feat: fallback to unsplash cover when article contains no image

lib/unsplash.ts

@@ -0,0 +1,29 @@
+import { UNSPLASH_API_KEY } from "./env.ts";
+
+const API_URL = "https://api.unsplash.com";
+
+export async function getImageBySearchTerm(
+  searchTerm: string,
+): Promise<string | undefined> {
+  if (!UNSPLASH_API_KEY) {
+    throw new Error("UNSPLASH_API_KEY is not set");
+  }
+
+  const url = new URL("/search/photos", API_URL);
+  url.searchParams.append("query", searchTerm);
+  url.searchParams.append("per_page", "1");
+  url.searchParams.append("orientation", "landscape");
+
+  const response = await fetch(url.toString(), {
+    headers: {
+      Authorization: `Client-ID ${UNSPLASH_API_KEY}`,
+    },
+  });
+
+  if (!response.ok) {
+    throw new Error(`Unsplash API request failed: ${response.statusText}`);
+  }
+
+  const data = await response.json();
+  return data.results[0]?.urls?.regular;
+}