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// Copyright 2022 Palantir Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use crate::service::{Layer, Service};
use http::header::{Entry, CACHE_CONTROL};
use http::{HeaderValue, Method, Request, Response};
#[allow(clippy::declare_interior_mutable_const)]
const DO_NOT_CACHE: HeaderValue = HeaderValue::from_static("no-cache, no-store, must-revalidate");
/// A layer which disables caching of responses to GET requests that do not already contain a `Cache-Control` header.
pub struct NoCachingLayer;
impl<S> Layer<S> for NoCachingLayer {
type Service = NoCachingService<S>;
fn layer(self, inner: S) -> Self::Service {
NoCachingService { inner }
}
}
pub struct NoCachingService<S> {
inner: S,
}
impl<S, B1, B2> Service<Request<B1>> for NoCachingService<S>
where
S: Service<Request<B1>, Response = Response<B2>> + Sync,
B1: Send,
{
type Response = S::Response;
async fn call(&self, req: Request<B1>) -> Self::Response {
let is_get = req.method() == Method::GET;
let mut response = self.inner.call(req).await;
if is_get {
if let Entry::Vacant(e) = response.headers_mut().entry(CACHE_CONTROL) {
e.insert(DO_NOT_CACHE);
}
}
response
}
}