update library

render.go

@@ -4,8 +4,30 @@ import (
 	"encoding/json"
 	"log/slog"
 	"net/http"
+	"strings"
 )
 
+type stringWriter struct {
+	builder strings.Builder
+	header  http.Header
+}
+
+func newStringWriter() *stringWriter {
+	return &stringWriter{
+		header: make(http.Header),
+	}
+}
+
+func (w *stringWriter) Header() http.Header {
+	return w.header
+}
+
+func (w *stringWriter) Write(b []byte) (int, error) {
+	return w.builder.Write(b)
+}
+
+func (w *stringWriter) WriteHeader(statusCode int) {}
+
 func (a *App) JSON(w http.ResponseWriter, code int, v any) {
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(code)
@@ -14,11 +36,21 @@ func (a *App) JSON(w http.ResponseWriter, code int, v any) {
 
 func (a *App) HTML(w http.ResponseWriter, code int, name string, td *TemplateData) {
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	w.WriteHeader(code)
 	err := a.Templates.Template(w, name, td)
 	if err != nil {
 		slog.Error("error rendering template", "error", err)
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
-	w.WriteHeader(code)
+}
+
+func (a *App) RenderHTML(name string, td *TemplateData) (string, error) {
+	sw := newStringWriter()
+	err := a.Templates.Template(sw, name, td)
+	if err != nil {
+		slog.Error("error rendering template", "error", err)
+		return "", err
+	}
+	return sw.builder.String(), nil
 }