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| 1 | +// The golink server runs http://go/, a company shortlink service. |
| 2 | +package main |
| 3 | + |
| 4 | +import ( |
| 5 | + "encoding/json" |
| 6 | + "flag" |
| 7 | + "fmt" |
| 8 | + "html" |
| 9 | + "log" |
| 10 | + "net/http" |
| 11 | + "net/url" |
| 12 | + "os" |
| 13 | + "path/filepath" |
| 14 | + "strings" |
| 15 | + "text/template" |
| 16 | + "time" |
| 17 | + |
| 18 | + "tailscale.com/client/tailscale" |
| 19 | + "tailscale.com/tsnet" |
| 20 | +) |
| 21 | + |
| 22 | +var ( |
| 23 | + verbose = flag.Bool("verbose", false, "be verbose") |
| 24 | + linkDir = flag.String("linkdir", "", "the directory to store one JSON file per go/ shortlink") |
| 25 | +) |
| 26 | + |
| 27 | +var localClient *tailscale.LocalClient |
| 28 | + |
| 29 | +// DiskLink is the JSON structure stored on disk in a file for each go short link. |
| 30 | +type DiskLink struct { |
| 31 | + Short string // the "foo" part of http://go/foo |
| 32 | + Long string // the target URL |
| 33 | + Created time.Time |
| 34 | + LastEdit time.Time // when the link was created |
| 35 | + Owner string // foo@tailscale.com |
| 36 | +} |
| 37 | + |
| 38 | +func main() { |
| 39 | + flag.Parse() |
| 40 | + |
| 41 | + if *linkDir == "" { |
| 42 | + log.Fatalf("--linkdir is required") |
| 43 | + } |
| 44 | + if fi, err := os.Stat(*linkDir); err != nil { |
| 45 | + log.Fatal(err) |
| 46 | + } else if !fi.IsDir() { |
| 47 | + log.Fatalf("--linkdir %q is not a directory", *linkDir) |
| 48 | + } |
| 49 | + |
| 50 | + srv := &tsnet.Server{ |
| 51 | + Hostname: "go", |
| 52 | + Logf: func(format string, args ...interface{}) {}, |
| 53 | + } |
| 54 | + if *verbose { |
| 55 | + srv.Logf = log.Printf |
| 56 | + } |
| 57 | + if err := srv.Start(); err != nil { |
| 58 | + log.Fatal(err) |
| 59 | + } |
| 60 | + localClient, _ = srv.LocalClient() |
| 61 | + |
| 62 | + l80, err := srv.Listen("tcp", ":80") |
| 63 | + if err != nil { |
| 64 | + log.Fatal(err) |
| 65 | + } |
| 66 | + |
| 67 | + log.Printf("Serving http://go/ ...") |
| 68 | + if err := http.Serve(l80, http.HandlerFunc(serveGo)); err != nil { |
| 69 | + log.Fatal(err) |
| 70 | + } |
| 71 | +} |
| 72 | + |
| 73 | +// homeCreate is the template used by the http://go/ index page where you can |
| 74 | +// create or edit links. |
| 75 | +var homeCreate *template.Template |
| 76 | + |
| 77 | +// homeData is the data used by the homeCreate template. |
| 78 | +type homeData struct { |
| 79 | + Short string |
| 80 | +} |
| 81 | + |
| 82 | +func init() { |
| 83 | + homeCreate = template.Must(template.New("home").Parse(`<html> |
| 84 | +<body> |
| 85 | +<h1>go/</h1> |
| 86 | +shortlink service. |
| 87 | +
|
| 88 | +<h2>create</h2> |
| 89 | +<form method="POST" action="/"> |
| 90 | +http://go/<input name=short size=20 value="{{.Short}}"> ==> <input name=long size=40> <input type=submit value="create"> |
| 91 | +</form> |
| 92 | +`)) |
| 93 | +} |
| 94 | + |
| 95 | +func linkPath(short string) string { |
| 96 | + name := url.PathEscape(strings.ToLower(short)) |
| 97 | + name = strings.ReplaceAll(name, ".", "%2e") |
| 98 | + return filepath.Join(*linkDir, name) |
| 99 | +} |
| 100 | + |
| 101 | +func loadLink(short string) (*DiskLink, error) { |
| 102 | + data, err := os.ReadFile(linkPath(short)) |
| 103 | + if err != nil { |
| 104 | + return nil, err |
| 105 | + } |
| 106 | + dl := new(DiskLink) |
| 107 | + if err := json.Unmarshal(data, dl); err != nil { |
| 108 | + return nil, err |
| 109 | + } |
| 110 | + return dl, nil |
| 111 | +} |
| 112 | + |
| 113 | +func serveGo(w http.ResponseWriter, r *http.Request) { |
| 114 | + if r.RequestURI == "/" { |
| 115 | + switch r.Method { |
| 116 | + case "GET": |
| 117 | + homeCreate.Execute(w, homeData{ |
| 118 | + Short: "", |
| 119 | + }) |
| 120 | + case "POST": |
| 121 | + serveSave(w, r) |
| 122 | + } |
| 123 | + return |
| 124 | + } |
| 125 | + |
| 126 | + short := strings.ToLower(strings.TrimPrefix(r.RequestURI, "/")) |
| 127 | + |
| 128 | + dl, err := loadLink(short) |
| 129 | + if os.IsNotExist(err) { |
| 130 | + homeCreate.Execute(w, homeData{ |
| 131 | + Short: short, |
| 132 | + }) |
| 133 | + return |
| 134 | + } |
| 135 | + if err != nil { |
| 136 | + log.Printf("serving %q: %v", short, err) |
| 137 | + http.Error(w, err.Error(), http.StatusInternalServerError) |
| 138 | + return |
| 139 | + } |
| 140 | + |
| 141 | + http.Redirect(w, r, dl.Long, http.StatusFound) |
| 142 | +} |
| 143 | + |
| 144 | +func serveSave(w http.ResponseWriter, r *http.Request) { |
| 145 | + short, long := r.FormValue("short"), r.FormValue("long") |
| 146 | + if short == "" || long == "" { |
| 147 | + http.Error(w, "short and long required", http.StatusBadRequest) |
| 148 | + return |
| 149 | + } |
| 150 | + res, err := localClient.WhoIs(r.Context(), r.RemoteAddr) |
| 151 | + if err != nil { |
| 152 | + http.Error(w, err.Error(), http.StatusInternalServerError) |
| 153 | + return |
| 154 | + } |
| 155 | + login := res.UserProfile.LoginName |
| 156 | + |
| 157 | + dl, err := loadLink(short) |
| 158 | + if err == nil && dl.Owner != login { |
| 159 | + http.Error(w, "not your link; owned by "+dl.Owner, http.StatusForbidden) |
| 160 | + return |
| 161 | + } |
| 162 | + |
| 163 | + now := time.Now() |
| 164 | + if dl == nil { |
| 165 | + dl = &DiskLink{ |
| 166 | + Short: short, |
| 167 | + Created: now, |
| 168 | + } |
| 169 | + } |
| 170 | + dl.Long = long |
| 171 | + dl.LastEdit = now |
| 172 | + dl.Owner = login |
| 173 | + j, err := json.MarshalIndent(dl, "", " ") |
| 174 | + if err != nil { |
| 175 | + http.Error(w, err.Error(), http.StatusInternalServerError) |
| 176 | + return |
| 177 | + } |
| 178 | + if err := os.WriteFile(linkPath(short), j, 0600); err != nil { |
| 179 | + http.Error(w, err.Error(), http.StatusInternalServerError) |
| 180 | + return |
| 181 | + } |
| 182 | + fmt.Fprintf(w, "<h1>saved</h1>made <a href='http://go/%s'>http://go/%s</a>", html.EscapeString(short), html.EscapeString(short)) |
| 183 | +} |
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