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

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

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

import java.util.*;

public abstract class AbstractSizeableSimplePanel extends AbstractSizeablePanel implements SizeableSingleWidgetContainer {
    private Widget mWidget;

    @Override
    public boolean anyChildren() {
        return (mWidget != null);
    }

    // vvvvvvvvvvv HasWidgets

    /**
     * Removes all child widgets.
     */
    @Override
    public void clear() {
        if ( anyChildren() ) {
            remove( mWidget );
        }
    }

    /**
     * Gets an iterator for the contained widgets. This iterator is required to
     * implement {@link Iterator#remove()}.
     */
    @Override
    public Iterator<Widget> iterator() {
        // Return a simple iterator that enumerates the 0 or 1 elements in this
        // panel.
        return new SingleWidgetIterator( mWidget ) {
            @Override
            public void remove() {
                clear();
            }
        };
    }

    /**
     * Adds a widget to this panel.
     *
     * @param pWidget the child widget to be added
     */
    @Override
    public void add( Widget pWidget ) {
        // Can't add() more than one widget to a SimplePanel.
        if ( getWidget() != null ) {
            throw new IllegalStateException( "SimplePanel can only contain one child widget" );
        }
        setWidget( pWidget );
    }

    /**
     * Removes a child widget.
     *
     * @param pWidget the widget to be removed
     *
     * @return <code>true</code> if the widget was present
     */
    @Override
    public boolean remove( Widget pWidget ) {
        if ( mWidget == pWidget ) {
            disown( pWidget );
            return true;
        }
        return false;
    }

    // ^^^^^^^^^^^ HasWidgets

    // vvvvvvvvvvv SingleWidgetContainer

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

    /**
     * Sets this panel's widget. Any existing child widget will be removed.
     */
    @Override
    public void setWidget( Widget pWidget ) {
        // If there is already a widget attached, remove it.
        if ( mWidget != null ) {
            disown( mWidget );
        }

        if ( pWidget != null ) {
            // Adopt the child.
            adopt( pWidget );
        }
    }

    // ^^^^^^^^^^^ SingleWidgetContainer

    @Override
    protected final Element adopt( Widget w, Element container ) {
        throw new IllegalStateException( "Inappropriate use of raw adopt( Widget w, Element container )" );
    }

    /**
     * Do everything to add pWidget
     *
     * @param pWidget !null
     */
    protected void adopt( Widget pWidget ) {
        if ( aboutToAdopt( pWidget ) ) {
            LLadopt( pWidget );
            justAdopted( pWidget );
        }
    }

    /**
     * Do everything to remove pWidget
     *
     * @param pWidget !null
     */
    @Override
    protected Element disown( Widget pWidget ) {
        if ( aboutToDisown( pWidget ) ) {
            LLdisown( pWidget );
            justDisowned( pWidget );
        }
        return null; // Don't care
    }

    protected void LLdisown( Widget pWidget ) {
        super.disown( pWidget ); // remove Widget from td
        mWidget = null;
    }

    protected void LLadopt( Widget pWidget ) {
        pWidget.removeFromParent();
        super.adopt( pWidget, getContainerElement() ); // put Widget in TD
        mWidget = pWidget;
    }

    /**
     * Override point for special behavior of addition, before adding.
     * Could throw an exception!
     *
     * @return true if OK to add
     */
    @SuppressWarnings({"UnusedDeclaration"})
    protected boolean aboutToAdopt( Widget pWidget ) {
        return true;
    }

    /**
     * Override point for special behavior of addition.
     * Should not throw an exception!
     */
    @SuppressWarnings({"UnusedDeclaration"})
    protected void justAdopted( Widget pWidget ) {
    }

    /**
     * Override point for special behavior of removal, before removing.
     * Could throw an exception!
     *
     * @return true if OK to add
     */
    @SuppressWarnings({"UnusedDeclaration"})
    protected boolean aboutToDisown( Widget pWidget ) {
        return true;
    }

    /**
     * Override point for special behavior of removal.
     * Should not throw an exception!
     */
    @SuppressWarnings({"UnusedDeclaration"})
    protected void justDisowned( Widget pWidget ) {
    }

    @Override
    public void setWidth( String width ) {
        super.setWidth( width ); // for stacktrace Debugging
    }

    @Override
    public void setHeight( String height ) {
        super.setHeight( height ); // for stacktrace Debugging
    }

    @Override
    protected void distributeToChildrenChangedWidth() {
        getHelper().applyChangedDimensionToChild( getWidget(), getWidthHelper() );
    }

    @Override
    protected void distributeToChildrenChangedHeight() {
        getHelper().applyChangedDimensionToChild( getWidget(), getHeightHelper() );
    }
}