import CursoredList;
import ListCursor;

/**
 * Strange static stuff from question A on exam 3 of CSC152 2000S.
 *
 * @author Hermione Hacker
 * @author Herman Hacker
 * @author Herr Doktor Professor Rebelsky
 * @version 1.0 of April 2000.
 */
public class CursoredListSorter 
{
    /**
     * Sort a cursored list, comparing things as strings.
     * Uses the selection sort algorithm.
     */
    public static void sort(CursoredList list) 
    {
      // Create a cursor.  This is the destination of each swap.
      ListCursor current = list.newCursor();
      // A second cursor identifies the smallest known element
      // of the list.
      ListCursor smallest;
      // Start at the beginning
      current.reset();
      // For each position in the list ...
      while (current.inList()) {
            // Find the smallest element in the sublist.
            smallest = findSmallest(list,current);
            // DEBUG
            // System.err.println("Smallest: " +
            //                    list.valueAt(smallest));
            // Swap the contents at the two positions.
            list.swap(current,smallest);
            // And move on.
            current.advance();
        } // while still in the list
    } // sort(CursoredList)

    /**
     * Put a cursor on the location of the smallest element
     * in a sublist that starts at a particular cursor.  Uses
     * string comparison to identify the proper place for an
     * element.
     * Pre: The sublist is nonempty.
     * Post: Does not move the starting cursor.
     */
    protected static ListCursor findSmallest(CursoredList list, 
                                             ListCursor start)
    {
        // Our guess as to the smallest.
        ListCursor guess = start.makeCopy();
        // The string that corresponds to that guess.
        String guessString = 
            list.valueAt(guess).toString().toLowerCase();
        // A cursor we can use to iterate through the list.  Start
        // it at the next element.
        ListCursor temp = start.makeCopy();
        temp.advance();
        // System.err.println("  First guess: " + guessString); // DEBUG
        // For each remaining position in the list 
        while (temp.inList()) {
          // Get the contents.
          String tempString = 
               list.valueAt(temp).toString().toLowerCase();
          // System.err.println("  Next guess: " + tempString); // DEBUG
          // If it's smaller, update our guess.
          if (tempString.compareTo(guessString) < 0) {
               guess.moveTo(temp);
               guessString = tempString;
          } // if it's smaller.
          // Move on to the next thing
          temp.advance();
        } // while
        // That's it, we're done.
        return guess;
    } // findSmallest
} // class CursoredListSorter