/**
 * This class represents a more realistic bank. 
 * 
 * When a user opens a bank account, we internally store the bank account and return only
 * the account id back to the user.
 * 
 * When the user wants to perform a transaction (e.g. withdraw or deposit) they must 
 * provide their account id.
 * 
 */
public class ArrayBank {   
    private final int INITIAL_LENGTH = 10;
    
    // These are the actual bank accounts
    private BankAccount[] accounts;
    
    // This is the account id for the next account to be opened
    private int nextAvailableAccountId;
            
    // To make this class more general, and to allow us to change how we
    // represent account ids in the future if we want, I have decided to 
    // create a separate integer variable to keep track of the next available
    // spot in the array.
    private int nextOpenSpot;

    
    /**
     * Constructs a new bank
     */
    public ArrayBank(){
        nextOpenSpot = 0;
        nextAvailableAccountId = 1;
        accounts = new BankAccount[INITIAL_LENGTH];
    }

    /**
     * Opens bank account with specified owner name and initial balance
     * @param owner The name of the owner of the account
     * @param initialBalance The initial balance in the account
     * @return The account id of the new account
     */
    public int openAccount(String owner, double initialBalance){
        BankAccount account = new BankAccount(owner, initialBalance, nextAvailableAccountId);
        nextAvailableAccountId++;
        
        // Note: there are many ways to test if the array is full. Here, we check if the
        // nextOpenSpot is equal to the size of the array. We could also have checked if
        // the last element in the array is null or not.
        if(nextOpenSpot < accounts.length){
            accounts[nextOpenSpot] = account;
        }
         else{   
            expandArray();
            accounts[nextOpenSpot] = account;        
        }
        nextOpenSpot++;
        return account.getAccountId();
    }
            
    /**
     * Returns the balance of the account or -1 if account is invalid
     * @param id The account id
     * @return The balance of the account
     */
    public double getBalance(int id){    
        BankAccount theAccount = idToAccount(id);
        if(theAccount != null){
            return theAccount.getBalance();
        }
        return -1;
    }

    /**
     * Deposits money into specified account
     * @param id The account id
     * @param amount The amount to be deposited
     * @return The new balance on the account or -1 if account id is invalid
     */
    public double deposit(int id, double amount){  
        BankAccount theAccount = idToAccount(id);
        if(theAccount != null){
            return theAccount.deposit(amount);
        }
        return -1;
    }

    /**
     * Withdraws money from the account if sufficient funds are available
     * @param id The account id
     * @param amount The amount to be deposited
     * @return The new balance on the account or -1 if account id is invalid
     */
    public double withdraw(int id, double amount){
        BankAccount theAccount = idToAccount(id);
        if(theAccount != null){
            return theAccount.withdraw(amount);           
        }
        return -1;
    }
    
    /**
     * Returns a string representation of all of the 
     * accounts opened with the bank
     * @param String A string representation of the bank
     */
    public String toString(){
        String str = "";
        for(int i = 0; i < nextOpenSpot; i++){
            str += accounts[i].toString() + "\n";
        }
        return str;
    }
    
    
    /*----------------------------------
     *      PRIVATE HELPER METHODS
     *----------------------------------*/       

    /**
     * This takes an account id and returns the corresponding bank account
     * or returns null if no such bank account exists
     * @param id The id of the account
     * @return The bank account or null if no such account exists
     */    
    private BankAccount idToAccount(int id){  
        for(int i = 0; i < nextOpenSpot; i++){
            if(accounts[i].getAccountId() == id){
                return accounts[i];
            }
        }        
        return null;
    }

    
     /**
     * This method doubles the size of the array. Copies over all the existing accounts.
     * Then updates the instance variables as necessary
     */    
    private void expandArray(){
        BankAccount[] temp = new BankAccount[accounts.length*2];
        for(int i = 0; i < accounts.length; i++){
            temp[i] = accounts[i];
        }
        accounts = temp;
    }    
}