/*

 *   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;

    }

  }

}