open registration toggle

module.nix

@@ -69,6 +69,12 @@ in
       description = "Maximum length for website URLs. 0 for unlimited.";
     };
 
+    openRegistration = mkOption {
+      type = types.bool;
+      default = true;
+      description = "Allow new guestbook submissions. When false, the form is hidden and submissions are rejected.";
+    };
+
     user = mkOption {
       type = types.str;
       default = "guestbook";
@@ -108,6 +114,7 @@ in
           BOOK_MAX_NAME_LENGTH = toString cfg.maxNameLength;
           BOOK_MAX_MESSAGE_LENGTH = toString cfg.maxMessageLength;
           BOOK_MAX_WEBSITE_LENGTH = toString cfg.maxWebsiteLength;
+          BOOK_OPEN_REGISTRATION = if cfg.openRegistration then "true" else "false";
         };
         serviceConfig = {
           Type = "simple";

src/config.rs

@@ -13,6 +13,7 @@ pub struct Config {
     pub max_name_length: usize,
     pub max_message_length: usize,
     pub max_website_length: usize,
+    pub open_registration: bool,
 }
 
 impl Config {
@@ -52,6 +53,9 @@ impl Config {
                 .unwrap_or_else(|_| "100".into())
                 .parse()
                 .map_err(|_| "BOOK_MAX_WEBSITE_LENGTH must be a number")?,
+            open_registration: env::var("BOOK_OPEN_REGISTRATION")
+                .map(|v| v != "false")
+                .unwrap_or(true),
         })
     }
 }

src/web.rs

@@ -39,11 +39,12 @@ pub fn router(state: Arc<AppState>) -> Router {
 async fn index(State(state): State<Arc<AppState>>) -> Html<String> {
     let entries_dir = state.config.data_dir.join("entries");
     let entries = entries::read_approved(&entries_dir);
+    let form = if state.config.open_registration { FORM_HTML } else { "" };
     let html = render::render_page(
         &state.config.site_title,
         &state.config.site_url,
         &entries,
-        FORM_HTML,
+        form,
     );
     Html(html)
 }
@@ -52,6 +53,10 @@ async fn submit(
     State(state): State<Arc<AppState>>,
     Form(form): Form<SubmitForm>,
 ) -> Html<String> {
+    if !state.config.open_registration {
+        return Html("Submissions are closed.".to_string());
+    }
+
     // Honeypot check — silently discard
     if state.config.honeypot && !form.url.is_empty() {
         return Html("Thanks! Your message is pending approval.".to_string());