feat: add inbound media understanding

Co-authored-by: Tristan Manchester <tmanchester96@gmail.com>

src/media/fetch.test.ts

@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vitest";
+
+import { fetchRemoteMedia } from "./fetch.js";
+
+function makeStream(chunks: Uint8Array[]) {
+  return new ReadableStream<Uint8Array>({
+    start(controller) {
+      for (const chunk of chunks) {
+        controller.enqueue(chunk);
+      }
+      controller.close();
+    },
+  });
+}
+
+describe("fetchRemoteMedia", () => {
+  it("rejects when content-length exceeds maxBytes", async () => {
+    const fetchImpl = async () =>
+      new Response(makeStream([new Uint8Array([1, 2, 3, 4, 5])]), {
+        status: 200,
+        headers: { "content-length": "5" },
+      });
+
+    await expect(
+      fetchRemoteMedia({
+        url: "https://example.com/file.bin",
+        fetchImpl,
+        maxBytes: 4,
+      }),
+    ).rejects.toThrow("exceeds maxBytes");
+  });
+
+  it("rejects when streamed payload exceeds maxBytes", async () => {
+    const fetchImpl = async () =>
+      new Response(makeStream([new Uint8Array([1, 2, 3]), new Uint8Array([4, 5, 6])]), {
+        status: 200,
+      });
+
+    await expect(
+      fetchRemoteMedia({
+        url: "https://example.com/file.bin",
+        fetchImpl,
+        maxBytes: 4,
+      }),
+    ).rejects.toThrow("exceeds maxBytes");
+  });
+});