/**
 * Copyright (c) 2010, Sebastian Sdorra
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of SCM-Manager; 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 REGENTS 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.
 *
 * http://bitbucket.org/sdorra/scm-manager
 *
 */



package sonia.scm.cli.cmd;

//~--- non-JDK imports --------------------------------------------------------

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import sonia.scm.ConfigurationException;
import sonia.scm.util.IOUtil;
import sonia.scm.util.Util;

//~--- JDK imports ------------------------------------------------------------

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import java.net.URL;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 *
 * @author Sebastian Sdorra
 */
public class SubCommandHandler
{

  /** Field description */
  public static final String RESOURCE_SERVICES =
    "META-INF/services/".concat(SubCommand.class.getName());

  /** Field description */
  private static volatile SubCommandHandler instance;

  /** the logger for SubCommandOptionHandler */
  private static final Logger logger =
    LoggerFactory.getLogger(SubCommandOptionHandler.class);

  //~--- constructors ---------------------------------------------------------

  /**
   * Constructs ...
   *
   */
  private SubCommandHandler()
  {
    subCommands = new HashMap<String, CommandDescriptor>();
    loadSubCommands();
  }

  //~--- get methods ----------------------------------------------------------

  /**
   * Method description
   *
   *
   * @return
   */
  public static SubCommandHandler getInstance()
  {
    if (instance == null)
    {
      synchronized (SubCommandHandler.class)
      {
        if (instance == null)
        {
          instance = new SubCommandHandler();
        }
      }
    }

    return instance;
  }

  /**
   * Method description
   *
   *
   * @param name
   *
   * @return
   */
  public CommandDescriptor getDescriptor(String name)
  {
    return subCommands.get(name);
  }

  /**
   * Method description
   *
   *
   * @return
   */
  public List<CommandDescriptor> getDescriptors()
  {
    List<CommandDescriptor> descs =
      new ArrayList<CommandDescriptor>(subCommands.values());

    Collections.sort(descs);

    return descs;
  }

  //~--- methods --------------------------------------------------------------

  /**
   * Method description
   *
   *
   * @param url
   */
  private void loadSubCommand(URL url)
  {
    BufferedReader reader = null;

    try
    {
      reader = new BufferedReader(new InputStreamReader(url.openStream()));

      String line = reader.readLine();

      while (line != null)
      {
        parseLine(line);
        line = reader.readLine();
      }
    }
    catch (IOException ex)
    {
      logger.error("could not load commands");
    }
    finally
    {
      IOUtil.close(reader);
    }
  }

  /**
   * Method description
   *
   */
  private void loadSubCommands()
  {
    try
    {
      Enumeration<URL> enm =
        SubCommandHandler.class.getClassLoader().getResources(
            RESOURCE_SERVICES);

      while (enm.hasMoreElements())
      {
        URL url = enm.nextElement();

        loadSubCommand(url);
      }
    }
    catch (IOException ex)
    {
      throw new ConfigurationException("could not load SubComamnds", ex);
    }
  }

  /**
   * Method description
   *
   *
   * @param line
   */
  private void parseLine(String line)
  {
    line = line.trim();

    if (Util.isNotEmpty(line) &&!line.startsWith("#"))
    {
      try
      {
        Class<? extends SubCommand> clazz =
          (Class<? extends SubCommand>) Class.forName(line);
        CommandDescriptor desc = new CommandDescriptor(clazz);

        subCommands.put(desc.getName(), desc);
      }
      catch (ClassNotFoundException ex)
      {
        logger.warn("could not found command class {}", line);
      }
    }
  }

  //~--- fields ---------------------------------------------------------------

  /** Field description */
  private Map<String, CommandDescriptor> subCommands;
}
