import { rangeResponse, resolveClip, segmentFor } from "@/lib/report/serve.mjs";

export const dynamic = "force-dynamic";

// The BUILT segment for one clip — the mp4 with the header and the QR burned in.
//
// /api/report/raw serves the raw source window, which is what you edit against.
// This serves what the renderer made of it, which is the only way to see the
// attribution line as it will actually appear: the header is drawn by ffmpeg
// from a text file, and no amount of HTML can promise it wrapped the same way.
//
// Names, never paths. A project id and a clip id, both members of the server's
// own scan, and the file name is built from the id the timeline vouched for.
//
// A re-render writes the SAME path, so the client passes the mtime it was told
// about as `v`. When it matches, the file is immutable for as long as that
// number holds and may be cached hard; when it does not, the client is looking
// at a stale idea of the file and the answer must not be cached at all. That is
// what makes "re-render, then watch it" show the new cut rather than the old.
//
// Range support is not optional: without a 206 the <video> element will not seek
// in a stream it did not fully download. rangeResponse() is the one
// implementation, shared with /api/report/video.

export async function GET(request: Request) {
  const url = new URL(request.url);
  const r = await resolveClip(
    url.searchParams.get("project") ?? "",
    url.searchParams.get("clip") ?? "",
  );
  if ("error" in r) return new Response(r.error, { status: r.status });

  const seg = await segmentFor(r.project, r.clip.id);
  if (!seg) {
    // A missing segment is the NORMAL state of a clip nobody has rendered yet,
    // not an error worth a stack trace. The bench says so in words.
    return new Response("no segment has been built for this clip yet", { status: 404 });
  }

  const fresh = url.searchParams.get("v") === String(seg.mtimeMs);
  const headers: Record<string, string> = {
    "content-type": "video/mp4",
    "accept-ranges": "bytes",
    "cache-control": fresh ? "private, max-age=3600, immutable" : "private, no-store",
    "x-segment-mtime": String(seg.mtimeMs),
    "x-segment": seg.rel,
  };

  return rangeResponse(request, { abs: seg.abs, size: seg.size, headers });
}