package org.cyclopsgroup.jmxterm.cc;
   
   import org.apache.commons.lang3.Validate;
   import org.cyclopsgroup.jcli.ArgumentProcessor;
   import org.cyclopsgroup.jcli.annotation.Argument;
   import org.cyclopsgroup.jcli.annotation.Cli;
   import org.cyclopsgroup.jcli.annotation.MultiValue;
   import org.cyclopsgroup.jmxterm.Command;
   import org.cyclopsgroup.jmxterm.io.RuntimeIOException;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * Command that display a help message
   *
   * @author <a href="mailto:jiaqi.guo@gmail.com">Jiaqi Guo</a>
   */
  @Cli(name = "help", description = "Display available commands or usage of a command",
      note = "Run \"help [command1] [command2] ...\" to display usage or certain command(s). Help without argument shows list of available commands")
  public class HelpCommand extends Command {
    private List<String> argNames = Collections.emptyList();
  
    private CommandCenter commandCenter = null;
  
    @Override
    public void execute() {
      Validate.notNull(commandCenter, "Command center hasn't been set yet");
      if (argNames.isEmpty()) {
        List<String> commandNames = new ArrayList<String>(commandCenter.getCommandNames());
        Collections.sort(commandNames);
        getSession().output.printMessage("following commands are available to use:");
        for (String commandName : commandNames) {
          Class<? extends Command> commandType = commandCenter.getCommandType(commandName);
          org.cyclopsgroup.jcli.spi.Cli cli =
              ArgumentProcessor.forType(commandType).createParsingContext().cli();
          getSession().output.println(String.format("%-8s - %s", commandName, cli.getDescription()));
        }
      } else {
        for (String argName : argNames) {
          Class<? extends Command> commandType = commandCenter.getCommandType(argName);
          if (commandType == null) {
            throw new IllegalArgumentException("Command " + argName + " is not found");
          }
          ArgumentProcessor<? extends Command> ap = ArgumentProcessor.forType(commandType);
          try {
            ap.printHelp(new PrintWriter(System.out, true));
          } catch (IOException e) {
            throw new RuntimeIOException("Can't print help message", e);
          }
        }
      }
    }
  
    /**
     * @param argNames Array of arguments
     */
    @MultiValue(listType = ArrayList.class)
    @Argument
    public final void setArgNames(List<String> argNames) {
      Validate.notNull(argNames, "argNames can't be NULL");
      this.argNames = argNames;
    }
  
    /**
     * @param commandCenter CommandCenter object that calls this help command
     */
    final void setCommandCenter(CommandCenter commandCenter) {
      Validate.notNull(commandCenter, "commandCenter can't be NULL");
      this.commandCenter = commandCenter;
    }
  }