ch9.6

internal/data/filters.go

@@ -1,6 +1,10 @@
 package data
 
-import "gitea.local.lab/Lbenedar/greenlight/internal/validator"
+import (
+	"strings"
+
+	"gitea.local.lab/Lbenedar/greenlight/internal/validator"
+)
 
 type Filters struct {
 	Page         int
@@ -17,3 +21,20 @@ func ValidateFilters(v *validator.Validator, f Filters) {
 
 	v.Check(validator.PermittedValue(f.Sort, f.SortSafelist...), "sort", "invalid sort values")
 }
+
+func (f Filters) sortColumn() string {
+	for _, safeValue := range f.SortSafelist {
+		if f.Sort == safeValue {
+			return strings.TrimPrefix(f.Sort, "-")
+		}
+	}
+
+	panic("unsafe sort parameter: " + f.Sort)
+}
+
+func (f Filters) sortDirection() string {
+	if strings.HasPrefix(f.Sort, "-") {
+		return "DESC"
+	}
+	return "ASC"
+}