fix: derive poster key from plan

apps/worker/src/__tests__/variants-sizes.test.ts

@@ -1,5 +1,5 @@
 import { test, expect } from "bun:test";
-import { computeImageVariantPlan } from "../variants";
+import { computeImageVariantPlan, pickSmallestVariantSize } from "../variants";
 
 test("computeImageVariantPlan includes 256 and 768 thumbs", () => {
   expect(computeImageVariantPlan()).toEqual([
@@ -7,3 +7,11 @@ test("computeImageVariantPlan includes 256 and 768 thumbs", () => {
     { kind: "thumb", size: 768 },
   ]);
 });
+
+test("pickSmallestVariantSize returns smallest poster size", () => {
+  const size = pickSmallestVariantSize([
+    { kind: "poster", size: 768 },
+    { kind: "poster", size: 256 },
+  ]);
+  expect(size).toBe(256);
+});

apps/worker/src/jobs.ts

@@ -7,7 +7,11 @@ import { Readable } from "stream";
 
 import sharp from "sharp";
 
-import { computeImageVariantPlan, computeVideoPosterPlan } from "./variants";
+import {
+  computeImageVariantPlan,
+  computeVideoPosterPlan,
+  pickSmallestVariantSize,
+} from "./variants";
 
 import {
   CopyObjectCommand,
@@ -499,6 +503,7 @@ export async function handleProcessAsset(raw: unknown) {
         rawTags = { ...rawTags, ffprobe: ffprobeData };
 
         const posterPlan = computeVideoPosterPlan();
+        const posterSmallest = pickSmallestVariantSize(posterPlan);
         const posterKeys: Record<number, string> = {};
         for (const item of posterPlan) {
           const size = item.size;
@@ -533,7 +538,7 @@ export async function handleProcessAsset(raw: unknown) {
           });
           posterKeys[size] = posterKey;
         }
-        updates.poster_key = posterKeys[256] ?? null;
+        updates.poster_key = posterSmallest ? posterKeys[posterSmallest] ?? null : null;
       }
 
       if (asset.media_type === "video" && typeof updates.poster_key !== "string") {

apps/worker/src/variants.ts

@@ -3,6 +3,11 @@ export type VariantPlanItem = {
   size: number;
 };
 
+export function pickSmallestVariantSize(plan: VariantPlanItem[]): number | null {
+  if (plan.length === 0) return null;
+  return plan.reduce((min, item) => (item.size < min ? item.size : min), plan[0].size);
+}
+
 export function computeImageVariantPlan(): VariantPlanItem[] {
   return [
     { kind: "thumb", size: 256 },