// 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.nonpublic.external.*;

public abstract class AbstractDragger implements DragGesture {
    private XY mMouseStartDrag;
    private boolean mCancelled;

    @Override
    public void start( MouseEvent e ) {
        mCancelled = false;
        mMouseStartDrag = new XY( e.getWidgetX(), e.getWidgetY() );
        // StatusBar.set( "dragStart" + mMouseStartDrag );

        // matg: disabled due to poor performance w/ complex windows
//        mTarget.addStyleName( "Dragging" );
    }

    @Override
    public void step( DragEvent e ) {
        if ( !mCancelled ) {
            XY xy = new XY( e.getWidgetX(), e.getWidgetY() );
            XY delta = xy.minus( mMouseStartDrag );
            // StatusBar.set( "MouseMove" + xy + "-" + mMouseStartDrag + "=" + delta );
            if ( !dragBy( delta.getX(), delta.getY() ) ) {
                finish();
                mCancelled = true;
            }
        }
    }

    @Override
    public void finish() {
        // StatusBar.set( "dragStop" );
        if ( !mCancelled ) {
            mMouseStartDrag = null;

            // matg: disabled due to poor performance w/ complex windows
//            mTarget.removeStyleName( "Dragging" );
        }
    }

    /**
     * @return false to prevent additional dragging
     */
    protected abstract boolean dragBy( int pDeltaX, int pDeltaY );

    private static class XY {
        private int mX, mY;

        public XY( int pX, int pY ) {
            mX = pX;
            mY = pY;
        }

        public int getX() {
            return mX;
        }

        public int getY() {
            return mY;
        }

        @Override
        public String toString() {
            return "(" + mX + ", " + mY + ")";
        }

        public XY add( XY them ) {
            return new XY( this.mX + them.mX, this.mY + them.mY );
        }

        public XY minus( XY them ) {
            return new XY( this.mX - them.mX, this.mY - them.mY );
        }

        public XY addX( int pX ) {
            return new XY( this.mX + pX, this.mY );
        }

        public XY minusX( int pX ) {
            return new XY( this.mX - pX, this.mY );
        }

        public XY addY( int pY ) {
            return new XY( this.mX, this.mY + pY );
        }

        public XY minusY( int pY ) {
            return new XY( this.mX, this.mY - pY );
        }
    }
}