/**
 * Serving an application (or a fixture page) to the browser under test, the way a deployment
 * would.
 */

import * as http from "node:http";
import type { Socket } from "node:net";

/**
 * Serve `handler` on an ephemeral port, and hand back a close that CLOSES.
 *
 * `server.close()` alone stops the listener and then waits for every keep-alive connection
 * to drain on its own — a browser that is still attached keeps the server half-alive long
 * after the harness believes it gone. These suites close a server while a browser is still
 * pointed at it (the wallet export does exactly that), so the sockets are tracked and
 * destroyed: "closed" has to mean closed, or the next thing to go wrong gets blamed on the
 * suite instead of on the connection nobody hung up.
 */
export function serveOnEphemeralPort(
  handler: (req: http.IncomingMessage, res: http.ServerResponse) => void,
): Promise<{ url: string; close: () => void }> {
  const server = http.createServer(handler);
  const open = new Set<Socket>();
  server.on("connection", (socket) => {
    open.add(socket);
    socket.on("close", () => open.delete(socket));
  });
  return new Promise((resolve) => {
    server.listen(0, "127.0.0.1", () => {
      const port = (server.address() as { port: number }).port;
      resolve({
        url: `http://127.0.0.1:${port}`,
        close: () => {
          server.close();
          for (const socket of open) socket.destroy();
          open.clear();
        },
      });
    });
  });
}