removing handwritten JS

ht_booking/src/controllers/calendar.rs

@@ -6,6 +6,8 @@
 //! court. Booked slots are coloured; free slots are blank. The same grid is
 //! reused by the admin dashboard with `is_admin = true`.
 
+use axum::http::{header, HeaderMap};
+use axum::response::Redirect;
 use axum_extra::extract::cookie::CookieJar;
 use chrono::{Datelike, Duration, NaiveDate, Utc};
 use loco_rs::prelude::*;
@@ -312,6 +314,46 @@ pub async fn index(
     format::render().view(&v, "calendar/week.html", &page)
 }
 
-pub fn routes() -> Routes {
-    Routes::new().add("/", get(index))
+#[derive(Debug, Deserialize)]
+pub struct LangForm {
+    pub lang: String,
+}
+
+/// Switches the UI language. The navbar's language buttons post here; the
+/// `lang` cookie is set server-side and the visitor is bounced back to the
+/// page they came from. This replaces the old client-side `setLang` script.
+#[debug_handler]
+pub async fn set_lang(headers: HeaderMap, Form(form): Form<LangForm>) -> Result<Response> {
+    // Only the two supported languages; anything else falls back to Slovak,
+    // matching `current_lang`.
+    let lang = if form.lang == "en" { "en" } else { "sk" };
+    let cookie = format!("lang={lang}; Path=/; Max-Age=31536000; SameSite=Lax");
+    Ok((
+        [(header::SET_COOKIE, cookie)],
+        Redirect::to(&back_path(&headers)),
+    )
+        .into_response())
+}
+
+/// On-site path of the page that submitted the form, read from `Referer`.
+/// Scheme and host are stripped so a stale or foreign header can only ever
+/// bounce the visitor to a path on this site, never off it.
+fn back_path(headers: &HeaderMap) -> String {
+    let raw = headers
+        .get(header::REFERER)
+        .and_then(|v| v.to_str().ok())
+        .unwrap_or("/");
+    match raw.split_once("://") {
+        Some((_, rest)) => match rest.find('/') {
+            Some(i) => rest[i..].to_string(),
+            None => "/".to_string(),
+        },
+        None => raw.to_string(),
+    }
+}
+
+pub fn routes() -> Routes {
+    Routes::new()
+        .add("/", get(index))
+        .add("/lang", post(set_lang))
 }