import java.util.Vector;

/**
 * An implementation of mutable lists that uses vectors.
 * the implementationa and the interface is different. The vector is stored and implemented backwards.
 *
 * @author Samuel A. Rebelsky
 * @author Yvonne Palm
 * @author Jonathan Wellons
 */
public class ReversedVectorBasedList
  implements MutableList
{
  // +-------+---------------------------------------------------
  // | Notes |
  // +-------+

  // +-----------+-----------------------------------------------
  // | Constants |
  // +-----------+

  // +--------+--------------------------------------------------
  // | Fields |
  // +--------+

  /**
   * The actual contents of the list, stored in a Vector.
   */
  Vector contents;


  // +--------------+--------------------------------------------
  // | Constructors |
  // +--------------+

  /**
   * Build an empty list.
   */
  public ReversedVectorBasedList()
  {
    this.contents = new Vector();
  } // ReversedVectorBasedList()

  // +------------------+----------------------------------------
  // | Exported Methods |
  // +------------------+

  /**
   * Determine if the list is empty
   */
  public boolean isEmpty()
  {
    return this.contents.isEmpty();
  } // isEmpty()

  /**
   * Update the vector by adding an element to the back.
   */
  public void addToFront(Object newThingy) {
    this.contents.add(newThingy);
  } // addToFront(Object)

  /**
   * Update the list by removing the last element in the vector.  Return
   * that element.
   */
  public Object removeFirst()
  {
    return this.contents.remove(last());
  } // removeFirst()


  // Find the position of the last element in the vector
  public int last(){
    if (this.contents.size() >= 1)
      return (this.contents.size() - 1);
    return (this.contents.size() - 1);	
  }//last()

  /**
   * Get the length.
   */
  public int length() 
  {
    return this.contents.size();
  } // length()

  /**
   * Get the first element of the list (non-destructively) by getting the last element of the vector.
   */
  public Object getFirst()
  {
    return this.contents.get(last());
  } // getFirst()

  /**
   * Convert to a string for ease of printing.
   */
  public String toString()
  {
    if (this.contents.isEmpty())
      return "()";
    String result = "(" + this.contents.get(last());
    for (int i = last()-1; i >= 0; i--)
      result = result + " " + this.contents.get(i);
    result = result + ")";
    return result;
  } // toString()

  /**
   * Make an independent copy of this list.
   */
  public MutableList copyMe()
  {
    return null;   // STUB
  } // copyMe()
} // class ReversedVectorBasedList