/*
 * $Id: ShadowRenderer.java 3100 2008-10-14 22:33:10Z rah003 $
 *
 * Copyright 2006 Sun Microsystems, Inc., 4150 Network Circle,
 * Santa Clara, California 95054, U.S.A. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
package consulo.ide.impl.desktop.awt.graphics;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;

/**
 * <p>A shadow renderer generates a drop shadow for any given picture, respecting
 * the transparency channel if present. The resulting picture contains the
 * shadow only and to create a drop shadow effect you will need to stack the
 * original picture and the shadow generated by the renderer.</p>
 * <h2>Shadow Properties</h2>
 * <p>A shadow is defined by three properties:
 * <ul>
 *   <li><i>size</i>: The size, in pixels, of the shadow. This property also
 *   defines the fuzzyness.</li>
 *   <li><i>opacity</i>: The opacity, between 0.0 and 1.0, of the shadow.</li>
 *   <li><i>color</i>: The color of the shadow. Shadows are not meant to be
 *   black only.</li>
 * </ul>
 * You can set these properties using the provided mutaters or the appropriate
 * constructor. Here are two ways of creating a green shadow of size 10 and
 * with an opacity of 50%:
 * <pre>
 * ShadowRenderer renderer = new ShadowRenderer(10, 0.5f, Color.GREEN);
 * // ..
 * renderer = new ShadowRenderer();
 * renderer.setSize(10);
 * renderer.setOpacity(0.5f);
 * renderer.setColor(Color.GREEN);
 * </pre>
 * The default constructor provides the following default values:
 * <ul>
 *   <li><i>size</i>: 5 pixels</li>
 *   <li><i>opacity</i>: 50%</li>
 *   <li><i>color</i>: Black</li>
 * </ul></p>
 * <h2>Generating a Shadow</h2>
 * <p>A shadow is generated as a <code>BufferedImage</code> from another
 * <code>BufferedImage</code>. Once the renderer is set up, you must call
 * {@link #createShadow} to actually generate the shadow:
 * <pre>
 * ShadowRenderer renderer = new ShadowRenderer();
 * // renderer setup
 * BufferedImage shadow = renderer.createShadow(bufferedImage);
 * </pre></p>
 * <p>The generated image dimensions are computed as following:</p>
 * <pre>
 * width  = imageWidth  + 2 * shadowSize
 * height = imageHeight + 2 * shadowSize
 * </pre>
 * <h2>Properties Changes</h2>
 * <p>This renderer allows to register property change listeners with
 * {@link #addPropertyChangeListener}. Listening to properties changes is very
 * useful when you emebed the renderer in a graphical component and give the API
 * user the ability to access the renderer. By listening to properties changes,
 * you can easily repaint the component when needed.</p>
 * <h2>Threading Issues</h2>
 * <p><code>ShadowRenderer</code> is not guaranteed to be thread-safe.</p>
 *
 * @author Romain Guy <romain.guy@mac.com>
 * @author Sebastien Petrucci
 */
public class ShadowRenderer {
  /**
   * <p>Identifies a change to the size used to render the shadow.</p>
   * <p>When the property change event is fired, the old value and the new
   * value are provided as <code>Integer</code> instances.</p>
   */
  public static final String SIZE_CHANGED_PROPERTY = "shadow_size";

  /**
   * <p>Identifies a change to the opacity used to render the shadow.</p>
   * <p>When the property change event is fired, the old value and the new
   * value are provided as <code>Float</code> instances.</p>
   */
  public static final String OPACITY_CHANGED_PROPERTY = "shadow_opacity";

  /**
   * <p>Identifies a change to the color used to render the shadow.</p>
   */
  public static final String COLOR_CHANGED_PROPERTY = "shadow_color";

  // size of the shadow in pixels (defines the fuzziness)
  private int size = 5;

  // opacity of the shadow
  private float opacity = 0.5f;

  // color of the shadow
  private Color color = Color.BLACK;

  // notifies listeners of properties changes
  private PropertyChangeSupport changeSupport;

  /**
   * <p>Creates a default good looking shadow generator.
   * The default shadow renderer provides the following default values:
   * <ul>
   *   <li><i>size</i>: 5 pixels</li>
   *   <li><i>opacity</i>: 50%</li>
   *   <li><i>color</i>: Black</li>
   * </ul></p>
   * <p>These properties provide a regular, good looking shadow.</p>
   */
  public ShadowRenderer() {
    this(5, 0.5f, Color.BLACK);
  }

  /**
   * <p>A shadow renderer needs three properties to generate shadows.
   * These properties are:</p>
   * <ul>
   *   <li><i>size</i>: The size, in pixels, of the shadow. This property also
   *   defines the fuzzyness.</li>
   *   <li><i>opacity</i>: The opacity, between 0.0 and 1.0, of the shadow.</li>
   *   <li><i>color</i>: The color of the shadow. Shadows are not meant to be
   *   black only.</li>
   * </ul>
   * @param size the size of the shadow in pixels. Defines the fuzziness.
   * @param opacity the opacity of the shadow.
   * @param color the color of the shadow.
   */
  public ShadowRenderer(final int size, final float opacity, final Color color) {
    //noinspection ThisEscapedInObjectConstruction
    changeSupport = new PropertyChangeSupport(this);

    setSize(size);
    setOpacity(opacity);
    setColor(color);
  }

  /**
   * <p>Add a PropertyChangeListener to the listener list. The listener is
   * registered for all properties. The same listener object may be added
   * more than once, and will be called as many times as it is added. If
   * <code>listener</code> is null, no exception is thrown and no action
   * is taken.</p>
   * @param listener the PropertyChangeListener to be added
   */
  public void addPropertyChangeListener(PropertyChangeListener listener) {
    changeSupport.addPropertyChangeListener(listener);
  }

  /**
   * <p>Remove a PropertyChangeListener from the listener list. This removes
   * a PropertyChangeListener that was registered for all properties. If
   * <code>listener</code> was added more than once to the same event source,
   * it will be notified one less time after being removed. If
   * <code>listener</code> is null, or was never added, no exception is thrown
   * and no action is taken.</p>
   * @param listener the PropertyChangeListener to be removed
   */
  public void removePropertyChangeListener(PropertyChangeListener listener) {
    changeSupport.removePropertyChangeListener(listener);
  }

  /**
   * <p>Gets the color used by the renderer to generate shadows.</p>
   * @return this renderer's shadow color
   */
  public Color getColor() {
    return color;
  }

  /**
   * <p>Sets the color used by the renderer to generate shadows.</p>
   * <p>Consecutive calls to {@link #createShadow} will all use this color
   * until it is set again.</p>
   * <p>If the color provided is null, the previous color will be retained.</p>
   * @param shadowColor the generated shadows color
   */
  public void setColor(final Color shadowColor) {
    if (shadowColor != null) {
      Color oldColor = this.color;
      this.color = shadowColor;
      changeSupport.firePropertyChange(COLOR_CHANGED_PROPERTY,
                                       oldColor,
                                       this.color);
    }
  }

  /**
   * <p>Gets the opacity used by the renderer to generate shadows.</p>
   * <p>The opacity is comprised between 0.0f and 1.0f; 0.0f being fully
   * transparent and 1.0f fully opaque.</p>
   * @return this renderer's shadow opacity
   */
  public float getOpacity() {
    return opacity;
  }

  /**
   * <p>Sets the opacity used by the renderer to generate shadows.</p>
   * <p>Consecutive calls to {@link #createShadow} will all use this opacity
   * until it is set again.</p>
   * <p>The opacity is comprised between 0.0f and 1.0f; 0.0f being fully
   * transparent and 1.0f fully opaque. If you provide a value out of these
   * boundaries, it will be restrained to the closest boundary.</p>
   * @param shadowOpacity the generated shadows opacity
   */
  public void setOpacity(final float shadowOpacity) {
    float oldOpacity = this.opacity;

    if (shadowOpacity < 0.0) {
      this.opacity = 0.0f;
    } else if (shadowOpacity > 1.0f) {
      this.opacity = 1.0f;
    } else {
      this.opacity = shadowOpacity;
    }

    changeSupport.firePropertyChange(OPACITY_CHANGED_PROPERTY,
                                     oldOpacity,
                                     this.opacity);
  }

  /**
   * <p>Gets the size in pixel used by the renderer to generate shadows.</p>
   * @return this renderer's shadow size
   */
  public int getSize() {
    return size;
  }

  /**
   * <p>Sets the size, in pixels, used by the renderer to generate shadows.</p>
   * <p>The size defines the blur radius applied to the shadow to create the
   * fuzziness.</p>
   * <p>There is virtually no limit to the size. The size cannot be negative.
   * If you provide a negative value, the size will be 0 instead.</p>
   * @param shadowSize the generated shadows size in pixels (fuzziness)
   */
  public void setSize(final int shadowSize) {
    int oldSize = this.size;

    if (shadowSize < 0) {
      this.size = 0;
    } else {
      this.size = shadowSize;
    }

    changeSupport.firePropertyChange(SIZE_CHANGED_PROPERTY,
                                     new Integer(oldSize),
                                     new Integer(this.size));
  }

  /**
   * <p>Generates the shadow for a given picture and the current properties
   * of the renderer.</p>
   * <p>The generated image dimensions are computed as following:</p>
   * <pre>
   * width  = imageWidth  + 2 * shadowSize
   * height = imageHeight + 2 * shadowSize
   * </pre>
   * @param image the picture from which the shadow must be cast
   * @return the picture containing the shadow of <code>image</code>
   */
  public BufferedImage createShadow(final BufferedImage image) {
    // Written by Sesbastien Petrucci
    int shadowSize = size * 2;

    int srcWidth = image.getWidth();
    int srcHeight = image.getHeight();

    int dstWidth = srcWidth + shadowSize;
    int dstHeight = srcHeight + shadowSize;

    int left = size;
    int right = shadowSize - left;

    int yStop = dstHeight - right;

    int shadowRgb = color.getRGB() & 0x00FFFFFF;
    int[] aHistory = new int[shadowSize];
    int historyIdx;

    int aSum;

    BufferedImage dst = new BufferedImage(dstWidth, dstHeight,
                                          BufferedImage.TYPE_INT_ARGB);

    int[] dstBuffer = new int[dstWidth * dstHeight];
    int[] srcBuffer = new int[srcWidth * srcHeight];

    GraphicsUtilities.getPixels(image, 0, 0, srcWidth, srcHeight, srcBuffer);

    int lastPixelOffset = right * dstWidth;
    float hSumDivider = 1.0f / shadowSize;
    float vSumDivider = opacity / shadowSize;

    int[] hSumLookup = new int[256 * shadowSize];
    for (int i = 0; i < hSumLookup.length; i++) {
      hSumLookup[i] = (int) (i * hSumDivider);
    }

    int[] vSumLookup = new int[256 * shadowSize];
    for (int i = 0; i < vSumLookup.length; i++) {
      vSumLookup[i] = (int) (i * vSumDivider);
    }

    int srcOffset;

    // horizontal pass : extract the alpha mask from the source picture and
    // blur it into the destination picture
    for (int srcY = 0, dstOffset = left * dstWidth; srcY < srcHeight; srcY++) {

      // first pixels are empty
      for (historyIdx = 0; historyIdx < shadowSize; ) {
        aHistory[historyIdx++] = 0;
      }

      aSum = 0;
      historyIdx = 0;
      srcOffset = srcY * srcWidth;

      // compute the blur average with pixels from the source image
      for (int srcX = 0; srcX < srcWidth; srcX++) {

        int a = hSumLookup[aSum];
        dstBuffer[dstOffset++] = a << 24;   // store the alpha value only
        // the shadow color will be added in the next pass

        aSum -= aHistory[historyIdx]; // substract the oldest pixel from the sum

        // extract the new pixel ...
        a = srcBuffer[srcOffset + srcX] >>> 24;
        aHistory[historyIdx] = a;   // ... and store its value into history
        aSum += a;                  // ... and add its value to the sum

        if (++historyIdx >= shadowSize) {
          historyIdx -= shadowSize;
        }
      }

      // blur the end of the row - no new pixels to grab
      for (int i = 0; i < shadowSize; i++) {

        int a = hSumLookup[aSum];
        dstBuffer[dstOffset++] = a << 24;

        // substract the oldest pixel from the sum ... and nothing new to add !
        aSum -= aHistory[historyIdx];

        if (++historyIdx >= shadowSize) {
          historyIdx -= shadowSize;
        }
      }
    }

    // vertical pass
    for (int x = 0, bufferOffset = 0; x < dstWidth; x++, bufferOffset = x) {

      aSum = 0;

      // first pixels are empty
      for (historyIdx = 0; historyIdx < left;) {
        aHistory[historyIdx++] = 0;
      }

      // and then they come from the dstBuffer
      for (int y = 0; y < right; y++, bufferOffset += dstWidth) {
        int a = dstBuffer[bufferOffset] >>> 24;         // extract alpha
        aHistory[historyIdx++] = a;                     // store into history
        aSum += a;                                      // and add to sum
      }

      bufferOffset = x;
      historyIdx = 0;

      // compute the blur avera`ge with pixels from the previous pass
      for (int y = 0; y < yStop; y++, bufferOffset += dstWidth) {

        int a = vSumLookup[aSum];
        dstBuffer[bufferOffset] = a << 24 | shadowRgb;  // store alpha value + shadow color

        aSum -= aHistory[historyIdx];   // substract the oldest pixel from the sum

        a = dstBuffer[bufferOffset + lastPixelOffset] >>> 24;   // extract the new pixel ...
        aHistory[historyIdx] = a;                               // ... and store its value into history
        aSum += a;                                              // ... and add its value to the sum

        if (++historyIdx >= shadowSize) {
          historyIdx -= shadowSize;
        }
      }

      // blur the end of the column - no pixels to grab anymore
      for (int y = yStop; y < dstHeight; y++, bufferOffset += dstWidth) {

        int a = vSumLookup[aSum];
        dstBuffer[bufferOffset] = a << 24 | shadowRgb;

        aSum -= aHistory[historyIdx];   // substract the oldest pixel from the sum

        if (++historyIdx >= shadowSize) {
          historyIdx -= shadowSize;
        }
      }
    }

    GraphicsUtilities.setPixels(dst, 0, 0, dstWidth, dstHeight, dstBuffer);
    return dst;
  }
}
