PersistenceDelegateBindingExtensionPointManager.java

/*******************************************************************************
 * Copyright (c) 2011, 2014 Wind River Systems, Inc. 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:
 * Wind River Systems - initial API and implementation
 *******************************************************************************/
package org.eclipse.tcf.te.runtime.persistence.internal;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import org.eclipse.core.expressions.EvaluationContext;
import org.eclipse.core.expressions.EvaluationResult;
import org.eclipse.core.expressions.Expression;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.Status;
import org.eclipse.tcf.te.runtime.extensions.AbstractExtensionPointManager;
import org.eclipse.tcf.te.runtime.extensions.ExecutableExtensionProxy;
import org.eclipse.tcf.te.runtime.persistence.activator.CoreBundleActivator;


/**
 */
public class PersistenceDelegateBindingExtensionPointManager extends AbstractExtensionPointManager<PersistenceDelegateBinding> {

	/*
	 * Thread save singleton instance creation.
	 */
	private static class LazyInstance {
		public static PersistenceDelegateBindingExtensionPointManager instance = new PersistenceDelegateBindingExtensionPointManager();
	}

	/**
	 * Constructor.
	 */
	PersistenceDelegateBindingExtensionPointManager() {
		super();
	}

	/**
	 * Returns the singleton instance of the extension point manager.
	 */
	public static PersistenceDelegateBindingExtensionPointManager getInstance() {
		return LazyInstance.instance;
	}

	/* (non-Javadoc)
	 * @see org.eclipse.tcf.te.runtime.extensions.AbstractExtensionPointManager#getExtensionPointId()
	 */
	@Override
	protected String getExtensionPointId() {
		return "org.eclipse.tcf.te.runtime.persistence.bindings"; //$NON-NLS-1$
	}

	/* (non-Javadoc)
	 * @see org.eclipse.tcf.te.runtime.extensions.AbstractExtensionPointManager#getConfigurationElementName()
	 */
	@Override
	protected String getConfigurationElementName() {
		return "binding"; //$NON-NLS-1$
	}

	/* (non-Javadoc)
	 * @see org.eclipse.tcf.te.runtime.extensions.AbstractExtensionPointManager#doCreateExtensionProxy(org.eclipse.core.runtime.IConfigurationElement)
	 */
	@Override
	protected ExecutableExtensionProxy<PersistenceDelegateBinding> doCreateExtensionProxy(IConfigurationElement element) throws CoreException {
		return new ExecutableExtensionProxy<PersistenceDelegateBinding>(element) {
			/* (non-Javadoc)
			 * @see org.eclipse.tcf.te.runtime.extensions.ExecutableExtensionProxy#newInstance()
			 */
			@Override
			public PersistenceDelegateBinding newInstance() {
				PersistenceDelegateBinding instance = new PersistenceDelegateBinding();
				try {
					instance.setInitializationData(getConfigurationElement(), null, null);
				} catch (CoreException e) {
					IStatus status = new Status(IStatus.ERROR, CoreBundleActivator.getUniqueIdentifier(),
									e.getLocalizedMessage(), e);
					Platform.getLog(CoreBundleActivator.getContext().getBundle()).log(status);
				}
				return instance;
			}
		};
	}

	/**
	 * Returns the applicable persistence delegate bindings for the given delegate context.
	 *
	 * @param context The delegate context or <code>null</code>.
	 * @return The list of applicable editor page bindings or an empty array.
	 */
	public PersistenceDelegateBinding[] getApplicableBindings(Object context, Object container) {
		List<PersistenceDelegateBinding> applicable = new ArrayList<PersistenceDelegateBinding>();

		for (PersistenceDelegateBinding binding : getBindings()) {
			Expression enablement = binding.getEnablement();

			// The binding is applicable by default if no expression is specified.
			boolean isApplicable = enablement == null;

			if (enablement != null) if (context != null) {
				// Set the default variable to the delegate context.
				EvaluationContext evalContext = new EvaluationContext(null, context);
				evalContext.addVariable("context", context); //$NON-NLS-1$
				if (context instanceof Class) evalContext.addVariable("contextClass", ((Class<?>)context).getName()); //$NON-NLS-1$
				else evalContext.addVariable("contextClass", context.getClass().getName()); //$NON-NLS-1$
				if (container != null) {
					evalContext.addVariable("container", container); //$NON-NLS-1$
					if (container instanceof Class) evalContext.addVariable("containerClass", ((Class<?>)container).getName()); //$NON-NLS-1$
					else evalContext.addVariable("containerClass", container.getClass().getName()); //$NON-NLS-1$
				}
				// Allow plugin activation
				evalContext.setAllowPluginActivation(true);
				// Evaluate the expression
				try {
					isApplicable = enablement.evaluate(evalContext).equals(EvaluationResult.TRUE);
				} catch (CoreException e) {
					IStatus status = new Status(IStatus.ERROR, CoreBundleActivator.getUniqueIdentifier(),
									e.getLocalizedMessage(), e);
					Platform.getLog(CoreBundleActivator.getContext().getBundle()).log(status);
				}
			}
			else // The enablement is false by definition if no delegate context is given.
				isApplicable = false;

			// Add the binding if applicable
			if (isApplicable) applicable.add(binding);
		}

		// Sort the applicable bindings by priority
		Collections.sort(applicable, new SortByPriority());

		if (applicable.size() > 1) {
			List<PersistenceDelegateBinding> overwritten = new ArrayList<PersistenceDelegateBinding>();
			for (PersistenceDelegateBinding candidate : applicable)
				for (PersistenceDelegateBinding overwriter : applicable) {
					String[] overwrites = overwriter.getOverwrites();
					if (overwrites != null && Arrays.asList(overwrites).contains(candidate.getId()))
						overwritten.add(candidate);
				}

			for (PersistenceDelegateBinding toRemove : overwritten)
				applicable.remove(toRemove);
		}

		return applicable.toArray(new PersistenceDelegateBinding[applicable.size()]);
	}

	/**
	 * Persistence delegate binding sort by priority comparator implementation.
	 */
	/* default */ static class SortByPriority implements Comparator<PersistenceDelegateBinding> {

		/* (non-Javadoc)
		 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
		 */
		@Override
		public int compare(PersistenceDelegateBinding o1, PersistenceDelegateBinding o2) {

			if (o1 != null && o2 != null) {
				String p1 = o1.getPriority();
				if (p1 == null || "".equals(p1)) p1 = "normal"; //$NON-NLS-1$ //$NON-NLS-2$
				String p2 = o2.getPriority();
				if (p2 == null || "".equals(p1)) p2 = "normal"; //$NON-NLS-1$ //$NON-NLS-2$

				int i1 = 0;
				if ("lowest".equalsIgnoreCase(p1)) i1 = -3; //$NON-NLS-1$
				if ("lower".equalsIgnoreCase(p1)) i1 = -2; //$NON-NLS-1$
				if ("low".equalsIgnoreCase(p1)) i1 = -1; //$NON-NLS-1$
				if ("high".equalsIgnoreCase(p1)) i1 = 1; //$NON-NLS-1$
				if ("higher".equalsIgnoreCase(p1)) i1 = 2; //$NON-NLS-1$
				if ("highest".equalsIgnoreCase(p1)) i1 = 3; //$NON-NLS-1$

				int i2 = 0;
				if ("lowest".equalsIgnoreCase(p2)) i2 = -3; //$NON-NLS-1$
				if ("lower".equalsIgnoreCase(p2)) i2 = -2; //$NON-NLS-1$
				if ("low".equalsIgnoreCase(p2)) i2 = -1; //$NON-NLS-1$
				if ("high".equalsIgnoreCase(p2)) i2 = 1; //$NON-NLS-1$
				if ("higher".equalsIgnoreCase(p2)) i2 = 2; //$NON-NLS-1$
				if ("highest".equalsIgnoreCase(p2)) i2 = 3; //$NON-NLS-1$

				if (i1 < i2) return 1;
				if (i1 > i2) return -1;
			}

			return 0;
		}
	}

	/**
	 * Returns the list of all contributed persistence delegate bindings.
	 *
	 * @return The list of contributed persistence delegate bindings, or an empty array.
	 */
	public PersistenceDelegateBinding[] getBindings() {
		List<PersistenceDelegateBinding> contributions = new ArrayList<PersistenceDelegateBinding>();
		Collection<ExecutableExtensionProxy<PersistenceDelegateBinding>> persistenceDelegateBindings = getExtensions().values();
		for (ExecutableExtensionProxy<PersistenceDelegateBinding> persistenceDelegateBinding : persistenceDelegateBindings) {
			PersistenceDelegateBinding instance = persistenceDelegateBinding.getInstance();
			if (instance != null && !contributions.contains(instance)) contributions.add(instance);
		}

		return contributions.toArray(new PersistenceDelegateBinding[contributions.size()]);
	}

	/**
	 * Returns the persistence delegate binding identified by its unique id. If no persistence
	 * delegate binding with the specified id is registered, <code>null</code> is returned.
	 *
	 * @param id The unique id of the persistence delegate binding or <code>null</code>
	 *
	 * @return The persistence delegate binding instance or <code>null</code>.
	 */
	public PersistenceDelegateBinding getBinding(String id) {
		PersistenceDelegateBinding contribution = null;
		if (getExtensions().containsKey(id)) {
			ExecutableExtensionProxy<PersistenceDelegateBinding> proxy = getExtensions().get(id);
			// Get the extension instance
			contribution = proxy.getInstance();
		}

		return contribution;
	}
}