EDIT

/**

* Copyright (C) 2018 EDIT

* European Distributed Institute of Taxonomy

* http://www.e-taxonomy.eu

*

* The contents of this file are subject to the Mozilla Public License Version 1.1

* See LICENSE.TXT at the top of this package for the full license terms.

*/

package eu.etaxonomy.vaadin.component;

import java.lang.reflect.Field;

import org.vaadin.viritin.fields.LazyComboBox;

import org.vaadin.viritin.fields.TypedSelect;

import com.vaadin.ui.AbstractField;

import com.vaadin.ui.AbstractSelect;

import com.vaadin.ui.ComboBox;

public class ReloadableLazyComboBox<T> extends LazyComboBox<T> implements ReloadableSelect, EntitySupport<T> {

    private static final long serialVersionUID = -4833661351090992884L;

//    boolean originalScrollToSelect;

    static Field lazySelectInternalValueField;

    static Field internalSelectField;

    static {

        try {

            lazySelectInternalValueField = AbstractField.class.getDeclaredField("value");

            lazySelectInternalValueField.setAccessible(true);

            lazySelectInternalValueField.setAccessible(true);

            internalSelectField = TypedSelect.class.getDeclaredField("select");

            internalSelectField.setAccessible(true);

        } catch (NoSuchFieldException | SecurityException e) {

            // NONE of these should ever happen, maybe only after dependency upgrades

            throw new RuntimeException(e);

        }

    }

    /**

     * @param itemType

     */

    public ReloadableLazyComboBox(Class<T> itemType) {

        super(itemType);

    }

    /**

     * {@inheritDoc}

     */

    @Override

    public void reload() {

        // in the LazyComboBox.initList() scrollToSelectedItem is set to false for better performance

        // but this breaks the refresh, so we need to set it now so that it can

        // affect the next component repaint which is triggered in refresh()

        ComboBox comboBox = (ComboBox)getSelect();

        comboBox.setScrollToSelectedItem(true);

        refresh(); // reload from persistence

        discard(); // reload from property data source

    }

    /**

     * This method allows updating the value even if the equals check done

     * in {@link com.vaadin.ui.AbstractField#setValue(Object)} would return true.

     * This is important when working with entity beans which have been modified.

     * For entity beans equality given when the type and id are equal, so data

     * modification is not respected by this concept of equality. Such entities

     * would be skipped in the {@link com.vaadin.ui.AbstractField#setValue(Object) setValue()}

     * method and {@link ValueChangeListener ValueChangeListeners} like the

     * {@link eu.etaxonomy.cdm.vaadin.event.ToOneRelatedEntityReloader ToOneRelatedEntityReloader}

     *  would not be triggered.

     *  <p>

     *  To circumvent this problem this method checks for object identity with the internal value of

     *  the select field and resets the internal select fields to cause the equality check to fail during

     *  the subsequent execution of the setValue() method. By this it is guaranteed the the value will be

     *  updated and that

     *  the {@link eu.etaxonomy.cdm.vaadin.event.ToOneRelatedEntityReloader ToOneRelatedEntityReloaders}

     *  will be triggered.

     *

     * @param bean

     */

    @Override

    public void replaceEntityValue(T bean){

        if(bean != internalValueByFieldAccess()){

            resetInternalValue();

        }

        setValue(bean);

    }

    /**

     *

     */

    private T internalValueByFieldAccess(){

        try {

            return (T) lazySelectInternalValueField.get(this);

        } catch (IllegalArgumentException | IllegalAccessException e) {

            // NONE of these should ever happen, maybe only after dependency upgrades

            throw new RuntimeException(e);

        }

    }

    /**

     * Directly sets the <b>internal value fields</b> of the nested <code>LazyComboBox</code> to <code>null</code>.

     *  <b>This method short circuits the setValue() method execution cascade completely</b>

     *  <p>

     *  See {@link #refreshSelectedValue(Object)} more more background information.

     */

    public void resetInternalValue() {

        try {

            AbstractSelect internalSelect = (AbstractSelect) internalSelectField.get(this);

            lazySelectInternalValueField.set(this, (Object)null);

            lazySelectInternalValueField.set(internalSelect, (Object)null);

        } catch (SecurityException | IllegalAccessException | IllegalArgumentException  e) {

            // NONE of these should ever happen, maybe only after dependency upgrades

            throw new RuntimeException(e);

        }

    }

}