fix: YouTube preview falls back to OEmbed on poor scrape

When OG scrape returns empty title or no image (common with
youtu.be short URLs), fall through to the YouTube OEmbed
endpoint which reliably returns title, thumbnail, and embed
HTML. Also cache successful results from all special preview
handlers (YouTube, Reddit, Twitter, Flickr) which were
previously only written to the response without being stored.

Author: stahnma

internal/handler/preview.go

@@ -134,13 +134,13 @@ func (h *Handler) OGPreviewHandler(w http.ResponseWriter, r *http.Request) {
 	if strings.Contains(urlParam, "reddit.com") {
 		meta, err := h.GetRedditPreview(urlParam)
 		if err == nil && len(meta) > 0 {
-			json.NewEncoder(w).Encode(meta)
+			h.cacheAndRespond(w, r, urlParam, meta)
 			return
 		}
 	} else if strings.Contains(urlParam, "twitter.com") || strings.Contains(urlParam, "x.com") {
 		meta, err := h.GetTwitterPreview(urlParam)
 		if err == nil {
-			json.NewEncoder(w).Encode(meta)
+			h.cacheAndRespond(w, r, urlParam, meta)
 			return
 		}
 		// If OEmbed returned ANY error (404, 403, etc.), we trust it. Do not fall back to scrape.
@@ -159,14 +159,14 @@ func (h *Handler) OGPreviewHandler(w http.ResponseWriter, r *http.Request) {
 	} else if strings.Contains(urlParam, "flickr.com") {
 		meta, err := h.GetFlickrPreview(urlParam)
 		if err == nil {
-			json.NewEncoder(w).Encode(meta)
+			h.cacheAndRespond(w, r, urlParam, meta)
 			return
 		}
 		// If not a single photo, fall through to normal OEmbed
 	} else if strings.Contains(urlParam, "youtube.com") || strings.Contains(urlParam, "youtu.be") {
 		meta, err := h.GetYouTubePreview(urlParam)
 		if err == nil {
-			json.NewEncoder(w).Encode(meta)
+			h.cacheAndRespond(w, r, urlParam, meta)
 			return
 		}
 		// If we detected a soft 404, stop here and return 404 so UI can render "missing" badge

internal/handler/preview_youtube.go

@@ -34,6 +34,12 @@ func (h *Handler) GetYouTubePreview(targetURL string) (map[string]string, error)
 	title = strings.TrimSuffix(title, " - YouTube")
 	meta["title"] = title
 
+	// If scrape yielded no real title or image, fall through to OEmbed
+	// which is more reliable for YouTube
+	if title == "" || meta["image"] == "" {
+		return nil, fmt.Errorf("incomplete scrape, falling back to oembed")
+	}
+
 	meta["type"] = "video"
 
 	return meta, nil