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// Copyright (C) 2019 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 main
import (
"bytes"
"encoding/json"
"fmt"
"io"
"log"
"net/http"
"os"
"sort"
"strings"
"time"
"github.com/alecthomas/kong"
"github.com/syncthing/syncthing/lib/httpcache"
"github.com/syncthing/syncthing/lib/upgrade"
_ "go.uber.org/automaxprocs"
)
type cli struct {
Listen string `default:":8080" help:"Listen address"`
URL string `short:"u" default:"https://api.github.com/repos/syncthing/syncthing/releases?per_page=25" help:"GitHub releases url"`
Forward []string `short:"f" help:"Forwarded pages, format: /path->https://example/com/url"`
CacheTime time.Duration `default:"15m" help:"Cache time"`
}
func main() {
var params cli
kong.Parse(¶ms)
if err := server(¶ms); err != nil {
fmt.Printf("Error: %v\n", err)
os.Exit(1)
}
}
func server(params *cli) error {
http.Handle("/meta.json", httpcache.SinglePath(&githubReleases{url: params.URL}, params.CacheTime))
for _, fwd := range params.Forward {
path, url, ok := strings.Cut(fwd, "->")
if !ok {
return fmt.Errorf("invalid forward: %q", fwd)
}
http.Handle(path, httpcache.SinglePath(&proxy{url: url}, params.CacheTime))
}
return http.ListenAndServe(params.Listen, nil)
}
type githubReleases struct {
url string
}
func (p *githubReleases) ServeHTTP(w http.ResponseWriter, _ *http.Request) {
log.Println("Fetching", p.url)
rels := upgrade.FetchLatestReleases(p.url, "")
if rels == nil {
http.Error(w, "no releases", http.StatusInternalServerError)
return
}
sort.Sort(upgrade.SortByRelease(rels))
rels = filterForLatest(rels)
// Move the URL used for browser downloads to the URL field, and remove
// the browser URL field. This avoids going via the GitHub API for
// downloads, since Syncthing uses the URL field.
for _, rel := range rels {
for j, asset := range rel.Assets {
rel.Assets[j].URL = asset.BrowserURL
rel.Assets[j].BrowserURL = ""
}
}
buf := new(bytes.Buffer)
_ = json.NewEncoder(buf).Encode(rels)
w.Header().Set("Content-Type", "application/json; charset=utf-8")
w.Header().Set("Access-Control-Allow-Origin", "*")
w.Header().Set("Access-Control-Allow-Methods", "GET")
w.Write(buf.Bytes())
}
type proxy struct {
url string
}
func (p *proxy) ServeHTTP(w http.ResponseWriter, req *http.Request) {
log.Println("Fetching", p.url)
req, err := http.NewRequestWithContext(req.Context(), http.MethodGet, p.url, nil)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
defer resp.Body.Close()
ct := resp.Header.Get("Content-Type")
w.Header().Set("Content-Type", ct)
if resp.StatusCode == http.StatusOK {
w.Header().Set("Cache-Control", "public, max-age=900")
w.Header().Set("Access-Control-Allow-Origin", "*")
w.Header().Set("Access-Control-Allow-Methods", "GET")
}
w.WriteHeader(resp.StatusCode)
if strings.HasPrefix(ct, "application/json") {
// Special JSON handling; clean it up a bit.
var v interface{}
if err := json.NewDecoder(resp.Body).Decode(&v); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
_ = json.NewEncoder(w).Encode(v)
} else {
_, _ = io.Copy(w, resp.Body)
}
}
// filterForLatest returns the latest stable and prerelease only. If the
// stable version is newer (comes first in the list) there is no need to go
// looking for a prerelease at all.
func filterForLatest(rels []upgrade.Release) []upgrade.Release {
var filtered []upgrade.Release
var havePre bool
for _, rel := range rels {
if !rel.Prerelease {
// We found a stable version, we're good now.
filtered = append(filtered, rel)
break
}
if rel.Prerelease && !havePre {
// We remember the first prerelease we find.
filtered = append(filtered, rel)
havePre = true
}
}
return filtered
}
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