Implement saving and loading for account data, currently a basic json file

pkg/accounts/accounts.go

@@ -0,0 +1,86 @@
+package accounts
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"github.com/google/uuid"
+)
+
+const kDefaultSavePath = "/tmp/accounts.json"
+
+// Account represents a registered user
+type Account struct {
+	// Name simply describes the account and must be unique
+	Name string `json:"name"`
+
+	// id represents a unique ID per account and is set one registered
+	Id uuid.UUID `json:"id"`
+}
+
+// Represents the accountant data to store
+type accountantData struct {
+	Accounts []Account `json:"accounts"`
+}
+
+// Accountant manages a set of accounts
+type Accountant struct {
+	data accountantData
+}
+
+// NewAccountant creates a new accountant
+func NewAccountant() *Accountant {
+	return &Accountant{}
+}
+
+// RegisterAccount adds an account to the set of internal accounts
+func (a *Accountant) RegisterAccount(acc Account) (Account, error) {
+
+	// Set the account ID to a new UUID
+	acc.Id = uuid.New()
+
+	// Verify this acount isn't already registered
+	for _, a := range a.data.Accounts {
+		if a.Name == acc.Name {
+			return Account{}, fmt.Errorf("Account name already registered")
+		} else if a.Id == acc.Id {
+			return Account{}, fmt.Errorf("Account ID already registered")
+		}
+	}
+
+	// Simply add the account to the list
+	a.data.Accounts = append(a.data.Accounts, acc)
+
+	return acc, nil
+}
+
+// Load will load the accountant from data
+func (a *Accountant) Load() error {
+	// Don't load anything if the file doesn't exist
+	_, err := os.Stat(kDefaultSavePath)
+	if os.IsNotExist(err) {
+		fmt.Printf("File %s didn't exist, loading with fresh accounts data\n", kDefaultSavePath)
+		return nil
+	}
+
+	if b, err := ioutil.ReadFile(kDefaultSavePath); err != nil {
+		return err
+	} else if err := json.Unmarshal(b, &a.data); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Save will save the accountant data out
+func (a *Accountant) Save() error {
+	if b, err := json.Marshal(a.data); err != nil {
+		return err
+	} else {
+		if err := ioutil.WriteFile(kDefaultSavePath, b, os.ModePerm); err != nil {
+			return err
+		}
+	}
+	return nil
+}

pkg/accounts/accounts_test.go

@@ -0,0 +1,92 @@
+package accounts
+
+import (
+	"testing"
+)
+
+func TestNewAccountant(t *testing.T) {
+	// Very basic verify here for now
+	accountant := NewAccountant()
+	if accountant == nil {
+		t.Error("Failed to create accountant")
+	}
+}
+
+func TestAccountant_RegisterAccount(t *testing.T) {
+
+	accountant := NewAccountant()
+
+	// Start by making two accounts
+
+	namea := "one"
+	a := Account{Name: namea}
+	acca, err := accountant.RegisterAccount(a)
+	if err != nil {
+		t.Error(err)
+	} else if acca.Name != namea {
+		t.Errorf("Missmatched account name after register, expected: %s, actual: %s", namea, acca.Name)
+	}
+
+	nameb := "two"
+	b := Account{Name: nameb}
+	accb, err := accountant.RegisterAccount(b)
+	if err != nil {
+		t.Error(err)
+	} else if accb.Name != nameb {
+		t.Errorf("Missmatched account name after register, expected: %s, actual: %s", nameb, acca.Name)
+	}
+
+	// Verify our accounts have differing IDs
+	if acca.Id == accb.Id {
+		t.Error("Duplicate account IDs fo separate accounts")
+	}
+
+	// Verify another request gets rejected
+	_, err = accountant.RegisterAccount(a)
+	if err == nil {
+		t.Error("Duplicate account name did not produce error")
+	}
+}
+
+func TestAccountant_LoadSave(t *testing.T) {
+	accountant := NewAccountant()
+	if len(accountant.data.Accounts) != 0 {
+		t.Error("New accountant created with non-zero account number")
+	}
+
+	name := "one"
+	a := Account{Name: name}
+	a, err := accountant.RegisterAccount(a)
+	if err != nil {
+		t.Error(err)
+	}
+
+	if len(accountant.data.Accounts) != 1 {
+		t.Error("No new account made")
+	} else if accountant.data.Accounts[0].Name != name {
+		t.Error("New account created with wrong name")
+	}
+
+	// Save out the accountant
+	if err := accountant.Save(); err != nil {
+		t.Error(err)
+	}
+
+	// Re-create the accountant
+	accountant = NewAccountant()
+	if len(accountant.data.Accounts) != 0 {
+		t.Error("New accountant created with non-zero account number")
+	}
+
+	// Load the old accountant data
+	if err := accountant.Load(); err != nil {
+		t.Error(err)
+	}
+
+	// Verify we have the same account again
+	if len(accountant.data.Accounts) != 1 {
+		t.Error("No account after load")
+	} else if accountant.data.Accounts[0].Name != name {
+		t.Error("New account created with wrong name")
+	}
+}