package commands;

import java.io.*;

import kernel.*;

/**
 * Prints help for specified command.
 * 
 * @author Tomáš Podskalský
 */
public class man extends AbstractProcess {
  private static String[] commands = { "cat", "date", "echo", "login", "man",
      "ps", "pwd", "shell", "exit", "ls", "cd", "grep", "kill", "shutdown" };

  public void realization() throws AppException {
    PipedOutputStream output = (this.getOut() != null) ? (PipedOutputStream) this
        .getOut()
        : null;
    ClassLoader loader = this.getClass().getClassLoader();
    AbstractProcess process = null;
    try {
      if (getArgs().size() == 0) {
        output.write(this.getHelp().getBytes());
        output.flush();
      } else {
        for (String arg : getArgs()) {
          try {
            process = (AbstractProcess) loader.loadClass("commands." + arg)
                .newInstance();
          } catch (Exception e) {
            process = null;
          }
          String s = new String("Příkaz:\n" + arg + "\n");
          s = s + (process != null ? process.getHelp() : "\nPříkaz nenalezen.");
          s = s + "\n";
          s = s + "------------------------------------------\n";
          output.write(s.getBytes());
          output.flush();
        }
      }
    } catch (IOException ioe) {
      ioe.printStackTrace();
      throw new AppException("Chyba I/O\n" + ioe.getMessage(), ioe);
    } catch (NullPointerException npe) {
      npe.printStackTrace();
      throw new AppException("Output není definován\n" + npe.getMessage(), npe);
    } catch (Exception e) {
      e.printStackTrace();
      throw new AppException("Neznámá Chyba.\n" + e.getMessage(), e);
    }

  }

  /**
   * Provides help for users.
   * 
   */

  public String getHelp() {
    return "\n\nDescription:\nPrints help for specified command.\n\nUsage:\n"
        + "man [command1 [command2 [...]]]\n\n"
        + "příkaz1, příkaz2, ...\tCommands that will be described. "
        + "If no agrument is given prints help for all available commands";
  }
}