import { FaceError, detectFace } from "@/lib/faces";

export const dynamic = "force-dynamic";

// WHERE THE DETECTOR LOOKED.
//
// Its own route, and not folded into the frame route, because the two cost
// wildly different amounts: a still is ~80ms of ffmpeg and this is ~0.94s of
// python decoding five frames and running YuNet on each. Bundling them would
// make every arrow key wait on the detector for a picture that is already
// cached, and the deck would feel broken while doing exactly what it should.
//
// So the deck fetches the frame immediately and the detection separately, and
// nothing is detected until a candidate is actually focused. Two of the corners
// on record find NO FACE AT ALL at their recorded time, which is a real answer
// this route has to be able to give: `face: null` with the frame size still
// filled in, so the deck can draw the picture and let a person crop it by hand.
export async function GET(request: Request) {
  const url = new URL(request.url);
  const video = url.searchParams.get("video") ?? "";
  const at = Number(url.searchParams.get("at"));

  if (!/^[A-Za-z0-9_-]+$/.test(video)) {
    return Response.json({ error: "bad video" }, { status: 400 });
  }
  if (!Number.isFinite(at) || at < 0) {
    return Response.json({ error: "bad time" }, { status: 400 });
  }

  try {
    return Response.json(await detectFace(video, at), {
      headers: { "cache-control": "no-store" },
    });
  } catch (e) {
    if (e instanceof FaceError) return Response.json({ error: e.message }, { status: e.status });
    return Response.json({ error: "could not run the detector" }, { status: 500 });
  }
}