/*******************************************************************************
 * Copyright (c) 2005, 2006 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.common.core.util;
import org.eclipse.core.runtime.*;
import org.eclipse.wst.common.core.search.SearchPlugin;
import org.osgi.framework.Bundle;


/**
 * Class to read a registry. It is meant to be subclassed to provide specific function.
 * 
 * @since 1.0.0
 */
public abstract class RegistryReader {

	private static final String JEM_PLUGIN_ID = "org.eclipse.jem.util"; //$NON-NLS-1$
	
	String pluginId;

	String extensionPointId;

	private static Bundle systemBundle;

	/**
	 * Utility method to get the plugin id of a configuation element
	 * 
	 * @param configurationElement
	 * @return plugin id of configuration element
	 * @since 1.0.0
	 */
	public static String getPluginId(IConfigurationElement configurationElement) {
		String pluginId = null;

		if (configurationElement != null) {
			IExtension extension = configurationElement.getDeclaringExtension();

			if (extension != null)
				pluginId = extension.getContributor().getName();
		}

		return pluginId;
	}

	/**
	 * Constructor for RegistryReader taking a registry, plugin id, and extension point id.
	 * 
	 * @param registry
	 * @param pluginID
	 * @param extensionPoint
	 * 
	 * @deprecated Use RegistryReader(plugin, extensionPoint) instead. The registry passed in is ignored.
	 * @since 1.0.0
	 */
	public RegistryReader(IPluginRegistry registry, String pluginID, String extensionPoint) {
		this(pluginID, extensionPoint);
	}

	/**
	 * Constructor for RegistryReader taking the plugin id and extension point id.
	 * 
	 * @param pluginID
	 * @param extensionPoint
	 * 
	 * @since 1.0.0
	 */
	public RegistryReader(String pluginID, String extensionPoint) {
		super();
		this.pluginId = pluginID;
		extensionPointId = extensionPoint;
	}

	private void internalReadElement(IConfigurationElement element) {
		boolean recognized = this.readElement(element);
		if (!recognized) {
			logError(element, "Error processing extension: " + element); //$NON-NLS-1$
		}
	}

	/*
	 * Logs the error in the desktop log using the provided text and the information in the configuration element.
	 */
	protected void logError(IConfigurationElement element, String text) {
		IExtension extension = element.getDeclaringExtension();
		StringBuffer buf = new StringBuffer();
		buf.append("Plugin " + extension.getContributor().getName() + ", extension " + extension.getExtensionPointUniqueIdentifier()); //$NON-NLS-1$ //$NON-NLS-2$
		buf.append("\n" + text); //$NON-NLS-1$
		SearchPlugin.logError(buf.toString());
	}

	/*
	 * Logs a very common registry error when a required attribute is missing.
	 */
	protected void logMissingAttribute(IConfigurationElement element, String attributeName) {
		logError(element, "Required attribute '" + attributeName + "' not defined"); //$NON-NLS-1$ //$NON-NLS-2$
	}

	/*
	 * Implement this method to read element attributes. If this element has subelements, the reader will recursively cycle through them and call this
	 * method so don't do it here.
	 */
	public abstract boolean readElement(IConfigurationElement element);

	/**
	 * Read the extension point and parse it.
	 * 
	 * @since 1.0.0
	 */
	public void readRegistry() {
		IExtensionPoint point = Platform.getExtensionRegistry().getExtensionPoint(pluginId, extensionPointId);
		if (point != null)
		{
			IConfigurationElement[] elements = point.getConfigurationElements();
			for (int i = 0; i < elements.length; i++) {
				internalReadElement(elements[i]);
			}
		}
		// the following code is to handle the contributions to the deprecated org.eclipse.jem.util extensions
		if (!JEM_PLUGIN_ID.equals(pluginId))
		{
			point = Platform.getExtensionRegistry().getExtensionPoint(JEM_PLUGIN_ID, extensionPointId);
			if (point != null)
			{
				IConfigurationElement[] elements = point.getConfigurationElements();
				for (int i = 0; i < elements.length; i++) {
					internalReadElement(elements[i]);
				}
			}
		}
	}

	/**
	 * Tests to see if it is valid at this point in time to create an executable extension. A valid reason not to would be that the workspace is
	 * shutting donw.
	 * 
	 * @param element
	 * @return <code>true</code> if it is valid point to create an executable extension.
	 * 
	 * @since 1.0.0
	 */
	public static boolean canCreateExecutableExtension(IConfigurationElement element) {
		if (Platform.isRunning() && getSystemBundle().getState() != Bundle.STOPPING)
			return true;
		return false;
	}

	/**
	 * Get the system bundle
	 * 
	 * @return system bundle.
	 * 
	 * @since 1.0.0
	 */
	protected static Bundle getSystemBundle() {
		if (systemBundle == null)
			systemBundle = Platform.getBundle("org.eclipse.osgi"); //$NON-NLS-1$
		return systemBundle;
	}
}