.getId(), desc);
  		}
  
  		synchronized(this) {
  			fDescriptors= Collections.unmodifiableMap(map);
  		}
  	}
  
  }
  