add fluent templates example

templating/fluent/src/lang_choice.rs

@@ -0,0 +1,40 @@
+use std::{
+    convert::Infallible,
+    future::{ready, Ready},
+};
+
+use actix_web::{dev, http::header::AcceptLanguage, FromRequest, HttpMessage as _, HttpRequest};
+use fluent_templates::LanguageIdentifier;
+use serde::Serialize;
+
+/// A convenient extractor that finds the clients's preferred language based on an Accept-Language
+/// header and falls back to English if header is not found. Serializes easily in Handlebars data.
+#[derive(Debug, Serialize)]
+#[serde(transparent)]
+pub struct LangChoice(String);
+
+impl LangChoice {
+    pub(crate) fn from_req(req: &HttpRequest) -> Self {
+        let lang = req
+            .get_header::<AcceptLanguage>()
+            .and_then(|lang| lang.preference().into_item())
+            .map(|lang| lang.to_string())
+            .map_or_else(|| "en".to_owned(), |lang| lang.to_string());
+
+        Self(lang)
+    }
+
+    pub fn lang_id(&self) -> LanguageIdentifier {
+        // unwrap: lang ID should be valid given extraction method
+        self.0.parse().unwrap()
+    }
+}
+
+impl FromRequest for LangChoice {
+    type Error = Infallible;
+    type Future = Ready<Result<Self, Self::Error>>;
+
+    fn from_request(req: &HttpRequest, _pl: &mut dev::Payload) -> Self::Future {
+        ready(Ok(Self::from_req(req)))
+    }
+}

templating/fluent/src/main.rs

@@ -0,0 +1,127 @@
+use std::io;
+
+use actix_web::{
+    body::BoxBody,
+    dev::ServiceResponse,
+    get,
+    http::{header::ContentType, StatusCode},
+    middleware::{ErrorHandlerResponse, ErrorHandlers},
+    web, App, HttpResponse, HttpServer, Responder, Result,
+};
+use actix_web_lab::{extract::Path, respond::Html};
+use fluent_templates::{static_loader, FluentLoader, Loader as _};
+use handlebars::Handlebars;
+use serde_json::json;
+
+mod lang_choice;
+use self::lang_choice::LangChoice;
+
+static_loader! {
+    static LOCALES = {
+        locales: "./locales",
+        fallback_language: "en",
+
+        // removes unicode isolating marks around arguments
+        // you typically should only set to false when testing.
+        customise: |bundle| bundle.set_use_isolating(false),
+    };
+}
+
+#[get("/")]
+async fn index(hb: web::Data<Handlebars<'_>>, lang: LangChoice) -> impl Responder {
+    let data = json!({ "lang": lang });
+    let body = hb.render("index", &data).unwrap();
+    Html(body)
+}
+
+#[get("/{user}/{data}")]
+async fn user(
+    hb: web::Data<Handlebars<'_>>,
+    Path(info): Path<(String, String)>,
+    lang: LangChoice,
+) -> impl Responder {
+    let data = json!({
+        "lang": lang,
+        "user": info.0,
+        "data": info.1
+    });
+    let body = hb.render("user", &data).unwrap();
+    Html(body)
+}
+
+#[actix_web::main]
+async fn main() -> io::Result<()> {
+    // Handlebars uses a repository for the compiled templates. This object must be shared between
+    // the application threads, and is therefore passed to the App in an Arc.
+    let mut handlebars = Handlebars::new();
+
+    // register template dir with Handlebars registry
+    handlebars
+        .register_templates_directory(".html", "./templates")
+        .unwrap();
+
+    // register Fluent helper with Handlebars registry
+    handlebars.register_helper("fluent", Box::new(FluentLoader::new(&*LOCALES)));
+
+    let handlebars = web::Data::new(handlebars);
+
+    HttpServer::new(move || {
+        App::new()
+            .wrap(error_handlers())
+            .app_data(web::Data::clone(&handlebars))
+            .service(index)
+            .service(user)
+    })
+    .bind(("127.0.0.1", 8080))?
+    .run()
+    .await
+}
+
+// Custom error handlers, to return HTML responses when an error occurs.
+fn error_handlers() -> ErrorHandlers<BoxBody> {
+    ErrorHandlers::new().handler(StatusCode::NOT_FOUND, not_found)
+}
+
+// Error handler for a 404 Page not found error.
+fn not_found<B>(res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<BoxBody>> {
+    let lang = LangChoice::from_req(res.request()).lang_id();
+    let error = LOCALES.lookup(&lang, "error-not-found").unwrap();
+
+    let response = get_error_response(&res, &error);
+
+    Ok(ErrorHandlerResponse::Response(ServiceResponse::new(
+        res.into_parts().0,
+        response.map_into_left_body(),
+    )))
+}
+
+// Generic error handler.
+fn get_error_response<B>(res: &ServiceResponse<B>, error: &str) -> HttpResponse<BoxBody> {
+    let req = res.request();
+    let lang = LangChoice::from_req(req);
+
+    // Provide a fallback to a simple plain text response in case an error occurs during the
+    // rendering of the error page.
+
+    let hb = req
+        .app_data::<web::Data<Handlebars>>()
+        .expect("correctly set up handlebars in app data");
+
+    let data = json!({
+        "lang": lang,
+        "error": error,
+        "status_code": res.status().as_str()
+    });
+
+    let body = hb.render("error", &data);
+
+    match body {
+        Ok(body) => HttpResponse::build(res.status())
+            .content_type(ContentType::html())
+            .body(body),
+
+        Err(_) => HttpResponse::build(res.status())
+            .content_type(ContentType::plaintext())
+            .body(error.to_string()),
+    }
+}