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// Copyright (C) 2023 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package httpcache
import (
"bytes"
"compress/gzip"
"context"
"fmt"
"net/http"
"strings"
"sync"
"time"
)
type SinglePathCache struct {
next http.Handler
keep time.Duration
mut sync.RWMutex
resp *recordedResponse
}
func SinglePath(next http.Handler, keep time.Duration) *SinglePathCache {
return &SinglePathCache{
next: next,
keep: keep,
}
}
type recordedResponse struct {
status int
header http.Header
data []byte
gzip []byte
when time.Time
keep time.Duration
}
func (resp *recordedResponse) ServeHTTP(w http.ResponseWriter, r *http.Request) {
for k, v := range resp.header {
w.Header()[k] = v
}
w.Header().Set("Cache-Control", fmt.Sprintf("public, max-age=%d", int(resp.keep.Seconds())))
if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
w.Header().Set("Content-Encoding", "gzip")
w.Header().Set("Content-Length", fmt.Sprint(len(resp.gzip)))
w.WriteHeader(resp.status)
_, _ = w.Write(resp.gzip)
return
}
w.Header().Set("Content-Length", fmt.Sprint(len(resp.data)))
w.WriteHeader(resp.status)
_, _ = w.Write(resp.data)
}
type responseRecorder struct {
resp *recordedResponse
}
func (r *responseRecorder) WriteHeader(status int) {
r.resp.status = status
}
func (r *responseRecorder) Write(data []byte) (int, error) {
r.resp.data = append(r.resp.data, data...)
return len(data), nil
}
func (r *responseRecorder) Header() http.Header {
return r.resp.header
}
func (s *SinglePathCache) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if r.Method != http.MethodGet && r.Method != http.MethodHead {
s.next.ServeHTTP(w, r)
return
}
w.Header().Set("X-Cache", "MISS")
s.mut.RLock()
ok := s.serveCached(w, r)
s.mut.RUnlock()
if ok {
return
}
s.mut.Lock()
defer s.mut.Unlock()
if s.serveCached(w, r) {
return
}
rec := &recordedResponse{status: http.StatusOK, header: make(http.Header), when: time.Now(), keep: s.keep}
childRec := r.Clone(context.Background())
childRec.Header.Del("Accept-Encoding") // don't let the client dictate the encoding
s.next.ServeHTTP(&responseRecorder{resp: rec}, childRec)
if rec.status == http.StatusOK {
buf := new(bytes.Buffer)
gw := gzip.NewWriter(buf)
_, _ = gw.Write(rec.data)
gw.Close()
rec.gzip = buf.Bytes()
s.resp = rec
}
rec.ServeHTTP(w, r)
}
func (s *SinglePathCache) serveCached(w http.ResponseWriter, r *http.Request) bool {
if s.resp == nil || time.Since(s.resp.when) > s.keep {
return false
}
w.Header().Set("X-Cache", "HIT")
w.Header().Set("X-Cache-From", s.resp.when.Format(time.RFC3339))
s.resp.ServeHTTP(w, r)
return true
}
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