Update README

README.md

@@ -1,8 +1,25 @@
 # webfs
 
-It's a WebDAV server.
-
-That's all it does. It serves WebDAV.
+It's a WebDAV server that generates and caches media thumbnails.
 
 I front-end it with Caddy,
 which handles authentication and access controls.
+Because the thumbnails live at the same path as the original media,
+so I don't need any special gubbins to protect thumbnails the same way.
+
+
+## Thumbnails
+
+If you put `?thumbnail` at the end of the URL,
+it will use `ffmpeg` to generate a WebP thumbnail that fits in a 320x200 box.
+
+I use WebP because it provides alpha channels, animations,
+and good compression. 
+If your browser doesn't have WebP support,
+that's a real pity,
+and this isn't a good software solution for you.
+
+Thumbnails are cached.
+No attempt is made to verify whether thumbnails are up-to-date,
+or to clean up the thumbnail directory.
+Something else is going to have to manage that.

cmd/webfs/main.go

@@ -20,6 +20,7 @@ type Handler struct {
 	webdav.Handler
 	dataRoot      string
 	thumbnailRoot string
+	filterVideo   string
 }
 
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -28,7 +29,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		if strings.HasSuffix(r.URL.Path, "/") {
 			r.URL.Path += "index.html"
 		}
-		if r.FormValue("thumbnail") != "" {
+		r.ParseForm()
+		if _, ok := r.Form["thumbnail"]; (h.thumbnailRoot != "") && ok {
 			h.ServeThumbnail(w, r)
 			return
 		}
@@ -51,22 +53,17 @@ func cleanPath(p string) string {
 	return path.Clean(p)
 }
 
-func (h *Handler) ServeThumbnail(w http.ResponseWriter, req *http.Request) {
-	reqPath := cleanPath(req.URL.Path)
-	reqPath = strings.TrimLeft(reqPath, "/")
-	thumbnailPath := path.Join(h.thumbnailRoot, reqPath) + ".webp"
-
-	// If there's not already a thumbnail, make one
-	if _, err := os.Stat(thumbnailPath); err != nil {
+func (h *Handler) makeThumbnail(reqPath, thumbnailPath string) error {
 	srcPath := path.Join(h.dataRoot, reqPath)
 
+	// Run ffprobe to figure out what kind of file this is
 	ffdata, err := ffprobe.ProbeURL(context.Background(), srcPath, "-hide_banner")
 	if err != nil {
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
+		return err
 	}
 	isVideo := ffdata.Format.DurationSeconds > 0.0
 
+	// Build up ffmpeg invocation
 	// XXX: some day soon you will want CommandContext
 	cmd := exec.Command("ffmpeg", "-hide_banner", "-loglevel", "error")
 	cmd.Stdout = os.Stdout
@@ -78,23 +75,39 @@ func (h *Handler) ServeThumbnail(w http.ResponseWriter, req *http.Request) {
 			"-ss", fmt.Sprintf("%f", skipSeconds),
 			"-i", srcPath,
 			"-frames:v", "5",
-				"-filter:v", "scale='min(320,iw)':'min(200,ih)':force_original_aspect_ratio=decrease,fps=2",
+			"-filter:v", h.filterVideo+",fps=2",
 			"-loop", "0",
 			thumbnailPath,
 		)
 	} else {
 		cmd.Args = append(cmd.Args,
 			"-i", srcPath,
-				"-filter:v", "scale='min(320,iw)':'min(200,ih)':force_original_aspect_ratio=decrease",
+			"-filter:v", h.filterVideo,
 			thumbnailPath,
 		)
 	}
 
+	// Make sure the thumbnail has a directory to live in
 	if err := os.MkdirAll(path.Dir(thumbnailPath), 0755); err != nil {
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
+		return err
 	}
+
+	// Convert!
 	if err := cmd.Run(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (h *Handler) ServeThumbnail(w http.ResponseWriter, req *http.Request) {
+	reqPath := cleanPath(req.URL.Path)
+	reqPath = strings.TrimLeft(reqPath, "/")
+	thumbnailPath := path.Join(h.thumbnailRoot, reqPath) + ".webp"
+
+	// If there's not already a thumbnail, make one
+	if _, err := os.Stat(thumbnailPath); err != nil {
+		if err := h.makeThumbnail(reqPath, thumbnailPath); err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
@@ -107,8 +120,18 @@ func main() {
 	address := flag.String("listen", ":8080", "Address to listen to")
 	dataRoot := flag.String("root", ".", "Directory to serve")
 	thumbnailRoot := flag.String("thumbnails", "/thumbnails", "Where to store thumbnails")
+	filterVideo := flag.String(
+		"filter:v",
+		"scale='min(320,iw)':'min(200,ih)':force_original_aspect_ratio=decrease",
+		"ffmpeg video filter",
+	)
 	flag.Parse()
 
+	if _, err := os.Stat(*thumbnailRoot); err != nil {
+		log.Println("Disabling thumbnail generation:", err)
+		*thumbnailRoot = ""
+	}
+
 	handler := &Handler{
 		Handler: webdav.Handler{
 			FileSystem: webdav.Dir(*dataRoot),
@@ -116,8 +139,9 @@ func main() {
 		},
 		dataRoot:      *dataRoot,
 		thumbnailRoot: *thumbnailRoot,
+		filterVideo:   *filterVideo,
 	}
 
 	log.Println("Listening on", *address)
-	http.ListenAndServe(*address, handler)
+	log.Fatal(http.ListenAndServe(*address, handler))
 }