fup: add file serving

This adds both redirect-to-signed-URL and proxy fileserving.

The proxy fileserving is somewhat limited: we don't support the Range header,
and it isn't easy to reuse the net/http ServeContent implementation because
that requires a SeekCloser. I think it might be possible to "bodge" a
SeekCloser on top of dynamically opening files, but it'll be a bit wonky and
will be slower than strictly necessary.

web/fup/cmd/serve.go

@@ -7,8 +7,10 @@ package cmd
 import (
 	"context"
 	"fmt"
+	"log"
 	"net/http"
 
+	"github.com/google/safehtml"
 	"github.com/spf13/cobra"
 	"hg.lukegb.com/lukegb/depot/web/fup/fuphttp"
 	"hg.lukegb.com/lukegb/depot/web/fup/fupstatic"
@@ -18,10 +20,12 @@ func init() {
 	rootCmd.AddCommand(serveCmd)
 
 	serveCmd.Flags().StringVarP(&serveBind, "listen", "l", ":8191", "Bind address for HTTP server.")
+	serveCmd.Flags().BoolVar(&serveDirectOnly, "direct-only", false, "If set, all file serving will be proxied, even if the backend supports signed URLs.")
 }
 
 var (
 	serveBind       string
+	serveDirectOnly bool
 
 	serveCmd = &cobra.Command{
 		Use:   "serve",
@@ -31,7 +35,9 @@ var (
 			cfg := &fuphttp.Config{
 				Templates:           fupstatic.Templates,
 				Static:              fupstatic.Static,
-				StaticRoot: "/static/",
+				StaticRoot:          safehtml.TrustedResourceURLFromConstant("/static/"),
+				StorageURL:          bucketURL,
+				RedirectToBlobstore: !serveDirectOnly,
 			}
 			a, err := fuphttp.New(ctx, cfg)
 			if err != nil {
@@ -39,6 +45,7 @@ var (
 			}
 			http.Handle("/", a.Handler())
 			http.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.FS(fupstatic.Static))))
+			log.Printf("Serving on %s", serveBind)
 			return http.ListenAndServe(serveBind, nil)
 		},
 	}

web/fup/fuphttp/fuphttp.go

@@ -7,39 +7,169 @@ package fuphttp
 import (
 	"context"
 	"fmt"
+	"io"
 	"io/fs"
+	"log"
 	"net/http"
+	"time"
 
 	"github.com/google/safehtml"
 	"github.com/google/safehtml/template"
 	"github.com/google/safehtml/template/uncheckedconversions"
 	shuncheckedconversions "github.com/google/safehtml/uncheckedconversions"
 	"github.com/gorilla/mux"
+	"gocloud.dev/blob"
+	"gocloud.dev/gcerrors"
 	"hg.lukegb.com/lukegb/depot/web/fup/hashfs"
 )
 
+const (
+	defaultRedirectExpiry = 5 * time.Minute
+)
+
 type Config struct {
 	Templates  fs.FS
 	Static     fs.FS
 	StaticRoot safehtml.TrustedResourceURL
+
+	// If set, redirects to a signed URL if possible instead of serving directly.
+	RedirectToBlobstore bool
+	RedirectExpiry      time.Duration // Defaults to 5 minutes.
+
+	// Set one of these, but not both.
+	StorageURL     string
+	StorageBackend *blob.Bucket
 }
 
 type Application struct {
 	indexTmpl      *template.Template
 	notFoundTmpl   *template.Template
+	storageBackend *blob.Bucket
+
+	redirectToBlobstore bool
+	redirectExpiry      time.Duration
 }
 
 func (a *Application) Handler() http.Handler {
 	r := mux.NewRouter()
 
-	r.NotFoundHandler = http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
-		rw.WriteHeader(http.StatusNotFound)
-		a.notFoundTmpl.Execute(rw, nil)
-	})
+	renderTemplate := func(t *template.Template) http.HandlerFunc {
+		return func(rw http.ResponseWriter, r *http.Request) {
+			if err := t.Execute(rw, nil); err != nil {
+				log.Printf("rendering template: %v", err)
+			}
+		}
+	}
+
+	r.NotFoundHandler = http.HandlerFunc(a.notFound)
+	r.HandleFunc("/", renderTemplate(a.indexTmpl))
+	r.HandleFunc("/raw/{filename}", a.rawDownload)
 
 	return r
 }
 
+func (a *Application) notFound(rw http.ResponseWriter, r *http.Request) {
+	rw.WriteHeader(http.StatusNotFound)
+	if err := a.notFoundTmpl.Execute(rw, nil); err != nil {
+		log.Printf("rendering 404 template: %v", err)
+	}
+}
+
+func (a *Application) internalError(rw http.ResponseWriter, r *http.Request) {
+	rw.Header().Set("Content-type", "text/plain")
+	rw.WriteHeader(http.StatusInternalServerError)
+	fmt.Fprintf(rw, "hammed server :(\n")
+}
+
+func (a *Application) rawDownload(rw http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	vars := mux.Vars(r)
+	filename := vars["filename"]
+
+	attrs, err := a.storageBackend.Attributes(ctx, filename)
+	switch gcerrors.Code(err) {
+	case gcerrors.NotFound:
+		a.notFound(rw, r)
+		return
+	default:
+		log.Printf("rawDownload(%q) Attributes: %v", filename, err)
+		a.internalError(rw, r)
+		return
+	case gcerrors.OK:
+		// OK
+	}
+	_ = attrs
+
+	// Do things with attributes?
+	if a.redirectToBlobstore {
+		u, err := a.storageBackend.SignedURL(ctx, filename, &blob.SignedURLOptions{
+			Expiry: a.redirectExpiry,
+		})
+		switch gcerrors.Code(err) {
+		case gcerrors.NotFound:
+			// This is unlikely to get returned.
+			a.notFound(rw, r)
+			return
+		case gcerrors.OK:
+			http.Redirect(rw, r, u, http.StatusFound)
+			return
+		case gcerrors.Unimplemented:
+			// Fall back to serving directly.
+		default:
+			log.Printf("rawDownload(%q) SignedURL (continuing with fallback): %v", filename, err)
+		}
+	}
+
+	// Perform direct serving.
+	a.rawDownloadDirect(ctx, rw, r, filename, attrs)
+}
+
+func (a *Application) rawDownloadDirect(ctx context.Context, rw http.ResponseWriter, r *http.Request, filename string, attrs *blob.Attributes) {
+	// TODO(lukegb): Range header and conditionals?.
+	rdr, err := a.storageBackend.NewReader(ctx, filename, nil)
+	switch gcerrors.Code(err) {
+	case gcerrors.NotFound:
+		a.notFound(rw, r)
+		return
+	default:
+		a.internalError(rw, r)
+		return
+	case gcerrors.OK:
+		// OK
+	}
+	defer rdr.Close()
+
+	if v := attrs.CacheControl; v != "" {
+		rw.Header().Set("Cache-Control", v)
+	}
+	if v := attrs.ContentDisposition; v != "" {
+		rw.Header().Set("Content-Disposition", v)
+	}
+	if v := attrs.ContentEncoding; v != "" {
+		rw.Header().Set("Content-Encoding", v)
+	}
+	if v := attrs.ContentLanguage; v != "" {
+		rw.Header().Set("Content-Language", v)
+	}
+	if v := attrs.ContentType; v != "" {
+		rw.Header().Set("Content-Type", v)
+	}
+	if v := attrs.ETag; v != "" {
+		rw.Header().Set("ETag", v)
+	}
+	if v := attrs.ModTime; !v.IsZero() {
+		rw.Header().Set("Last-Modified", v.UTC().Format(http.TimeFormat))
+	}
+
+	if v := attrs.Size; v != 0 {
+		rw.Header().Set("Content-Length", fmt.Sprintf("%d", v))
+	}
+
+	if _, err := io.Copy(rw, rdr); err != nil {
+		log.Printf("rawDownloadDirect(%q) copy: %v", filename, err)
+	}
+}
+
 func parseTemplate(t *template.Template, fsys fs.FS, name string) (*template.Template, error) {
 	bs, err := fs.ReadFile(fsys, name)
 	if err != nil {
@@ -64,7 +194,22 @@ func loadTemplate(fsys fs.FS, name string, funcs template.FuncMap) (*template.Te
 }
 
 func New(ctx context.Context, cfg *Config) (*Application, error) {
-	a := new(Application)
+	a := &Application{
+		redirectToBlobstore: cfg.RedirectToBlobstore,
+		redirectExpiry:      cfg.RedirectExpiry,
+	}
+	if a.redirectExpiry == 0 {
+		a.redirectExpiry = defaultRedirectExpiry
+	}
+
+	bkt := cfg.StorageBackend
+	if bkt == nil {
+		var err error
+		if bkt, err = blob.OpenBucket(ctx, cfg.StorageURL); err != nil {
+			return nil, fmt.Errorf("opening bucket %q: %v", cfg.StorageURL, err)
+		}
+	}
+	a.storageBackend = bkt
 
 	tmpls := []struct {
 		t    **template.Template