feat(rewriter): add redirect(), get_cookie(), add_cookie() methods to rule engine (#36)

internal/proxy/director/layer/rewriter/api.go

@@ -0,0 +1,79 @@
+package rewriter
+
+import (
+	"context"
+	"fmt"
+
+	"forge.cadoles.com/cadoles/bouncer/internal/rule"
+	"github.com/expr-lang/expr"
+	"github.com/pkg/errors"
+)
+
+type errRedirect struct {
+	statusCode int
+	url        string
+}
+
+func (e *errRedirect) StatusCode() int {
+	return e.statusCode
+}
+
+func (e *errRedirect) URL() string {
+	return e.url
+}
+
+func (e *errRedirect) Error() string {
+	return fmt.Sprintf("redirect %d %s", e.statusCode, e.url)
+}
+
+func newErrRedirect(statusCode int, url string) *errRedirect {
+	return &errRedirect{
+		url:        url,
+		statusCode: statusCode,
+	}
+}
+
+var _ error = &errRedirect{}
+
+func redirectFunc() expr.Option {
+	return expr.Function(
+		"redirect",
+		func(params ...any) (any, error) {
+			_, err := rule.Assert[context.Context](params[0])
+			if err != nil {
+				return nil, errors.WithStack(err)
+			}
+
+			statusCode, err := rule.Assert[int](params[1])
+			if err != nil {
+				return nil, errors.WithStack(err)
+			}
+
+			if statusCode < 300 || statusCode >= 400 {
+				return nil, errors.Errorf("unexpected redirect status code '%d'", statusCode)
+			}
+
+			url, err := rule.Assert[string](params[2])
+			if err != nil {
+				return nil, errors.WithStack(err)
+			}
+
+			return nil, newErrRedirect(statusCode, url)
+		},
+		new(func(context.Context, int, string) bool),
+	)
+}
+
+func WithRewriterFuncs() rule.OptionFunc {
+	return func(opts *rule.Options) {
+		funcs := []expr.Option{
+			redirectFunc(),
+		}
+
+		if len(opts.Expr) == 0 {
+			opts.Expr = make([]expr.Option, 0)
+		}
+
+		opts.Expr = append(opts.Expr, funcs...)
+	}
+}