/**
 * Representation for an interest-bearing savings account
 * 
 * @author Russell C. Bjork 
 * @version May 28, 2009
 */
public class SavingsAccount
{
    private final int accountNumber;
    private Customer owner;
    private int currentBalance;     // Represented in cents
    private static int nextAccountNumber = 1;
    private static double annualInterestRate;
    
    /**
     * Constructor for objects of class SavingsAccount
     * 
     * @param owner the owner of this account
     * 
     * The account number will be set to the first available unused number
     * The balance will be set to zero
     */
    public SavingsAccount(Customer owner)
    {
        accountNumber = nextAccountNumber ++;
        this.owner = owner;
        owner.addAccount(this);
        currentBalance = 0;
    }

    /**
     * Deposit money
     * 
     * @param amount the amount to deposit (in cents)
     */
    public void deposit(int amount)
    {
        currentBalance += amount;
    }
    
    /**
     * Withdraw money
     * 
     * @param amount the amount to withdraw (in cents)
     * @exception IllegalArgumentException if insufficient balance on hand
     */
    public void withdraw(int amount)
    {
        if (currentBalance < amount)
            throw new IllegalArgumentException();
        currentBalance -= amount;
    }
    
    /**
     * Modify the interest rate
     *
     * @param newRate the new annual interest rate
     */
    public static void setAnnualInterestRate(double newRate)
    {
        annualInterestRate = newRate;
    }
    
    /**
     * Calculate interest for one month.
     */
    public void calculateInterest()
    {
        if (currentBalance >= MINIMUM_AMOUNT_FOR_INTEREST)
            currentBalance += (int) (currentBalance * annualInterestRate / 12.0);
    }
    
    /** 
     * Report current balance. 
	 * @return current balance, formatted neatly as dollars and
     * 		   cents, with a dollar sign and decimal point
     */
    public String reportBalance()
    {
        String result = "$" + currentBalance/100 + ".";
        int cents = currentBalance % 100;
        if (cents < 10)
            result += "0";
        result += cents;
        return result;
    }
    
    /** Accessor for account number
     * 
     * @return account number for this account
     */
    public int getAccountNumber()
    {
        return accountNumber;
    }
    
    /** The minimum balance an account can have and still receive interest
     */
    public static final int MINIMUM_AMOUNT_FOR_INTEREST = 500;
}