package com.onaro.util.jfc;

import java.awt.Dimension;

import javax.swing.ComboBoxModel;
import javax.swing.JList;
import javax.swing.event.ListDataEvent;

import com.onaro.commons.swing.OnaroSwingUtilities;

public class OnaroDynamicComboBox<T> extends OnaroComboBox<T> {
    private static final long serialVersionUID = 1L;
    
    /*
     * Extra padding necessary to account for drop-down list box decoration
     * that increases its width beyond that of the text it contains.
     * Unfortunately, its hard to determine a platform-independent value.
     * But it's OK to err on the high side.
     */
    private static int PADDING = 6;
    
    /*
     * List used only to determine width of items in the drop-down list box.
     * Would like to use JComboBox.popupList, but unfortunately it's
     * private and doesn't have an accessor.
     */
    private JList<T> dropDownList;

    /**
     * Create a combo box containing the given items. The box will be
     * as wide as the widest given item string. Its size will not vary.
     * <p>
     * The drop-down list will initially be the same width as the box.
     * It will be made wider if wider items are added. It will not narrow.
     * 
     * @param items Objects selected in drop-down list
     */
    @SafeVarargs
    public OnaroDynamicComboBox (T... items) {
        super (items);
        dropDownList = new JList<T> (items);
    }

    /**
     * Create a combo box containing the given items. The box will be as
     * wide as the widest given item string up to the specified maximum width.
     * Its size will not vary. The drop-down list will initially be as wide as
     * necessary to show all the given item strings.
     * <p>
     * The drop-down list will initially be the same width as the box.
     * It will be made wider if wider items are added. It will not narrow.
     * <p>
     * If {@link #setPreferredSize} or  {@link #setPreferredSize} is invoked
     * before the box is rendered, then the arguments passed to those methods
     * will determine the box and initial list size.
     * 
     * @param maxBoxWidth Maximum allowed width of the box
     * @param items Objects selected in drop-down list
     */
    @SafeVarargs
    public OnaroDynamicComboBox (int maxBoxWidth, T... items) {
        super (maxBoxWidth, items);
        dropDownList = new JList<T> (items);
    }

    @Override
    public void setModel (ComboBoxModel<T> model) {
        super.setModel (model);
        dropDownList = new JList<T> (model);
    }
    
    @Override
    public void intervalAdded (ListDataEvent event) {
        ComboBoxModel<T> model = getModel();
        if (model != null) {
            adjustWidth (event, model);
        }
        super.intervalAdded (event);
    }
    
    private void adjustWidth (final ListDataEvent event, final ComboBoxModel<T> model) {
     
        // Get bounds of interval. Note bounds are inclusive.
        int first = event.getIndex0();
        if (first < 0) {
            first = 0;
        }
        int last = event.getIndex1();
        if (last < 0 || last >= model.getSize()) {
            last = model.getSize() - 1;
        }
        
        // Get current metrics.
        Dimension size = getSize();
        int listWidth = size.width;
        
        // Determine new size.
        for (int i = first; i <= last; i++) {
            T item = model.getElementAt (i);
            // Allow room to display item with selection and focus.
            int itemWidth = getRenderer()
                .getListCellRendererComponent (dropDownList, item, i, false, false)
                .getPreferredSize().width + PADDING;
            if (i >= getMaximumRowCount()) {
                if (i == getMaximumRowCount()) {
                    // Increase list width to allow for the scroll bar that will be added.
                    listWidth += OnaroSwingUtilities.getDefaultScrollBarWidth();
                }
                // Increase item width to allow for the scroll bar.
                itemWidth += OnaroSwingUtilities.getDefaultScrollBarWidth(); 
            }
            listWidth = Math.max (listWidth, itemWidth);
        }
        
        // Adjust size.
        if (listWidth != size.width) {
            size.width = listWidth;
            setSize (size);
        }
    }
}