import { existsSync } from "node:fs";
import { sourceWav } from "@/lib/clips";
import { readWavWindow, peakBuckets } from "@/lib/wav";

export const dynamic = "force-dynamic";

// Waveform peaks for a window, so the canvas can redraw when the view widens
// without shipping samples. A 13-minute view is 1,200 buckets either way.
export async function GET(request: Request, ctx: { params: Promise<{ key: string }> }) {
  const { key } = await ctx.params;
  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 decoded = decodeURIComponent(key);
  const at = decoded.lastIndexOf("@");
  const video = at > 0 ? decoded.slice(0, at) : decoded;
  const file = sourceWav(video);
  if (!existsSync(file)) return Response.json({ error: "source missing" }, { status: 404 });

  const region = await readWavWindow(file, 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" } },
  );
}