/**
   A class that records the purchase and sale of stocks, and provides the
   capital gain or loss.
   
   @author Frank M. Carrano
   @author Timothy M. Henry
   @version 5.0
*/
public class StockLedger
{
  private QueueInterface<StockPurchase> ledger;
  
  public StockLedger()
  {
     ledger = new LinkedQueue<>();
  } // end default constructor
  
  /** Records a stock purchase in this ledger.
      @param sharesBought   The number of shares purchased.
      @param pricePerShare  The price per share. */
  public void buy(int sharesBought, double pricePerShare)
  {
    while (sharesBought > 0)
    {
       StockPurchase purchase = new StockPurchase(pricePerShare);
       ledger.enqueue(purchase);
       sharesBought--;
    } // end while
  } // end buy
  
  /** Removes from this ledger any shares that were sold 
      and computes the capital gain or loss.
      @param sharesSold     The number of shares sold.
      @param pricePerShare  The price per share.
      @return  The capital gain (loss). */
  public double sell(int sharesSold, double pricePerShare)
  {
     double saleAmount = sharesSold * pricePerShare;
     double totalCost = 0;
    
     while (sharesSold > 0)
     {
        StockPurchase share = ledger.dequeue();
        double shareCost = share.getCostPerShare();
        totalCost = totalCost + shareCost;
        sharesSold--;
     } // end while
    
     return saleAmount - totalCost; // Gain or loss
  } // end sell
} // end StockLedger