fix: show recommended card thumbnails

src/utils/postResourceAdapter.test.ts

@@ -0,0 +1,93 @@
+import { describe, expect, it } from "vitest";
+import type { Post } from "../types/post";
+import { postToResource } from "./postResourceAdapter";
+
+const basePost: Post = {
+  id: "post-1",
+  postType: "link",
+  categoryId: 1,
+  categorySlug: "official-announcement",
+  language: "zh",
+  title: "Link post",
+  text: "https://example.com/article",
+  attachments: [],
+  isRecommended: true,
+  publishedAt: "2026-05-30T00:00:00Z",
+};
+
+describe("postToResource", () => {
+  it("uses link preview images as the resource cover when there is no attachment", () => {
+    const resource = postToResource(
+      {
+        ...basePost,
+        linkPreview: {
+          url: "https://example.com/article",
+          canonicalUrl: "https://example.com/article",
+          siteName: "Example",
+          title: "Example article",
+          description: "Example description",
+          imageUrl: "https://example.com/preview.jpg",
+        },
+      },
+      "zh-TW",
+    );
+
+    expect(resource.coverImage).toBe("https://example.com/preview.jpg");
+    expect(resource.previewUrl).toBe("https://example.com/preview.jpg");
+  });
+
+  it("uses document thumbnails before poster URLs", () => {
+    const resource = postToResource(
+      {
+        ...basePost,
+        postType: "pdf",
+        attachments: [
+          {
+            id: "att-1",
+            kind: "document",
+            url: "/uploads/file.pdf",
+            mime: "application/pdf",
+            filename: "file.pdf",
+            sizeBytes: 123,
+            posterUrl: "/uploads/file.pdf",
+            thumbnailUrl: "/uploads/thumb.jpg",
+          },
+        ],
+      },
+      "zh-TW",
+    );
+
+    expect(resource.coverImage).toBe("/uploads/thumb.jpg");
+    expect(resource.previewUrl).toBe("/uploads/thumb.jpg");
+  });
+
+  it("keeps an attachment thumbnail ahead of a link preview image", () => {
+    const resource = postToResource(
+      {
+        ...basePost,
+        attachments: [
+          {
+            id: "att-1",
+            kind: "image",
+            url: "/uploads/full.jpg",
+            mime: "image/jpeg",
+            filename: "full.jpg",
+            sizeBytes: 123,
+            thumbnailUrl: "/uploads/thumb.jpg",
+          },
+        ],
+        linkPreview: {
+          url: "https://example.com/article",
+          canonicalUrl: "https://example.com/article",
+          siteName: "Example",
+          title: "Example article",
+          description: "Example description",
+          imageUrl: "https://example.com/preview.jpg",
+        },
+      },
+      "zh-TW",
+    );
+
+    expect(resource.coverImage).toBe("/uploads/thumb.jpg");
+  });
+});