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static.go
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static.go
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// Copyright Google Inc.
//
// 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 backend
import (
"log"
"net/http"
"net/http/httputil"
"net/url"
"os"
"strings"
"google.golang.org/appengine"
"google.golang.org/appengine/urlfetch"
)
const (
MAX_AGE_IN_SECONDS = 180 // three minutes
OLD_ADDRESS = "amp-by-example.appspot.com"
DIST_DIR = "dist"
)
func InitStatic() {
fileserver := http.FileServer(http.Dir(DIST_DIR))
http.Handle("/", serveStaticFiles(handleNotFound(fileserver)))
}
func handleNotFound(h http.Handler) http.HandlerFunc {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if strings.HasSuffix(r.URL.Path, "/") && !exists(DIST_DIR+r.URL.Path+"index.html") {
http.NotFound(w, r)
return
}
h.ServeHTTP(w, r)
})
}
func serveStaticFiles(h http.Handler) http.Handler {
return SetVary(EnableCors(
func(w http.ResponseWriter, r *http.Request) {
if r.Host == OLD_ADDRESS || IsInsecureRequest(r) {
RedirectToSecureVersion(w, r)
return
}
if isAMP(r) && shouldProxy(r) {
p := proxyGAE(PACKAGER_PREFIX, r)
t := r.URL.String()
r.URL.RawQuery = "sign=" + url.QueryEscape(NEW_ADDRESS+r.URL.Path)
r.URL.Path = "/priv/doc"
log.Printf("Proxying request for [%s] to [%s]", t, r.URL.String())
p.ServeHTTP(w, r)
} else {
if strings.HasSuffix(r.URL.Path, ".json") {
w.Header().Set("Content-Type", "application/json")
}
SetDefaultMaxAge(w)
h.ServeHTTP(w, r)
}
}))
}
func proxyGAE(prefix string, r *http.Request) *httputil.ReverseProxy {
u, err := url.Parse(prefix)
if err != nil {
log.Fatal(err)
}
p := httputil.NewSingleHostReverseProxy(u)
// Fiddling with the transport might not be necessary with the Go 1.11 runtime:
// https://cloud.google.com/blog/products/application-development/go-1-11-is-now-available-on-app-engine
p.Transport = &urlfetch.Transport{
Context: appengine.NewContext(r),
}
return p
}
func shouldProxy(r *http.Request) bool {
return r.Header.Get("amp-cache-transform") != ""
}
func isAMP(r *http.Request) bool {
// TODO Improve heuristics...
return !strings.HasSuffix(r.URL.Path, ".json")
}
func exists(path string) bool {
if _, err := os.Stat(path); err == nil {
return true
}
return false
}