/*******************************************************************************
 * 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.ui.contribution;

import org.eclipse.jface.action.ActionContributionItem;
import org.eclipse.jface.action.IAction;
import org.eclipse.jface.action.IContributionItem;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.ui.ISelectionService;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.actions.CompoundContributionItem;
import org.simantics.DatabaseJob;
import org.simantics.Simantics;
import org.simantics.db.ReadGraph;
import org.simantics.db.common.request.UniqueRead;
import org.simantics.db.common.utils.RequestUtil;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.management.ISessionContext;
import org.simantics.ui.SimanticsUI;
import org.simantics.utils.ui.ErrorLogger;

/**
 * A more or less carbon copy of CompoundContributionItem with the exception of
 * adding Simantics Graph database traits to the menu filling process.
 * 
 * <p>
 * The simplest way to use this class is to override the
 * {@link #getActions(ReadGraph, Object[])} method which should return any
 * actions that you want to be performed on the specified selection. Another way
 * is to override {@link #getContributionItems(ReadGraph, Object[])} that by
 * default simply invokes the simplest method
 * {@link #getActions(ReadGraph, Object[])}. Overriding it allows you to create
 * e.g. submenus, which you cannot do with actions.
 * </p>
 * 
 * <p>
 * To customize what gets passed to either
 * {@link #getActions(ReadGraph, Object[])} or
 * {@link #getContributionItems(ReadGraph, Object[])} as the selection
 * parameter, override {@link #getSelectedObjects()}
 * </p>
 * 
 * @author Tuukka Lehtonen
 */
public abstract class DynamicMenuContribution extends CompoundContributionItem {

    protected static final Object[] NO_OBJECTS = {};
    protected static final IAction[] NO_ACTIONS = {};
    protected static final IContributionItem[] NONE = {};

    /**
     * Creates a contribution item with a <code>null</code> id.
     */
    protected DynamicMenuContribution() {
        super();
    }

    /**
     * Creates a contribution item with the given (optional) id.
     *
     * @param id the contribution item identifier, or <code>null</code>
     */
    protected DynamicMenuContribution(String id) {
        super(id);
    }

    /* (non-Javadoc)
     * @see org.eclipse.ui.actions.CompoundContributionItem#getContributionItems()
     */
    @Override
    protected final IContributionItem[] getContributionItems() {
        if (DatabaseJob.inProgress())
            return NONE;
        ISessionContext ctx = Simantics.getSessionContext();
        if (ctx != null) {
            final Object[] selection = getSelectedObjects();
            //System.out.println(getClass().getSimpleName() + "@" + System.identityHashCode(this) + "( " + System.identityHashCode(selection) + ": " + Arrays.toString(selection) + " )");
            if (!preAcceptSelection(selection))
                return NONE;
            try {
                return RequestUtil.trySyncRequest(
                        Simantics.getSession(),
                        SimanticsUI.UI_THREAD_REQUEST_START_TIMEOUT,
                        SimanticsUI.UI_THREAD_REQUEST_EXECUTION_TIMEOUT_LONG,
                        NONE,
                        new UniqueRead<IContributionItem[]>() {
                    @Override
                    public IContributionItem[] perform(ReadGraph graph) throws DatabaseException {
                        return getContributionItems(graph, selection);
                    }
                    @Override
                    public String toString() {
                        return DynamicMenuContribution.this.toString();
                    }
                });
            } catch (DatabaseException | InterruptedException e) {
                ErrorLogger.defaultLogError(e);
            }
        }
        return NONE;
    }

    /* (non-Javadoc)
     * @see org.eclipse.ui.actions.CompoundContributionItem#isDynamic()
     */
    @Override
    public boolean isDynamic() {
        return true;
    }

    //////////////////////////////////////////////////////////////////////////

    protected ISelection getSelection() {
        IWorkbenchWindow window = PlatformUI.getWorkbench().getActiveWorkbenchWindow();
        ISelectionService service = window.getSelectionService();
        return service.getSelection();
    }

    protected Object[] getSelectedObjects() {
        ISelection sel = getSelection();
        if (!(sel instanceof IStructuredSelection))
            return NO_OBJECTS;
        return ((IStructuredSelection) sel).toArray();
    }

    protected Object getSingleSelectedObject() {
        Object[] resources = getSelectedObjects();
        return resources.length == 1 ? resources[0] : null;
    }

    protected IContributionItem[] toContributionItems(IAction... actions) {
        if (actions == null)
            return NONE;

        IContributionItem[] ret = new IContributionItem[actions.length];
        for (int i = 0; i < actions.length; ++i)
            ret[i] = new ActionContributionItem(actions[i]);

        return ret;
    }

    //////////////////////////////////////////////////////////////////////////
    // Override these where needed

    /**
     * Tests the input selection for whether it can produce any meaningful
     * contribution items in the first place. This is a filter that is invoked
     * before performing a database request to find out more about the possible
     * contributions.
     * 
     * <p>
     * The default implementation checks that the input selection is not empty.
     * To be able to provide contributions for empty selection, you must
     * override this method.
     * 
     * @param selection
     * @return
     */
    protected boolean preAcceptSelection(Object[] selection) {
        return selection != null && selection.length > 0;
    }

    protected IContributionItem[] getContributionItems(ReadGraph graph, Object[] selection) throws DatabaseException {
        return toContributionItems( getActions(graph, selection) );
    }

    protected IAction[] getActions(ReadGraph graph, Object[] selection) throws DatabaseException {
        return new IAction[0];
    }

}