/*
 * Copyright (c) 2003-2004, KNOPFLERFISH project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 * - Neither the name of the KNOPFLERFISH project nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.knopflerfish.bundle.cm;

import org.knopflerfish.service.log.*;

import org.osgi.service.cm.*;
import org.osgi.framework.*;

import java.util.Enumeration;
import java.util.Dictionary;
import java.util.Hashtable;
import java.util.Vector;

/**
 ** This class is responsible for managing ConfigurationPlugins.
 **
 ** @author Per Gustafson
 ** @version 1.0
 **/

final class PluginManager {
  private final static String CM_RANKING = "service.cmRanking";
  private final static String CM_TARGET = ConfigurationPlugin.CM_TARGET;
  private final static String SERVICE_PID = Constants.SERVICE_PID;
  private final static String OBJECT_CLASS = Constants.OBJECTCLASS;
  private final static String SERVICE_ID = Constants.SERVICE_ID;

  /**
   ** Sorted Vector of ServiceReferences to ConfigurationPlugins.
   **/

  Vector preModificationPlugins = new Vector();
  
  /**
   ** Sorted Vector of ServiceReferences to ConfigurationPlugins.
   **/

  Vector modifyingPlugins = new Vector();
  
  /**
   ** Sorted Vector of ServiceReferences to ConfigurationPlugins.
   **/

  Vector postModificationPlugins = new Vector();

  /**
   ** Hashtable mapping a ServiceReference to its ranking (Integer).
   **/

  Hashtable rankings = new Hashtable();

  /**
   ** Construct a PluginManager
   **/

  PluginManager() {
  }

  /**
   ** Handle ConfigurationPlugin ServiceEvents.
   **
   ** @param serviceReference ServiceReference of the plugin the event concerns
   ** @param eventType Type of the event that caused the change
   **/

  public synchronized void configurationPluginChanged(ServiceReference serviceReference, int eventType) {
    Object rankingProperty = serviceReference.getProperty(CM_RANKING);
    if(rankingProperty == null) {
      rankingProperty = new Integer(0);
    } else if(rankingProperty.getClass() != Integer.class) {
      rankingProperty = new Integer(0);
    }

    Long serviceId = (Long)serviceReference.getProperty(SERVICE_ID);
    if(serviceId == null) {
      Activator.log.error("Missing service id for a ConfigurationPlugin");
      return;
    }

    int ranking = ((Integer)rankingProperty).intValue();

    switch(eventType) {
      case ServiceEvent.REGISTERED:
          rankings.put(serviceId, rankingProperty);
          insertPluginReference(serviceReference, ranking);
        break;
      case ServiceEvent.MODIFIED:
          int oldRanking = ((Integer)rankings.get(serviceId)).intValue();
          if(ranking == oldRanking) {
           return;
          }
          removePluginReference(serviceId, oldRanking);
          rankings.put(serviceId, rankingProperty);
          insertPluginReference(serviceReference, ranking);
        break;
      case ServiceEvent.UNREGISTERING:
          rankings.remove(serviceId);
          removePluginReference(serviceId, ranking);
        break;
      default:
        break;
    }
  }

  /**
   ** Insert a ServiceReference to a ConfigurationPlugin in the correct
   ** Vector based on its ranking.
   **
   ** @param serviceReference The ServiceReference.
   ** @param ranking The ranking the ServiceReference.
   **/

  private void insertPluginReference(ServiceReference serviceReference, int ranking) {
    if(ranking < 0) {
      insertPluginReference(serviceReference, ranking, preModificationPlugins);
    } else if(0 <= ranking && ranking <= 1000) {
      insertPluginReference(serviceReference, ranking, modifyingPlugins);
    } else if(ranking > 1000) {
      insertPluginReference(serviceReference, ranking, postModificationPlugins);
    } else {
      // Shouldn't happen
    }
  }

  /**
   ** Insert a ServiceReference in a Vector sorted on cm.ranking property.
   **
   ** @param serviceReference The ServiceReference.
   ** @param pluginsVector The vector.
   **/

  private void insertPluginReference(ServiceReference serviceReference, int ranking, Vector pluginsVector) {
    int i;
    for(i = 0 ; i < pluginsVector.size(); ++i) {
      ServiceReference nextReference =
	      (ServiceReference)pluginsVector.elementAt(i);
      Long serviceId = (Long)nextReference.getProperty(SERVICE_ID);
      Integer rankingOfNextReference = (Integer)rankings.get(serviceId);
      if(ranking < rankingOfNextReference.intValue()) {
	      break;
      }
    }
    pluginsVector.insertElementAt(serviceReference, i);
  }

  /**
   ** Remove a ServiceReference to a ConfigurationPlugin given
   ** a service.id and a ranking.
   **
   ** @param serviceId The service.id of the ConfigurationPlugin.
   ** @param ranking The ranking of the ConfigurationPlugin.
   **/

  private void removePluginReference(Object serviceId, int ranking) {
    if(ranking < 0) {
      removePluginReference(serviceId, preModificationPlugins);
    } else if(0 <= ranking && ranking <= 1000) {
      removePluginReference(serviceId, modifyingPlugins);
    } else if(ranking > 1000) {
      removePluginReference(serviceId, postModificationPlugins);
    } else {
      // Shouldn't happen
    }
  }

  private void removePluginReference(Object serviceId, Vector pluginsVector) {
    for(int i = 0; i < pluginsVector.size(); ++i) {
      ServiceReference serviceReference =
          (ServiceReference)pluginsVector.elementAt(i);
      Long currentId = (Long)serviceReference.getProperty(SERVICE_ID);
      if(currentId.equals(serviceId)) {
        pluginsVector.removeElementAt(i);
        return;
      }
    }
  }

  /**
   ** Call all applicable ConfigurationPlugins given a pid and a dictionary.
   **
   ** @param pid The pid of the target ManagedService(Factory).
   ** @param dictionary The configuration dictionary to be modified.
   **
   ** @return The description of what the method returns.
   **/

  public synchronized ConfigurationDictionary callPluginsAndCreateACopy(ServiceReference targetServiceReference, ConfigurationDictionary dictionary) {
    if(targetServiceReference == null) {
      return dictionary;
    }
    if(dictionary == null) {
      return null;
    }
    callPlugins(targetServiceReference, dictionary, preModificationPlugins, false);

    dictionary = callPlugins(targetServiceReference, dictionary, modifyingPlugins, true);

    callPlugins(targetServiceReference, dictionary, postModificationPlugins, false);

    if(dictionary != null) {
      dictionary = dictionary.createCopyIfRealAndRemoveLocation();
    }
    return dictionary;
  }

  /**
   ** Call all plugins contained in a Vector and
   ** optionally allow modifications.
   **
   ** @param targetServiceReference Reference to the target ManagedService(Factory).
   ** @param dictionary The configuration dictionary to process.
   ** @param plugins Vector of references to ConfigurationPlugins.
   ** @param allowModification Should modifications to the configuration dictionary be allowed.
   **
   ** @return The modified configuration dictionary.
   **/

  private ConfigurationDictionary callPlugins(ServiceReference targetServiceReference, ConfigurationDictionary dictionary, Vector plugins, boolean allowModification) {
    String pid = (String)targetServiceReference.getProperty(SERVICE_PID);
    ConfigurationDictionary currentDictionary = dictionary;
    Enumeration e = plugins.elements();
    while(e.hasMoreElements()) {
      ServiceReference pluginReference = (ServiceReference)e.nextElement();
      
      // Only call the plugin if no cm.target is specified or if it
      // matches the pid of the target service
      String cmTarget = (String)pluginReference.getProperty(CM_TARGET);
      if(cmTarget == null || cmTarget.equals(pid)) {
        ConfigurationPlugin plugin =
            (ConfigurationPlugin)Activator.bc.getService(pluginReference);
        if(plugin == null) {
          continue;
        }
        ConfigurationDictionary dictionaryCopy = currentDictionary.createCopyAndRemoveLocation();
        try {
          plugin.modifyConfiguration(targetServiceReference, dictionaryCopy);
          if(allowModification && validateDictionary(dictionaryCopy)) {
            currentDictionary = dictionaryCopy;
          }
        } catch(Exception exception) {
          Activator.log.error("[CM] Exception thrown by plugin: " + exception.getMessage());
        }
      }
    }
    return currentDictionary;
  }

  /**
   ** Verify that a dictionary that has been modified by
   ** a plugin still is valid.
   **
   ** Might restore some keys.
   **
   ** @param dictionary The dictionary to validate.
   **
   ** @return true if valid, false otherwise.
   **/

  private boolean validateDictionary(Dictionary dictionary) {
    ConfigurationDictionary.validateDictionary(dictionary);
    return true;
  }
}