/*******************************************************************************
 * Copyright (c) 2001, 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.validation.internal;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Platform;
import org.eclipse.wst.validation.internal.plugin.ValidationPlugin;

public class ValidationSelectionHandlerRegistryReader {

	public static final String VALIDATION_SELECTION_HANDLER = "validationSelectionHandler"; //$NON-NLS-1$
	static final String ATT_ID = "id"; //$NON-NLS-1$ 
	
	/** handlerClass - */
	static final String ATT_HANDLER_CLASS = "handlerClass"; //$NON-NLS-1$
	
	static final String ATT_SELECTION_TYPE = "selectionType"; //$NON-NLS-1$
	private static ValidationSelectionHandlerRegistryReader INSTANCE;
	private List<IValidationSelectionHandler> _validationSelectionHandlers;
	
	public ValidationSelectionHandlerRegistryReader() {
	}
	
	public static ValidationSelectionHandlerRegistryReader getInstance() {
		if (INSTANCE == null) {
			INSTANCE = new ValidationSelectionHandlerRegistryReader();
			INSTANCE.readRegistry();
		}
		return INSTANCE;
	}

	/**
	 * Read the extension point and parse it.
	 */
	public void readRegistry() {
		IExtensionPoint point = Platform.getExtensionRegistry()
			.getExtensionPoint(ValidationPlugin.PLUGIN_ID, VALIDATION_SELECTION_HANDLER);
		if (point == null)return;
		IConfigurationElement[] elements = point.getConfigurationElements();
		for (int i = 0; i < elements.length; i++) {
			internalReadElement(elements[i]);
		}
	}
	
	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); //$NON-NLS-1$
		ValidationPlugin.getPlugin().logMessage(IStatus.ERROR, buf.toString());
	}
	

	/* (non-Javadoc)
	 * @see org.eclipse.jem.util.RegistryReader#readElement(org.eclipse.core.runtime.IConfigurationElement)
	 */
	public boolean readElement(IConfigurationElement element) {
		if (!element.getName().equals(VALIDATION_SELECTION_HANDLER))
			return false;
		
//		String handlerClass = element.getAttribute(ATT_HANDLER_CLASS);
		String selectionType = element.getAttribute(ATT_SELECTION_TYPE); 
		
		IValidationSelectionHandler handler = null;
		try {
			handler = (IValidationSelectionHandler) element.createExecutableExtension(ATT_HANDLER_CLASS);
			handler.setValidationTypeString(selectionType);
			getValidationSelectionHandlers().add(handler);
			return true;
		} catch (Exception e) {
			e.printStackTrace();
		}
	   return false;
	}
	
	private List<IValidationSelectionHandler> getValidationSelectionHandlers() {
		if (_validationSelectionHandlers == null)
			_validationSelectionHandlers = new ArrayList<IValidationSelectionHandler>();
		return _validationSelectionHandlers;
	}
	
	public Object getExtendedType(Object selection) {
		Object result = null;
		for (IValidationSelectionHandler handler : getValidationSelectionHandlers()) {
			result = handler.getBaseValidationType(selection);
			if (result != null)break;
		}
		return result;
	}
}