import { existsSync } from "node:fs";
import { TRIM_SETS, stemPath } from "@/lib/trim";
import { readWavWindow, peakBuckets } from "@/lib/wav";

export const dynamic = "force-dynamic";

// Peaks over a window of the STEM.
//
// This deliberately duplicates ~15 lines of app/api/clip/[key]/peaks rather
// than generalising it. That route's `sourceWav(video)` is a load-bearing
// constraint on a well-exercised path -- the whole um-triage deck runs through
// it -- and parameterising its source to also accept a stem would put this
// editor's failure modes into that deck. Fifteen duplicated lines are cheaper.

export async function GET(request: Request, ctx: { params: Promise<{ set: string }> }) {
  const { set: id } = await ctx.params;
  const set = TRIM_SETS[id];
  if (!set) return Response.json({ error: "no such trim set" }, { status: 404 });

  const url = new URL(request.url);
  const from = Number(url.searchParams.get("from"));
  const to = Number(url.searchParams.get("to"));
  const buckets = Math.max(64, Math.min(4000, Number(url.searchParams.get("n") ?? 1200)));
  if (!Number.isFinite(from) || !Number.isFinite(to) || to <= from) {
    return new Response("bad window", { status: 400 });
  }

  const file = stemPath(set);
  if (!existsSync(file)) return Response.json({ error: "stem missing" }, { status: 404 });

  const region = await readWavWindow(file, Math.max(0, from), to);
  const { min, max } = peakBuckets(region.x, buckets);
  return Response.json(
    { from: region.from, to: region.to, duration: region.duration, min, max },
    { headers: { "cache-control": "no-store" } },
  );
}