// Registry tarballs for specs that install real packages, served from
// tests/fixtures/tarballs/<registry path> (gitignored) and fetched from registry.npmjs.org
// only on a miss. A tarball URL never changes content and the kernel checks every one
// against its lockfile integrity, so the cached copy is the bytes the network would
// send; after one run the suite installs offline. TARBALLS_OFFLINE=1 fails a miss, and
// any other request that leaves localhost, which proves a spec needs no network.
import { existsSync, mkdirSync, readFileSync, renameSync, writeFileSync } from "node:fs";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";
import type { BrowserContext } from "@playwright/test";

const CACHE = fileURLToPath(new URL("fixtures/tarballs", import.meta.url));
const CORS = { "access-control-allow-origin": "*" };

const cachePath = (url: string): string => join(CACHE, decodeURIComponent(new URL(url).pathname));

function store(file: string, body: Buffer): void {
  mkdirSync(dirname(file), { recursive: true });
  // Parallel workers may fetch the same tarball: write aside, then rename into place.
  const partial = `${file}.${process.pid}.partial`;
  writeFileSync(partial, body);
  renameSync(partial, file);
}

/** One tarball's bytes for a spec that reads a package outside the browser. */
export async function tarball(url: string): Promise<Buffer> {
  const file = cachePath(url);
  if (!existsSync(file)) {
    if (process.env.TARBALLS_OFFLINE === "1") throw new Error(`${url} is not cached`);
    const res = await fetch(url);
    if (!res.ok) throw new Error(`${url}: ${res.status}`);
    store(file, Buffer.from(await res.arrayBuffer()));
  }
  return readFileSync(file);
}

export async function cacheTarballs(context: BrowserContext): Promise<void> {
  // Registered first, so every other route (a spec's own registry answers) runs before it.
  if (process.env.TARBALLS_OFFLINE === "1") {
    await context.route((url) => url.hostname !== "localhost" && url.hostname !== "127.0.0.1", (route) => route.abort("internetdisconnected"));
  }
  await context.route(/^https:\/\/registry\.npmjs\.org\/.+\/-\/[^/]+\.tgz$/, async (route) => {
    const req = route.request();
    if (req.method() !== "GET") return route.fallback();
    const file = cachePath(req.url());
    if (!existsSync(file)) {
      if (process.env.TARBALLS_OFFLINE === "1") return route.abort("internetdisconnected");
      const res = await route.fetch();
      if (res.status() !== 200) return route.fulfill({ response: res });
      store(file, await res.body());
    }
    return route.fulfill({ status: 200, headers: CORS, contentType: "application/octet-stream", body: readFileSync(file) });
  });
}