// Withdrawal.java
// Represents a withdrawal ATM transaction

public class Withdrawal extends Transaction
{
    private int amount; // amount to withdraw
    private Keypad keypad; // reference to keypad
    private CashDispenser cashDispenser; // reference to cash dispenser

    // constant corresponding to menu option to cancel
    private final static int CANCELED = 6;

    // Withdrawal constructor
    public Withdrawal( int userAccountNumber, Screen atmScreen,
    BankDatabase atmBankDatabase, Keypad atmKeypad,
    CashDispenser atmCashDispenser )
    {
        // initialize superclass variables
        super( userAccountNumber, atmScreen, atmBankDatabase );

        // initialize references to keypad and cash dispenser
        keypad = atmKeypad;
        cashDispenser = atmCashDispenser;
    } // end Withdrawal constructor

    // perform transaction
    @Override
    public void execute()
    {
        boolean cashDispensed = false; // cash was not dispensed yet
        double availableBalance; // amount available for withdrawal

        // get references to bank database and screen
        BankDatabase bankDatabase = getBankDatabase();
        Screen screen = getScreen();

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

            // check whether user chose a withdrawal amount or canceled
            if ( amount != CANCELED )
            {
                // get available balance of account involved
                availableBalance =
                bankDatabase.getAvailableBalance( getAccountNumber() );

                // 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 ) )
                    {
                        // update the account involved to reflect the withdrawal
                        bankDatabase.debit( getAccountNumber(), amount );

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

                        // instruct user to take cash
                        screen.displayMessageLine( "\nYour cash has been" +
                        " dispensed. Please take your cash now." );
                    } // end if
                    else // cash dispenser does not have enough cash
                    screen.displayMessageLine(
                    "\nInsufficient cash available in the ATM." +
                    "\n\nPlease choose a smaller amount." );
                } // end if
                else // not enough money available in user's account
                {
                    screen.displayMessageLine(
                    "\nInsufficient funds in your account." +
                    "\n\nPlease choose a smaller amount." );
                } // end else
            } // end if
            else // user chose cancel menu option
            {
                screen.displayMessageLine( "\nCanceling transaction..." );
                return; // return to main menu because user canceled
            } // end else
        } while ( !cashDispensed );

    } // end method execute

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

     Screen screen = getScreen(); // get screen reference

     // 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 withdrawal menu
         screen.displayMessageLine( "\nWithdrawal Menu:" );
         screen.displayMessageLine( "1 - $20" );
         screen.displayMessageLine( "2 - $40" );
         screen.displayMessageLine( "3 - $60" );
         screen.displayMessageLine( "4 - $100" );
         screen.displayMessageLine( "5 - $200" );
         screen.displayMessageLine( "6 - Cancel transaction" );
         screen.displayMessage( "\nChoose a withdrawal amount: " );

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

         // determine how to proceed based on the input value
         switch ( input )
         {
             case 1: // if the user chose a withdrawal amount
             case 2: // (i.e., chose option 1, 2, 3, 4 or 5), return the
             case 3: // corresponding amount from amounts array
             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: // the user did not enter a value from 1-6
             screen.displayMessageLine(
             "\nInvalid selection. Try again." );
         } // end switch
        } // end while

        return userChoice; // return withdrawal amount or CANCELED
    } // end method displayMenuOfAmounts
} // end class Withdrawal