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Private implementation of the Apache MyFaces Trinidad project
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/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.apache.myfaces.trinidadinternal.image.encode;


import org.apache.myfaces.trinidad.util.ArrayMap;

import org.apache.myfaces.trinidadinternal.image.PropertyInstantiator;

/**
 * ImageEncoderManager maintains a registry of image encodings.
 * Currently, clients must use the getDefaultImageEncoderManager()
 * to obtain a reference to the single, shared ImageEncoderManager.
 *
 * @version $Name:  $ ($Revision: adfrt/faces/adf-faces-impl/src/main/java/oracle/adfinternal/view/faces/image/encode/ImageEncoderManager.java#0 $) $Date: 10-nov-2005.19:05:18 $
 */
public class ImageEncoderManager
{
  /**
   * Mime type for GIF
   */
  public static final String GIF_TYPE = "image/gif";

  /**
   * Mime type for PNG
   */
  public static final String PNG_TYPE = "image/png";

  // Private for now
  private ImageEncoderManager() {}

  /**
   * Returns the default ImageEncoderManager
   */
  static public ImageEncoderManager getDefaultImageEncoderManager()
  {
    return _sDefaultInstance;
  }

  /**
   * Returns the ImageEncoder for the specified encoding.
   * @param type The mime type for the encoding, eg. "image/gif".
   */
  public ImageEncoder getImageEncoder(String type)
  {
    synchronized (this)
    {
      Object encoder = _encoders.get(type);
      
      if (encoder instanceof PropertyInstantiator)
      {
        encoder = ((PropertyInstantiator)encoder).instantiate();
        
        assert (encoder instanceof ImageEncoder);
        
        _encoders.put(type, encoder);
      }

      return (ImageEncoder)encoder;
    }
  }

  /**
   * Returns the file extension for the specified type.
   * @param type The mime type for the encoding, eg. "image/gif".
   */
  public String getImageExtension(String type)
  {
    return _extensions.get(type);
  }

  /**
   * Registers an encoding.
   * @param type The mime type of the encoding
   * @param extension The file extension for the encoding
   * @param encoder The ImageEncoder instance to use for this encoding
   */
  public void registerEncoding(
    String type,
    String extension,
    ImageEncoder encoder
    )
  {
    synchronized (this)
    {
      _encoders.put(type, encoder);
      _extensions.put(type, extension);
    }
  }

  /**
   * Registers an encoding.
   * The ImageEncoder is instantiated using the specified class name when
   * it is first requested.
   * @param type The mime type of the encoding
   * @param extension The file extension for the encoding
   * @param encoderClassName The name of a class which implements
   *   the ImageEncoder interface
   */
  public void registerEncoding(
    String type,
    String extension,
    String encoderClassName
    )
  {
    synchronized (this)
    {
      _encoders.put(type, new PropertyInstantiator(encoderClassName));
      _extensions.put(type, extension);
    }
  }

  /**
   * Unregisters an encoding
   * @param type The mime type of the encoding to unregister
   */
  public void unregisterEncoding(String type)
  {
    synchronized (this)
    {
      _encoders.remove(type);
      _extensions.remove(type);
    }
  }

  // Registers default encodings
  static private void _registerDefaultEncodings(ImageEncoderManager manager)
  {
    // Register the default GIF encoder
    manager.registerEncoding(
      GIF_TYPE,
      _GIF_EXTENSION,
      "org.apache.myfaces.trinidadinternal.image.encode.DefaultGIFEncoder"
      );

    manager.registerEncoding(
      PNG_TYPE,
      _PNG_EXTENSION,
      "org.apache.myfaces.trinidadinternal.image.encode.DefaultPNGEncoder"
      );
  }

  // Maps mime type to ImageEncoder objects
  private ArrayMap _encoders = new ArrayMap();

  // Maps mime type to extension
  private ArrayMap _extensions = new ArrayMap();

  static private ImageEncoderManager _sDefaultInstance = 
    new ImageEncoderManager();

  static
  {
    _registerDefaultEncodings(_sDefaultInstance);
  }

  static private final String _GIF_EXTENSION = ".gif";
  static private final String _PNG_EXTENSION = ".png";
}