package commands;

import java.io.BufferedWriter;
import java.io.File;
import java.io.IOException;
import java.io.OutputStreamWriter;

import kernel.AppException;
import kernel.AbstractProcess;

/**
 * @author Vaclav Podlena
 * 
 */
public class ls extends AbstractProcess {
  /**
   * implentation of the ls command
   * 
   * @throws AppException
   *             Exception caused by an error in the virtual machines manager.
   */
  public void realization() throws AppException {
    BufferedWriter out = new BufferedWriter(new OutputStreamWriter(this
        .getOut()));
    File dir = new File(getParentCurrentPath());
    // Get the directory to list
    if (getArgs().size() > 0) {
      if (getArgs().get(0).equals(".")) {
      } else if (getArgs().get(0).equals("..")) {
        dir = dir.getParentFile();
      } else {
        File paramDir = new File(getArgs().get(0));
        if (paramDir.isAbsolute())
          dir = new File(paramDir.getAbsolutePath());
        else
          dir = new File(dir.getAbsolutePath()
              + System.getProperty("file.separator") + getArgs().get(0));
      }
    }
    // Ensure the listed directory does exist
    if (dir == null || !dir.exists()) {
      try {
        this.getErrOut().write(
            ("ls: "
                + (dir == null ? "Can't find parent directory for "
                    + getParentCurrentPath() : dir.getAbsolutePath()
                    + " doesn't exist") + "\n").getBytes());
        this.getErrOut().flush();
      } catch (IOException e) {
        e.printStackTrace();
      }
    } else
      try {
        for (File file : dir.listFiles()) {
          if (file.isDirectory())
            out.write("[" + file.getName() + "]");
          else
            out.write(file.getName());
          out.newLine();
          out.flush();
          if (isInterrupted())
            break;
        }
      } catch (IOException ioe) {
        ioe.printStackTrace();
        throw new AppException("I/O operation error\n" + ioe.getMessage(), ioe);
      } catch (Exception e) {
        e.printStackTrace();
        throw new AppException("Unexpected error\n" + e.getMessage(), e);
      }
  }

  /**
   * Provides help for users.
   * 
   */
  public String getHelp() {
    return "\n\nDescription:\n Lists the given directory\n\nUsage:\n"
        + "ls [dir]\n\n"
        + "dir\tDirectory to be listed ('.', '..', relative path, absolute path). "
        + "If this argument isn't used, the current directory is listed.";
  }
}