Cache preview frames for Discord video attachments

media-scrape/test/run.ts

@@ -522,6 +522,10 @@ void (async () => {
             "https://media.discordapp.net/attachments/1/2/pic.png?width=320&height=320&format=webp"
         );
         assert.equal(previewUrlFor({ url: "https://www.youtube.com/watch?v=x", kind: "video" }), null);
+        assert.equal(
+            previewUrlFor({ url: "https://cdn.discordapp.com/attachments/1/2/clip.mp4?ex=abc", kind: "video" }),
+            "https://media.discordapp.net/attachments/1/2/clip.mp4?ex=abc&width=320&height=320&format=webp"
+        );
         assert.equal(
             previewUrlFor({
                 url: "https://www.youtube.com/watch?v=x",
@@ -599,7 +603,10 @@ void (async () => {
             {
                 messages: [
                     message("600", {
-                        attachments: [attachment({ filename: "prev.png", contentType: "image/png" })],
+                        attachments: [
+                            attachment({ filename: "prev.png", contentType: "image/png" }),
+                            attachment({ filename: "clip.mp4", contentType: "video/mp4" })
+                        ],
                         embeds: [
                             {
                                 type: "video",
@@ -643,9 +650,10 @@ void (async () => {
 
         const meta = engine.get(started.id);
         assert.equal(meta?.state, "done");
-        assert.equal(meta?.previewed, 2);
+        assert.equal(meta?.previewed, 3);
         assert.equal(fetched.some(url => url.includes("ytimg.com")), true);
         assert.equal(fetched.some(url => url.includes("youtube.com/watch")), false);
+        assert.equal(fetched.some(url => url.includes("clip.mp4") && url.includes("format=webp")), true);
 
         const store = new ScrapeStore(join(root, started.id));
         const row = store.queryMedia({ kind: "image" })[0];