use actix_web::Error;
use actix_web::dev::{Service, ServiceRequest, ServiceResponse, Transform, forward_ready};
use actix_web::http::header::{CACHE_CONTROL, HeaderValue};
use std::future::{Future, Ready, ready};
use std::pin::Pin;

#[derive(Clone, Debug, Default)]
pub struct CacheControl {
    header_value: Option<HeaderValue>,
}

impl CacheControl {
    pub fn new(header_value: Option<HeaderValue>) -> Self {
        Self { header_value }
    }
}

impl<S, B> Transform<S, ServiceRequest> for CacheControl
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
    S::Future: 'static,
    B: 'static,
{
    type Response = ServiceResponse<B>;
    type Error = Error;
    type InitError = ();
    type Transform = CacheControlMiddleware<S>;
    type Future = Ready<Result<Self::Transform, Self::InitError>>;

    fn new_transform(&self, service: S) -> Self::Future {
        ready(Ok(CacheControlMiddleware {
            service,
            header_value: self.header_value.clone(),
        }))
    }
}

pub struct CacheControlMiddleware<S> {
    service: S,
    header_value: Option<HeaderValue>,
}

impl<S, B> Service<ServiceRequest> for CacheControlMiddleware<S>
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
    S::Future: 'static,
    B: 'static,
{
    type Response = ServiceResponse<B>;
    type Error = Error;
    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;

    forward_ready!(service);

    fn call(&self, req: ServiceRequest) -> Self::Future {
        let is_asset = req.path().starts_with("/assets/");
        let header_value = self.header_value.clone();
        let fut = self.service.call(req);
        Box::pin(async move {
            let mut res = fut.await?;
            // HTML pages can contain personalized content and configuration-dependent
            // links, so they must not be retained by browser or intermediary caches.
            // Static assets set their own (long-lived) cache policy in the asset handler.
            if is_asset {
                if let Some(value) = header_value {
                    res.headers_mut().insert(CACHE_CONTROL, value);
                }
            } else {
                res.headers_mut()
                    .insert(CACHE_CONTROL, HeaderValue::from_static("no-store"));
            }
            Ok(res)
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use actix_web::{App, HttpResponse, http::header::HeaderValue, test};

    #[actix_web::test]
    async fn pages_are_not_cached_but_asset_policy_is_preserved() {
        let app = test::init_service(
            App::new()
                .wrap(CacheControl::new(Some(HeaderValue::from_static(
                    "public, max-age=31536000, immutable",
                ))))
                .route(
                    "/login",
                    actix_web::web::get().to(|| async { HttpResponse::Ok().finish() }),
                )
                .route(
                    "/assets/app.css",
                    actix_web::web::get().to(|| async {
                        HttpResponse::Ok()
                            .insert_header((CACHE_CONTROL, "public, max-age=31536000, immutable"))
                            .finish()
                    }),
                ),
        )
        .await;

        let page =
            test::call_service(&app, test::TestRequest::get().uri("/login").to_request()).await;
        assert_eq!(page.headers().get(CACHE_CONTROL).unwrap(), "no-store");

        let asset = test::call_service(
            &app,
            test::TestRequest::get().uri("/assets/app.css").to_request(),
        )
        .await;
        assert_eq!(
            asset.headers().get(CACHE_CONTROL).unwrap(),
            "public, max-age=31536000, immutable"
        );
    }
}