1// Copyright 2013 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Package redirect provides hooks to register HTTP handlers that redirect old
6// godoc paths to their new equivalents and assist in accessing the issue
7// tracker, wiki, code review system, etc.
8package redirect // import "golang.org/x/tools/godoc/redirect"
9
10import (
11	"context"
12	"fmt"
13	"html/template"
14	"net/http"
15	"os"
16	"regexp"
17	"strconv"
18	"strings"
19	"sync"
20	"time"
21
22	"golang.org/x/net/context/ctxhttp"
23)
24
25// Register registers HTTP handlers that redirect old godoc paths to their new
26// equivalents and assist in accessing the issue tracker, wiki, code review
27// system, etc. If mux is nil it uses http.DefaultServeMux.
28func Register(mux *http.ServeMux) {
29	if mux == nil {
30		mux = http.DefaultServeMux
31	}
32	handlePathRedirects(mux, pkgRedirects, "/pkg/")
33	handlePathRedirects(mux, cmdRedirects, "/cmd/")
34	for prefix, redirect := range prefixHelpers {
35		p := "/" + prefix + "/"
36		mux.Handle(p, PrefixHandler(p, redirect))
37	}
38	for path, redirect := range redirects {
39		mux.Handle(path, Handler(redirect))
40	}
41	// NB: /src/pkg (sans trailing slash) is the index of packages.
42	mux.HandleFunc("/src/pkg/", srcPkgHandler)
43	mux.HandleFunc("/cl/", clHandler)
44	mux.HandleFunc("/change/", changeHandler)
45	mux.HandleFunc("/design/", designHandler)
46}
47
48func handlePathRedirects(mux *http.ServeMux, redirects map[string]string, prefix string) {
49	for source, target := range redirects {
50		h := Handler(prefix + target + "/")
51		p := prefix + source
52		mux.Handle(p, h)
53		mux.Handle(p+"/", h)
54	}
55}
56
57// Packages that were renamed between r60 and go1.
58var pkgRedirects = map[string]string{
59	"asn1":              "encoding/asn1",
60	"big":               "math/big",
61	"cmath":             "math/cmplx",
62	"csv":               "encoding/csv",
63	"exec":              "os/exec",
64	"exp/template/html": "html/template",
65	"gob":               "encoding/gob",
66	"http":              "net/http",
67	"http/cgi":          "net/http/cgi",
68	"http/fcgi":         "net/http/fcgi",
69	"http/httptest":     "net/http/httptest",
70	"http/pprof":        "net/http/pprof",
71	"json":              "encoding/json",
72	"mail":              "net/mail",
73	"rand":              "math/rand",
74	"rpc":               "net/rpc",
75	"rpc/jsonrpc":       "net/rpc/jsonrpc",
76	"scanner":           "text/scanner",
77	"smtp":              "net/smtp",
78	"tabwriter":         "text/tabwriter",
79	"template":          "text/template",
80	"template/parse":    "text/template/parse",
81	"url":               "net/url",
82	"utf16":             "unicode/utf16",
83	"utf8":              "unicode/utf8",
84	"xml":               "encoding/xml",
85}
86
87// Commands that were renamed between r60 and go1.
88var cmdRedirects = map[string]string{
89	"gofix":     "fix",
90	"goinstall": "go",
91	"gopack":    "pack",
92	"gotest":    "go",
93	"govet":     "vet",
94	"goyacc":    "yacc",
95}
96
97var redirects = map[string]string{
98	"/blog":       "/blog/",
99	"/build":      "http://build.golang.org",
100	"/change":     "https://go.googlesource.com/go",
101	"/cl":         "https://go-review.googlesource.com",
102	"/cmd/godoc/": "https://pkg.go.dev/golang.org/x/tools/cmd/godoc",
103	"/issue":      "https://github.com/golang/go/issues",
104	"/issue/new":  "https://github.com/golang/go/issues/new",
105	"/issues":     "https://github.com/golang/go/issues",
106	"/issues/new": "https://github.com/golang/go/issues/new",
107	"/play":       "http://play.golang.org",
108	"/design":     "https://go.googlesource.com/proposal/+/master/design",
109
110	// In Go 1.2 the references page is part of /doc/.
111	"/ref": "/doc/#references",
112	// This next rule clobbers /ref/spec and /ref/mem.
113	// TODO(adg): figure out what to do here, if anything.
114	// "/ref/": "/doc/#references",
115
116	// Be nice to people who are looking in the wrong place.
117	"/doc/mem":  "/ref/mem",
118	"/doc/spec": "/ref/spec",
119
120	"/talks": "http://talks.golang.org",
121	"/tour":  "http://tour.golang.org",
122	"/wiki":  "https://github.com/golang/go/wiki",
123
124	"/doc/articles/c_go_cgo.html":                    "/blog/c-go-cgo",
125	"/doc/articles/concurrency_patterns.html":        "/blog/go-concurrency-patterns-timing-out-and",
126	"/doc/articles/defer_panic_recover.html":         "/blog/defer-panic-and-recover",
127	"/doc/articles/error_handling.html":              "/blog/error-handling-and-go",
128	"/doc/articles/gobs_of_data.html":                "/blog/gobs-of-data",
129	"/doc/articles/godoc_documenting_go_code.html":   "/blog/godoc-documenting-go-code",
130	"/doc/articles/gos_declaration_syntax.html":      "/blog/gos-declaration-syntax",
131	"/doc/articles/image_draw.html":                  "/blog/go-imagedraw-package",
132	"/doc/articles/image_package.html":               "/blog/go-image-package",
133	"/doc/articles/json_and_go.html":                 "/blog/json-and-go",
134	"/doc/articles/json_rpc_tale_of_interfaces.html": "/blog/json-rpc-tale-of-interfaces",
135	"/doc/articles/laws_of_reflection.html":          "/blog/laws-of-reflection",
136	"/doc/articles/slices_usage_and_internals.html":  "/blog/go-slices-usage-and-internals",
137	"/doc/go_for_cpp_programmers.html":               "/wiki/GoForCPPProgrammers",
138	"/doc/go_tutorial.html":                          "http://tour.golang.org/",
139}
140
141var prefixHelpers = map[string]string{
142	"issue":  "https://github.com/golang/go/issues/",
143	"issues": "https://github.com/golang/go/issues/",
144	"play":   "http://play.golang.org/",
145	"talks":  "http://talks.golang.org/",
146	"wiki":   "https://github.com/golang/go/wiki/",
147}
148
149func Handler(target string) http.Handler {
150	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
151		url := target
152		if qs := r.URL.RawQuery; qs != "" {
153			url += "?" + qs
154		}
155		http.Redirect(w, r, url, http.StatusMovedPermanently)
156	})
157}
158
159var validID = regexp.MustCompile(`^[A-Za-z0-9-]*/?$`)
160
161func PrefixHandler(prefix, baseURL string) http.Handler {
162	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
163		if p := r.URL.Path; p == prefix {
164			// redirect /prefix/ to /prefix
165			http.Redirect(w, r, p[:len(p)-1], http.StatusFound)
166			return
167		}
168		id := r.URL.Path[len(prefix):]
169		if !validID.MatchString(id) {
170			http.Error(w, "Not found", http.StatusNotFound)
171			return
172		}
173		target := baseURL + id
174		http.Redirect(w, r, target, http.StatusFound)
175	})
176}
177
178// Redirect requests from the old "/src/pkg/foo" to the new "/src/foo".
179// See http://golang.org/s/go14nopkg
180func srcPkgHandler(w http.ResponseWriter, r *http.Request) {
181	r.URL.Path = "/src/" + r.URL.Path[len("/src/pkg/"):]
182	http.Redirect(w, r, r.URL.String(), http.StatusMovedPermanently)
183}
184
185func clHandler(w http.ResponseWriter, r *http.Request) {
186	const prefix = "/cl/"
187	if p := r.URL.Path; p == prefix {
188		// redirect /prefix/ to /prefix
189		http.Redirect(w, r, p[:len(p)-1], http.StatusFound)
190		return
191	}
192	id := r.URL.Path[len(prefix):]
193	// support /cl/152700045/, which is used in commit 0edafefc36.
194	id = strings.TrimSuffix(id, "/")
195	if !validID.MatchString(id) {
196		http.Error(w, "Not found", http.StatusNotFound)
197		return
198	}
199	target := ""
200
201	if n, err := strconv.Atoi(id); err == nil && isRietveldCL(n) {
202		// Issue 28836: if this Rietveld CL happens to
203		// also be a Gerrit CL, render a disambiguation HTML
204		// page with two links instead. We need to make a
205		// Gerrit API call to figure that out, but we cache
206		// known Gerrit CLs so it's done at most once per CL.
207		if ok, err := isGerritCL(r.Context(), n); err == nil && ok {
208			w.Header().Set("Content-Type", "text/html; charset=utf-8")
209			clDisambiguationHTML.Execute(w, n)
210			return
211		}
212
213		target = "https://codereview.appspot.com/" + id
214	} else {
215		target = "https://go-review.googlesource.com/" + id
216	}
217	http.Redirect(w, r, target, http.StatusFound)
218}
219
220var clDisambiguationHTML = template.Must(template.New("").Parse(`<!DOCTYPE html>
221<html lang="en">
222	<head>
223		<title>Go CL {{.}} Disambiguation</title>
224		<meta name="viewport" content="width=device-width">
225	</head>
226	<body>
227		CL number {{.}} exists in both Gerrit (the current code review system)
228		and Rietveld (the previous code review system). Please make a choice:
229
230		<ul>
231			<li><a href="https://go-review.googlesource.com/{{.}}">Gerrit CL {{.}}</a></li>
232			<li><a href="https://codereview.appspot.com/{{.}}">Rietveld CL {{.}}</a></li>
233		</ul>
234	</body>
235</html>`))
236
237// isGerritCL reports whether a Gerrit CL with the specified numeric change ID (e.g., "4247")
238// is known to exist by querying the Gerrit API at https://go-review.googlesource.com.
239// isGerritCL uses gerritCLCache as a cache of Gerrit CL IDs that exist.
240func isGerritCL(ctx context.Context, id int) (bool, error) {
241	// Check cache first.
242	gerritCLCache.Lock()
243	ok := gerritCLCache.exist[id]
244	gerritCLCache.Unlock()
245	if ok {
246		return true, nil
247	}
248
249	// Query the Gerrit API Get Change endpoint, as documented at
250	// https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#get-change.
251	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
252	defer cancel()
253	resp, err := ctxhttp.Get(ctx, nil, fmt.Sprintf("https://go-review.googlesource.com/changes/%d", id))
254	if err != nil {
255		return false, err
256	}
257	resp.Body.Close()
258	switch resp.StatusCode {
259	case http.StatusOK:
260		// A Gerrit CL with this ID exists. Add it to cache.
261		gerritCLCache.Lock()
262		gerritCLCache.exist[id] = true
263		gerritCLCache.Unlock()
264		return true, nil
265	case http.StatusNotFound:
266		// A Gerrit CL with this ID doesn't exist. It may get created in the future.
267		return false, nil
268	default:
269		return false, fmt.Errorf("unexpected status code: %v", resp.Status)
270	}
271}
272
273var gerritCLCache = struct {
274	sync.Mutex
275	exist map[int]bool // exist is a set of Gerrit CL IDs that are known to exist.
276}{exist: make(map[int]bool)}
277
278var changeMap *hashMap
279
280// LoadChangeMap loads the specified map of Mercurial to Git revisions,
281// which is used by the /change/ handler to intelligently map old hg
282// revisions to their new git equivalents.
283// It should be called before calling Register.
284// The file should remain open as long as the process is running.
285// See the implementation of this package for details.
286func LoadChangeMap(filename string) error {
287	f, err := os.Open(filename)
288	if err != nil {
289		return err
290	}
291	m, err := newHashMap(f)
292	if err != nil {
293		return err
294	}
295	changeMap = m
296	return nil
297}
298
299func changeHandler(w http.ResponseWriter, r *http.Request) {
300	const prefix = "/change/"
301	if p := r.URL.Path; p == prefix {
302		// redirect /prefix/ to /prefix
303		http.Redirect(w, r, p[:len(p)-1], http.StatusFound)
304		return
305	}
306	hash := r.URL.Path[len(prefix):]
307	target := "https://go.googlesource.com/go/+/" + hash
308	if git := changeMap.Lookup(hash); git > 0 {
309		target = fmt.Sprintf("https://go.googlesource.com/%v/+/%v", git.Repo(), git.Hash())
310	}
311	http.Redirect(w, r, target, http.StatusFound)
312}
313
314func designHandler(w http.ResponseWriter, r *http.Request) {
315	const prefix = "/design/"
316	if p := r.URL.Path; p == prefix {
317		// redirect /prefix/ to /prefix
318		http.Redirect(w, r, p[:len(p)-1], http.StatusFound)
319		return
320	}
321	name := r.URL.Path[len(prefix):]
322	target := "https://go.googlesource.com/proposal/+/master/design/" + name + ".md"
323	http.Redirect(w, r, target, http.StatusFound)
324}
325