frontend: Add dropdown for timezone selection

crates/frontend/src/lib.rs

@@ -33,6 +33,7 @@ use crate::routes::{
     app_token::{route_delete_app_token, route_post_app_token},
     calendar::{route_calendar, route_calendar_restore},
     login::{route_get_login, route_post_login, route_post_logout},
+    timezones::route_timezones,
     user::{route_get_home, route_root, route_user_named},
 };
 #[cfg(not(feature = "dev"))]
@@ -79,7 +80,11 @@ pub fn frontend_router<AP: AuthenticationProvider, CS: CalendarStore, AS: Addres
         .route("/", get(route_root))
         .nest("/user", user_router)
         .route("/login", get(route_get_login).post(route_post_login::<AP>))
-        .route("/logout", post(route_post_logout));
+        .route("/logout", post(route_post_logout))
+        .route(
+            "/_timezones.json",
+            get(route_timezones).head(route_timezones),
+        );
 
     #[cfg(not(feature = "dev"))]
     let mut router = router.route_service("/assets/{*file}", EmbedService::<Assets>::default());

crates/frontend/src/routes/mod.rs

@@ -4,4 +4,5 @@ pub mod app_token;
 pub mod calendar;
 pub mod calendars;
 pub mod login;
+pub mod timezones;
 pub mod user;

crates/frontend/src/routes/timezones.rs

@@ -0,0 +1,30 @@
+use axum::response::{IntoResponse, Response};
+use headers::{CacheControl, ContentType, HeaderMapExt};
+use http::{HeaderMap, HeaderValue, Method};
+use itertools::Itertools;
+use std::{sync::LazyLock, time::Duration};
+
+static VTIMEZONES_JSON: LazyLock<String> = LazyLock::new(|| {
+    serde_json::to_string(
+        &vtimezones_rs::VTIMEZONES
+            .keys()
+            .sorted()
+            .collect::<Vec<_>>(),
+    )
+    .unwrap()
+});
+
+pub async fn route_timezones(method: Method) -> Response {
+    let mut headers = HeaderMap::new();
+    headers.typed_insert(ContentType::json());
+    headers.insert(
+        "ETag",
+        HeaderValue::from_static(vtimezones_rs::IANA_TZDB_VERSION),
+    );
+    headers.typed_insert(CacheControl::new().with_max_age(Duration::from_hours(2)));
+
+    if method == Method::HEAD {
+        return headers.into_response();
+    }
+    (headers, VTIMEZONES_JSON.as_str()).into_response()
+}