chore: rename regexp file to filter

pkg/gotenberg/filter.go

@@ -0,0 +1,53 @@
+package gotenberg
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/dlclark/regexp2"
+)
+
+// ErrFiltered happens if a value is filtered by the [FilterDeadline] function.
+var ErrFiltered = errors.New("value filtered")
+
+// FilterDeadline checks if given value is allowed and not denied according to
+// regex patterns. It returns a [context.DeadlineExceeded] if it takes too long
+// to process.
+func FilterDeadline(allowed, denied *regexp2.Regexp, s string, deadline time.Time) error {
+	// FIXME: not ideal to compile everytime, but is there another way to create a clone?
+	if allowed.String() != "" {
+		allow := regexp2.MustCompile(allowed.String(), 0)
+		allow.MatchTimeout = time.Until(deadline)
+
+		ok, err := allow.MatchString(s)
+		if err != nil {
+			if time.Now().After(deadline) {
+				return context.DeadlineExceeded
+			}
+			return fmt.Errorf("'%s' cannot handle '%s': %w", allow.String(), s, err)
+		}
+		if !ok {
+			return fmt.Errorf("'%s' does not match the expression from the allowed list: %w", s, ErrFiltered)
+		}
+	}
+
+	if denied.String() != "" {
+		deny := regexp2.MustCompile(denied.String(), 0)
+		deny.MatchTimeout = time.Until(deadline)
+
+		ok, err := deny.MatchString(s)
+		if err != nil {
+			if time.Now().After(deadline) {
+				return context.DeadlineExceeded
+			}
+			return fmt.Errorf("'%s' cannot handle '%s': %w", deny.String(), s, err)
+		}
+		if ok {
+			return fmt.Errorf("'%s' matches the expression from the denied list: %w", s, ErrFiltered)
+		}
+	}
+
+	return nil
+}