/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * 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:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.modeling.ui.modelBrowser.handlers;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.handlers.HandlerUtil;
import org.simantics.Simantics;
import org.simantics.databoard.Bindings;
import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.common.request.ResourceRead;
import org.simantics.db.common.utils.Logger;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.layer0.variable.Variable;
import org.simantics.modeling.ModelingResources;
import org.simantics.modeling.PropertyVariables;
import org.simantics.ui.selection.WorkbenchSelectionUtils;
import org.simantics.utils.ui.AdaptionUtils;

public class ContextualHelp extends AbstractHandler {

    private static String getPossibleId(ExecutionEvent event) {
        String id = null;
        try {
            Resource element = WorkbenchSelectionUtils.getPossibleResource(event);
            id = Simantics.getSession().syncRequest(new ResourceRead<String>(element) {

                @Override
                public String perform(ReadGraph graph) throws DatabaseException {
                    ModelingResources MOD = ModelingResources.getInstance(graph);
                    Resource component = graph.getPossibleObject(element, MOD.ElementToComponent);
                    if (component != null)
                        return graph.getPossibleRelatedValue2(component, MOD.contextualHelpId, Bindings.STRING);

                    Variable var = WorkbenchSelectionUtils.getPossibleVariable(event);
                    if (var != null)
                        return var.getPossiblePropertyValue(graph, MOD.contextualHelpId, Bindings.STRING);

                    ISelection sel = HandlerUtil.getCurrentSelection(event);
                    if (sel != null) {
                        PropertyVariables vars = AdaptionUtils.adaptToSingle(sel, PropertyVariables.class);
                        if (vars != null) {
                            var = vars.getConfiguration();
                            if (var != null)
                                var.getPossiblePropertyValue(graph, MOD.contextualHelpId, Bindings.STRING);
                        }
                    }
                    return null;
                }
            });
        } catch (DatabaseException e) {
            Logger.defaultLogError(e);
        }
        return id;
    }

    @Override
    public Object execute(ExecutionEvent event) throws ExecutionException {

        String id = getPossibleId(event);
        if (id != null)
            PlatformUI.getWorkbench().getHelpSystem().displayHelp(id);

        return null;

    }

}