Resolve external embed previews and keep their real MIME types

media-scrape/src/engine.ts

@@ -13,6 +13,7 @@ import {
     videoPoster,
     type DownloadOptions
 } from "./download.js";
+import { resolveEmbedPreview } from "./embed-preview.js";
 import {
     createScrapeDirs,
     listScrapes,
@@ -358,18 +359,38 @@ export class ScrapeEngine {
                 return;
             }
 
-            const outcome = await downloadPreview(row, join(dir, "thumbs"), options);
+            // Some providers (fxtwitter, vxReddit, ...) ship no thumbnail in Discord's data;
+            // resolve one from the provider or the page before caching it.
+            let previewRow = row;
+            if (row.source === "embed" && !row.preview_url) {
+                const resolved = await resolveEmbedPreview(row, options);
+                if (!resolved) {
+                    store.markPreviewError(row.id, "no preview source");
+                    this.persist(dir, meta);
+                    await this.sleep(downloadGapMs(options));
+                    continue;
+                }
+                previewRow = { ...row, preview_url: resolved };
+            }
+
+            const outcome = await downloadPreview(previewRow, join(dir, "thumbs"), options);
 
             if (outcome.state === "downloaded" && outcome.hash) {
-                store.markPreview(row.id, { hash: outcome.hash, bytes: outcome.bytes ?? 0 });
+                const ext = outcome.ext ?? "webp";
+                store.markPreview(row.id, { hash: outcome.hash, bytes: outcome.bytes ?? 0, ext });
                 meta.previewed = (meta.previewed ?? 0) + 1;
 
                 // Embed thumbnails also land in the custom destination, so the download has a
                 // viewable poster for embeds while the media tab keeps its local copy.
                 if (options.destinationDir && row.source === "embed") {
-                    const target = join(options.destinationDir, meta.id, "thumbnails", `${outcome.hash}.webp`);
+                    const target = join(
+                        options.destinationDir,
+                        meta.id,
+                        "thumbnails",
+                        `${outcome.hash}.${ext}`
+                    );
                     mkdirSync(dirname(target), { recursive: true });
-                    copyFileSync(join(dir, "thumbs", `${outcome.hash}.webp`), target);
+                    copyFileSync(join(dir, "thumbs", `${outcome.hash}.${ext}`), target);
                 }
             } else {
                 store.markPreviewError(row.id, outcome.error ?? outcome.state);