/*

  *   SONEWS News Server

  *   see AUTHORS for the list of contributors

  *

  *   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 3 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, see <http://www.gnu.org/licenses/>.

  */

 package org.sonews.daemon;

 import java.util.HashMap;

 import java.util.Map;

 import java.util.concurrent.ConcurrentHashMap;

 import org.sonews.daemon.command.Command;

 import org.sonews.daemon.command.UnsupportedCommand;

 import org.sonews.util.Log;

 import org.sonews.util.io.Resource;

 /**

  * Selects the correct command processing class.

  * @author Christian Lins

  * @since sonews/1.0

  */

 public class CommandSelector

 {

   private static Map<Thread, CommandSelector> instances

     = new ConcurrentHashMap<Thread, CommandSelector>();

   private static Map<String, Class<?>> commandClassesMapping

     = new ConcurrentHashMap<String, Class<?>>();

   static

   {

     String[] classes = Resource.getAsString("helpers/commands.list", true).split("\n");

     for(String className : classes)

     {

       if(className.charAt(0) == '#')

       {

         // Skip comments

         continue;

       }

       try

       {

         addCommandHandler(className);

       }

       catch(ClassNotFoundException ex)

       {

         Log.get().warning("Could not load command class: " + ex);

       }

       catch(InstantiationException ex)

       {

         Log.get().severe("Could not instantiate command class: " + ex);

       }

       catch(IllegalAccessException ex)

       {

         Log.get().severe("Could not access command class: " + ex);

       }

     }

   }

   public static void addCommandHandler(String className)

     throws ClassNotFoundException, InstantiationException, IllegalAccessException

   {

     Class<?> clazz = Class.forName(className);

     Command cmd = (Command)clazz.newInstance();

     String[] cmdStrs = cmd.getSupportedCommandStrings();

     for (String cmdStr : cmdStrs)

     {

       commandClassesMapping.put(cmdStr, clazz);

     }

   }

   public static CommandSelector getInstance()

   {

     CommandSelector csel = instances.get(Thread.currentThread());

     if(csel == null)

     {

       csel = new CommandSelector();

       instances.put(Thread.currentThread(), csel);

     }

     return csel;

   }

   private Map<String, Command> commandMapping = new HashMap<String, Command>();

   private Command              unsupportedCmd = new UnsupportedCommand();

   private CommandSelector()

   {}

   public Command get(String commandName)

   {

     try

     {

       commandName = commandName.toUpperCase();

       Command cmd = this.commandMapping.get(commandName);

       if(cmd == null)

       {

         Class<?> clazz = commandClassesMapping.get(commandName);

         if(clazz == null)

         {

           cmd = this.unsupportedCmd;

         }

         else

         {

           cmd = (Command)clazz.newInstance();

           this.commandMapping.put(commandName, cmd);

         }

       }

       else if(cmd.isStateful())

       {

         cmd = cmd.getClass().newInstance();

       }

       return cmd;

     }

     catch(Exception ex)

     {

       ex.printStackTrace();

       return this.unsupportedCmd;

     }

   }

 }