리다이렉트 경로 처리, 파일 정보 변환, 상태 표시 UI 등 중복된 코드를 통합하고 모듈 간 순환 의존성 및 계층 위반 해소

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/routes/api/file/[id=int]/[[thumbnail=thumbnail]]/download/+server.ts

@@ -0,0 +1,40 @@
+import { authorize } from "#lib/server/auth.ts";
+import { handleAppErrors } from "#lib/server/http.ts";
+import { FileService } from "#lib/server/services/index.ts";
+import { parseRangeHeader, getContentRangeHeader } from "#lib/shared/http.ts";
+import type { RequestEvent, RequestHandler } from "./$types";
+
+const downloadHandler = async ({ locals, params, request }: RequestEvent) => {
+  const { userId } = await authorize(locals, "activeClient");
+  const { id } = params;
+
+  const getStream = params.thumbnail
+    ? FileService.getFileThumbnailStream
+    : FileService.getFileStream;
+  const { encContentStream, range, isRangeRequest } = await getStream(
+    userId,
+    id,
+    parseRangeHeader(request.headers.get("Range")),
+  );
+  return {
+    stream: encContentStream,
+    status: isRangeRequest ? 206 : 200,
+    headers: {
+      "Accept-Ranges": "bytes",
+      "Content-Length": String(range.end - range.start + 1),
+      "Content-Type": "application/octet-stream",
+      ...(isRangeRequest ? getContentRangeHeader(range) : {}),
+    },
+  };
+};
+
+export const GET: RequestHandler = handleAppErrors(async (event) => {
+  const { stream, ...init } = await downloadHandler(event);
+  return new Response(stream as ReadableStream, init);
+});
+
+export const HEAD: RequestHandler = handleAppErrors(async (event) => {
+  const { stream, ...init } = await downloadHandler(event);
+  await stream.cancel();
+  return new Response(null, init);
+});