Adding ValidateFilters method in filters.go and use it in our listMoviesHandler

internal/data/filters.go

@@ -1,7 +1,21 @@
 package data
 
+import "greenlight.craftr.fr/internal/validator"
+
 type Filters struct {
-	Page     int
-	PageSize int
-	Sort     string
+	Page         int
+	PageSize     int
+	Sort         string
+	SortSafelist []string
+}
+
+func ValidateFilters(v *validator.Validator, f Filters) {
+	// Check that the page and page_size parameters contain sensible values
+	v.Check(f.Page > 0, "page", "must be greater than 0")
+	v.Check(f.Page <= 10_000_000, "page", "must be a maximum of 10 million")
+	v.Check(f.PageSize > 0, "page_size", "must be greater than 0")
+	v.Check(f.PageSize <= 100, "page_size", "must be a maximum of 100")
+
+	// Check that the sort parameter matches a value in the safelist
+	v.Check(validator.PermittedValue(f.Sort, f.SortSafelist...), "sort", "invalid sort value")
 }