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
+}