style(backend): improve error handling

backend/internal/domain/errors.go

@@ -1,18 +1,20 @@
 package domain
 
+import "fmt"
+
 type ErrorCode string
 
 const (
 	// File errors
-	ErrFileNotFound     ErrorCode = "FILE_NOT_FOUND"
-	ErrMIMENotSupported ErrorCode = "MIME_NOT_SUPPORTED"
+	ErrCodeFileNotFound     ErrorCode = "FILE_NOT_FOUND"
+	ErrCodeMIMENotSupported ErrorCode = "MIME_NOT_SUPPORTED"
 
 	// Tag errors
-	ErrTagNotFound ErrorCode = "TAG_NOT_FOUND"
+	ErrCodeTagNotFound ErrorCode = "TAG_NOT_FOUND"
 
 	// General errors
-	ErrValidation ErrorCode = "VALIDATION_ERROR"
-	ErrInternal   ErrorCode = "INTERNAL_SERVER_ERROR"
+	ErrCodeBadRequest ErrorCode = "BAD_REQUEST"
+	ErrCodeInternal   ErrorCode = "INTERNAL_SERVER_ERROR"
 )
 
 type DomainError struct {
@@ -22,25 +24,42 @@ type DomainError struct {
 	Details []any     `json:"-"`
 }
 
-func (e *DomainError) Error() string {
-	if e.Err != nil {
-		return e.Message + ": " + e.Err.Error()
-	}
-	return e.Message
+func (e *DomainError) Wrap(err error) *DomainError {
+	e.Err = err
+	return e
 }
 
-func NewDomainError(err error, code ErrorCode, details ...any) *DomainError {
+func NewErrorFileNotFound(file_id string) *DomainError {
 	return &DomainError{
-		Err:     err,
-		Code:    code,
-		Details: details,
+		Code:    ErrCodeFileNotFound,
+		Message: fmt.Sprintf("File not found: %q", file_id),
 	}
 }
 
-func NewUnexpectedError(err error) *DomainError {
+func NewErrorMIMENotSupported(mime string) *DomainError {
 	return &DomainError{
-		Err:     err,
-		Code:    ErrInternal,
+		Code:    ErrCodeMIMENotSupported,
+		Message: fmt.Sprintf("MIME not supported: %q", mime),
+	}
+}
+
+func NewErrorTagNotFound(tag_id string) *DomainError {
+	return &DomainError{
+		Code:    ErrCodeTagNotFound,
+		Message: fmt.Sprintf("Tag not found: %q", tag_id),
+	}
+}
+
+func NewErrorBadRequest(message string) *DomainError {
+	return &DomainError{
+		Code:    ErrCodeBadRequest,
+		Message: message,
+	}
+}
+
+func NewErrorUnexpected() *DomainError {
+	return &DomainError{
+		Code:    ErrCodeInternal,
 		Message: "An unexpected error occured",
 	}
 }