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
 		}
@@ -51,6 +53,53 @@ func cleanPath(p string) string {
 	return path.Clean(p)
 }
 
+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 {
+		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
+	cmd.Stderr = os.Stderr
+
+	if isVideo {
+		skipSeconds := ffdata.Format.StartTimeSeconds + (ffdata.Format.DurationSeconds * 0.25)
+		cmd.Args = append(cmd.Args,
+			"-ss", fmt.Sprintf("%f", skipSeconds),
+			"-i", srcPath,
+			"-frames:v", "5",
+			"-filter:v", h.filterVideo+",fps=2",
+			"-loop", "0",
+			thumbnailPath,
+		)
+	} else {
+		cmd.Args = append(cmd.Args,
+			"-i", srcPath,
+			"-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 {
+		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, "/")
@@ -58,43 +107,7 @@ func (h *Handler) ServeThumbnail(w http.ResponseWriter, req *http.Request) {
 
 	// If there's not already a thumbnail, make one
 	if _, err := os.Stat(thumbnailPath); err != nil {
-		srcPath := path.Join(h.dataRoot, reqPath)
-
-		ffdata, err := ffprobe.ProbeURL(context.Background(), srcPath, "-hide_banner")
-		if err != nil {
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
-		}
-		isVideo := ffdata.Format.DurationSeconds > 0.0
-
-		// XXX: some day soon you will want CommandContext
-		cmd := exec.Command("ffmpeg", "-hide_banner", "-loglevel", "error")
-		cmd.Stdout = os.Stdout
-		cmd.Stderr = os.Stderr
-
-		if isVideo {
-			skipSeconds := ffdata.Format.StartTimeSeconds + (ffdata.Format.DurationSeconds * 0.25)
-			cmd.Args = append(cmd.Args,
-				"-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",
-				"-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",
-				thumbnailPath,
-			)
-		}
-
-		if err := os.MkdirAll(path.Dir(thumbnailPath), 0755); err != nil {
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
-		}
-		if err := cmd.Run(); 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))
 }