/**
 * A program to carry on conversations with a human user.
 * This version:
 *   Uses advanced search for keywords
 *   Will transform statements as well as react to keywords
 * @author Laurie White
 * @version April 2012
 *
 */
public class Magpie4{
  /**
   * Get a default greeting
   * @return a greeting
   */
  public String getGreeting(){
    return "Hello, let's talk.";
  }

  /**
   * Gives a response to a user statement
   *
   * @param statement
   *            the user statement
   * @return a response based on the rules given
   */
  public String getResponse(String statement){
    String response = "";
    if (statement.length() == 0){
      response = "Say something, please.";
    }

    else if (findKeyword(statement, "no") >= 0){
      response = "Why so negative?";
    }
    else if (findKeyword(statement, "mother") >= 0
               || findKeyword(statement, "father") >= 0
               || findKeyword(statement, "sister") >= 0
               || findKeyword(statement, "brother") >= 0){
      response = "Tell me more about your family.";
    }

    // Responses which require transformations
    else if (findKeyword(statement, "I want to", 0) >= 0){
      response = transformIWantToStatement(statement);
    }

    else{
      // Look for a two word (you <something> me) pattern
      int psn = findKeyword(statement, "you", 0);

      if (psn >= 0 && findKeyword(statement, "me", psn) >= 0){
        response = transformYouMeStatement(statement);
      }
      else{
        response = getRandomResponse();
      }
    }
    return response;
  }

  /**
   * Take a statement with "I want to <something>." and transform it into
   * "What would it mean to <something>?"
   * @param statement the user statement, assumed to contain "I want to"
   * @return the transformed statement
   */
  private String transformIWantToStatement(String statement){
    //  Remove the final period, if there is one
    statement = statement.trim();
    String lastChar = statement.substring(statement.length() - 1);
    if (lastChar.equals(".")){
      statement = statement.substring(0, statement.length() - 1);
    }

    //  Chop off "I want" to and add the rest to "What would it mean to"
    int psn = findKeyword (statement, "I want to", 0);
    String restOfStatement = statement.substring(psn + 9).trim();
    return "What would it mean to " + restOfStatement + "?";
  }

 private String transformIWantStatement(String statement

  /**
   * Take a statement with "you <something> me" and transform it into
   * "What makes you think that I <something> you?"
   * @param statement the user statement, assumed to contain "you" followed by "me"
   * @return the transformed statement
   */
  private String transformYouMeStatement(String statement)
  {
    //  Remove the final period, if there is one
    statement = statement.trim();
    String lastChar = statement.substring(statement.length() - 1);
    if (lastChar.equals(".")){
      statement = statement.substring(0, statement.length() - 1);
    }

    // Find the location of the words "you" and "me"
    int psnOfYou = findKeyword (statement, "you", 0);
    int psnOfMe = findKeyword (statement, "me", psnOfYou + 3);

    // Chop out restOfStatement which is the words between "you" and "me"
    String restOfStatement = statement.substring(psnOfYou + 3, psnOfMe).trim();
    return "What makes you think that I " + restOfStatement + " you?";
  }





  /**
   * Search for one word in phrase. The search is not case
   * sensitive. This method will check that the given goal
   * is not a substring of a longer string (so, for
   * example, "I know" does not contain "no").
   *
   * @param statement
   *            the string to search
   * @param goal
   *            the string to search for
   * @param startPos
   *            the character of the string to begin the
   *            search at
   * @return the index of the first occurrence of goal in
   *         statement or -1 if it's not found
   */
  private int findKeyword(String statement, String goal, int startPos){
    String phrase = statement.trim().toLowerCase();
    goal = goal.toLowerCase();

    // The only change to incorporate the startPos is in
    // the line below
    int psn = phrase.indexOf(goal, startPos);

    // Refinement--make sure the goal isn't part of a word
    while (psn >= 0){
      // Find the string of length 1 before and after the word
      String before = " ", after = " ";
      if (psn > 0){
        before = phrase.substring(psn - 1, psn);
      }
      if (psn + goal.length() < phrase.length()){
        after = phrase.substring(psn + goal.length(), psn + goal.length() + 1);
      }

      // If before and after aren't letters, we've
      // found the word
      if (((before.compareTo("a") < 0) || (before.compareTo("z") > 0)) // before is not a letter
            && ((after.compareTo("a") < 0) || (after.compareTo("z") > 0))){ // after is not a letter
        return psn;
      }

      // The last position didn't work, so let's find
      // the next, if there is one.
      psn = phrase.indexOf(goal, psn + 1);

    }

    return -1;
  }

  /**
   * Search for one word in phrase.  The search is not case sensitive.
   * This method will check that the given goal is not a substring of a longer string
   * (so, for example, "I know" does not contain "no").  The search begins at the beginning of the string.
   * @param statement the string to search
   * @param goal the string to search for
   * @return the index of the first occurrence of goal in statement or -1 if it's not found
   */
  private int findKeyword(String statement, String goal){
    return findKeyword (statement, goal, 0);
  }



  /**
   * Pick a default response to use if nothing else fits.
   * @return a non-committal string
   */
  private String getRandomResponse(){
    final int NUMBER_OF_RESPONSES = 4;
    double r = Math.random();
    int whichResponse = (int)(r * NUMBER_OF_RESPONSES);
    String response = "";

    if (whichResponse == 0){
      response = "Interesting, tell me more.";
    }
    else if (whichResponse == 1){
      response = "Hmmm.";
    }
    else if (whichResponse == 2){
      response = "Do you really think so?";
    }
    else if (whichResponse == 3){
      response = "You don't say.";
    }

    return response;
  }

}