serviceworker.go RawHistoryFolder

1// SPDX-License-Identifier: AGPL-3.0-or-later
2
3package web
4
5import (
6	"bytes"
7	"crypto/sha256"
8	"encoding/hex"
9	"net/http"
10	"time"
11)
12
13// ServiceWorkerPath is where the service worker of the installed app is
14// served. Its default scope would be "/-/"; Service-Worker-Allowed widens it to
15// the whole site. It lives under /-/ (a name no repository can take) rather
16// than at /sw.js, which a repository could be named.
17const ServiceWorkerPath = "/-/sw.js"
18
19// serviceWorker is static/sw.js with its entity tag.
20type serviceWorker struct {
21	body []byte
22	etag string
23}
24
25func loadServiceWorker() (serviceWorker, error) {
26	b, err := staticFS.ReadFile("static/sw.js")
27	if err != nil {
28		return serviceWorker{}, err
29	}
30	sum := sha256.Sum256(b)
31	return serviceWorker{body: b, etag: `"` + hex.EncodeToString(sum[:8]) + `"`}, nil
32}
33
34// serve answers GET /-/sw.js. The script has no hash in its name (the browser
35// needs one address to look for a new version), so it is revalidated on every
36// check: no-cache plus an entity tag, which makes the check a 304. An answer
37// the session marked no-store (it clears a stale cookie) stays no-store.
38func (sw serviceWorker) serve(w http.ResponseWriter, r *http.Request) {
39	h := w.Header()
40	h.Set("Content-Type", "text/javascript; charset=utf-8")
41	if h.Get("Cache-Control") != noStore {
42		h.Set("Cache-Control", "no-cache")
43	}
44	h.Set("Service-Worker-Allowed", "/")
45	h.Set("ETag", sw.etag)
46	http.ServeContent(w, r, "", time.Time{}, bytes.NewReader(sw.body))
47}