EDIT

/*******************************************************************************

 * Copyright (c) 2003, 2010 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.ui.internal.navigator.extensions;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.ListIterator;

import java.util.Set;

import java.util.TreeSet;

import org.eclipse.osgi.util.NLS;

import org.eclipse.core.expressions.ElementHandler;

import org.eclipse.core.expressions.EvaluationResult;

import org.eclipse.core.expressions.Expression;

import org.eclipse.core.expressions.ExpressionConverter;

import org.eclipse.core.expressions.IEvaluationContext;

import org.eclipse.core.runtime.CoreException;

import org.eclipse.core.runtime.IConfigurationElement;

import org.eclipse.core.runtime.IStatus;

import org.eclipse.jface.viewers.ILabelProvider;

import org.eclipse.jface.viewers.IStructuredSelection;

import org.eclipse.jface.viewers.ITreeContentProvider;

import org.eclipse.ui.IPluginContribution;

import org.eclipse.ui.WorkbenchException;

import org.eclipse.ui.internal.navigator.CommonNavigatorMessages;

import org.eclipse.ui.internal.navigator.CustomAndExpression;

import org.eclipse.ui.internal.navigator.NavigatorPlugin;

import org.eclipse.ui.internal.navigator.Policy;

import org.eclipse.ui.navigator.ICommonContentProvider;

import org.eclipse.ui.navigator.ICommonLabelProvider;

import org.eclipse.ui.navigator.INavigatorContentDescriptor;

import org.eclipse.ui.navigator.OverridePolicy;

import org.eclipse.ui.navigator.Priority;

/**

 * Encapsulates the <code>org.eclipse.ui.navigator.navigatorContent</code>

 * extension point.

 * 

 * @since 3.2

 */

public final class NavigatorContentDescriptor implements

		INavigatorContentDescriptor, INavigatorContentExtPtConstants {

	private static final int HASH_CODE_NOT_COMPUTED = -1;

	private String id;

	private String name;

	private IConfigurationElement configElement;

	private int priority = Priority.NORMAL_PRIORITY_VALUE;

	/**

	 * This is calculated based on the priority and appearsBeforeId when all of the descriptors

	 * are first loaded. This is what's used to sort on after that.

	 */

	private int sequenceNumber;

	private String appearsBeforeId;

	private Expression enablement;

	private Expression possibleChildren;

	private Expression initialActivation;

	private String icon;

	private boolean activeByDefault;

	private IPluginContribution contribution;

	private boolean sortOnly;

	private Set overridingExtensions;

	private List overridingExtensionsList; // FIXME: will replace 'overridingExtensions' in 3.6

	private OverridePolicy overridePolicy;

	private String suppressedExtensionId;

	private INavigatorContentDescriptor overriddenDescriptor;

	private int hashCode = HASH_CODE_NOT_COMPUTED;

	private boolean providesSaveables;

	/**

	 * Creates a new content descriptor from a configuration element.

	 * 

	 * @param configElement

	 *            configuration element to create a descriptor from

	 * 

	 * @throws WorkbenchException

	 *             if the configuration element could not be parsed. Reasons

	 *             include:

	 *             <ul>

	 *             <li>A required attribute is missing.</li>

	 *             <li>More elements are define than is allowed.</li>

	 *             </ul>

	 */

	/* package */ NavigatorContentDescriptor(IConfigurationElement configElement)

			throws WorkbenchException {

		super();

		this.configElement = configElement;

		init();

	}

	/*

	 * (non-Javadoc)

	 * 

	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorContentDescriptor#getId()

	 */

	public String getId() {

		return id;

	}

	/*

	 * (non-Javadoc)

	 * 

	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorContentDescriptor#getName()

	 */

	public String getName() {

		return name;

	}

	/*

	 * (non-Javadoc)

	 * 

	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorContentDescriptor#getPriority()

	 */

	public int getPriority() {

		return priority;

	}

	/**

	 * @return the sequence number

	 */

	public int getSequenceNumber() {

		return sequenceNumber;

	}

	void setSequenceNumber(int num) {

		sequenceNumber = num;

	}

	/**

	 * 

	 * @return The value specified by the <i>appearsBefore</i> attribute of the

	 *         <navigatorContent/> element.

	 */

	public String getAppearsBeforeId() {

		return appearsBeforeId;

	}

	public boolean isSortOnly() {

		return sortOnly;

	}

	/**

	 * Parses the configuration element.

	 * 

	 * @throws WorkbenchException

	 *             if the configuration element could not be parsed. Reasons

	 *             include:

	 *             <ul>

	 *             <li>A required attribute is missing.</li>

	 *             <li>More elements are define than is allowed.</li>

	 *             </ul>

	 */

	private void init() throws WorkbenchException {

		id = configElement.getAttribute(ATT_ID);

		name = configElement.getAttribute(ATT_NAME);

		String priorityString = configElement.getAttribute(ATT_PRIORITY);

		icon = configElement.getAttribute(ATT_ICON);

		String activeByDefaultString = configElement

				.getAttribute(ATT_ACTIVE_BY_DEFAULT);

		activeByDefault = (activeByDefaultString != null && activeByDefaultString

				.length() > 0) ? Boolean.valueOf(activeByDefaultString)

				.booleanValue() : true;

		String providesSaveablesString = configElement

			.getAttribute(ATT_PROVIDES_SAVEABLES);

		providesSaveables = (providesSaveablesString != null && providesSaveablesString

				.length() > 0) ? Boolean.valueOf(providesSaveablesString)

						.booleanValue() : false;

		appearsBeforeId = configElement.getAttribute(ATT_APPEARS_BEFORE);

		if (priorityString != null) {

			try {

				Priority p = Priority.get(priorityString);

				priority = p != null ? p.getValue()

						: Priority.NORMAL_PRIORITY_VALUE;

			} catch (NumberFormatException exception) {

				priority = Priority.NORMAL_PRIORITY_VALUE;

			}

		}

		// We start with this because the sort ExtensionPriorityComparator works 

		// from the sequenceNumber

		sequenceNumber = priority;

		String sortOnlyString = configElement.getAttribute(ATT_SORT_ONLY);

		sortOnly = (sortOnlyString != null && sortOnlyString.length() > 0) ? Boolean.valueOf(

				sortOnlyString).booleanValue() : false;

		if (id == null) {

			throw new WorkbenchException(NLS.bind(

					CommonNavigatorMessages.Attribute_Missing_Warning,

					new Object[] {

							ATT_ID,

							id,

							configElement.getDeclaringExtension()

									.getNamespaceIdentifier() }));

		}

		contribution = new IPluginContribution() {

			public String getLocalId() {

				return getId();

			}

			public String getPluginId() {

				return configElement.getDeclaringExtension().getNamespaceIdentifier();

			}

		};

		IConfigurationElement[] children;

		children = configElement.getChildren(TAG_INITIAL_ACTIVATION);

		if (children.length > 0) {

			if (children.length == 1) {

				initialActivation = new CustomAndExpression(children[0]);

			} else {

				throw new WorkbenchException(NLS.bind(

						CommonNavigatorMessages.Attribute_Missing_Warning, new Object[] {

								TAG_INITIAL_ACTIVATION, id,

								configElement.getDeclaringExtension().getNamespaceIdentifier() }));

			}

		}

		if (sortOnly)

			return;

		children = configElement.getChildren(TAG_ENABLEMENT);

		if (children.length == 0) {

			children = configElement.getChildren(TAG_TRIGGER_POINTS);

			if (children.length == 1) {

				enablement = new CustomAndExpression(children[0]);

			} else {

				throw new WorkbenchException(NLS.bind(

						CommonNavigatorMessages.Attribute_Missing_Warning,

						new Object[] {

								TAG_TRIGGER_POINTS,

								id,

								configElement.getDeclaringExtension()

										.getNamespaceIdentifier() }));

			}

			children = configElement.getChildren(TAG_POSSIBLE_CHILDREN);

			if (children.length == 1) {

				possibleChildren = new CustomAndExpression(children[0]);

			} else if(children.length > 1){

				throw new WorkbenchException(NLS.bind(

						CommonNavigatorMessages.Attribute_Missing_Warning,

						new Object[] {

								TAG_POSSIBLE_CHILDREN,

								id,

								configElement.getDeclaringExtension()

										.getNamespaceIdentifier() }));

			}

		} else if (children.length == 1) {

			try {

				enablement = ElementHandler.getDefault().create(

						ExpressionConverter.getDefault(), children[0]);

			} catch (CoreException e) {

				NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);

			}

		} else if (children.length > 1) {

			throw new WorkbenchException(NLS.bind(

					CommonNavigatorMessages.Attribute_Missing_Warning,

					new Object[] {

							TAG_ENABLEMENT,

							id,

							configElement.getDeclaringExtension()

									.getNamespaceIdentifier() }));

		}

		children = configElement.getChildren(TAG_OVERRIDE);

		if (children.length == 0) {

			overridePolicy = OverridePolicy.get(OverridePolicy.InvokeAlwaysRegardlessOfSuppressedExt_LITERAL);

		} else if (children.length == 1) {

			suppressedExtensionId = children[0]

					.getAttribute(ATT_SUPPRESSED_EXT_ID);

			overridePolicy = OverridePolicy.get(children[0]

					.getAttribute(ATT_POLICY));

		} else if (children.length > 1) {

			throw new WorkbenchException(NLS.bind(

					CommonNavigatorMessages.Too_many_elements_Warning,

					new Object[] {

							TAG_OVERRIDE,

							id,configElement.getDeclaringExtension()

							.getNamespaceIdentifier() }));

		}

	}

	/**

	 * @return Returns the icon.

	 */

	public String getIcon() {

		return icon;

	}

	/**

	 * @return Returns the suppressedExtensionId or null if none specified.

	 */

	public String getSuppressedExtensionId() {

		return suppressedExtensionId;

	}

	/**

	 * @return Returns the overridePolicy or null if this extension does not

	 *         override another extension.

	 */

	public OverridePolicy getOverridePolicy() {

		return overridePolicy;

	}

	/**

	 * @return Returns the contribution.

	 */

	public IPluginContribution getContribution() {

		return contribution;

	}

	/**

	 * @return the configuration element

	 */

	public IConfigurationElement getConfigElement() {

		return configElement;

	}

	/**

	 * The content provider could be an instance of

	 * {@link ICommonContentProvider}, but only {@link ITreeContentProvider} is

	 * required.

	 * 

	 * 

	 * @return An instance of the Content provider defined for this extension.

	 * @throws CoreException

	 *             if an instance of the executable extension could not be

	 *             created for any reason

	 * 

	 */

	public ITreeContentProvider createContentProvider() throws CoreException {

		if (Policy.DEBUG_EXTENSION_SETUP)

			System.out.println("createContentProvider: " + this); //$NON-NLS-1$

		return (ITreeContentProvider) configElement

				.createExecutableExtension(ATT_CONTENT_PROVIDER);

	}

	/**

	 * 

	 * The content provider could be an instance of {@link ICommonLabelProvider},

	 * but only {@link ILabelProvider} is required.

	 * 

	 * @return An instance of the Label provider defined for this extension

	 * @throws CoreException

	 *             if an instance of the executable extension could not be

	 *             created for any reason

	 */

	public ILabelProvider createLabelProvider() throws CoreException {

		if (Policy.DEBUG_EXTENSION_SETUP)

			System.out.println("createLabelProvider: " + this); //$NON-NLS-1$

		return (ILabelProvider) configElement

				.createExecutableExtension(ATT_LABEL_PROVIDER);

	}

	/*

	 * (non-Javadoc)

	 * 

	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorContentDescriptor#isActiveByDefault()

	 */

	public boolean isActiveByDefault() {

		if (activeByDefault)

			return true;

		if (initialActivation == null)

			return false;

		IEvaluationContext context = NavigatorPlugin.getEvalContext(new Object());

		return NavigatorPlugin.safeEvaluate(initialActivation, context) == EvaluationResult.TRUE;

	}

	/**

	 * Determine if this content extension would be able to provide children for

	 * the given element.

	 * 

	 * @param anElement

	 *            The element that should be used for the evaluation.

	 * @return True if and only if the extension is enabled for the element.

	 */

	public boolean isTriggerPoint(Object anElement) {

		if (enablement == null || anElement == null) {

			return false;

		}

		IEvaluationContext context = NavigatorPlugin.getEvalContext(anElement);

		return NavigatorPlugin.safeEvaluate(enablement, context) == EvaluationResult.TRUE;

	}

	/**

	 * Determine if this content extension could provide the given element as a

	 * child.

	 * 

	 * <p>

	 * This method is used to determine what the parent of an element could be

	 * for Link with Editor support.

	 * </p>

	 * 

	 * @param anElement

	 *            The element that should be used for the evaluation.

	 * @return True if and only if the extension might provide an object of this

	 *         type as a child.

	 */

	public boolean isPossibleChild(Object anElement) {

		if ((enablement == null && possibleChildren == null)

				|| anElement == null) {

			return false;

		} else if(anElement instanceof IStructuredSelection) {

			return arePossibleChildren((IStructuredSelection) anElement);

		}

		IEvaluationContext context = NavigatorPlugin.getEvalContext(anElement);

		if (possibleChildren != null) {

			return NavigatorPlugin.safeEvaluate(possibleChildren, context) == EvaluationResult.TRUE;

		} else if (enablement != null) {

			return NavigatorPlugin.safeEvaluate(enablement, context) == EvaluationResult.TRUE;

		}

		return false;

	}

	/**

	 * A convenience method to check all elements in a selection.

	 * 

	 * @param aSelection A non-null selection

	 * @return True if and only if every element in the selection is a possible child.

	 */

	public boolean arePossibleChildren(IStructuredSelection aSelection) {

		if(aSelection.isEmpty()) {

			return false;

		}

		for (Iterator iter = aSelection.iterator(); iter.hasNext();) {

			Object element = iter.next();

			if(!isPossibleChild(element)) {

				return false;

			}

		}

		return true;

	}

	/**

	 * 

	 * Does not force the creation of the set of overriding extensions.

	 * 

	 * @return True if this extension has overriding extensions.

	 */

	public boolean hasOverridingExtensions() {

		return overridingExtensions != null && overridingExtensions.size() > 0;

	}

	/**

	 * @return The set of overriding extensions (of type

	 *         {@link INavigatorContentDescriptor}

	 */

	public Set getOverriddingExtensions() {

		if (overridingExtensions == null) {

			overridingExtensions = new TreeSet(ExtensionSequenceNumberComparator.DESCENDING);

		}

		return overridingExtensions;

	}

	/**

	 *  Returns a list iterator over the overriding extensions.

	 * 

	 * @param fromStart

	 *            <code>true</code> if list iterator starts at the beginning and

	 *            <code>false</code> if it starts at the end of the list

	 * @return a list iterator over the overriding extensions which are ordered

	 *         by ExtensionPriorityComparator.DESCENDING

	 */

	public ListIterator getOverridingExtensionsListIterator(boolean fromStart) {

		if (overridingExtensions == null)

			return Collections.EMPTY_LIST.listIterator();

		if (overridingExtensionsList == null)

			overridingExtensionsList = new ArrayList(overridingExtensions);

		return overridingExtensionsList.listIterator(fromStart ? 0 : overridingExtensionsList.size());

	}

	/*

	 * (non-Javadoc)

	 * 

	 * @see java.lang.Object#toString()

	 */

	public String toString() {

		return "Content[" + id  + "(" + sequenceNumber + ") " + ", \"" + name + "\"]"; //$NON-NLS-1$ //$NON-NLS-2$//$NON-NLS-3$ //$NON-NLS-4$ //$NON-NLS-5$

	}

	/* (non-Javadoc)

	 * @see java.lang.Object#hashCode()

	 */

	public int hashCode() {

		if (hashCode == HASH_CODE_NOT_COMPUTED) {

			String hashCodeString = configElement.getNamespaceIdentifier() + getId();

			hashCode = hashCodeString.hashCode();

			if (hashCode == HASH_CODE_NOT_COMPUTED)

				hashCode++;

		}

		return hashCode;

	}

	/**

	 * @return The descriptor of the <code>suppressedExtensionId</code> if

	 *         non-null.

	 */

	public INavigatorContentDescriptor getOverriddenDescriptor() {

		return overriddenDescriptor;

	}

	/**

	 * @param theOverriddenDescriptor

	 *            The overriddenDescriptor to set.

	 */

	/* package */void setOverriddenDescriptor(

			INavigatorContentDescriptor theOverriddenDescriptor) {

		overriddenDescriptor = theOverriddenDescriptor;

	}

	/* (non-Javadoc)

	 * @see org.eclipse.ui.navigator.INavigatorContentDescriptor#hasSaveablesProvider()

	 */

	public boolean hasSaveablesProvider() {

		return providesSaveables;

	}

}