package parser;

/**
 * Class to act as the superclass of all Parser execeptions.
 *
 * @author Bryan J. Higgs
 */
public abstract class ParserException extends Exception
{
  /**
   * Gets the message associated with an exception.
   * (Abstract method)
   */
  @Override
  public abstract String getMessage();

  /**
   * Gets the Line of source where the exception occurred
   */
  public String getLine()
  {
    return m_line;
  }

  /**
   * Gets the character offset within the line where the
   * exception occurred.
   */
  public int getOffset()
  {
    return m_offset;
  }

  /**
   * Gets a formatted message of the form:
   *
   * <message>
   * <contents of line>
   *       ^
   * (the above caret is aligned with the character
   *  corresponding to the offset within the line).
   */
  public String getFormattedMessage()
  {
    String msg = getMessage() + "\n";
    msg += getLine() + "\n";
    for (int i = 0; i < getOffset(); i++)
    {
      msg += " ";
    }
    msg += "^\n"; // The caret (^) should point to the error location.

    return msg;
  }

  /**
   * Constructor
   * (protected because it's only used by derived classes)
   */
  protected ParserException(String line, int offset)
  {
    m_line = line;
    m_offset = offset;
  }

  /// Private data ///
  private String  m_line;   // The line containing the expression
  private int     m_offset; // The offset within the line
}