// Package account handles bank accounts.
package account
import "sync"
// Account represents a bank account.
type Account struct {
	open    bool
	balance int
	sync.Mutex
}
// Open return a new Account, with initial balance as a parameter.
func Open(initial int) *Account {
	if initial < 0 {
		return nil
	}
	return &Account{
		open:    true,
		balance: initial,
	}
}
// Balance returns the balance of an open Account.
func (acc *Account) Balance() (int, bool) {
	if !acc.open {
		return 0, false
	}
	return acc.balance, true
}
// Close closes the Account. Forbids further deposits.
func (acc *Account) Close() (int, bool) {
	acc.Lock()
	if !acc.open {
		acc.Unlock()
		return 0, false
	}
	acc.open = false
	acc.Unlock()
	return acc.balance, true
}
// Deposit makes a transaction on the Account.
func (acc *Account) Deposit(amount int) (int, bool) {
	acc.Lock()
	if !acc.open || amount < 0 && -amount > acc.balance {
		acc.Unlock()
		return 0, false
	}
	acc.balance += amount
	acc.Unlock()
	return acc.balance, true
}