/*******************************************************************************
 * Copyright (c) 2004 Stefan Zeiger and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.novocode.com/legal/epl-v10.html
 * 
 * Contributors:
 *     Stefan Zeiger (szeiger@novocode.com) - initial API and implementation
 *     IBM Corporation - original SWT CLabel implementation on which this class is based
 *******************************************************************************/

package com.novocode.naf.swt.custom;

import org.eclipse.swt.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.events.*;


/**
 * A hyperlink text label.
 * <p>
 * This control displays a line of text (with an optional underline) which can
 * be clicked to send a Selection event. Colors for the text and underline in
 * their normal, mouse hover and active state can be set independently. The text
 * can contain a mnemonic character for triggering the link via keyboard. Unless
 * the control is created with the NO_FOCUS style, it accepts keyboard focus and
 * can be triggered with RETURN and SPACE while focused.
 * </p><p>
 * Note: This control should not be resized beyond its minimum / preferred size.
 * </p><p>
 * <dl>
 * <dt><b>Styles:</b></dt>
 * <dd>NO_FOCUS</dd>
 * <dt><b>Events:</b></dt>
 * <dd>Selection</dd>
 * </dl>
 * </p>
 * 
 * @author Stefan Zeiger (szeiger@novocode.com)
 * @since Mar 2, 2004
 * @version $Id: Hyperlink.java,v 1.6 2005/06/04 19:21:45 szeiger Exp $
 */

public final class Hyperlink extends Canvas
{
  private String text = "";
  private Cursor handCursor, arrowCursor;
  private Color normalForeground, activeForeground, hoverForeground;
  private Color normalUnderline, activeUndeline, hoverUnderline;
  private boolean isActive;
  private boolean cursorInControl;
  private Rectangle cachedClientArea;
  private Listener shellListener;
  private Shell shell;
  private int mnemonic = -1;


  /**
   * Constructs a new instance of this class given its parent
   * and a style value describing its behavior and appearance.
   * <p>
   * The style value is either one of the style constants defined in
   * class <code>SWT</code> which is applicable to instances of this
   * class, or must be built by <em>bitwise OR</em>'ing together 
   * (that is, using the <code>int</code> "|" operator) two or more
   * of those <code>SWT</code> style constants. The class description
   * lists the style constants that are applicable to the class.
   * Style bits are also inherited from superclasses.
   * </p>
   *
   * @param parent a widget which will be the parent of the new instance (cannot be null)
   * @param style the style of widget to construct
   *
   * @exception IllegalArgumentException <ul>
   *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
   * </ul>
   * @exception SWTException <ul>
   *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
   * </ul>
   */

  public Hyperlink(Composite parent, int style)
  {
    super(parent, checkStyle(style));

    handCursor = new Cursor(getDisplay(), SWT.CURSOR_HAND);
    arrowCursor = new Cursor(getDisplay(), SWT.CURSOR_ARROW);
    setCursor(handCursor);
    
    normalForeground = getDisplay().getSystemColor(SWT.COLOR_BLUE);
    hoverForeground  = normalForeground;
    activeForeground = getDisplay().getSystemColor(SWT.COLOR_RED);

    normalUnderline  = null;
    hoverUnderline   = normalForeground;
    activeUndeline   = activeForeground;
    
    super.setForeground(normalForeground);

    addPaintListener(new PaintListener()
    {
      public void paintControl(PaintEvent event)
      {
        onPaint(event);
      }
    });

    addDisposeListener(new DisposeListener()
    {
      public void widgetDisposed(DisposeEvent e)
      {
        if(handCursor != null)
        {
          handCursor.dispose();
          handCursor = null;
        }
        if(arrowCursor != null)
        {
          arrowCursor.dispose();
          arrowCursor = null;
        }
        if(shellListener != null)
        {
          shell.removeListener(SWT.Activate, shellListener);
          shell.removeListener(SWT.Deactivate, shellListener);
          shellListener = null;
        }
        text = null;
      }
    });
    
    addListener(SWT.MouseDown, new Listener()
    {
      public void handleEvent(Event event)
      {
        isActive = true;
        cursorInControl = true;
        redraw();
      }
    });

    addListener(SWT.MouseUp, new Listener()
    {
      public void handleEvent(Event event)
      {
        isActive = false;
        redraw();
        if(cursorInControl) linkActivated();
      }
    });

    addListener(SWT.Resize, new Listener()
    {
      public void handleEvent(Event event)
      {
        cachedClientArea = getClientArea();
      }
    });

    Listener mouseListener = new Listener()
    {
      public void handleEvent(Event event)
      {
        boolean newCursorInControl = isInClientArea(event);
        if(cursorInControl != newCursorInControl)
        {
          cursorInControl = newCursorInControl;
          if(cursorInControl) setCursor(handCursor);
          else if(isActive) setCursor(arrowCursor);
          if(isActive || (normalForeground != hoverForeground) || (normalUnderline != hoverUnderline)) redraw();
        }
      }
    };
    addListener(SWT.MouseMove, mouseListener);
    addListener(SWT.MouseEnter, mouseListener);
    addListener(SWT.MouseExit, mouseListener);
    
    cachedClientArea = getClientArea();

    if((style & SWT.NO_FOCUS) == 0) // Take focus
    {
      addListener(SWT.KeyDown, new Listener()
      {
        public void handleEvent(Event event)
        {
          if(event.character == ' ') linkActivated();
        }
      });

      addListener(SWT.Traverse, new Listener()
      {
        public void handleEvent(Event event)
        {
          if(event.detail == SWT.TRAVERSE_RETURN)
          {
            linkActivated();
            event.doit = false;
          }
          else if(event.detail == SWT.TRAVERSE_MNEMONIC)
          {
            if(mnemonic != -1 && Character.toLowerCase(event.character) == mnemonic)
            {
              setFocus();
              linkActivated();
              event.doit = false;
            }
            else event.doit = true;
          }
          else event.doit = true; // Accept all other traversal keys
        }
      });

      addListener(SWT.FocusIn, new Listener()
      {
        public void handleEvent(Event event)
        {
          //System.out.println("FocusIn");
          redraw();
        }
      });
  
      addListener(SWT.FocusOut, new Listener()
      {
        public void handleEvent(Event event)
        {
          //System.out.println("FocusOut");
          redraw();
        }
      });
    }
    else // Don't take focus but still support mnemonics
    {
      addListener(SWT.Traverse, new Listener()
      {
        public void handleEvent(Event event)
        {
          if(event.detail == SWT.TRAVERSE_MNEMONIC && mnemonic != -1 && Character.toLowerCase(event.character) == mnemonic)
          {
            linkActivated();
            event.doit = false;
          }
        }
      });
    }

    Composite shellComp = getParent();
    while(shellComp != null && (!(shellComp instanceof Shell))) shellComp = shellComp.getParent();
    shell = (Shell)shellComp;

    if(shell != null)
    {
      shellListener = new Listener() // Remove stale mouse hover on shell activation / deactivation
      {
        public void handleEvent(Event event)
        {
          boolean newCursorInControl = getDisplay().getCursorControl() == Hyperlink.this;
          //System.out.println("Shell (de)activated. Cursor over control: "+newCursorInControl);
          if(cursorInControl != newCursorInControl)
          {
            cursorInControl = newCursorInControl;
            if(cursorInControl) setCursor(handCursor);
            else if(isActive) setCursor(arrowCursor);
            if(isActive || (normalForeground != hoverForeground) || (normalUnderline != hoverUnderline)) redraw();
          }
        }
      };
  
      shell.addListener(SWT.Activate, shellListener);
      shell.addListener(SWT.Deactivate, shellListener);
    }
  }


  private void linkActivated()
  {
    //System.out.println("Link clicked!");
    Event e = new Event();
    e.widget = this;
    e.type = SWT.Selection;
    notifyListeners(SWT.Selection, e);
  }


  private boolean isInClientArea(Event event)
  {
    return event.x >= cachedClientArea.x && event.x < cachedClientArea.x+cachedClientArea.width &&
           event.y >= cachedClientArea.y && event.y < cachedClientArea.y+cachedClientArea.height;
  }


  public boolean isReparentable ()
  {
    checkWidget ();
    return false;
  }


  /**
   * Check the style bits to ensure that no invalid styles are applied.
   */

  private static int checkStyle(int style)
  {
    style = style & SWT.NO_FOCUS;

    // [NOTE] The following transparency workaround was taken from CLabel
    //TEMPORARY CODE
    /*
     * The default background on carbon and some GTK themes is not a solid color 
     * but a texture.  To show the correct default background, we must allow
     * the operating system to draw it and therefore, we can not use the 
     * NO_BACKGROUND style.  The NO_BACKGROUND style is not required on platforms
     * that use double buffering which is true in both of these cases.
     */
    String platform = SWT.getPlatform();
    if ("carbon".equals(platform) || "gtk".equals(platform)) return style;
    return style | SWT.NO_BACKGROUND;
  }


  public Point computeSize(int wHint, int hHint, boolean changed)
  {
    checkWidget();
    Point e = getTotalSize(text);
    if (wHint != SWT.DEFAULT) e.x = wHint;
    if (hHint != SWT.DEFAULT) e.y = hHint;
    return e;
  }


  /**
   * Compute the minimum size.
   */

  private Point getTotalSize(String text)
  {
    Point size = new Point(0, 0);
    GC gc = new GC(this);

    if (text != null && text.length() > 0)
    {
      Point e = gc.textExtent(text, SWT.DRAW_MNEMONIC);
      size.x += e.x;
      size.y = Math.max(size.y, e.y);
    }
    else size.y = Math.max(size.y, gc.getFontMetrics().getHeight());

    gc.dispose();
    return size;
  }


  /**
   * Return the Hyperlink's displayed text.
   * 
   * @return the text of the hyperlink or null
   */

  public String getText()
  {
    return text;
  }


  private void onPaint(PaintEvent event)
  {
    Rectangle rect = cachedClientArea; // getClientArea();
    if (rect.width == 0 || rect.height == 0) return;

    Point extent = getTotalSize(text);

    GC gc = event.gc;

    if ((getStyle() & SWT.NO_BACKGROUND) != 0)
    {
      gc.setBackground(getBackground());
      gc.fillRectangle(rect);
    }

    if(isFocusControl()) gc.drawFocus(rect.x, rect.y, rect.width, rect.height);

    Color textFG, lineFG;
    
    if(cursorInControl)
    {
      textFG = isActive ? activeForeground : hoverForeground;
      lineFG = isActive ? activeUndeline : hoverUnderline;
    }
    else
    {
      textFG = /* isActive ? mouseOverForeground : */ normalForeground;
      lineFG = /* isActive ? mouseOverUnderline : */ normalUnderline;
    }

    if(textFG == null) textFG = normalForeground;
    if(textFG == null) textFG = getDisplay().getSystemColor(SWT.COLOR_WIDGET_FOREGROUND);

    int textHeight = gc.getFontMetrics().getHeight();

    gc.setForeground(textFG);
    gc.drawText(text, rect.x, rect.y + (rect.height - textHeight) / 2, SWT.DRAW_TRANSPARENT | SWT.DRAW_MNEMONIC);

    int uy = (rect.y + (rect.height - textHeight) / 2) + gc.getFontMetrics().getAscent() + gc.getFontMetrics().getLeading() + 1;
    int lineWidth = extent.x > rect.width ? rect.width : extent.x;

    if(lineFG != null)
    {
      if(lineFG != textFG) gc.setForeground(lineFG);
      gc.drawLine(rect.x, uy, rect.x + lineWidth, uy);
    }
  }


  public void setForeground(Color color)
  {
    super.setForeground(color);
    this.normalForeground = color;
    redraw();
  }


  public void setHoverForeground(Color color)
  {
    this.hoverForeground = color;
    redraw();
  }


  public void setActiveForeground(Color color)
  {
    this.activeForeground = color;
    redraw();
  }
  
  
  public void setUnderline(Color color)
  {
    this.normalUnderline = color;
    redraw();
  }


  public void setHoverUnderline(Color color)
  {
    this.hoverUnderline = color;
    redraw();
  }


  public void setActiveUnderline(Color color)
  {
    this.activeUndeline = color;
    redraw();
  }


  public Color getHoverForeground()
  {
    return this.hoverForeground;
  }


  public Color getActiveForeground()
  {
    return this.activeForeground;
  }


  public Color getUnderline()
  {
    return this.normalUnderline;
  }


  public Color getHoverUnderline()
  {
    return this.hoverUnderline;
  }


  public Color getActiveUnderline()
  {
    return this.activeUndeline;
  }


  public void setBackground(Color color)
  {
    super.setBackground(color);
    redraw();
  }


  public void setFont(Font font)
  {
    super.setFont(font);
    redraw();
  }


  /**
   * Set the Hyperlink's displayed text.
   * The value <code>null</code> clears it.
   * <p>
   * Mnemonics are indicated by an '&amp' that causes the next
   * character to be the mnemonic.  When the user presses a
   * key sequence that matches the mnemonic, a selection
   * event occurs. On most platforms, the mnemonic appears
   * underlined but may be emphasised in a platform specific
   * manner.  The mnemonic indicator character '&amp' can be
   * escaped by doubling it in the string, causing a single
   * '&amp' to be displayed.
   * </p>
   * 
   * @param text the text to be displayed in the hyperlink or null
   * 
   * @exception SWTException <ul>
   *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
   *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
   * </ul>
   */

  public void setText(String text)
  {
    checkWidget();
    if (text == null) text = "";
    if (!text.equals(this.text))
    {
      this.text = text;
      int i = text.indexOf('&');
      if(i == -1 || i == text.length()-1) mnemonic = -1;
      else mnemonic = Character.toLowerCase(text.charAt(i+1));
      redraw();
    }
  }
  
  
  /**  
   * Adds the listener to receive events.
   *
   * @param listener the listener
   *
   * @exception SWTError(ERROR_THREAD_INVALID_ACCESS)
   * when called from the wrong thread
   * @exception SWTError(ERROR_WIDGET_DISPOSED)
   * when the widget has been disposed
   * @exception SWTError(ERROR_NULL_ARGUMENT)
   * when listener is null
   */

  public void addSelectionListener(SelectionListener listener)
  {
    checkWidget();
    if (listener == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
    TypedListener typedListener = new TypedListener(listener);
    addListener(SWT.Selection, typedListener);
    addListener(SWT.DefaultSelection, typedListener);
  }


  /**  
   * Removes the listener.
   *
   * @param listener the listener
   *
   * @exception SWTError(ERROR_THREAD_INVALID_ACCESS)
   * when called from the wrong thread
   * @exception SWTError(ERROR_WIDGET_DISPOSED)
   * when the widget has been disposed
   * @exception SWTError(ERROR_NULL_ARGUMENT)
   * when listener is null
   */

  public void removeSelectionListener(SelectionListener listener)
  {
    checkWidget();
    if (listener == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
    removeListener(SWT.Selection, listener);
    removeListener(SWT.DefaultSelection, listener);
  }
}