feat: add SliceValidationError

internal/domain/error.go

@@ -6,9 +6,8 @@ import (
 )
 
 var (
-	ErrNothingToUpdate          = errors.New("nothing to update")
-	ErrUnsupportedSortBy        = errors.New("unsupported sort by")
-	ErrUnsupportedSortDirection = errors.New("unsupported sort direction")
+	ErrNothingToUpdate   = errors.New("nothing to update")
+	ErrUnsupportedSortBy = errors.New("unsupported sort by")
 )
 
 type ErrorCode uint8
@@ -34,6 +33,7 @@ func (e ErrorCode) String() string {
 
 type Error interface {
 	error
+	// UserError is a message that is returned to a user in, for example, an http response.
 	UserError() string
 	Code() ErrorCode
 }
@@ -59,6 +59,28 @@ func (e ValidationError) Unwrap() error {
 	return e.Err
 }
 
+type SliceValidationError struct {
+	Field string
+	Index int
+	Err   error
+}
+
+func (e SliceValidationError) Error() string {
+	return fmt.Sprintf("%s[%d]: %s", e.Field, e.Index, e.Err)
+}
+
+func (e SliceValidationError) UserError() string {
+	return e.Error()
+}
+
+func (e SliceValidationError) Code() ErrorCode {
+	return ErrorCodeValidationError
+}
+
+func (e SliceValidationError) Unwrap() error {
+	return e.Err
+}
+
 type MaxError struct {
 	Max int
 }

internal/domain/error_test.go

@@ -33,6 +33,23 @@ func TestValidationError(t *testing.T) {
 	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
 }
 
+func TestSliceValidationError(t *testing.T) {
+	t.Parallel()
+
+	err := domain.SliceValidationError{
+		Field: "test",
+		Index: 15,
+		Err: domain.MinError{
+			Min: 25,
+		},
+	}
+	var _ domain.Error = err
+	assert.Equal(t, fmt.Sprintf("%s[%d]: %s", err.Field, err.Index, err.Err.Error()), err.Error())
+	assert.Equal(t, err.Error(), err.UserError())
+	assert.ErrorIs(t, err, err.Err)
+	assert.Equal(t, domain.ErrorCodeValidationError, err.Code())
+}
+
 func TestMinError(t *testing.T) {
 	t.Parallel()
 

internal/domain/sort_direction.go

@@ -1,10 +1,15 @@
 package domain
 
 import (
+	"errors"
 	"fmt"
 	"strings"
 )
 
+var (
+	ErrUnsupportedSortDirection = errors.New("unsupported sort direction")
+)
+
 type SortDirection uint8
 
 const (

internal/router/rest/query_params.go

@@ -11,6 +11,10 @@ import (
 	"gitea.dwysokinski.me/twhelp/core/internal/domain"
 )
 
+const (
+	sortKey = "sort"
+)
+
 type queryParams[Sort any] struct {
 	values  url.Values
 	newSort func(by string, direction string) (Sort, error)
@@ -85,7 +89,7 @@ func (q queryParams[Sort]) sort() ([]Sort, error) {
 		return nil, errors.New("newSort is nil, can't proceed")
 	}
 
-	vals := q.values["sort"]
+	vals := q.values[sortKey]
 	if len(vals) == 0 {
 		return nil, nil
 	}
@@ -94,16 +98,18 @@ func (q queryParams[Sort]) sort() ([]Sort, error) {
 	for i, v := range vals {
 		index := strings.IndexByte(v, ':')
 		if index == -1 {
-			return nil, domain.ValidationError{
-				Field: fmt.Sprintf("sort[%d]", i),
+			return nil, domain.SliceValidationError{
+				Field: sortKey,
+				Index: i,
 				Err:   fmt.Errorf("parsing \"%s\": invalid syntax, expected field:direction", v),
 			}
 		}
 
 		s, err := q.newSort(v[:index], v[index+1:])
 		if err != nil {
-			return nil, domain.ValidationError{
-				Field: fmt.Sprintf("sort[%d]", i),
+			return nil, domain.SliceValidationError{
+				Field: sortKey,
+				Index: i,
 				Err:   err,
 			}
 		}