import { createReadStream, statSync } from "node:fs";
import { Readable } from "node:stream";
import type { NextRequest } from "next/server";

export function streamVideoFile(req: NextRequest, filePath: string, downloadName: string): Response {
  let size: number;
  try {
    size = statSync(filePath).size;
  } catch {
    return new Response("File not found on disk", { status: 404 });
  }

  const headers: Record<string, string> = {
    "Content-Type": "video/mp4",
    "Accept-Ranges": "bytes",
  };
  if (req.nextUrl.searchParams.get("download") === "1") {
    headers["Content-Disposition"] = `attachment; filename="${downloadName}"`;
  }

  const range = req.headers.get("range");
  const match = range ? /bytes=(\d+)-(\d*)/.exec(range) : null;

  if (match) {
    const start = Number(match[1]);
    const end = match[2] ? Number(match[2]) : size - 1;
    const stream = createReadStream(filePath, { start, end });
    return new Response(Readable.toWeb(stream) as ReadableStream, {
      status: 206,
      headers: {
        ...headers,
        "Content-Range": `bytes ${start}-${end}/${size}`,
        "Content-Length": String(end - start + 1),
      },
    });
  }

  const stream = createReadStream(filePath);
  return new Response(Readable.toWeb(stream) as ReadableStream, {
    headers: { ...headers, "Content-Length": String(size) },
  });
}