// Withdrawal.cs
// Class Withdrawal represents an ATM withdrawal transaction.
public class Withdrawal : Transaction
{
   private decimal amount; // amount to withdraw
   private Keypad keypad; // reference to Keypad
   private CashDispenser cashDispenser; // reference to cash dispenser

   // constant that corresponds to menu option to cancel
   private const int CANCELED = 6;

   // five-parameter constructor
   public Withdrawal( int userAccountNumber, Screen atmScreen, 
      BankDatabase atmBankDatabase, Keypad atmKeypad, 
      CashDispenser atmCashDispenser )
      : base( userAccountNumber, atmScreen, atmBankDatabase )
   {
      // initialize references to keypad and cash dispenser
      keypad = atmKeypad;
      cashDispenser = atmCashDispenser;
   } // end constructor

   // perform transaction, overrides Transaction's abstract method
   public override void Execute()
   {
      bool cashDispensed = false; // cash was not dispensed yet

      // transaction was not canceled yet
      bool transactionCanceled = false;

      // loop until cash is dispensed or the user cancels
      do
      {
         // obtain the chosen withdrawal amount from the user
         int selection = DisplayMenuOfAmounts();

         // check whether user chose a withdrawal amount or canceled
         if ( selection != CANCELED )
         {
            // set amount to the selected dollar amount
            amount = selection; 

            // get available balance of account involved
            decimal availableBalance = 
               Database.GetAvailableBalance( AccountNumber );

            // check whether the user has enough money in the account
            if ( amount <= availableBalance )
            {
               // check whether the cash dispenser has enough money
               if ( cashDispenser.IsSufficientCashAvailable( amount ) )
               {
                  // debit the account to reflect the withdrawal
                  Database.Debit( AccountNumber, amount );

                  cashDispenser.DispenseCash( amount ); // dispense cash
                  cashDispensed = true; // cash was dispensed

                  // instruct user to take cash
                  UserScreen.DisplayMessageLine(
                     "\nPlease take your cash from the cash dispenser." );
               } // end innermost if
               else // cash dispenser does not have enough cash
                  UserScreen.DisplayMessageLine(
                     "\nInsufficient cash available in the ATM." +
                     "\n\nPlease choose a smaller amount." );
            } // end middle if
            else // not enough money available in user's account
               UserScreen.DisplayMessageLine(
                  "\nInsufficient cash available in your account." +
                  "\n\nPlease choose a smaller amount." );
         } // end outermost if
         else
         {
            UserScreen.DisplayMessageLine( "\nCanceling transaction..." );
            transactionCanceled = true; // user canceled the transaction
         } // end else
      } while ( ( !cashDispensed ) && ( !transactionCanceled ) );
   } // end method Execute

   // display a menu of withdrawal amounts and the option to cancel;
   // return the chosen amount or 6 if the user chooses to cancel
   private int DisplayMenuOfAmounts()
   {
      int userChoice = 0; // variable to store return value

      // array of amounts to correspond to menu numbers
      int[] amounts = { 0, 20, 40, 60, 100, 200 };

      // loop while no valid choice has been made
      while ( userChoice == 0 )
      {
         // display the menu
         UserScreen.DisplayMessageLine( "\nWithdrawal options:" );
         UserScreen.DisplayMessageLine( "1 - $20" );
         UserScreen.DisplayMessageLine( "2 - $40" );
         UserScreen.DisplayMessageLine( "3 - $60" );
         UserScreen.DisplayMessageLine( "4 - $100" );
         UserScreen.DisplayMessageLine( "5 - $200" );
         UserScreen.DisplayMessageLine( "6 - Cancel transaction" );
         UserScreen.DisplayMessage( 
            "\nChoose a withdrawal option (1-6): " );

         // get user input through keypad
         int input = keypad.GetInput();

         // determine how to proceed based on the input value
         switch ( input )
         {
            // if the user chose a withdrawal amount (i.e., option
            // 1, 2, 3, 4, or 5), return the corresponding amount 
            // from the amounts array
            case 1: case 2: case 3: case 4: case 5:
               userChoice = amounts[ input ]; // save user's choice
               break;
            case CANCELED: // the user chose to cancel
               userChoice = CANCELED; // save user's choice
               break;
            default:
               UserScreen.DisplayMessageLine(
                  "\nInvalid selection. Try again." );
               break;
         } // end switch
      } // end while

      return userChoice;
   } // end method DisplayMenuOfAmounts
} // end class Withdrawal

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 * (C) Copyright 1992-2006 by Deitel & Associates, Inc. and               *
 * Pearson Education, Inc. All Rights Reserved.                           *
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