/**
 * This class contains methods to extract parts of an input line of the
 * form (Station1, Station2, line).  The strings Station1, Station2 and line
 * may contain any characters (including spaces) except commas and right parens.
 * The strings returned will have all leading and trailing spaces trimmed.
 * <p>
 * For use in Assignment 6
 *
 * @author Margaret Lamb
 */
public class GraphInput {

  /**
   * A type of exception to raise if there is an error in the input format.
   * Because it is a subclass of RuntimeException, the user does not have to
   * use a try/catch around methods that throw this exception.
   */
  public static class GraphInputFormatError extends RuntimeException {
    /**
     * Creates a new GraphInputFormatError exception with a message identifying
     * the problem
     *
     * @param msg a message identifying the format error (e.g. input line
     * does not start with a left paren)
     */
    public GraphInputFormatError(String msg) {
      super(msg);
    } // end constructor
  } // end class GraphInputFormatError

  /**
   * Extracts the first station name from an input line of the form
   * "(Station1, Station2, line)".  The station name will have all leading
   * and trailing spaces trimmed.  For example, if the input line is <br>
   * "  (  Baker Street  ,  Royal Albert,  Victoria Line  )  ",  this
   * method will return "Baker Street".
   *
   * @param inputLine the line of input
   * @return the first station name from the input line
   * @exception GraphInputFormatError if the input line does not have the
   * correct format (e.g. doesn't start with a left paren, or doesn't have
   * two commas)
   */
  public static String getStation1(String inputLine) {
    inputLine = inputLine.trim(); // remove any leading spaces
    if (inputLine.length() == 0 || inputLine.charAt(0) != '(') {
      // doesn't start with a left paren
      throw new GraphInputFormatError(
        "input line does not start with left paren");
    } // end if

    int commaPos = inputLine.indexOf(','); // position of first comma
    if (commaPos == -1) {
      // no commas in input line
      throw new GraphInputFormatError(
        "input line does not contain a comma");
    } // end if

    // Station1 is everything after the left paren and before the comma,
    // minus any leading or trailing spaces
    return inputLine.substring(1, commaPos).trim();
  } // end getStation1

  /**
   * Extracts the second station name from an input line of the form
   * "(Station1, Station2, line)".  The station name will have all leading
   * and trailing spaces trimmed.  For example, if the input line is <br>
   * "  (  Baker Street  ,  Royal Albert,  Victoria Line  )  ",  this
   * method will return "Royal Albert".
   *
   * @param inputLine the line of input
   * @return the second station name from the input line
   * @exception GraphInputFormatError if the input line does not have the
   * correct format (e.g. doesn't start with a left paren, or doesn't have
   * two commas)
   */
  public static String getStation2(String inputLine) {
    int commaPos1 = inputLine.indexOf(','); // position of first comma
    if (commaPos1 == -1) {
      // no commas in input line
      throw new GraphInputFormatError(
        "input line does not contain a comma");
    } // end if

    int commaPos2 = inputLine.indexOf(',', commaPos1+1);
    if (commaPos2 == -1) {
      // only one comma in input line
      throw new GraphInputFormatError(
        "input line contains only one comma");
    } // end if

    // Station1 is everything between the two commas,
    // minus any leading or trailing spaces
    return inputLine.substring(commaPos1+1, commaPos2).trim();
  } // end getStation2

  /**
   * Extracts the line name from an input line of the form
   * "(Station1, Station2, line)".  The line name will have all leading
   * and trailing spaces trimmed.  For example, if the input line is <br>
   * "  (  Baker Street  ,  Royal Albert,  Victoria Line  )  ",  this
   * method will return "Victoria Line".
   *
   * @param inputLine the line of input
   * @return the line name from the input line
   * @exception GraphInputFormatError if the input line does not have the
   * correct format (e.g. doesn't start with a left paren, or doesn't have
   * two commas)
   */
  public static String getLine(String inputLine) {
    // trim any trailing blanks so the ')' is at the end
    inputLine = inputLine.trim();
    int commaPos1 = inputLine.indexOf(','); // position of first comma
    if (commaPos1 == -1) {
      // no commas in input line
      throw new GraphInputFormatError(
        "input line does not contain a comma");
    } // end if

    int commaPos2 = inputLine.indexOf(',', commaPos1+1); // position of 2nd comma
    if (commaPos2 == -1) {
      // only one comma in input line
      throw new GraphInputFormatError(
        "input line contains only one comma");
    } // end if

    int parenPos = inputLine.length() - 1;

    if (inputLine.charAt(parenPos) != ')') {
      // input line doesn't end with right paren
      throw new GraphInputFormatError(
        "input line does not end with a right paren");
    } // end if

    // Station1 is everything between the second comma and the right paren
    // minus any leading or trailing spaces
    return inputLine.substring(commaPos2+1, parenPos).trim();
  } // end getLine

  /**
   * method to test this class
   */
  public static void test () {
    String samples[] = {
      "  (  Baker Street  ,  Royal Albert,  Victoria Line  )  ",
      "(long station with spaces,longstationwithnospaces,line)",
      "(Acton_Town,    Ealing_Common,  Distric)",
      "(Acton_Town,    South_Ealing,   Piccadilly_Line)"
    };
    for (int i = 0; i < samples.length; i++) {
      System.out.println("Input Line: \"" + samples[i] + "\"");
      //      Vertex v = new Vertex(getStation1(samples[i]));
      System.out.println("   Station1 = \"" + getStation1(samples[i]) + "\"");
      System.out.println("   Station2 = \"" + getStation2(samples[i]) + "\"");
      System.out.println("   line = \"" + getLine(samples[i]) + "\"");
    } // end for
  } // end test

} // end class GraphInput