feat(media): add reference-aware S3 image delivery

app/media/[id]/route.ts

@@ -0,0 +1,75 @@
+import * as z from "zod";
+
+import { getAdminSession } from "@/lib/auth/server";
+import { getMediaVisibility } from "@/lib/content/queries";
+import { getReadyMedia } from "@/lib/media/repository";
+import { getMediaStorage } from "@/lib/media/storage";
+import { parseByteRange } from "@/lib/media/validation";
+
+async function serveMedia(
+  request: Request,
+  context: { params: Promise<{ id: string }> },
+  headOnly: boolean,
+) {
+  const { id } = await context.params;
+  if (!z.string().uuid().safeParse(id).success) {
+    return new Response("Not found", { status: 404 });
+  }
+  const record = await getReadyMedia(id);
+  if (!record) return new Response("Not found", { status: 404 });
+  const visibility = await getMediaVisibility(id);
+  if (!visibility.public && !(await getAdminSession())) {
+    return new Response("Not found", { status: 404 });
+  }
+
+  const file = getMediaStorage().file(record.objectKey);
+  let stat: Awaited<ReturnType<typeof file.stat>>;
+  try {
+    stat = await file.stat();
+  } catch {
+    return new Response("Not found", { status: 404 });
+  }
+  const rangeHeader = request.headers.get("range");
+  const range = parseByteRange(rangeHeader, stat.size);
+  if (rangeHeader && !range) {
+    return new Response(null, {
+      status: 416,
+      headers: { "Content-Range": `bytes */${stat.size}` },
+    });
+  }
+  const headers = new Headers({
+    "Accept-Ranges": "bytes",
+    "Content-Type": record.mimeType,
+    "Content-Disposition": `inline; filename*=UTF-8''${encodeURIComponent(record.fileName)}`,
+    "Cache-Control": visibility.public
+      ? "public, max-age=60, must-revalidate"
+      : "private, no-store",
+    ETag: stat.etag,
+    "X-Content-Type-Options": "nosniff",
+  });
+  if (range) {
+    const length = range.end - range.start + 1;
+    headers.set("Content-Length", String(length));
+    headers.set("Content-Range", `bytes ${range.start}-${range.end}/${stat.size}`);
+    return new Response(
+      headOnly ? null : file.slice(range.start, range.end + 1).stream(),
+      { status: 206, headers },
+    );
+  }
+  headers.set("Content-Length", String(stat.size));
+  return new Response(headOnly ? null : file.stream(), { status: 200, headers });
+}
+
+export async function GET(
+  request: Request,
+  context: { params: Promise<{ id: string }> },
+) {
+  return serveMedia(request, context, false);
+}
+
+export async function HEAD(
+  request: Request,
+  context: { params: Promise<{ id: string }> },
+) {
+  return serveMedia(request, context, true);
+}