import { deckStill, scheduleForPreview, stillTimeOf } from "@/lib/report/onscreen.mjs";
import { resolveReport } from "@/lib/report/serve.mjs";
import { deckOn, validateChrome } from "umtool-report-to-video/deck";

export const dynamic = "force-dynamic";

// A TRUE still of the deck: the composition at one moment, screenshotted by
// the same browser engine the render uses, as a PNG of the deck region
// (1920 × deck.height, transparent outside the panel).
//
// The live preview is an iframe in the page's own browser, which is close to
// the render and not the same thing -- fonts, text fitting and the QR are
// where they differ. This is the answer to "is that what the video will show".
//
// ?project&variant& one of:
//   clip=<entry id>   the middle of that entry's segment
//   at=<seconds>      a moment in the cut's clock
//
// Drawn from the same schedule the preview uses (the build's when it matches
// the cut, else an estimate), saved text only -- a still is of what is saved.
export async function GET(request: Request) {
  const url = new URL(request.url);
  const r = await resolveReport(url.searchParams.get("project") ?? "", url.searchParams.get("variant"));
  if ("error" in r) return new Response(r.error, { status: r.status });

  const { variantManifest, schedule } = await scheduleForPreview(r.project, r.manifest, r.variant);
  const render = (variantManifest.render ?? {}) as Record<string, unknown>;
  if (!deckOn(render)) return new Response("the deck is off for this manifest", { status: 409 });
  const { chrome, ...rest } = render;
  const errors = validateChrome(chrome, rest);
  if (errors.length) return new Response(`render.chrome: ${errors.join("; ")}`, { status: 400 });

  const clip = url.searchParams.get("clip");
  const atRaw = url.searchParams.get("at");
  let t: number | null;
  if (clip) {
    t = stillTimeOf(schedule, clip);
    if (t === null) return new Response(`no entry ${clip} in the ${r.variant} cut`, { status: 404 });
  } else if (atRaw !== null && atRaw !== "") {
    t = Number(atRaw);
    if (!Number.isFinite(t) || t < 0 || t > schedule.total) {
      return new Response(`at must be a number of seconds from 0 to ${schedule.total}`, { status: 400 });
    }
  } else {
    return new Response("name a clip= or an at=", { status: 400 });
  }

  let png: Buffer;
  try {
    png = await deckStill(r.project, r.variant, schedule, t);
  } catch (e) {
    return new Response(e instanceof Error ? e.message : String(e), { status: 500 });
  }
  return new Response(new Uint8Array(png), {
    headers: {
      "content-type": "image/png",
      "content-length": String(png.length),
      "cache-control": "no-store",
      "x-still-at": String(t),
      "x-schedule-estimated": String(!!schedule.estimated),
    },
  });
}