bundles/org.eclipse.platform.discovery.compatibility/src/org/eclipse/platform/discovery/compatibility/internal/contributors/impl/DynamicRegistryContributor.java

/*******************************************************************************
 * Copyright (c) 2010 SAP AG, Walldorf
 * 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:
 *    SAP AG - initial API and implementation
 *******************************************************************************/
package org.eclipse.platform.discovery.compatibility.internal.contributors.impl;

import java.util.ArrayList;
import java.util.Collection;

import org.eclipse.core.runtime.IContributor;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.platform.discovery.compatibility.internal.contributors.ContributionFailedException;
import org.eclipse.platform.discovery.compatibility.internal.contributors.IDynamicRegistryContributor;
import org.eclipse.platform.discovery.runtime.internal.xp.IContributionsReader;
import org.w3c.dom.Element;

/**
 * A dynamic registry contributor contributes extensions to search console based on extensions to some other extension point, possibly org.eclipse.search  
 * @param <T> - the type of extensions based on which data is contributed.
 */
public abstract class DynamicRegistryContributor<T> extends BasicRegistryContributor implements IDynamicRegistryContributor {
	

	private final IContributionsReader<T> contributionsReader;
	private final String targetExtensionPointId;
	private final String targetElementName;

	
	public DynamicRegistryContributor(IContributionsReader<T> contributionsReader, String targetExtensionPointId, String targetElementName) {
		this.contributionsReader = contributionsReader;
		this.targetExtensionPointId = targetExtensionPointId;
		this.targetElementName = targetElementName;
	}
	
	@Override
	public void contribute(IExtensionRegistry registry, IContributor contributor, Object token) throws ContributionFailedException {
		
		Collection<T> failedContributors = new ArrayList<T>();
		for (T data : contributionsReader.readContributions()) {

			Element plugin = createPluginSnippet(targetExtensionPointId);

			configurePluginElement(data, plugin);
			
			boolean success = writeToRegistry(plugin, registry, contributor, token, getContributionDescription(data));
			
			if(!success) {
				/*
				 * it's very likely the implementation will never reach here. the underlying registry returns false if
				 * there was a parsing problem with the contribution (unexpected because the XML was generated by us)
				 * or an IOException (also unexpected, we're only dealing with in-memory objects).
				 * In case flow does reach here, create an error message and continue with the loop, contributing the rest of the stuff on a
				 * best-effort basis.
				 */
				failedContributors.add(data);
			}
		}
		
		if(!failedContributors.isEmpty()) {
			throw new ContributionFailedException(getFailureMessage(failedContributors)); //$NON-NLS-1$
		}

	}
	

	protected abstract String getFailureMessage(Collection<T> failedContributors);

	/**
	 * A description for the dynamic contribution which is being made based on <code>data</code>. It will be used as the "name" under which the contribution will be written in the
	 * platform extension registry.
	 */
	protected abstract String getContributionDescription(T data);

	/* adds an object type element to the plugin snippet passed, using the provided pageDescription*/
	private void configurePluginElement(T data, Element element) {
		
		Element targetElement = element.getOwnerDocument().createElement(targetElementName);
		configureTargetElement(targetElement, data);
		addElementToPluginSnippet(element, targetElement);
	}

	/**
	 * Configure the target element attributes/children/executable extensions. It will already have its name set to <code>targetElementName</code>
	 */
	protected abstract void configureTargetElement(Element element, T data);

	
	
}