Created
June 5, 2019 17:51
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package main | |
import ( | |
"errors" | |
"fmt" | |
"testing" | |
"github.com/stretchr/testify/require" | |
) | |
// BankAccount represents a bank account | |
type BankAccount interface { | |
// Balance returns the current balance of the account | |
Balance() (float64, error) | |
// Deposit deposits money onto the account | |
Deposit(value float64) error | |
// Withdraw widthdraws money from the account | |
Withdraw(value float64) error | |
} | |
// SavingsAccount represents a savings bank account | |
type SavingsAccount interface { | |
// Embedded public interface | |
BankAccount | |
// SetWithdrawalLimit sets a new withdrawal limit | |
SetWithdrawalLimit(newLimit float64) error | |
} | |
/*************************************************\ | |
BASIC BANK ACCOUNT | |
\*************************************************/ | |
// NewBankAccount creates a new bank account instance | |
func NewBankAccount(id string) (BankAccount, error) { | |
return newBankAccount(id) | |
} | |
func newBankAccount(id string) (*bankAccount, error) { | |
if len(id) < 1 { | |
return nil, errors.New("invalid bank account id") | |
} | |
return &bankAccount{ | |
id: id, | |
blocked: false, | |
balance: 0, | |
}, nil | |
} | |
type bankAccount struct { | |
// Private fields | |
id string | |
blocked bool | |
balance float64 | |
} | |
func (ba *bankAccount) checkBlocked() error { | |
if ba.blocked { | |
return fmt.Errorf("account %s is blocked", ba.id) | |
} | |
return nil | |
} | |
func (ba *bankAccount) Balance() (float64, error) { | |
if err := ba.checkBlocked(); err != nil { | |
return 0, err | |
} | |
return ba.balance, nil | |
} | |
func (ba *bankAccount) Deposit(value float64) error { | |
if err := ba.checkBlocked(); err != nil { | |
return err | |
} | |
if value > 0 { | |
ba.balance += value | |
return nil | |
} | |
return fmt.Errorf("invalid deposit value: %f", value) | |
} | |
func (ba *bankAccount) Withdraw(value float64) error { | |
if err := ba.checkBlocked(); err != nil { | |
return err | |
} | |
if ba.balance-value < 0 { | |
return errors.New("insufficient funds") | |
} | |
ba.balance -= value | |
return nil | |
} | |
// TestBankAccount tests BankAccount | |
func TestBankAccount(t *testing.T) { | |
account, err := NewBankAccount("ABC") | |
require.NoError(t, err) | |
require.NotNil(t, account) | |
b1, err := account.Balance() | |
require.NoError(t, err) | |
require.Equal(t, 0.0, b1) | |
require.NoError(t, account.Deposit(4.5)) | |
b2, err := account.Balance() | |
require.NoError(t, err) | |
require.Equal(t, 4.5, b2) | |
require.NoError(t, account.Withdraw(2.5)) | |
b3, err := account.Balance() | |
require.NoError(t, err) | |
require.Equal(t, 2.0, b3) | |
} | |
/*************************************************\ | |
SAVINGS BANK ACCOUNT | |
- composes a basic account | |
- overwrites method Withdraw | |
\*************************************************/ | |
// NewSavingsAccount creates a new savings bank account instance | |
func NewSavingsAccount(id string) (SavingsAccount, error) { | |
return newSavingsAccount(id) | |
} | |
func newSavingsAccount(id string) (*savingsAccount, error) { | |
newBankAccount, err := newBankAccount(id) | |
if err != nil { | |
return nil, err | |
} | |
return &savingsAccount{ | |
bankAccount: newBankAccount, | |
withdrawalLimit: 0.0, | |
}, nil | |
} | |
type savingsAccount struct { | |
// Embedded private struct | |
*bankAccount | |
// Private fields | |
withdrawalLimit float64 | |
} | |
func (ba *savingsAccount) Withdraw(value float64) error { | |
if value > ba.withdrawalLimit { | |
return fmt.Errorf("withdrawal limit (%f) exceeded", ba.withdrawalLimit) | |
} | |
return ba.bankAccount.Withdraw(value) | |
} | |
func (ba *savingsAccount) SetWithdrawalLimit(newLimit float64) error { | |
if newLimit < 0 { | |
return fmt.Errorf("invalid withdrawal limit: %f", newLimit) | |
} | |
ba.withdrawalLimit = newLimit | |
return nil | |
} | |
// TestSavingsAccount tests SavingsAccount | |
func TestSavingsAccount(t *testing.T) { | |
account, err := NewSavingsAccount("mysavings") | |
require.NoError(t, err) | |
require.NotNil(t, account) | |
b1, err := account.Balance() | |
require.NoError(t, err) | |
require.Equal(t, 0.0, b1) | |
require.NoError(t, account.Deposit(12.0)) | |
b2, err := account.Balance() | |
require.NoError(t, err) | |
require.Equal(t, 12.0, b2) | |
account.SetWithdrawalLimit(4.0) | |
require.Error(t, account.Withdraw(5.0)) | |
require.NoError(t, account.Withdraw(4.0)) | |
b3, err := account.Balance() | |
require.NoError(t, err) | |
require.Equal(t, 8.0, b3) | |
} |
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