/**
   * Move the cursor <i>where</i> characters.
   *
   * @param where if less than 0, move abs(<i>where</i>) to the left, otherwise move <i>where</i> to
   *     the right.
   * @return the number of spaces we moved
   */
  public final int moveCursor(final int num) throws IOException {
    int where = num;

    if ((buf.cursor == 0) && (where < 0)) {
      return 0;
    }

    if ((buf.cursor == buf.buffer.length()) && (where > 0)) {
      return 0;
    }

    if ((buf.cursor + where) < 0) {
      where = -buf.cursor;
    } else if ((buf.cursor + where) > buf.buffer.length()) {
      where = buf.buffer.length() - buf.cursor;
    }

    moveInternal(where);

    return where;
  }
  /**
   * Read a line from the <i>in</i> {@link InputStream}, and return the line (without any trailing
   * newlines).
   *
   * @param prompt the prompt to issue to the console, may be null.
   * @return a line that is read from the terminal, or null if there was null input (e.g.,
   *     <i>CTRL-D</i> was pressed).
   */
  public String readLine(final String prompt, final Character mask) throws IOException {
    this.mask = mask;
    if (prompt != null) this.prompt = prompt;

    try {
      terminal.beforeReadLine(this, this.prompt, mask);

      if ((this.prompt != null) && (this.prompt.length() > 0)) {
        out.write(this.prompt);
        out.flush();
      }

      // if the terminal is unsupported, just use plain-java reading
      if (!terminal.isSupported()) {
        return readLine(in);
      }

      while (true) {
        int[] next = readBinding();

        if (next == null) {
          return null;
        }

        int c = next[0];
        int code = next[1];

        if (c == -1) {
          return null;
        }

        boolean success = true;

        switch (code) {
          case EXIT: // ctrl-d
            if (buf.buffer.length() == 0) {
              return null;
            }

          case COMPLETE: // tab
            success = complete();
            break;

          case MOVE_TO_BEG:
            success = setCursorPosition(0);
            break;

          case KILL_LINE: // CTRL-K
            success = killLine();
            break;

          case CLEAR_SCREEN: // CTRL-L
            success = clearScreen();
            break;

          case KILL_LINE_PREV: // CTRL-U
            success = resetLine();
            break;

          case NEWLINE: // enter
            moveToEnd();
            printNewline(); // output newline
            return finishBuffer();

          case DELETE_PREV_CHAR: // backspace
            success = backspace();
            break;

          case DELETE_NEXT_CHAR: // delete
            success = deleteCurrentCharacter();
            break;

          case MOVE_TO_END:
            success = moveToEnd();
            break;

          case PREV_CHAR:
            success = moveCursor(-1) != 0;
            break;

          case NEXT_CHAR:
            success = moveCursor(1) != 0;
            break;

          case NEXT_HISTORY:
            success = moveHistory(true);
            break;

          case PREV_HISTORY:
            success = moveHistory(false);
            break;

          case REDISPLAY:
            break;

          case PASTE:
            success = paste();
            break;

          case DELETE_PREV_WORD:
            success = deletePreviousWord();
            break;

          case PREV_WORD:
            success = previousWord();
            break;

          case NEXT_WORD:
            success = nextWord();
            break;

          case START_OF_HISTORY:
            success = history.moveToFirstEntry();
            if (success) setBuffer(history.current());
            break;

          case END_OF_HISTORY:
            success = history.moveToLastEntry();
            if (success) setBuffer(history.current());
            break;

          case CLEAR_LINE:
            moveInternal(-(buf.buffer.length()));
            killLine();
            break;

          case INSERT:
            buf.setOvertyping(!buf.isOvertyping());
            break;

          case UNKNOWN:
          default:
            if (c != 0) { // ignore null chars
              ActionListener action =
                  (ActionListener) triggeredActions.get(new Character((char) c));
              if (action != null) action.actionPerformed(null);
              else putChar(c, true);
            } else success = false;
        }

        if (!(success)) {
          beep();
        }

        flushConsole();
      }
    } finally {
      terminal.afterReadLine(this, this.prompt, mask);
    }
  }