content: /*
   *    This program is free software; you can redistribute it and/or modify
   *    it under the terms of the GNU General Public License as published by
   *    the Free Software Foundation; either version 2 of the License, or
   *    (at your option) any later version.
   *
   *    This program 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 General Public License for more details.
   *
   *    You should have received a copy of the GNU General Public License
   *    along with this program; if not, write to the Free Software
   *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  /*
   *    PluginManager.java
   *    Copyright (C) 2011 University of Waikato, Hamilton, New Zealand
   *
   */
  
  package weka.gui.beans;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  
  /**
   * Class that manages a global map of plugins. The knowledge flow
   * uses this to manage plugins other than step components and
   * perspectives. Is general purpose, so can be used by other Weka
   * components. Provides static methods for registering and instantiating
   * plugins.
   * 
   * @author Mark Hall (mhall{[at]}pentaho{[dot]}com)
   * @version $Revision: 7643 $
   */
  public class PluginManager {
    
    /** 
     * Global map that is keyed by plugin base class/interface type. The inner
     * Map then stores individual plugin instances of the interface type, keyed
     * by plugin name/short title with values the actual fully qualified class
     * name
     */
    protected static Map<String, Map<String, String>> PLUGINS = 
      new HashMap<String, Map<String, String>>();
    
    /**
     * Get a set of names of plugins that implement the supplied interface.
     * 
     * @param interfaceName the fully qualified name of the interface to list
     * plugins for
     * 
     * @return a set of names of plugins
     */
    public static Set<String> getPluginNamesOfType(String interfaceName) {        
      if (PLUGINS.get(interfaceName) != null) {
        return PLUGINS.get(interfaceName).keySet();
      }
          
      return null;
    }
    
    /**
     * Add a plugin.
     * 
     * @param interfaceName the fully qualified interface name that the
     * plugin implements
     * 
     * @param name the name/short description of the plugin
     * @param concreteType the fully qualified class name of the actual
     * concrete implementation
     */
    public static void addPlugin(String interfaceName, String name, 
        String concreteType) {
      if (PLUGINS.get(interfaceName) == null) {
        Map<String, String> pluginsOfInterfaceType = 
          new TreeMap<String, String>();
        pluginsOfInterfaceType.put(name, concreteType);
        PLUGINS.put(interfaceName, pluginsOfInterfaceType);      
      } else {
        PLUGINS.get(interfaceName).put(name, concreteType);
      }
    }
    
    /**
     * Get an instance of a concrete implementation of a plugin type
     * 
     * @param interfaceType the fully qualified interface name of the
     * plugin type
     * @param name the name/short description of the plugin to get
     * @return the concrete plugin
     * @throws Exception if the plugin can't be found or instantiated
     */
    public static Object getPluginInstance(String interfaceType, String name) 
      throws Exception {
      if (PLUGINS.get(interfaceType) == null ||
          PLUGINS.get(interfaceType).size() == 0) {
        throw new Exception("No plugins of interface type: " + interfaceType 
            + " available!!");
      }
      
      Map<String, String> pluginsOfInterfaceType = 
        PLUGINS.get(interfaceType);
      if (pluginsOfInterfaceType.get(name) == null) {
        throw new Exception("Can't find named plugin '" + name + "' of type '" +
        		interfaceType + "'!");
      }
      
      String concreteImpl = pluginsOfInterfaceType.get(name);
      Object plugin = Class.forName(concreteImpl).newInstance();
      
      return plugin;
    }
  }
  