Add app engine app to mirror html docs from chromium.googlesource.com

doc/appengine/main.go

Index: doc/appengine/main.go
diff --git a/doc/appengine/main.go b/doc/appengine/main.go
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index 0000000000000000000000000000000000000000..57d7af1348712d84ee3ab1f95aeaa59a1170f086
--- /dev/null
+++ b/doc/appengine/main.go
@@ -0,0 +1,118 @@
+// Copyright 2015 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package crashpad mirrors crashpad documentation from Chromium’s git repo.
+package crashpad
+
+import (
+	"encoding/base64"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"path"
+	"strings"
+	"time"
+
+	"google.golang.org/appengine"
+	"google.golang.org/appengine/memcache"
+	"google.golang.org/appengine/urlfetch"
+)
+
+const baseURL = "https://chromium.googlesource.com/crashpad/crashpad/+/doc/doc/generated/?format=TEXT"
+
+func init() {
+	http.HandleFunc("/", handler)
+}
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	ctx := appengine.NewContext(r)
+	client := urlfetch.Client(ctx)
+
+	// Don’t show dotfiles.
+	if strings.HasPrefix(path.Base(r.URL.Path), ".") {
+		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
+		return
+	}
+
+	u, err := url.Parse(baseURL)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	// Redirect directories to their index pages (/doc/ -> /doc/index.html).
+	if strings.HasSuffix(r.URL.Path, "/") {
+		http.Redirect(w, r, r.URL.Path+"index.html", http.StatusFound)
+		return
+	}
+
+	u.Path = path.Join(u.Path, r.URL.Path)
+	urlStr := u.String()
+
+	item, err := memcache.Get(ctx, urlStr)
+	if err == memcache.ErrCacheMiss {
+		resp, err := client.Get(urlStr)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			w.WriteHeader(resp.StatusCode)
+			w.Header().Set("Content-Type", "text/html")

[Mark Mentovai, 2015/10/08 21:46:17]

If you’re going to copy the response: carry the Content-Type from the server
too?

+			io.Copy(w, resp.Body)

[Mark Mentovai, 2015/10/08 21:46:17]

Is it actually kosher to do this? Might leak something we don’t want to expose
publicly.

+			return
+		}
+		decoder := base64.NewDecoder(base64.StdEncoding, resp.Body)
+		b, err := ioutil.ReadAll(decoder)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		item = &memcache.Item{
+			Key:        urlStr,
+			Value:      b,
+			Expiration: 24 * time.Hour,
+		}
+		if err := memcache.Set(ctx, item); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	} else if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", contentType(path.Base(u.Path)))
+	fmt.Fprintf(w, "%s", item.Value)
+}
+
+var contentTypes = map[string]string{
+	".html": "text/html",
+	".css":  "text/css",
+	".js":   "text/javascript",
+	".png":  "image/png",
+}
+
+// contentType returns the appropriate content type header for file.
+func contentType(file string) string {
+	for suffix, typ := range contentTypes {
+		if strings.HasSuffix(file, suffix) {
+			return typ + "; charset=UTF-8"
+		}
+	}
+	return "text/plain; charset=UTF-8"
+}