podcastdistributiona/app/api/public/episodes/[shareId]/cover/route.ts

import { Readable } from "node:stream";
import { NextRequest } from "next/server";
import { prisma } from "@/lib/db";
import { rateLimit, LIMITS } from "@/lib/ratelimit";
import { storage } from "@/lib/storage";

export const dynamic = "force-dynamic";

const CONTENT_TYPES: Record<string, string> = {
  png: "image/png",
  jpg: "image/jpeg",
  jpeg: "image/jpeg",
  webp: "image/webp",
};

/** Best-effort client IP for anonymous rate limiting. */
function clientKey(req: NextRequest): string {
  const fwd = req.headers.get("x-forwarded-for");
  if (fwd) return fwd.split(",")[0].trim();
  return req.headers.get("x-real-ip") ?? "anon";
}

/**
 * Serve an episode's cover art to anonymous visitors, authorized by a valid,
 * still-enabled public `shareId`. Used as a fallback when the storage provider
 * doesn't expose a directly-fetchable public URL for cover art. The file is
 * streamed off disk rather than buffered whole to avoid memory-amplification DoS.
 */
export async function GET(
  req: NextRequest,
  { params }: { params: Promise<{ shareId: string }> }
) {
  // Rate-limit by client IP (never by shareId alone).
  const rl = await rateLimit("public-cover", clientKey(req), LIMITS.publicMedia);
  if (!rl.ok) {
    return new Response("Too many requests", {
      status: 429,
      headers: { "Retry-After": String(rl.retryAfterSec ?? 1) },
    });
  }

  const { shareId } = await params;

  const episode = await prisma.episode.findUnique({
    where: { shareId },
    select: { coverArt: { select: { storageKey: true } } },
  });
  const key = episode?.coverArt?.storageKey;
  if (!key) return new Response("Not found", { status: 404 });

  const total = await storage().size(key);
  if (total === null) return new Response("Not found", { status: 404 });

  const ext = key.split(".").pop()?.toLowerCase() ?? "png";
  const node = storage().createReadStream!(key);
  const body = Readable.toWeb(node as Readable) as unknown as BodyInit;
  return new Response(body, {
    headers: {
      "Content-Type": CONTENT_TYPES[ext] ?? "image/png",
      "Content-Length": String(total),
      "Cache-Control": "public, max-age=3600",
    },
  });
}