package vendingMachine;

// A Java implementation of VendingMachine.
// Original in C++ by Liu Ling,
// Taken from a paper by Mary Jean Harrold.
// Translated to Java by Jeff Offutt, January 2004
// Updated for Java 1.5, 2006 (probably imperfectly), Jeff Offutt.
// Main added later for testing.
// The original text can be retrieved from 
// http://cs.gmu.edu/~offutt/softwaretest/ms-level-syllabus/assigns/vendingMachine.java
//
// Several modifications have been made to the reference file (Y. Ledru, 2012):
// - declared a package vendingMachine;
// - changed the name to VendingMachine (Using a leading uppercase).
// - the constructor is now public.
// - getCredit and getStock have been added to increase testability
// - the main() method has been commented out.

import java.util.*;
import java.io.*;

public class VendingMachine
{
private int credit;
private LinkedList<String> stock;

// Maximum size of vendingMachine
private static final int MAX = 10;

// In the C++ version, Ling used a C++ list<string>
// with operations like push(), pop(), etc to look
// a lot like a queue.
// list<string> stock; ??
// In the Java version I'm emulating a queue on top of the
// LinkedList. Ugly, but I don't want to redesign.

//************************************************
// Constructor
// vendingmachine starts empty.
//************************************************
public VendingMachine()
{
   credit = 0;
   stock  = new LinkedList<String>(); // Empty stock.
}

//************************************************
// A coin is given to the vendingMachine.
// Must be a dime, quarter or dollar.
// Ignores invalid input
//************************************************
public void coin (int coin) {
   if (coin != 10 && coin != 25 && coin != 100)
      return;
   if (credit >= 90)
      return;
   credit = credit + coin;
   return;
}

//************************************************
// User asks for a chocolate.
// Returns the change and the sets the
// parameter StringBuffer variable Choc.
// If not enough money or no chocolates,
// returns 0 and a blank string.
//************************************************
// Necessary because strings are immutable
// C++ version returned both choc and change as parameters
public int getChoc (StringBuffer choc) {
   int change;
   if (credit < 90 || stock.size() <= 0) {
      change = 0;
      choc.replace (0, choc.length(), "");
      return (change);
   }
   change = credit - 90;
   credit = 0;
   choc.replace (0, choc.length(), (String) stock.removeFirst());
   return (change);
}

//************************************************
// Adds one new piece of chocolate to the machine
// If machine is full, nothing happens
//************************************************
public void addChoc (String choc)
{
   if (stock.size() >= MAX)
      return;
   stock.add (choc);
   return;
}



//Needed for testing -- increases observability
public int getCredit ()
{
return (credit);
}

//Needed for testing -- increases observability
public LinkedList<String> getStock ()
{
return (stock);
}
//************************************************
// mainV1() for initial testing.
//************************************************
/*public static void main (String[] argv)
{
   StringBuffer choc = new StringBuffer ("xx");
   VendingMachine v = new VendingMachine ();
   v.addChoc ("c1");
   v.addChoc ("c2");
   v.addChoc ("c3");
   v.coin (10);
   v.coin (25);
   v.coin (100);
   int ch = v.getChoc (choc);
   System.out.println ("First get, c: " + choc + ", ch: " + ch);

   ch = v.getChoc (choc);
   v.coin (100);
   ch = v.getChoc (choc);
   System.out.println ("Second get, c: " + choc + ", ch: " + ch);
}
*/
} // End class vendingMachine