/*******************************************************************************
 * 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
 *******************************************************************************/
/*
 * 23.8.2006
 */
package org.simantics.utils.ui.jface;

import org.eclipse.core.runtime.ListenerList;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.ISelectionChangedListener;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.jface.viewers.SelectionChangedEvent;
import org.eclipse.jface.viewers.StructuredSelection;

/**
 * BaseSelectionProvider is a base implementation ISelectionProvider -interface.
 * <p>
 * Usage: 1) instantiate 2) call {@link #setAndFireSelection(ISelection)} to
 * send a selection event
 * 
 * <p>
 * Contains an empty StructuredSelection by default.
 * {@link #setSelection(ISelection)} by default will not notify
 * {@link ISelectionChangedListener}s of changes in the selection.
 * </p>
 * 
 * @author Toni Kalajainen
 * 
 * @see ActiveSelectionProvider
 */
public class BaseSelectionProvider implements ISelectionProvider {

    protected ListenerList selectionListeners = new ListenerList();

    protected ISelection selection = StructuredSelection.EMPTY;

    /**
     * Create new BaseSelectionProvider. Selection change notifications will run
     * synchronously in the thread that invoked
     * {@link ISelectionProvider#setSelection(ISelection)}.
     */
    public BaseSelectionProvider() {
    }

    public void addSelectionChangedListener(ISelectionChangedListener listener) {
        selectionListeners.add(listener);
    }

    public ISelection getSelection() {
        return selection;
    }

    public void removeSelectionChangedListener(ISelectionChangedListener listener) {
        selectionListeners.remove(listener);
    }

    public void setSelection(ISelection selection) {
        setSelectionWithoutFiring(selection);
    }

    protected Object[] getListeners() {
        return selectionListeners.getListeners();
    }

    /**
     * Notify other UIs that selection has changed
     * @param selection new selection
     */
    public void fireSelection(ISelection selection) {
        if (selection == null)
            return;
        SelectionChangedEvent e = new SelectionChangedEvent(BaseSelectionProvider.this, selection);
        for (Object l : getListeners())
            ((ISelectionChangedListener) l).selectionChanged(e);
    }

    public void setSelectionWithoutFiring(ISelection selection) {
        this.selection = selection;
    }


    /**
     * Sets a new selection and always fires a SelectionChangedEvent about it.
     * 
     * @param selection the new selection
     */
    public void setAndFireSelection(ISelection selection) {
        setSelection(selection);
        fireSelection(selection);
    }

    /**
     * Sets the new selection for this provider and fires all selection change
     * listeners if the specified selection differs from the current selection.
     * If the selection is either the same object or considered equal to the
     * current selection, the listeners are not fired.
     * 
     * @param selection the new selection
     */
    public void setAndFireNonEqualSelection(ISelection selection) {
        ISelection old = getSelection();
        if (selection == old)
            return;

        this.selection = selection;
        if (selection != null && !selection.equals(old))
            fireSelection(selection);
    }

    public boolean selectionEquals(ISelection s) {
        if (s == selection)
            return true;
        if (s == null)
            // Old selection had to be non-null
            return true;
        return s.equals(selection);
    }

}