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package net.sf.cuf.model.ui;

import net.sf.cuf.model.ValueModel;

import javax.swing.ComboBoxModel;
import javax.swing.event.ChangeListener;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ListDataListener;
import javax.swing.event.ListDataEvent;


/**
 * A ComboBoxModelAdapter connects a model of a JComboBox to a ValueModel
 * holding an Integer with the index for the selected combobox item.
 * The ValueModel holding the Integer is often the selectionHolder()
 * of a SelectionInList ValueModel.
 * Whenever either the selection of the combobox or
 * the index of the ValueModel changes, the other model
 * is adjusted accordingly.
 * The "magic value" of -1 is used to signal no selection at all.
 * A ComboBoxModelAdapter is not a ValueModel itself, but connects a
 * ValueModel holding an integer to a ComboBoxModel.
 */
public class ComboBoxModelAdapter implements ListDataListener, ChangeListener
{
    /** the value model we are watching, never null */
    private ValueModel mSelectionHolder;
    /** the combobox model, never null */
    private ComboBoxModel       mComboBoxModel;
    /** marker if we are in an list data or state changed callback */
    private boolean             mInCallback;

    /** no item is selected */
    public static final Integer NO_SELECTION= -1;

    /**
     * Creates a new adapter between a ValueModel holding an Integer
     * and a list of ButtonModels
     * Whenever one of the models changes, the other is adjusted accordingly.
     * The initial selected buttonmodel is taken from the value model.
     *
     * @param pSelectionHolder ValueModel holding an Integer
     * @param pComboBoxModel a combobox model
     * @throws IllegalArgumentException if pSelectionHolder or pComboBoxModel is null
     */
    public ComboBoxModelAdapter(final ValueModel pSelectionHolder, final ComboBoxModel pComboBoxModel)
    {
        if (pSelectionHolder==null)
            throw new IllegalArgumentException("selection holder must not be null");
        if (pComboBoxModel==null)
            throw new IllegalArgumentException("combobox model must not be null");

        mSelectionHolder= pSelectionHolder;
        mComboBoxModel   = pComboBoxModel;
        mInCallback     = false;

        mSelectionHolder.addChangeListener(this);
        mComboBoxModel.addListDataListener(this);

        adjustCombobox();
    }

    public void intervalAdded(final ListDataEvent pEvent)
    {
        handleComboboxModelChange();
    }

    public void intervalRemoved(final ListDataEvent pEvent)
    {
        handleComboboxModelChange();
    }

    public void contentsChanged(final ListDataEvent pEvent)
    {
        handleComboboxModelChange();
    }

    /**
     * Common code of the combobox call back.
     */
    private void handleComboboxModelChange()
    {
        if (mInCallback)
        {
            return;
        }

        Object  selectedItem= mComboBoxModel.getSelectedItem();
        Integer index       = NO_SELECTION;
        if (selectedItem!=null)
        {
            for (int i= 0, n= mComboBoxModel.getSize(); i