package org.litesoft.GWT.client.widgets.range;

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

/**
 * Factory for Slider "Widgets".
 * <p>
 * If the platform (browser) supports HTML5's range input, then a Widget that utilizes that is returned.
 * If the platform is not "mobile" then (e.g. Firefox) then a mouse/JavaScript based Slider Widget is created.
 * Otherwise, null is returned to indicated that the "mobile" browser is too old, and probably the processor is too weak to support a JavaScript Slider.
 * </p>
 * Note: If null is returned, then the UI should be adjusted to be reasonable w/o a Slider!
 */
public abstract class SliderFactory {
    private static SliderFactory mFactory;

    public static synchronized SliderFactory getFactory() {
        return (mFactory != null) ? mFactory : (mFactory = createFactory());
    }

    /**
     * Return a Slider "Widget" if the current platform supports a Slider; with Min==0, Step==1, & Max==100 (useful for simple percentages).
     *
     * @return A Slider "Widget" or null if Sliders are not supported.
     */
    public final Slider createSlider() {
        return createSlider( 100 );
    }

    /**
     * Return a Slider "Widget" if the current platform supports a Slider; with Min==0, & Step==1.
     *
     * @param pMax Maximum value of the range.
     *
     * @return A Slider "Widget" or null if Sliders are not supported.
     */
    public final Slider createSlider( int pMax ) {
        return createSlider( 0, 1, pMax );
    }

    /**
     * Return a Slider "Widget" if the current platform supports a Slider.
     *
     * @param pMin  Minimum value of the range.
     * @param pStep This is Step scale factor of the slider.
     * @param pMax  Maximum value of the range.
     *
     * @return A Slider "Widget" or null if Sliders are not supported.
     */
    abstract public Slider createSlider( int pMin, int pStep, int pMax );

    private static SliderFactory createFactory() {
        if ( inputRangeSupported() ) {
            return new SliderFactory() {
                @Override
                public Slider createSlider( int pMin, int pStep, int pMax ) {
                    return new SliderHTML5InputRange( pMin, pStep, pMax );
                }
            };
        }
        if ( DeviceType.Desktop == UserAgent.getInstance().getDeviceType() ) {
            return new SliderFactory() {
                @Override
                public Slider createSlider( int pMin, int pStep, int pMax ) {
                    return new SliderEmulated( pMin, pStep, pMax );
                }
            };
        }
        return new SliderFactory() {
            @Override
            public Slider createSlider( int pMin, int pStep, int pMax ) {
                return null;
            }
        };
    }

    /**
     * Check if browser supports the <input type='range'/>
     * <p/>
     * Pulled directly from "Dive into HTML5".
     */
    private static native boolean inputRangeSupported() /*-{
        var e = document.createElement( "input" );
        e.setAttribute( "type", "range" );
        return e.type !== "text";
    }-*/;
}