// Chapter 30 example: an account whose methods guard the balance.
// Run with: go run exercises/30/01-account.go

package main

import "fmt"

type account struct {
	owner   string
	balance int
}

func newAccount(owner string) *account {
	return &account{owner: owner}
}

func (a *account) deposit(amount int) error {
	if amount <= 0 {
		return fmt.Errorf("cannot deposit %d", amount)
	}
	a.balance = a.balance + amount
	return nil
}

func (a *account) withdraw(amount int) error {
	if amount <= 0 {
		return fmt.Errorf("cannot withdraw %d", amount)
	}
	if amount > a.balance {
		return fmt.Errorf("cannot withdraw %d: the balance is %d", amount, a.balance)
	}
	a.balance = a.balance - amount
	return nil
}

func (a *account) getBalance() int {
	return a.balance
}

func main() {
	acc := newAccount("Keiko")

	err := acc.deposit(100)
	if err != nil {
		fmt.Println("Error:", err)
	}

	err = acc.withdraw(30)
	if err != nil {
		fmt.Println("Error:", err)
	}
	fmt.Println(acc.getBalance()) // 70

	err = acc.withdraw(1000)
	if err != nil {
		fmt.Println("Error:", err) // Error: cannot withdraw 1000: the balance is 70
	}
	fmt.Println(acc.getBalance()) // 70

	// Try this: add a method canAfford(amount int) bool that returns true when
	// the balance is at least amount, and use it before a withdraw.
}