// This Source Code is in the Public Domain per: http://unlicense.org
package org.litesoft.GWT.client.widgets;

import java.util.*;

import org.litesoft.GWT.client.widgets.nonpublic.*;

import com.google.gwt.user.client.ui.*;

public class SizeableScrollPanel extends AbstractSizeableComposite implements SourcesScrollEvents,
                                                                              ScrollListener,
                                                                              SizeableSingleWidgetContainer
{
    private ScrollListenerCollection scrollListeners;

    protected ScrollPanel mScrollPanel = new ScrollPanel();

    /**
     * Creates an empty SizeableScrollPanel.
     */
    public SizeableScrollPanel()
    {
        mScrollPanel.setWidth( "200" );
        mScrollPanel.setHeight( "160" );
        initWidget( new ConstrainingSizeableOuterLayers( mScrollPanel, "LayoutSizeableScrollPanel" ) );

        CommonElementHelper.setOverflowAuto( mScrollPanel.getElement() ); // remove their overlow
        mScrollPanel.addStyleName( AbstractSizeableHelper.LAYOUT_OVERFLOW_AUTO ); // add our overflow!

        LLstretchable();
    }

    /**
     * Creates a new SizeableScrollPanel with the given child widget.
     *
     * @param child the widget to be wrapped by the scroll panel
     */
    public SizeableScrollPanel( Widget child )
    {
        this();
        mScrollPanel.setWidget( child );
    }

    public SizeableScrollPanel style( String pStyleName )
    {
        addStyleName( pStyleName );
        return this;
    }

    @Override
    public void onScroll( Widget widget, int scrollLeft, int scrollTop )
    {
        if ( scrollListeners != null )
        {
            scrollListeners.fireScroll( this, scrollLeft, scrollTop );
        }
    }

    @Override
    public void addScrollListener( ScrollListener listener )
    {
        if ( scrollListeners == null )
        {
            scrollListeners = new ScrollListenerCollection();
            mScrollPanel.addScrollListener( this );
        }
        //noinspection unchecked
        scrollListeners.add( listener );
    }

    /**
     * Ensures that the specified item is visible, by adjusting the panel's scroll position.
     *
     * @param item the item whose visibility is to be ensured
     */
    public void ensureVisible( UIObject item )
    {
        mScrollPanel.ensureVisible( item );
    }

    /**
     * Gets the horizontal scroll position.
     *
     * @return the horizontal scroll position, in pixels
     */
    public int getHorizontalScrollPosition()
    {
        return mScrollPanel.getHorizontalScrollPosition();
    }

    /**
     * Gets the vertical scroll position.
     *
     * @return the vertical scroll position, in pixels
     */
    public int getScrollPosition()
    {
        return mScrollPanel.getScrollPosition();
    }

    @Override
    public void removeScrollListener( ScrollListener listener )
    {
        if ( scrollListeners != null )
        {
            scrollListeners.remove( listener );
            if ( scrollListeners.isEmpty() )
            {
                scrollListeners = null;
                mScrollPanel.removeScrollListener( this );
            }
        }
    }

    /**
     * Sets the horizontal scroll position.
     *
     * @param position the new horizontal scroll position, in pixels
     */
    public void setHorizontalScrollPosition( int position )
    {
        mScrollPanel.setHorizontalScrollPosition( position );
    }

    /**
     * Sets the vertical scroll position.
     *
     * @param position the new vertical scroll position, in pixels
     */
    public void setScrollPosition( int position )
    {
        mScrollPanel.setScrollPosition( position );
    }

    /**
     * Adds a widget to this panel.
     *
     * @param w the child widget to be added
     */
    @Override
    public void add( Widget w )
    {
        mScrollPanel.add( w );
    }

    /**
     * Gets the panel's child widget.
     *
     * @return the child widget, or <code>null</code> if none is present
     */
    @Override
    public Widget getWidget()
    {
        return mScrollPanel.getWidget();
    }

    @Override
    public Iterator<Widget> iterator()
    {
        return mScrollPanel.iterator();
    }

    @Override
    public boolean remove( Widget w )
    {
        return mScrollPanel.remove( w );
    }

    /**
     * Sets this panel's widget. Any existing child widget will be removed.
     *
     * @param pWidget
     */
    @Override
    public void setWidget( Widget pWidget )
    {
        mScrollPanel.setWidget( pWidget );
    }

    @Override
    public void clear()
    {
        mScrollPanel.clear();
    }
}