/**
   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 4.0
*/
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