/*******************************************************************************
 * Copyright (c) 2000, 2005 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.ide.registry;

import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.ui.WorkbenchException;
import org.eclipse.ui.internal.ide.Category;
import org.eclipse.ui.internal.ide.IDEWorkbenchPlugin;

/**
 * This class is used to read project capabilities and capability
 * categories from the platform's plugin registry and store the results in
 * a capability registry.
 */
public class CapabilityRegistryReader extends IDERegistryReader {
    private static final String TAG_CAPABILITY = "capability"; //$NON-NLS-1$

    private static final String TAG_CATEGORY = "category"; //$NON-NLS-1$

    private static final String TAG_HANDLE_UI = "handleUI"; //$NON-NLS-1$

    private static final String TAG_PERSPECTIVE_CHOICE = "perspectiveChoice"; //$NON-NLS-1$

    private static final String ATT_ID = "id"; //$NON-NLS-1$

    private CapabilityRegistry capabilityRegistry;

    private Capability currentCapability;

    /**
     * Reads an element of the plugin registry and adds it to the capability
     * registry if it is a capability or category (or a handleUI element, a
     * child of a capability. A handleUI element represents another capability
     * for which this capability controls the user interface).
     */
    protected boolean readElement(IConfigurationElement element) {
        String name = element.getName();
        if (name.equals(TAG_CAPABILITY))
            return readCapability(element);
        if (name.equals(TAG_CATEGORY))
            return readCategory(element);
        if (name.equals(TAG_HANDLE_UI))
            return readHandleUI(element);
        if (name.equals(TAG_PERSPECTIVE_CHOICE))
            return readPerspectiveChoice(element);
        return false;
    }

    /**
     * Reads a capability and adds it to the capability registry. Reads all
     * children elements (which will be handleUI elements) as well and adds
     * them to the capability.
     */
    private boolean readCapability(IConfigurationElement element) {
        try {
            Capability capability = new Capability(element, this);
            capabilityRegistry.addCapability(capability);
            currentCapability = capability;
            readElementChildren(element);
            currentCapability = null;
            return true;
        } catch (WorkbenchException e) {
            currentCapability = null;
            return false;
        }
    }

    /**
     * Reads a capability category and adds it to the capability registry.
     */
    private boolean readCategory(IConfigurationElement element) {
        try {
            Category category = new Category(element);
            capabilityRegistry.addCategory(category);
        } catch (WorkbenchException e) {
            // log an error since its not safe to show a dialog here
            IDEWorkbenchPlugin.log(
                    "Unable to create capability category. ", e.getStatus()); //$NON-NLS-1$
        }
        return true;
    }

    /**
     * Reads handleUI elements. These elements contain the ids of other
     * capabilities. The capability that is the parent of the handleUI element
     * controls the user interface for the capabilities whose ids are stored
     * in the handleUI element.
     */
    private boolean readHandleUI(IConfigurationElement element) {
        String capabilityId = element.getAttribute(ATT_ID);

        if (capabilityId == null) {
            logMissingAttribute(element, ATT_ID);
        }

        if (currentCapability != null)
            currentCapability.addHandleUI(capabilityId);
        return true;
    }

    /**
     * Reads perspectiveChoice elements. These elements contain the ids of
     * perspectives.
     */
    private boolean readPerspectiveChoice(IConfigurationElement element) {
        String perspId = element.getAttribute(ATT_ID);

        if (perspId == null) {
            logMissingAttribute(element, ATT_ID);
        }

        if (currentCapability != null)
            currentCapability.addPerspectiveChoice(perspId);
        return true;
    }

    /**
     * Reads project capabilities and capability categories from the provided
     * plugin registry and stores them in the provided capability registry.
     */
    public void read(IExtensionRegistry registry, CapabilityRegistry out) {
        capabilityRegistry = out;
        readRegistry(registry, IDEWorkbenchPlugin.IDE_WORKBENCH,
                IDEWorkbenchPlugin.PL_CAPABILITIES);
    }
}