package util;

// Java imports
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

// Wrapper around JComboBox<String> to enforce desired behaviors
public class UComboBox extends JComboBox<String> {

    // Instance fields
    private HashMap<ActionListener, ActionListener> actionListeners;



    ///////////////////////////////////////////////////////////////////////////
    //                               Constants                               //
    ///////////////////////////////////////////////////////////////////////////

    // Empty item set
    private static final String[] EMPTY = new String[0];



    ///////////////////////////////////////////////////////////////////////////
    //                             Constructors                              //
    ///////////////////////////////////////////////////////////////////////////

    // Default constructor
    public UComboBox() {
        this(null);
    }

    // List constructor
    public UComboBox(String[] items) {
        super();
        actionListeners = new HashMap<ActionListener, ActionListener>();
        setItems(items);
    }



    ///////////////////////////////////////////////////////////////////////////
    //                            Public Methods                             //
    ///////////////////////////////////////////////////////////////////////////

    // Add a listener to receive action events
    public void addActionListener(ActionListener l) {

        // Error checking
        if (l == null)
            return;

        // Wrap the event listener in a guard
        ActionListener L = e->{

            // Search the stack trace for an invocation not from Java itself
            var trace = Thread.currentThread().getStackTrace();
            for (int x = 2; x < trace.length; x++)
                if (trace[x].getModuleName() == null)
                    return;

            // Call the event handler
            l.actionPerformed(e);
        };

        // Manage the collections
        actionListeners.put(l, L);
        super.addActionListener(L);
    }

    // Retrieve a list of the current action listeners
    public ActionListener[] getActionListeners() {
        return actionListeners.keySet().toArray(
            new ActionListener[actionListeners.size()]);
    }

    // Remove an action listener from the collection
    public void removeActionListener(ActionListener l) {
        var L = actionListeners.get(l);
        if (L == null)
            return;
        actionListeners.remove(l);
        super.removeActionListener(L);
    }

    // Update the items in the list
    public void setItems(String[] items) {
        int index = getSelectedIndex();
        setModel(new DefaultComboBoxModel<String>(
            items != null ? items : EMPTY));
        setSelectedIndex(index);
    }

}