Improve [2FA] Error Message (#15)

- [+] feat(error.go): add global error variables for common error cases
- [+] refactor(middleware.go): replace inline errors with global error variables
- [+] refactor(storage.go): replace inline errors with global error variables
- [+] refactor(storage.go): wrap errors using fmt.Errorf for ErrorFailedToDeleteInfo and ErrorFailedToResetStorage

error.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2024 H0llyW00dz All rights reserved.
+//
+// License: BSD 3-Clause License
+
+package twofa
+
+import "errors"
+
+// Global error variables
+var (
+	ErrorFailedToRetrieveInfo       = errors.New("failed to retrieve 2FA information")
+	ErrorFailedToUnmarshalInfo      = errors.New("failed to unmarshal 2FA information")
+	ErrorFailedToMarshalInfo        = errors.New("failed to marshal updated 2FA information")
+	ErrorFailedToStoreInfo          = errors.New("failed to store updated 2FA information")
+	ErrorFailedToDeleteInfo         = errors.New("failed to delete 2FA information")
+	ErrorFailedToResetStorage       = errors.New("failed to reset storage")
+	ErrorFailedToCloseStorage       = errors.New("failed to close storage")
+	ErrorContextKeyNotSet           = errors.New("ContextKey is not set")
+	ErrorFailedToRetrieveContextKey = errors.New("failed to retrieve context key")
+)

middleware.go

@@ -5,7 +5,6 @@
 package twofa
 
 import (
-	"fmt"
 	"strings"
 	"time"
 
@@ -110,12 +109,12 @@ func (m *Middleware) isPathSkipped(path string) bool {
 // getContextKey retrieves the context key from c.Locals using the provided ContextKey.
 func (m *Middleware) getContextKey(c *fiber.Ctx) (string, error) {
 	if m.Config.ContextKey == "" {
-		return "", fmt.Errorf("ContextKey is not set")
+		return "", ErrorContextKeyNotSet
 	}
 
 	contextKeyValue, ok := c.Locals(m.Config.ContextKey).(string)
 	if !ok {
-		return "", fmt.Errorf("failed to retrieve context key")
+		return "", ErrorFailedToRetrieveContextKey
 	}
 
 	return contextKeyValue, nil

storage.go

@@ -55,7 +55,7 @@ func (i *Info) SetExpirationTime(expiration time.Time) {
 func (m *Middleware) getInfoFromStorage(contextKey string) (*Info, error) {
 	rawInfo, err := m.Config.Storage.Get(contextKey)
 	if err != nil {
-		return nil, fmt.Errorf("failed to retrieve 2FA information")
+		return nil, ErrorFailedToRetrieveInfo
 	}
 
 	if rawInfo == nil {
@@ -64,7 +64,7 @@ func (m *Middleware) getInfoFromStorage(contextKey string) (*Info, error) {
 
 	var info Info
 	if err := m.Config.JSONUnmarshal(rawInfo, &info); err != nil {
-		return nil, fmt.Errorf("failed to unmarshal 2FA information")
+		return nil, ErrorFailedToUnmarshalInfo
 	}
 
 	return &info, nil
@@ -74,12 +74,12 @@ func (m *Middleware) getInfoFromStorage(contextKey string) (*Info, error) {
 func (m *Middleware) updateInfoInStorage(contextKey string, info *Info) error {
 	updatedRawInfo, err := m.Config.JSONMarshal(info)
 	if err != nil {
-		return fmt.Errorf("failed to marshal updated 2FA information")
+		return ErrorFailedToMarshalInfo
 	}
 
 	err = m.Config.Storage.Set(contextKey, updatedRawInfo, time.Duration(m.Config.CookieMaxAge)*time.Second)
 	if err != nil {
-		return fmt.Errorf("failed to store updated 2FA information")
+		return ErrorFailedToStoreInfo
 	}
 
 	return nil
@@ -89,7 +89,7 @@ func (m *Middleware) updateInfoInStorage(contextKey string, info *Info) error {
 func (m *Middleware) deleteInfoFromStorage(contextKey string) error {
 	err := m.Config.Storage.Delete(contextKey)
 	if err != nil {
-		return fmt.Errorf("failed to delete 2FA information: %w", err)
+		return fmt.Errorf("%w: %v", ErrorFailedToDeleteInfo, err)
 	}
 
 	return nil
@@ -99,7 +99,7 @@ func (m *Middleware) deleteInfoFromStorage(contextKey string) error {
 func (m *Middleware) resetStorage() error {
 	err := m.Config.Storage.Reset()
 	if err != nil {
-		return fmt.Errorf("failed to reset storage: %w", err)
+		return fmt.Errorf("%w: %v", ErrorFailedToResetStorage, err)
 	}
 
 	return nil
@@ -109,7 +109,7 @@ func (m *Middleware) resetStorage() error {
 func (m *Middleware) closeStorage() error {
 	err := m.Config.Storage.Close()
 	if err != nil {
-		return fmt.Errorf("failed to close storage: %w", err)
+		return ErrorFailedToCloseStorage
 	}
 
 	return nil