polygerrit-ui/server.go - gerrit - Git at Google

 // Copyright (C) 2015 The Android Open Source Project
 //
 // 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 main

 import (
 	"archive/zip"
 	"bufio"
 	"bytes"
 	"compress/gzip"
 	"encoding/json"
 	"errors"
 	"flag"
 	"io"
 	"io/ioutil"
 	"log"
 	"net"
 	"net/http"
 	"net/url"
 	"os"
 	"path/filepath"
 	"regexp"
 	"strings"

 	"golang.org/x/tools/godoc/vfs/httpfs"
 	"golang.org/x/tools/godoc/vfs/zipfs"
 )

 var (
 	plugins               = flag.String("plugins", "", "comma seperated plugin paths to serve")
 	port                  = flag.String("port", "localhost:8081", "address to serve HTTP requests on")
 	host                  = flag.String("host", "gerrit-review.googlesource.com", "Host to proxy requests to")
 	scheme                = flag.String("scheme", "https", "URL scheme")
 	cdnPattern            = regexp.MustCompile("https://cdn.googlesource.com/polygerrit_ui/[0-9.]*")
 	bundledPluginsPattern = regexp.MustCompile("https://cdn.googlesource.com/polygerrit_assets/[0-9.]*")
 )

 type redirectTarget struct {
 	NpmModule string            `json:"npm_module"`
 	Dir       string            `json:"dir"`
 	Files     map[string]string `json:"files"`
 }

 type redirects struct {
 	From string         `json:"from"`
 	To   redirectTarget `json:"to"`
 }

 type redirectsJson struct {
 	Redirects []redirects `json:"redirects"`
 }

 func readRedirects() []redirects {
 	redirectsFile, err := os.Open("app/redirects.json")
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer redirectsFile.Close()
 	redirectsFileContent, err := ioutil.ReadAll(redirectsFile)
 	if err != nil {
 		log.Fatal(err)
 	}
 	var result redirectsJson
 	json.Unmarshal([]byte(redirectsFileContent), &result)
 	return result.Redirects
 }

 func main() {
 	flag.Parse()

 	fontsArchive, err := openDataArchive("fonts.zip")
 	if err != nil {
 		log.Fatal(err)
 	}

 	workspace := os.Getenv("BUILD_WORKSPACE_DIRECTORY")
 	if err := os.Chdir(filepath.Join(workspace, "polygerrit-ui")); err != nil {
 		log.Fatal(err)
 	}

 	redirects := readRedirects()

 	dirListingMux := http.NewServeMux()
 	dirListingMux.Handle("/styles/", http.StripPrefix("/styles/", http.FileServer(http.Dir("app/styles"))))
 	dirListingMux.Handle("/elements/", http.StripPrefix("/elements/", http.FileServer(http.Dir("app/elements"))))
 	dirListingMux.Handle("/behaviors/", http.StripPrefix("/behaviors/", http.FileServer(http.Dir("app/behaviors"))))

 	http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) { handleSrcRequest(redirects, dirListingMux, w, req) })

 	http.Handle("/fonts/",
 		addDevHeadersMiddleware(http.FileServer(httpfs.New(zipfs.New(fontsArchive, "fonts")))))

 	http.HandleFunc("/index.html", handleIndex)
 	http.HandleFunc("/changes/", handleProxy)
 	http.HandleFunc("/accounts/", handleProxy)
 	http.HandleFunc("/config/", handleProxy)
 	http.HandleFunc("/projects/", handleProxy)
 	http.HandleFunc("/static/", handleProxy)
 	http.HandleFunc("/accounts/self/detail", handleAccountDetail)

 	if len(*plugins) > 0 {
 		http.Handle("/plugins/", http.StripPrefix("/plugins/",
 			http.FileServer(http.Dir("../plugins"))))
 		log.Println("Local plugins from", "../plugins")
 	} else {
 		http.HandleFunc("/plugins/", handleProxy)
 		// Serve local plugins from `plugins_`
 		http.Handle("/plugins_/", http.StripPrefix("/plugins_/",
 			http.FileServer(http.Dir("../plugins"))))
 	}
 	log.Println("Serving on port", *port)
 	log.Fatal(http.ListenAndServe(*port, &server{}))
 }

 func addDevHeadersMiddleware(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(writer http.ResponseWriter, req *http.Request) {
 		addDevHeaders(writer)
 		h.ServeHTTP(writer, req)
 	})
 }

 func addDevHeaders(writer http.ResponseWriter) {
 	writer.Header().Set("Access-Control-Allow-Origin", "*")
 	writer.Header().Set("Cache-Control", "public, max-age=10, must-revalidate")

 }

 func getFinalPath(redirects []redirects, originalPath string) string {
 	testComponentsPrefix := "/components/"
 	if strings.HasPrefix(originalPath, testComponentsPrefix) {
 		return "/../node_modules/" + originalPath[len(testComponentsPrefix):]
 	}

 	for _, redirect := range redirects {
 		fromDir := redirect.From
 		if !strings.HasSuffix(fromDir, "/") {
 			fromDir = fromDir + "/"
 		}
 		if strings.HasPrefix(originalPath, fromDir) {
 			targetDir := ""
 			if redirect.To.NpmModule != "" {
 				targetDir = "node_modules/" + redirect.To.NpmModule
 			} else {
 				targetDir = redirect.To.Dir
 			}
 			if !strings.HasSuffix(targetDir, "/") {
 				targetDir = targetDir + "/"
 			}
 			if !strings.HasPrefix(targetDir, "/") {
 				targetDir = "/" + targetDir
 			}
 			filename := originalPath[len(fromDir):]
 			if redirect.To.Files != nil {
 				newfilename, found := redirect.To.Files[filename]
 				if found {
 					filename = newfilename
 				}
 			}
 			return targetDir + filename
 		}
 	}
 	return originalPath
 }

 func handleSrcRequest(redirects []redirects, dirListingMux *http.ServeMux, writer http.ResponseWriter, originalRequest *http.Request) {
 	parsedUrl, err := url.Parse(originalRequest.RequestURI)
 	if err != nil {
 		writer.WriteHeader(500)
 		return
 	}
 	if parsedUrl.Path != "/" && strings.HasSuffix(parsedUrl.Path, "/") {
 		dirListingMux.ServeHTTP(writer, originalRequest)
 		return
 	}
 	if parsedUrl.Path == "/bower_components/web-component-tester/browser.js" {
 		http.Redirect(writer, originalRequest, "/bower_components/wct-browser-legacy/browser.js", 301)
 		return
 	}

 	requestPath := getFinalPath(redirects, parsedUrl.Path)

 	if !strings.HasPrefix(requestPath, "/") {
 		requestPath = "/" + requestPath
 	}

 	data, err := readFile(parsedUrl.Path, requestPath)
 	if err != nil {
 		writer.WriteHeader(404)
 		return
 	}
 	if strings.HasSuffix(requestPath, ".js") {
 		r := regexp.MustCompile("(?m)^(import.*)'([^/.].*)';$")
 		data = r.ReplaceAll(data, []byte("$1 '/node_modules/$2'"))
 		writer.Header().Set("Content-Type", "application/javascript")
 	} else if strings.HasSuffix(requestPath, ".css") {
 		writer.Header().Set("Content-Type", "text/css")
 	} else if strings.HasSuffix(requestPath, ".html") {
 		writer.Header().Set("Content-Type", "text/html")
 	}
 	writer.WriteHeader(200)
 	addDevHeaders(writer)
 	writer.Write(data)
 }

 func readFile(originalPath string, redirectedPath string) ([]byte, error) {
 	pathsToTry := []string{"app" + redirectedPath}
 	bowerComponentsSuffix := "/bower_components/"
 	nodeModulesPrefix := "/node_modules/"

 	if strings.HasPrefix(originalPath, bowerComponentsSuffix) {
 		pathsToTry = append(pathsToTry, "node_modules/wct-browser-legacy/node_modules/"+originalPath[len(bowerComponentsSuffix):])
 		pathsToTry = append(pathsToTry, "node_modules/"+originalPath[len(bowerComponentsSuffix):])
 	}

 	if strings.HasPrefix(originalPath, nodeModulesPrefix) {
 		pathsToTry = append(pathsToTry, "node_modules/"+originalPath[len(nodeModulesPrefix):])
 	}

 	for _, path := range pathsToTry {
 		data, err := ioutil.ReadFile(path)
 		if err == nil {
 			return data, nil
 		}
 	}

 	return nil, errors.New("File not found")
 }

 func openDataArchive(path string) (*zip.ReadCloser, error) {
 	absBinPath, err := resourceBasePath()
 	if err != nil {
 		return nil, err
 	}
 	return zip.OpenReader(absBinPath + ".runfiles/gerrit/polygerrit-ui/" + path)
 }

 func resourceBasePath() (string, error) {
 	return filepath.Abs(os.Args[0])
 }

 func handleIndex(writer http.ResponseWriter, originalRequest *http.Request) {
 	fakeRequest := &http.Request{
 		URL: &url.URL{
 			Path:     "/",
 			RawQuery: originalRequest.URL.RawQuery,
 		},
 	}
 	handleProxy(writer, fakeRequest)
 }

 func handleProxy(writer http.ResponseWriter, originalRequest *http.Request) {
 	patchedRequest := &http.Request{
 		Method: "GET",
 		URL: &url.URL{
 			Scheme:   *scheme,
 			Host:     *host,
 			Opaque:   originalRequest.URL.EscapedPath(),
 			RawQuery: originalRequest.URL.RawQuery,
 		},
 	}
 	response, err := http.DefaultClient.Do(patchedRequest)
 	if err != nil {
 		http.Error(writer, err.Error(), http.StatusInternalServerError)
 		return
 	}
 	defer response.Body.Close()
 	for name, values := range response.Header {
 		for _, value := range values {
 			if name != "Content-Length" {
 				writer.Header().Add(name, value)
 			}
 		}
 	}
 	writer.WriteHeader(response.StatusCode)
 	if _, err := io.Copy(writer, patchResponse(originalRequest, response)); err != nil {
 		log.Println("Error copying response to ResponseWriter:", err)
 		return
 	}
 }

 func getJsonPropByPath(json map[string]interface{}, path []string) interface{} {
 	prop, path := path[0], path[1:]
 	if json[prop] == nil {
 		return nil
 	}
 	switch json[prop].(type) {
 	case map[string]interface{}: // map
 		return getJsonPropByPath(json[prop].(map[string]interface{}), path)
 	case []interface{}: // array
 		return json[prop].([]interface{})
 	default:
 		return json[prop].(interface{})
 	}
 }

 func setJsonPropByPath(json map[string]interface{}, path []string, value interface{}) {
 	prop, path := path[0], path[1:]
 	if json[prop] == nil {
 		return // path not found
 	}
 	if len(path) > 0 {
 		setJsonPropByPath(json[prop].(map[string]interface{}), path, value)
 	} else {
 		json[prop] = value
 	}
 }

 func patchResponse(req *http.Request, res *http.Response) io.Reader {
 	switch req.URL.EscapedPath() {
 	case "/":
 		return rewriteHostPage(res.Body)
 	case "/config/server/info":
 		return injectLocalPlugins(res.Body)
 	default:
 		return res.Body
 	}
 }

 func rewriteHostPage(reader io.Reader) io.Reader {
 	buf := new(bytes.Buffer)
 	buf.ReadFrom(reader)
 	original := buf.String()

 	// Simply remove all CDN references, so files are loaded from the local file system  or the proxy
 	// server instead.
 	replaced := cdnPattern.ReplaceAllString(original, "")

 	// Modify window.INITIAL_DATA so that it has the same effect as injectLocalPlugins. To achieve
 	// this let's add JavaScript lines at the end of the <script>...</script> snippet that also
 	// contains window.INITIAL_DATA=...
 	// Here we rely on the fact that the <script> snippet that we want to append to is the first one.
 	if len(*plugins) > 0 {
 		// If the host page contains a reference to a plugin bundle that would be preloaded, then remove it.
 		replaced = bundledPluginsPattern.ReplaceAllString(replaced, "")

 		insertionPoint := strings.Index(replaced, "</script>")
 		builder := new(strings.Builder)
 		builder.WriteString(
 			"window.INITIAL_DATA['/config/server/info'].plugin.html_resource_paths = []; ")
 		builder.WriteString(
 			"window.INITIAL_DATA['/config/server/info'].plugin.js_resource_paths = []; ")
 		for _, p := range strings.Split(*plugins, ",") {
 			if filepath.Ext(p) == ".html" {
 				builder.WriteString(
 					"window.INITIAL_DATA['/config/server/info'].plugin.html_resource_paths.push('" + p + "'); ")
 			}
 			if filepath.Ext(p) == ".js" {
 				builder.WriteString(
 					"window.INITIAL_DATA['/config/server/info'].plugin.js_resource_paths.push('" + p + "'); ")
 			}
 		}
 		replaced = replaced[:insertionPoint] + builder.String() + replaced[insertionPoint:]
 	}

 	return strings.NewReader(replaced)
 }

 func injectLocalPlugins(reader io.Reader) io.Reader {
 	if len(*plugins) == 0 {
 		return reader
 	}
 	// Skip escape prefix
 	io.CopyN(ioutil.Discard, reader, 5)
 	dec := json.NewDecoder(reader)

 	var response map[string]interface{}
 	err := dec.Decode(&response)
 	if err != nil {
 		log.Fatal(err)
 	}

 	// Configuration path in the JSON server response
 	jsPluginsPath := []string{"plugin", "js_resource_paths"}
 	htmlPluginsPath := []string{"plugin", "html_resource_paths"}
 	htmlResources := getJsonPropByPath(response, htmlPluginsPath).([]interface{})
 	jsResources := getJsonPropByPath(response, jsPluginsPath).([]interface{})

 	for _, p := range strings.Split(*plugins, ",") {
 		if filepath.Ext(p) == ".html" {
 			htmlResources = append(htmlResources, p)
 		}

 		if filepath.Ext(p) == ".js" {
 			jsResources = append(jsResources, p)
 		}
 	}

 	setJsonPropByPath(response, jsPluginsPath, jsResources)
 	setJsonPropByPath(response, htmlPluginsPath, htmlResources)

 	reader, writer := io.Pipe()
 	go func() {
 		defer writer.Close()
 		io.WriteString(writer, ")]}'") // Write escape prefix
 		err := json.NewEncoder(writer).Encode(&response)
 		if err != nil {
 			log.Fatal(err)
 		}
 	}()
 	return reader
 }

 func handleAccountDetail(w http.ResponseWriter, r *http.Request) {
 	http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
 }

 type gzipResponseWriter struct {
 	io.WriteCloser
 	http.ResponseWriter
 }

 func newGzipResponseWriter(w http.ResponseWriter) *gzipResponseWriter {
 	gz := gzip.NewWriter(w)
 	return &gzipResponseWriter{WriteCloser: gz, ResponseWriter: w}
 }

 func (w gzipResponseWriter) Write(b []byte) (int, error) {
 	return w.WriteCloser.Write(b)
 }

 func (w gzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	h, ok := w.ResponseWriter.(http.Hijacker)
 	if !ok {
 		return nil, nil, errors.New("gzipResponseWriter: ResponseWriter does not satisfy http.Hijacker interface")
 	}
 	return h.Hijack()
 }

 type server struct{}

 // Any path prefixes that should resolve to index.html.
 var (
 	fePaths    = []string{"/q/", "/c/", "/p/", "/x/", "/dashboard/", "/admin/", "/settings/"}
 	issueNumRE = regexp.MustCompile(`^\/\d+\/?$`)
 )

 func (_ *server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	log.Printf("%s %s %s %s\n", r.Proto, r.Method, r.RemoteAddr, r.URL)
 	for _, prefix := range fePaths {
 		if strings.HasPrefix(r.URL.Path, prefix) || r.URL.Path == "/" {
 			r.URL.Path = "/index.html"
 			log.Println("Redirecting to /index.html")
 			break
 		} else if match := issueNumRE.Find([]byte(r.URL.Path)); match != nil {
 			r.URL.Path = "/index.html"
 			log.Println("Redirecting to /index.html")
 			break
 		}
 	}
 	if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
 		http.DefaultServeMux.ServeHTTP(w, r)
 		return
 	}
 	w.Header().Set("Content-Encoding", "gzip")
 	addDevHeaders(w)
 	gzw := newGzipResponseWriter(w)
 	defer gzw.Close()
 	http.DefaultServeMux.ServeHTTP(gzw, r)
 }
	// Copyright (C) 2015 The Android Open Source Project
	//
	// 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 main

	import (
	"archive/zip"
	"bufio"
	"bytes"
	"compress/gzip"
	"encoding/json"
	"errors"
	"flag"
	"io"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"golang.org/x/tools/godoc/vfs/httpfs"
	"golang.org/x/tools/godoc/vfs/zipfs"
	)

	var (
	plugins = flag.String("plugins", "", "comma seperated plugin paths to serve")
	port = flag.String("port", "localhost:8081", "address to serve HTTP requests on")
	host = flag.String("host", "gerrit-review.googlesource.com", "Host to proxy requests to")
	scheme = flag.String("scheme", "https", "URL scheme")
	cdnPattern = regexp.MustCompile("https://cdn.googlesource.com/polygerrit_ui/[0-9.]*")
	bundledPluginsPattern = regexp.MustCompile("https://cdn.googlesource.com/polygerrit_assets/[0-9.]*")
	)

	type redirectTarget struct {
	NpmModule string `json:"npm_module"`
	Dir string `json:"dir"`
	Files map[string]string `json:"files"`
	}

	type redirects struct {
	From string `json:"from"`
	To redirectTarget `json:"to"`
	}

	type redirectsJson struct {
	Redirects []redirects `json:"redirects"`
	}

	func readRedirects() []redirects {
	redirectsFile, err := os.Open("app/redirects.json")
	if err != nil {
	log.Fatal(err)
	}
	defer redirectsFile.Close()
	redirectsFileContent, err := ioutil.ReadAll(redirectsFile)
	if err != nil {
	log.Fatal(err)
	}
	var result redirectsJson
	json.Unmarshal([]byte(redirectsFileContent), &result)
	return result.Redirects
	}

	func main() {
	flag.Parse()

	fontsArchive, err := openDataArchive("fonts.zip")
	if err != nil {
	log.Fatal(err)
	}

	workspace := os.Getenv("BUILD_WORKSPACE_DIRECTORY")
	if err := os.Chdir(filepath.Join(workspace, "polygerrit-ui")); err != nil {
	log.Fatal(err)
	}

	redirects := readRedirects()

	dirListingMux := http.NewServeMux()
	dirListingMux.Handle("/styles/", http.StripPrefix("/styles/", http.FileServer(http.Dir("app/styles"))))
	dirListingMux.Handle("/elements/", http.StripPrefix("/elements/", http.FileServer(http.Dir("app/elements"))))
	dirListingMux.Handle("/behaviors/", http.StripPrefix("/behaviors/", http.FileServer(http.Dir("app/behaviors"))))

	http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) { handleSrcRequest(redirects, dirListingMux, w, req) })

	http.Handle("/fonts/",
	addDevHeadersMiddleware(http.FileServer(httpfs.New(zipfs.New(fontsArchive, "fonts")))))

	http.HandleFunc("/index.html", handleIndex)
	http.HandleFunc("/changes/", handleProxy)
	http.HandleFunc("/accounts/", handleProxy)
	http.HandleFunc("/config/", handleProxy)
	http.HandleFunc("/projects/", handleProxy)
	http.HandleFunc("/static/", handleProxy)
	http.HandleFunc("/accounts/self/detail", handleAccountDetail)

	if len(*plugins) > 0 {
	http.Handle("/plugins/", http.StripPrefix("/plugins/",
	http.FileServer(http.Dir("../plugins"))))
	log.Println("Local plugins from", "../plugins")
	} else {
	http.HandleFunc("/plugins/", handleProxy)
	// Serve local plugins from `plugins_`
	http.Handle("/plugins_/", http.StripPrefix("/plugins_/",
	http.FileServer(http.Dir("../plugins"))))
	}
	log.Println("Serving on port", *port)
	log.Fatal(http.ListenAndServe(*port, &server{}))
	}

	func addDevHeadersMiddleware(h http.Handler) http.Handler {
	return http.HandlerFunc(func(writer http.ResponseWriter, req *http.Request) {
	addDevHeaders(writer)
	h.ServeHTTP(writer, req)
	})
	}

	func addDevHeaders(writer http.ResponseWriter) {
	writer.Header().Set("Access-Control-Allow-Origin", "*")
	writer.Header().Set("Cache-Control", "public, max-age=10, must-revalidate")

	}

	func getFinalPath(redirects []redirects, originalPath string) string {
	testComponentsPrefix := "/components/"
	if strings.HasPrefix(originalPath, testComponentsPrefix) {
	return "/../node_modules/" + originalPath[len(testComponentsPrefix):]
	}

	for _, redirect := range redirects {
	fromDir := redirect.From
	if !strings.HasSuffix(fromDir, "/") {
	fromDir = fromDir + "/"
	}
	if strings.HasPrefix(originalPath, fromDir) {
	targetDir := ""
	if redirect.To.NpmModule != "" {
	targetDir = "node_modules/" + redirect.To.NpmModule
	} else {
	targetDir = redirect.To.Dir
	}
	if !strings.HasSuffix(targetDir, "/") {
	targetDir = targetDir + "/"
	}
	if !strings.HasPrefix(targetDir, "/") {
	targetDir = "/" + targetDir
	}
	filename := originalPath[len(fromDir):]
	if redirect.To.Files != nil {
	newfilename, found := redirect.To.Files[filename]
	if found {
	filename = newfilename
	}
	}
	return targetDir + filename
	}
	}
	return originalPath
	}

	func handleSrcRequest(redirects []redirects, dirListingMux http.ServeMux, writer http.ResponseWriter, originalRequest http.Request) {
	parsedUrl, err := url.Parse(originalRequest.RequestURI)
	if err != nil {
	writer.WriteHeader(500)
	return
	}
	if parsedUrl.Path != "/" && strings.HasSuffix(parsedUrl.Path, "/") {
	dirListingMux.ServeHTTP(writer, originalRequest)
	return
	}
	if parsedUrl.Path == "/bower_components/web-component-tester/browser.js" {
	http.Redirect(writer, originalRequest, "/bower_components/wct-browser-legacy/browser.js", 301)
	return
	}

	requestPath := getFinalPath(redirects, parsedUrl.Path)

	if !strings.HasPrefix(requestPath, "/") {
	requestPath = "/" + requestPath
	}

	data, err := readFile(parsedUrl.Path, requestPath)
	if err != nil {
	writer.WriteHeader(404)
	return
	}
	if strings.HasSuffix(requestPath, ".js") {
	r := regexp.MustCompile("(?m)^(import.)'([^/.].)';$")
	data = r.ReplaceAll(data, []byte("$1 '/node_modules/$2'"))
	writer.Header().Set("Content-Type", "application/javascript")
	} else if strings.HasSuffix(requestPath, ".css") {
	writer.Header().Set("Content-Type", "text/css")
	} else if strings.HasSuffix(requestPath, ".html") {
	writer.Header().Set("Content-Type", "text/html")
	}
	writer.WriteHeader(200)
	addDevHeaders(writer)
	writer.Write(data)
	}

	func readFile(originalPath string, redirectedPath string) ([]byte, error) {
	pathsToTry := []string{"app" + redirectedPath}
	bowerComponentsSuffix := "/bower_components/"
	nodeModulesPrefix := "/node_modules/"

	if strings.HasPrefix(originalPath, bowerComponentsSuffix) {
	pathsToTry = append(pathsToTry, "node_modules/wct-browser-legacy/node_modules/"+originalPath[len(bowerComponentsSuffix):])
	pathsToTry = append(pathsToTry, "node_modules/"+originalPath[len(bowerComponentsSuffix):])
	}

	if strings.HasPrefix(originalPath, nodeModulesPrefix) {
	pathsToTry = append(pathsToTry, "node_modules/"+originalPath[len(nodeModulesPrefix):])
	}

	for _, path := range pathsToTry {
	data, err := ioutil.ReadFile(path)
	if err == nil {
	return data, nil
	}
	}

	return nil, errors.New("File not found")
	}

	func openDataArchive(path string) (*zip.ReadCloser, error) {
	absBinPath, err := resourceBasePath()
	if err != nil {
	return nil, err
	}
	return zip.OpenReader(absBinPath + ".runfiles/gerrit/polygerrit-ui/" + path)
	}

	func resourceBasePath() (string, error) {
	return filepath.Abs(os.Args[0])
	}

	func handleIndex(writer http.ResponseWriter, originalRequest *http.Request) {
	fakeRequest := &http.Request{
	URL: &url.URL{
	Path: "/",
	RawQuery: originalRequest.URL.RawQuery,
	},
	}
	handleProxy(writer, fakeRequest)
	}

	func handleProxy(writer http.ResponseWriter, originalRequest *http.Request) {
	patchedRequest := &http.Request{
	Method: "GET",
	URL: &url.URL{
	Scheme: *scheme,
	Host: *host,
	Opaque: originalRequest.URL.EscapedPath(),
	RawQuery: originalRequest.URL.RawQuery,
	},
	}
	response, err := http.DefaultClient.Do(patchedRequest)
	if err != nil {
	http.Error(writer, err.Error(), http.StatusInternalServerError)
	return
	}
	defer response.Body.Close()
	for name, values := range response.Header {
	for _, value := range values {
	if name != "Content-Length" {
	writer.Header().Add(name, value)
	}
	}
	}
	writer.WriteHeader(response.StatusCode)
	if _, err := io.Copy(writer, patchResponse(originalRequest, response)); err != nil {
	log.Println("Error copying response to ResponseWriter:", err)
	return
	}
	}

	func getJsonPropByPath(json map[string]interface{}, path []string) interface{} {
	prop, path := path[0], path[1:]
	if json[prop] == nil {
	return nil
	}
	switch json[prop].(type) {
	case map[string]interface{}: // map
	return getJsonPropByPath(json[prop].(map[string]interface{}), path)
	case []interface{}: // array
	return json[prop].([]interface{})
	default:
	return json[prop].(interface{})
	}
	}

	func setJsonPropByPath(json map[string]interface{}, path []string, value interface{}) {
	prop, path := path[0], path[1:]
	if json[prop] == nil {
	return // path not found
	}
	if len(path) > 0 {
	setJsonPropByPath(json[prop].(map[string]interface{}), path, value)
	} else {
	json[prop] = value
	}
	}

	func patchResponse(req http.Request, res http.Response) io.Reader {
	switch req.URL.EscapedPath() {
	case "/":
	return rewriteHostPage(res.Body)
	case "/config/server/info":
	return injectLocalPlugins(res.Body)
	default:
	return res.Body
	}
	}

	func rewriteHostPage(reader io.Reader) io.Reader {
	buf := new(bytes.Buffer)
	buf.ReadFrom(reader)
	original := buf.String()

	// Simply remove all CDN references, so files are loaded from the local file system or the proxy
	// server instead.
	replaced := cdnPattern.ReplaceAllString(original, "")

	// Modify window.INITIAL_DATA so that it has the same effect as injectLocalPlugins. To achieve
	// this let's add JavaScript lines at the end of the <script>...</script> snippet that also
	// contains window.INITIAL_DATA=...
	// Here we rely on the fact that the <script> snippet that we want to append to is the first one.
	if len(*plugins) > 0 {
	// If the host page contains a reference to a plugin bundle that would be preloaded, then remove it.
	replaced = bundledPluginsPattern.ReplaceAllString(replaced, "")

	insertionPoint := strings.Index(replaced, "</script>")
	builder := new(strings.Builder)
	builder.WriteString(
	"window.INITIAL_DATA['/config/server/info'].plugin.html_resource_paths = []; ")
	builder.WriteString(
	"window.INITIAL_DATA['/config/server/info'].plugin.js_resource_paths = []; ")
	for _, p := range strings.Split(*plugins, ",") {
	if filepath.Ext(p) == ".html" {
	builder.WriteString(
	"window.INITIAL_DATA['/config/server/info'].plugin.html_resource_paths.push('" + p + "'); ")
	}
	if filepath.Ext(p) == ".js" {
	builder.WriteString(
	"window.INITIAL_DATA['/config/server/info'].plugin.js_resource_paths.push('" + p + "'); ")
	}
	}
	replaced = replaced[:insertionPoint] + builder.String() + replaced[insertionPoint:]
	}

	return strings.NewReader(replaced)
	}

	func injectLocalPlugins(reader io.Reader) io.Reader {
	if len(*plugins) == 0 {
	return reader
	}
	// Skip escape prefix
	io.CopyN(ioutil.Discard, reader, 5)
	dec := json.NewDecoder(reader)

	var response map[string]interface{}
	err := dec.Decode(&response)
	if err != nil {
	log.Fatal(err)
	}

	// Configuration path in the JSON server response
	jsPluginsPath := []string{"plugin", "js_resource_paths"}
	htmlPluginsPath := []string{"plugin", "html_resource_paths"}
	htmlResources := getJsonPropByPath(response, htmlPluginsPath).([]interface{})
	jsResources := getJsonPropByPath(response, jsPluginsPath).([]interface{})

	for _, p := range strings.Split(*plugins, ",") {
	if filepath.Ext(p) == ".html" {
	htmlResources = append(htmlResources, p)
	}

	if filepath.Ext(p) == ".js" {
	jsResources = append(jsResources, p)
	}
	}

	setJsonPropByPath(response, jsPluginsPath, jsResources)
	setJsonPropByPath(response, htmlPluginsPath, htmlResources)

	reader, writer := io.Pipe()
	go func() {
	defer writer.Close()
	io.WriteString(writer, ")]}'") // Write escape prefix
	err := json.NewEncoder(writer).Encode(&response)
	if err != nil {
	log.Fatal(err)
	}
	}()
	return reader
	}

	func handleAccountDetail(w http.ResponseWriter, r *http.Request) {
	http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
	}

	type gzipResponseWriter struct {
	io.WriteCloser
	http.ResponseWriter
	}

	func newGzipResponseWriter(w http.ResponseWriter) *gzipResponseWriter {
	gz := gzip.NewWriter(w)
	return &gzipResponseWriter{WriteCloser: gz, ResponseWriter: w}
	}

	func (w gzipResponseWriter) Write(b []byte) (int, error) {
	return w.WriteCloser.Write(b)
	}

	func (w gzipResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
	h, ok := w.ResponseWriter.(http.Hijacker)
	if !ok {
	return nil, nil, errors.New("gzipResponseWriter: ResponseWriter does not satisfy http.Hijacker interface")
	}
	return h.Hijack()
	}

	type server struct{}

	// Any path prefixes that should resolve to index.html.
	var (
	fePaths = []string{"/q/", "/c/", "/p/", "/x/", "/dashboard/", "/admin/", "/settings/"}
	issueNumRE = regexp.MustCompile(`^\/\d+\/?$`)
	)

	func (_ server) ServeHTTP(w http.ResponseWriter, r http.Request) {
	log.Printf("%s %s %s %s\n", r.Proto, r.Method, r.RemoteAddr, r.URL)
	for _, prefix := range fePaths {
	if strings.HasPrefix(r.URL.Path, prefix) \|\| r.URL.Path == "/" {
	r.URL.Path = "/index.html"
	log.Println("Redirecting to /index.html")
	break
	} else if match := issueNumRE.Find([]byte(r.URL.Path)); match != nil {
	r.URL.Path = "/index.html"
	log.Println("Redirecting to /index.html")
	break
	}
	}
	if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
	http.DefaultServeMux.ServeHTTP(w, r)
	return
	}
	w.Header().Set("Content-Encoding", "gzip")
	addDevHeaders(w)
	gzw := newGzipResponseWriter(w)
	defer gzw.Close()
	http.DefaultServeMux.ServeHTTP(gzw, r)
	}