package com.ganteater.ae.desktop.ui;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;

import javax.swing.JLabel;
import javax.swing.border.EmptyBorder;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.Document;
import javax.swing.text.JTextComponent;

/**
 *  The TextPrompt class will display a prompt over top of a text component when
 *  the Document of the text field is empty. The Show property is used to
 *  determine the visibility of the prompt.
 *
 *  The Font and foreground Color of the prompt will default to those properties
 *  of the parent text component. You are free to change the properties after
 *  class construction.
 */
public class TextPrompt extends JLabel
        implements FocusListener, DocumentListener
{
        public enum Show
        {
                ALWAYS,
                FOCUS_GAINED,
                FOCUS_LOST;
        }

        private JTextComponent component;
        private Document document;

        private Show show;
        private boolean showPromptOnce;
        private int focusLost;

        public TextPrompt(String text, JTextComponent component)
        {
                this(text, component, Show.ALWAYS);
        }

        public TextPrompt(String text, JTextComponent component, Show show)
        {
                this.component = component;
                setShow( show );
                document = component.getDocument();

                setText( text );
                setForeground( component.getForeground().brighter().brighter() );
                setFont( component.getFont() );
                setBorder( new EmptyBorder(component.getInsets()) );
                setHorizontalAlignment(JLabel.LEADING);

                component.addFocusListener( this );
                document.addDocumentListener( this );

                component.setLayout( new BorderLayout() );
                component.add( this );
                checkForPrompt();
        }

        /**
         *  Convenience method to change the alpha value of the current foreground
         *  Color to the specifice value.
         *
         *  @param alpha value in the range of 0 - 1.0.
         */
        public void changeAlpha(float alpha)
        {
                changeAlpha( (int)(alpha * 255) );
        }

        /**
         *  Convenience method to change the alpha value of the current foreground
         *  Color to the specifice value.
         *
         *  @param alpha value in the range of 0 - 255.
         */
        public void changeAlpha(int alpha)
        {
                alpha = alpha > 255 ? 255 : alpha < 0 ? 0 : alpha;

                Color foreground = getForeground();
                int red = foreground.getRed();
                int green = foreground.getGreen();
                int blue = foreground.getBlue();

                Color withAlpha = new Color(red, green, blue, alpha);
                super.setForeground( withAlpha );
        }

        /**
         *  Convenience method to change the style of the current Font. The style
         *  values are found in the Font class. Common values might be:
         *  Font.BOLD, Font.ITALIC and Font.BOLD + Font.ITALIC.
         *
         *  @param style value representing the the new style of the Font.
         */
        public void changeStyle(int style)
        {
                setFont( getFont().deriveFont( style ) );
        }

        /**
         *  Get the Show property
         *
         *  @return the Show property.
         */
        public Show getShow()
        {
                return show;
        }

        /**
         *  Set the prompt Show property to control when the promt is shown.
         *  Valid values are:
         *
         *  Show.AWLAYS (default) - always show the prompt
         *  Show.Focus_GAINED - show the prompt when the component gains focus
         *      (and hide the prompt when focus is lost)
         *  Show.Focus_LOST - show the prompt when the component loses focus
         *      (and hide the prompt when focus is gained)
         *
         *  @param show a valid Show enum
         */
        public void setShow(Show show)
        {
                this.show = show;
        }

        /**
         *  Get the showPromptOnce property
         *
         *  @return the showPromptOnce property.
         */
        public boolean getShowPromptOnce()
        {
                return showPromptOnce;
        }

        /**
         *  Show the prompt once. Once the component has gained/lost focus
         *  once, the prompt will not be shown again.
         *
         *  @param showPromptOnce  when true the prompt will only be shown once,
         *                         otherwise it will be shown repeatedly.
         */
        public void setShowPromptOnce(boolean showPromptOnce)
        {
                this.showPromptOnce = showPromptOnce;
        }

        /**
         *      Check whether the prompt should be visible or not. The visibility
         *  will change on updates to the Document and on focus changes.
         */
        private void checkForPrompt()
        {
                //  Text has been entered, remove the prompt

                if (document.getLength() > 0)
                {
                        setVisible( false );
                        return;
                }

                //  Prompt has already been shown once, remove it

                if (showPromptOnce && focusLost > 0)
                {
                        setVisible(false);
                        return;
                }

                //  Check the Show property and component focus to determine if the
                //  prompt should be displayed.

        if (component.hasFocus())
        {
                if (show == Show.ALWAYS
                ||  show ==     Show.FOCUS_GAINED)
                        setVisible( true );
                else
                        setVisible( false );
        }
        else
        {
                if (show == Show.ALWAYS
                ||  show ==     Show.FOCUS_LOST)
                        setVisible( true );
                else
                        setVisible( false );
        }
        }

//  Implement FocusListener

        public void focusGained(FocusEvent e)
        {
                checkForPrompt();
        }

        public void focusLost(FocusEvent e)
        {
                focusLost++;
                checkForPrompt();
        }

//  Implement DocumentListener

        public void insertUpdate(DocumentEvent e)
        {
                checkForPrompt();
        }

        public void removeUpdate(DocumentEvent e)
        {
                checkForPrompt();
        }

        public void changedUpdate(DocumentEvent e) {}
}