//An instance of this class represents a basic bank account that permits
// transactions with any non-negative transaction amount. 
//
//Unique account numbers are generated by an internal process whenever a
// new account is created
//
//Any attempted transaction with a negative amount results in aborting
// the transaction 
//
//PUBLIC INTERFACE
//
// Constructors:
//    1) BasicBankAccount()
//       Creates a new account with 0.0 balance, and unique account number
//    2) BasicBankAccount(double amount)
//       Creates a new account with a given non-negative initial balance 
//          and a unique account number
// Accessors:
//    1) String getNumber()
//       Returns the number of this BasicBankAccount
//    2) double getBalance()
//       Returna the balance of this BasicBankAccount
// Mutators:
//    1) void credit(double amount)
//       Increases the balance of an account by a given non-negative amount
//    2) void debit(double amount)
//       Decreases the balance of an account by a given non-negative amount
//       The account balance is permitted to go negative
// Other Methods:
//    1) String toString()
//       Returns a printable description of the state of an account
//
// Norman Pestaina   COP 2210    Summer 2016
//
public class BasicBankAccount
{
   //Instance (State) Variables
   private final String number;  //Account number
   private double balance; //Current balance
   
   //Parameterless Constructor: 
   // Creates a new BasicBankAccount with zero balance
   public BasicBankAccount()
   {
      this.number = newNumber();
      this.balance = 0.0;
   }
   
   //Initializing  Constructor: 
   // Creates a new BasicBankAccount with a given balance (must be >= 0.0)
   public BasicBankAccount(double amount)
   {
      validate(amount);
      this.number = newNumber();
      this.balance = amount;
   }
   
   //Accessor: 
   // Returns the number of this BasicBankAccount
   public String getNumber()
   {
      return this.number;
   }
   
   //Accessor: 
   // Returns the balance of this BasicBankAccount
   public double getBalance()
   {
      return this.balance;
   }
   
   //Mutator: 
   // Increase the balance of this BasicBankAccount by a given amount
   public void credit(double amount)
   {
      validate(amount);
      this.balance = this.balance + amount;
   }
   
   //Mutator: 
   // Decrease the balance of this BasicBankAccount by a given amount        
   public void debit(double amount)
   {
      validate(amount);
      this.balance = this.balance - amount;
   }
   
   //Returns a printable image of this BasicBankAccount
   public String toString()
   {
      return "Account #" + this.number + " Balance: $" + this.balance;
   }
   
   //*********************************************************************
   //*********************************************************************
   //Class Variables and Methods      
   private static int seedNumber = 7000000;  //Base account number
   
   //Returns a new unique account #
   private static String newNumber()
   {
      seedNumber = seedNumber + 1;
      String number = "" + seedNumber;
      return number.substring(0, 1) + "-" +
             number.substring(1, 4) + "-" +
             number.substring(4);
   }
   
   //Validates the amount of any BasicBankAccount creation or transaction
   //Throws a RuntimeException if the amount is negative (< 0.0)
   private static void validate(double amount)
   {
      if (amount < 0.0)
         throw new RuntimeException("Invalid amount $" + amount);
   }      
}