ui.go

/*
Copyright 2011 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 server

import (
	"errors"
	"fmt"
	"log"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"

	"camlistore.org/pkg/blob"
	"camlistore.org/pkg/blobserver"
	"camlistore.org/pkg/constants"
	"camlistore.org/pkg/fileembed"
	"camlistore.org/pkg/httputil"
	"camlistore.org/pkg/jsonconfig"
	"camlistore.org/pkg/jsonsign/signhandler"
	"camlistore.org/pkg/misc/closure"
	"camlistore.org/pkg/search"
	"camlistore.org/pkg/server/app"
	"camlistore.org/pkg/sorted"
	"camlistore.org/pkg/syncutil"
	uistatic "camlistore.org/server/camlistored/ui"
	closurestatic "camlistore.org/server/camlistored/ui/closure"
	"camlistore.org/third_party/code.google.com/p/rsc/qr"
	fontawesomestatic "camlistore.org/third_party/fontawesome"
	glitchstatic "camlistore.org/third_party/glitch"
	lessstatic "camlistore.org/third_party/less"
	reactstatic "camlistore.org/third_party/react"
)

var (
	staticFilePattern = regexp.MustCompile(`^([a-zA-Z0-9\-\_\.]+\.(html|js|css|png|jpg|gif|svg))$`)
	identOrDotPattern = regexp.MustCompile(`^[a-zA-Z\_]+(\.[a-zA-Z\_]+)*$`)

	// Download URL suffix:
	//   $1: blobref (checked in download handler)
	//   $2: optional "/filename" to be sent as recommended download name,
	//       if sane looking
	downloadPattern = regexp.MustCompile(`^download/([^/]+)(/.*)?$`)

	thumbnailPattern   = regexp.MustCompile(`^thumbnail/([^/]+)(/.*)?$`)
	treePattern        = regexp.MustCompile(`^tree/([^/]+)(/.*)?$`)
	closurePattern     = regexp.MustCompile(`^closure/(([^/]+)(/.*)?)$`)
	lessPattern        = regexp.MustCompile(`^less/(.+)$`)
	reactPattern       = regexp.MustCompile(`^react/(.+)$`)
	fontawesomePattern = regexp.MustCompile(`^fontawesome/(.+)$`)
	glitchPattern      = regexp.MustCompile(`^glitch/(.+)$`)

	disableThumbCache, _ = strconv.ParseBool(os.Getenv("CAMLI_DISABLE_THUMB_CACHE"))
)

// UIHandler handles serving the UI and discovery JSON.
type UIHandler struct {
	// JSONSignRoot is the optional path or full URL to the JSON
	// Signing helper. Only used by the UI and thus necessary if
	// UI is true.
	// TODO(bradfitz): also move this up to the root handler,
	// if we start having clients (like phones) that we want to upload
	// but don't trust to have private signing keys?
	JSONSignRoot string
	publishRoots map[string]*publishRoot

	prefix string // of the UI handler itself
	root   *RootHandler
	search *search.Handler
	sigh   *signhandler.Handler // or nil

	// Cache optionally specifies a cache blob server, used for
	// caching image thumbnails and other emphemeral data.
	Cache blobserver.Storage // or nil

	// Limit peak RAM used by concurrent image thumbnail calls.
	resizeSem *syncutil.Sem
	thumbMeta *ThumbMeta // optional thumbnail key->blob.Ref cache

	// sourceRoot optionally specifies the path to root of Camlistore's
	// source. If empty, the UI files must be compiled in to the
	// binary (with go run make.go).  This comes from the "sourceRoot"
	// ui handler config option.
	sourceRoot string

	uiDir string // if sourceRoot != "", this is sourceRoot+"/server/camlistored/ui"

	closureHandler         http.Handler
	fileLessHandler        http.Handler
	fileReactHandler       http.Handler
	fileFontawesomeHandler http.Handler
	fileGlitchHandler      http.Handler
}

func init() {
	blobserver.RegisterHandlerConstructor("ui", uiFromConfig)
}

// newKVOrNil wraps sorted.NewKeyValue and adds the ability
// to pass a nil conf to get a (nil, nil) response.
func newKVOrNil(conf jsonconfig.Obj) (sorted.KeyValue, error) {
	if len(conf) == 0 {
		return nil, nil
	}
	return sorted.NewKeyValue(conf)
}

func uiFromConfig(ld blobserver.Loader, conf jsonconfig.Obj) (h http.Handler, err error) {
	checkType := func(key string, htype string) {
		v := conf.OptionalString(key, "")
		if v == "" {
			return
		}
		ct := ld.GetHandlerType(v)
		if ct == "" {
			err = fmt.Errorf("UI handler's %q references non-existant %q", key, v)
		} else if ct != htype {
			err = fmt.Errorf("UI handler's %q references %q of type %q; expected type %q", key, v, ct, htype)
		}
	}
	checkType("searchRoot", "search")
	checkType("jsonSignRoot", "jsonsign")
	if err != nil {
		return
	}
	ui := &UIHandler{
		prefix:       ld.MyPrefix(),
		JSONSignRoot: conf.OptionalString("jsonSignRoot", ""),
		sourceRoot:   conf.OptionalString("sourceRoot", ""),
		resizeSem: syncutil.NewSem(int64(conf.OptionalInt("maxResizeBytes",
			constants.DefaultMaxResizeMem))),
	}
	cachePrefix := conf.OptionalString("cache", "")
	scaledImageConf := conf.OptionalObject("scaledImage")
	if err = conf.Validate(); err != nil {
		return
	}

	if ui.JSONSignRoot != "" {
		h, _ := ld.GetHandler(ui.JSONSignRoot)
		if sigh, ok := h.(*signhandler.Handler); ok {
			ui.sigh = sigh
		}
	}

	scaledImageKV, err := newKVOrNil(scaledImageConf)
	if err != nil {
		return nil, fmt.Errorf("in UI handler's scaledImage: %v", err)
	}
	if scaledImageKV != nil && cachePrefix == "" {
		return nil, fmt.Errorf("in UI handler, can't specify scaledImage without cache")
	}
	if cachePrefix != "" {
		bs, err := ld.GetStorage(cachePrefix)
		if err != nil {
			return nil, fmt.Errorf("UI handler's cache of %q error: %v", cachePrefix, err)
		}
		ui.Cache = bs
		ui.thumbMeta = NewThumbMeta(scaledImageKV)
	}

	if ui.sourceRoot == "" {
		ui.sourceRoot = os.Getenv("CAMLI_DEV_CAMLI_ROOT")
		if uistatic.IsAppEngine {
			if _, err = os.Stat(filepath.Join(uistatic.GaeSourceRoot,
				filepath.FromSlash("server/camlistored/ui/index.html"))); err != nil {
				hint := fmt.Sprintf("\"sourceRoot\" was not specified in the config,"+
					" and the default sourceRoot dir %v does not exist or does not contain"+
					" \"server/camlistored/ui/index.html\". devcam appengine can do that for you.",
					uistatic.GaeSourceRoot)
				log.Print(hint)
				return nil, errors.New("No sourceRoot found; UI not available.")
			}
			log.Printf("Using the default \"%v\" as the sourceRoot for AppEngine", uistatic.GaeSourceRoot)
			ui.sourceRoot = uistatic.GaeSourceRoot
		}
	}
	if ui.sourceRoot != "" {
		ui.uiDir = filepath.Join(ui.sourceRoot, filepath.FromSlash("server/camlistored/ui"))
		// Ignore any fileembed files:
		Files = &fileembed.Files{
			DirFallback: filepath.Join(ui.sourceRoot, filepath.FromSlash("pkg/server")),
		}
		uistatic.Files = &fileembed.Files{
			DirFallback: ui.uiDir,
			Listable:    true,
			// In dev_appserver, allow edit-and-reload without
			// restarting. In production, though, it's faster to just
			// slurp it in.
			SlurpToMemory: uistatic.IsProdAppEngine,
		}
	}

	ui.closureHandler, err = ui.makeClosureHandler(ui.sourceRoot)
	if err != nil {
		return nil, fmt.Errorf(`Invalid "sourceRoot" value of %q: %v"`, ui.sourceRoot, err)
	}

	if ui.sourceRoot != "" {
		ui.fileReactHandler, err = makeFileServer(ui.sourceRoot, filepath.Join("third_party", "react"), "react.js")
		if err != nil {
			return nil, fmt.Errorf("Could not make react handler: %s", err)
		}
		ui.fileGlitchHandler, err = makeFileServer(ui.sourceRoot, filepath.Join("third_party", "glitch"), "npc_piggy__x1_walk_png_1354829432.png")
		if err != nil {
			return nil, fmt.Errorf("Could not make glitch handler: %s", err)
		}
		ui.fileFontawesomeHandler, err = makeFileServer(ui.sourceRoot, filepath.Join("third_party", "fontawesome"), "css/font-awesome.css")
		if err != nil {
			return nil, fmt.Errorf("Could not make fontawesome handler: %s", err)
		}
		ui.fileLessHandler, err = makeFileServer(ui.sourceRoot, filepath.Join("third_party", "less"), "less.js")
		if err != nil {
			return nil, fmt.Errorf("Could not make less handler: %s", err)
		}
	}

	rootPrefix, _, err := ld.FindHandlerByType("root")
	if err != nil {
		return nil, errors.New("No root handler configured, which is necessary for the ui handler")
	}
	if h, err := ld.GetHandler(rootPrefix); err == nil {
		ui.root = h.(*RootHandler)
		ui.root.registerUIHandler(ui)
	} else {
		return nil, errors.New("failed to find the 'root' handler")
	}

	return ui, nil
}

type publishRoot struct {
	Name      string
	Permanode blob.Ref
	Prefix    string
}

// InitHandler goes through all the other configured handlers to discover
// the publisher ones, and uses them to populate ui.publishRoots.
func (ui *UIHandler) InitHandler(hl blobserver.FindHandlerByTyper) error {
	// InitHandler is called after all handlers have been setup, so the bootstrap
	// of the camliRoot node for publishers in dev-mode is already done.
	searchPrefix, _, err := hl.FindHandlerByType("search")
	if err != nil {
		return errors.New("No search handler configured, which is necessary for the ui handler")
	}
	var sh *search.Handler
	htype, hi := hl.AllHandlers()
	if h, ok := hi[searchPrefix]; !ok {
		return errors.New("failed to find the \"search\" handler")
	} else {
		sh = h.(*search.Handler)
		ui.search = sh
	}
	camliRootQuery := func(camliRoot string) (*search.SearchResult, error) {
		return sh.Query(&search.SearchQuery{
			Limit: 1,
			Constraint: &search.Constraint{
				Permanode: &search.PermanodeConstraint{
					Attr:  "camliRoot",
					Value: camliRoot,
				},
			},
		})
	}
	for prefix, typ := range htype {
		if typ != "app" {
			continue
		}
		ah, ok := hi[prefix].(*app.Handler)
		if !ok {
			panic(fmt.Sprintf("UI: handler for %v has type \"app\" but is not app.Handler", prefix))
		}
		if ah.ProgramName() != "publisher" {
			continue
		}
		appConfig := ah.AppConfig()
		if appConfig == nil {
			log.Printf("UI: app handler for %v has no appConfig", prefix)
			continue
		}
		camliRoot, ok := appConfig["camliRoot"].(string)
		if !ok {
			log.Printf("UI: camliRoot in appConfig is %T, want string", appConfig["camliRoot"])
			continue
		}
		result, err := camliRootQuery(camliRoot)
		if err != nil {
			log.Printf("UI: could not find permanode for camliRoot %v: %v", camliRoot, err)
			continue
		}
		if len(result.Blobs) == 0 || !result.Blobs[0].Blob.Valid() {
			log.Printf("UI: no valid permanode for camliRoot %v", camliRoot)
			continue
		}
		if ui.publishRoots == nil {
			ui.publishRoots = make(map[string]*publishRoot)
		}
		ui.publishRoots[prefix] = &publishRoot{
			Name:      camliRoot,
			Prefix:    prefix,
			Permanode: result.Blobs[0].Blob,
		}
	}
	return nil
}

func (ui *UIHandler) makeClosureHandler(root string) (http.Handler, error) {
	return makeClosureHandler(root, "ui")
}

// makeClosureHandler returns a handler to serve Closure files.
// root is either:
// 1) empty: use the Closure files compiled in to the binary (if
//    available), else redirect to the Internet.
// 2) a URL prefix: base of Camlistore to get Closure to redirect to
// 3) a path on disk to the root of camlistore's source (which
//    contains the necessary subset of Closure files)
func makeClosureHandler(root, handlerName string) (http.Handler, error) {
	// devcam server environment variable takes precedence:
	if d := os.Getenv("CAMLI_DEV_CLOSURE_DIR"); d != "" {
		log.Printf("%v: serving Closure from devcam server's $CAMLI_DEV_CLOSURE_DIR: %v", handlerName, d)
		return http.FileServer(http.Dir(d)), nil
	}
	if root == "" {
		fs, err := closurestatic.FileSystem()
		if err == os.ErrNotExist {
			log.Printf("%v: no configured setting or embedded resources; serving Closure via %v", handlerName, closureBaseURL)
			return closureBaseURL, nil
		}
		if err != nil {
			return nil, fmt.Errorf("error loading embedded Closure zip file: %v", err)
		}
		log.Printf("%v: serving Closure from embedded resources", handlerName)
		return http.FileServer(fs), nil
	}
	if strings.HasPrefix(root, "http") {
		log.Printf("%v: serving Closure using redirects to %v", handlerName, root)
		return closureRedirector(root), nil
	}

	path := filepath.Join("third_party", "closure", "lib", "closure")
	return makeFileServer(root, path, filepath.Join("goog", "base.js"))
}

func makeFileServer(sourceRoot string, pathToServe string, expectedContentPath string) (http.Handler, error) {
	fi, err := os.Stat(sourceRoot)
	if err != nil {
		return nil, err
	}
	if !fi.IsDir() {
		return nil, errors.New("not a directory")
	}
	dirToServe := filepath.Join(sourceRoot, pathToServe)
	_, err = os.Stat(filepath.Join(dirToServe, expectedContentPath))
	if err != nil {
		return nil, fmt.Errorf("directory doesn't contain %s; wrong directory?", expectedContentPath)
	}
	return http.FileServer(http.Dir(dirToServe)), nil
}

const closureBaseURL closureRedirector = "https://closure-library.googlecode.com/git"

// closureRedirector is a hack to redirect requests for Closure's million *.js files
// to https://closure-library.googlecode.com/git.
// TODO: this doesn't work when offline. We need to run genjsdeps over all of the Camlistore
// UI to figure out which Closure *.js files to fileembed and generate zembed. Then this
// type can be deleted.
type closureRedirector string

func (base closureRedirector) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
	newURL := string(base) + "/" + path.Clean(httputil.PathSuffix(req))
	http.Redirect(rw, req, newURL, http.StatusTemporaryRedirect)
}

func camliMode(req *http.Request) string {
	return req.URL.Query().Get("camli.mode")
}

func wantsBlobRef(req *http.Request) bool {
	_, ok := blob.ParseKnown(httputil.PathSuffix(req))
	return ok
}

func wantsDiscovery(req *http.Request) bool {
	return httputil.IsGet(req) &&
		(req.Header.Get("Accept") == "text/x-camli-configuration" ||
			camliMode(req) == "config")
}

func wantsUploadHelper(req *http.Request) bool {
	return req.Method == "POST" && camliMode(req) == "uploadhelper"
}

func wantsPermanode(req *http.Request) bool {
	return httputil.IsGet(req) && blob.ValidRefString(req.FormValue("p"))
}

func wantsBlobInfo(req *http.Request) bool {
	return httputil.IsGet(req) && blob.ValidRefString(req.FormValue("b"))
}

func wantsFileTreePage(req *http.Request) bool {
	return httputil.IsGet(req) && blob.ValidRefString(req.FormValue("d"))
}

func getSuffixMatches(req *http.Request, pattern *regexp.Regexp) bool {
	if httputil.IsGet(req) {
		suffix := httputil.PathSuffix(req)
		return pattern.MatchString(suffix)
	}
	return false
}

func (ui *UIHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
	suffix := httputil.PathSuffix(req)

	rw.Header().Set("Vary", "Accept")
	switch {
	case wantsDiscovery(req):
		ui.root.serveDiscovery(rw, req)
	case wantsUploadHelper(req):
		ui.serveUploadHelper(rw, req)
	case strings.HasPrefix(suffix, "download/"):
		ui.serveDownload(rw, req)
	case strings.HasPrefix(suffix, "thumbnail/"):
		ui.serveThumbnail(rw, req)
	case strings.HasPrefix(suffix, "tree/"):
		ui.serveFileTree(rw, req)
	case strings.HasPrefix(suffix, "qr/"):
		ui.serveQR(rw, req)
	case getSuffixMatches(req, closurePattern):
		ui.serveClosure(rw, req)
	case getSuffixMatches(req, lessPattern):
		ui.serveFromDiskOrStatic(rw, req, lessPattern, ui.fileLessHandler, lessstatic.Files)
	case getSuffixMatches(req, reactPattern):
		ui.serveFromDiskOrStatic(rw, req, reactPattern, ui.fileReactHandler, reactstatic.Files)
	case getSuffixMatches(req, glitchPattern):
		ui.serveFromDiskOrStatic(rw, req, glitchPattern, ui.fileGlitchHandler, glitchstatic.Files)
	case getSuffixMatches(req, fontawesomePattern):
		ui.serveFromDiskOrStatic(rw, req, fontawesomePattern, ui.fileFontawesomeHandler, fontawesomestatic.Files)
	default:
		file := ""
		if m := staticFilePattern.FindStringSubmatch(suffix); m != nil {
			file = m[1]
		} else {
			switch {
			case wantsBlobRef(req):
				file = "index.html"
			case wantsPermanode(req):
				file = "permanode.html"
			case wantsBlobInfo(req):
				file = "blobinfo.html"
			case wantsFileTreePage(req):
				file = "filetree.html"
			case req.URL.Path == httputil.PathBase(req):
				file = "index.html"
			default:
				http.Error(rw, "Illegal URL.", http.StatusNotFound)
				return
			}
		}
		if file == "deps.js" {
			serveDepsJS(rw, req, ui.uiDir)
			return
		}
		ServeStaticFile(rw, req, uistatic.Files, file)
	}
}

// ServeStaticFile serves file from the root virtual filesystem.
func ServeStaticFile(rw http.ResponseWriter, req *http.Request, root http.FileSystem, file string) {
	f, err := root.Open("/" + file)
	if err != nil {
		http.NotFound(rw, req)
		log.Printf("Failed to open file %q from embedded resources: %v", file, err)
		return
	}
	defer f.Close()
	var modTime time.Time
	if fi, err := f.Stat(); err == nil {
		modTime = fi.ModTime()
	}
	// TODO(wathiede): should pkg/magic be leveraged here somehow?  It has a
	// slightly different purpose.
	if strings.HasSuffix(file, ".svg") {
		rw.Header().Set("Content-Type", "image/svg+xml")
	}
	http.ServeContent(rw, req, file, modTime, f)
}

func (ui *UIHandler) populateDiscoveryMap(m map[string]interface{}) {
	pubRoots := map[string]interface{}{}
	for _, v := range ui.publishRoots {
		m := map[string]interface{}{
			"name":             v.Name,
			"prefix":           []string{v.Prefix},
			"currentPermanode": v.Permanode.String(),
		}
		pubRoots[v.Name] = m
	}

	uiDisco := map[string]interface{}{
		"jsonSignRoot":    ui.JSONSignRoot,
		"uiRoot":          ui.prefix,
		"uploadHelper":    ui.prefix + "?camli.mode=uploadhelper", // hack; remove with better javascript
		"downloadHelper":  path.Join(ui.prefix, "download") + "/",
		"directoryHelper": path.Join(ui.prefix, "tree") + "/",
		"publishRoots":    pubRoots,
	}
	// TODO(mpl): decouple discovery of the sig handler from the
	// existence of a ui handler.
	if ui.sigh != nil {
		uiDisco["signing"] = ui.sigh.DiscoveryMap(ui.JSONSignRoot)
	}
	for k, v := range uiDisco {
		if _, ok := m[k]; ok {
			log.Fatalf("Duplicate discovery key %q", k)
		}
		m[k] = v
	}
}

func (ui *UIHandler) serveDownload(rw http.ResponseWriter, req *http.Request) {
	if ui.root.Storage == nil {
		http.Error(rw, "No BlobRoot configured", 500)
		return
	}

	suffix := httputil.PathSuffix(req)
	m := downloadPattern.FindStringSubmatch(suffix)
	if m == nil {
		httputil.ErrorRouting(rw, req)
		return
	}

	fbr, ok := blob.Parse(m[1])
	if !ok {
		http.Error(rw, "Invalid blobref", 400)
		return
	}

	dh := &DownloadHandler{
		Fetcher: ui.root.Storage,
		Search:  ui.search,
		Cache:   ui.Cache,
	}
	dh.ServeHTTP(rw, req, fbr)
}

func (ui *UIHandler) serveThumbnail(rw http.ResponseWriter, req *http.Request) {
	if ui.root.Storage == nil {
		http.Error(rw, "No BlobRoot configured", 500)
		return
	}

	suffix := httputil.PathSuffix(req)
	m := thumbnailPattern.FindStringSubmatch(suffix)
	if m == nil {
		httputil.ErrorRouting(rw, req)
		return
	}

	query := req.URL.Query()
	width, _ := strconv.Atoi(query.Get("mw"))
	height, _ := strconv.Atoi(query.Get("mh"))
	blobref, ok := blob.Parse(m[1])
	if !ok {
		http.Error(rw, "Invalid blobref", 400)
		return
	}

	if width == 0 {
		width = search.MaxImageSize
	}
	if height == 0 {
		height = search.MaxImageSize
	}

	th := &ImageHandler{
		Fetcher:   ui.root.Storage,
		Cache:     ui.Cache,
		MaxWidth:  width,
		MaxHeight: height,
		ThumbMeta: ui.thumbMeta,
		ResizeSem: ui.resizeSem,
		Search:    ui.search,
	}
	th.ServeHTTP(rw, req, blobref)
}

func (ui *UIHandler) serveFileTree(rw http.ResponseWriter, req *http.Request) {
	if ui.root.Storage == nil {
		http.Error(rw, "No BlobRoot configured", 500)
		return
	}

	suffix := httputil.PathSuffix(req)
	m := treePattern.FindStringSubmatch(suffix)
	if m == nil {
		httputil.ErrorRouting(rw, req)
		return
	}

	blobref, ok := blob.Parse(m[1])
	if !ok {
		http.Error(rw, "Invalid blobref", 400)
		return
	}

	fth := &FileTreeHandler{
		Fetcher: ui.root.Storage,
		file:    blobref,
	}
	fth.ServeHTTP(rw, req)
}

func (ui *UIHandler) serveClosure(rw http.ResponseWriter, req *http.Request) {
	suffix := httputil.PathSuffix(req)
	if ui.closureHandler == nil {
		log.Printf("%v not served: closure handler is nil", suffix)
		http.NotFound(rw, req)
		return
	}
	m := closurePattern.FindStringSubmatch(suffix)
	if m == nil {
		httputil.ErrorRouting(rw, req)
		return
	}
	req.URL.Path = "/" + m[1]
	ui.closureHandler.ServeHTTP(rw, req)
}

// serveFromDiskOrStatic matches rx against req's path and serves the match either from disk (if non-nil) or from static (embedded in the binary).
func (ui *UIHandler) serveFromDiskOrStatic(rw http.ResponseWriter, req *http.Request, rx *regexp.Regexp, disk http.Handler, static *fileembed.Files) {
	suffix := httputil.PathSuffix(req)
	m := rx.FindStringSubmatch(suffix)
	if m == nil {
		panic("Caller should verify that rx matches")
	}
	file := m[1]
	if disk != nil {
		req.URL.Path = "/" + file
		disk.ServeHTTP(rw, req)
	} else {
		ServeStaticFile(rw, req, static, file)
	}

}

func (ui *UIHandler) serveQR(rw http.ResponseWriter, req *http.Request) {
	url := req.URL.Query().Get("url")
	if url == "" {
		http.Error(rw, "Missing url parameter.", http.StatusBadRequest)
		return
	}
	code, err := qr.Encode(url, qr.L)
	if err != nil {
		http.Error(rw, err.Error(), http.StatusInternalServerError)
		return
	}
	rw.Header().Set("Content-Type", "image/png")
	rw.Write(code.PNG())
}

// serveDepsJS serves an auto-generated Closure deps.js file.
func serveDepsJS(rw http.ResponseWriter, req *http.Request, dir string) {
	var root http.FileSystem
	if dir == "" {
		root = uistatic.Files
	} else {
		root = http.Dir(dir)
	}

	b, err := closure.GenDeps(root)
	if err != nil {
		log.Print(err)
		http.Error(rw, "Server error", 500)
		return
	}
	rw.Header().Set("Content-Type", "text/javascript; charset=utf-8")
	rw.Write([]byte("// auto-generated from camlistored\n"))
	rw.Write(b)
}