#include <sys/types.h>

#include <sys/procdesc.h>
#include <sys/socket.h>
#include <sys/wait.h>

#include <err.h>
#include <poll.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

// From libnv.
extern int fd_send(int sock, const int *fds, size_t nfds);
extern int fd_recv(int sock, int *fds, size_t nfds);

int main() {
	for (;;) {
		pid_t pid;
		int child_fd;
		int sock[2];

		fprintf(stderr, "next gen\n");

		if (socketpair(PF_UNIX, SOCK_STREAM, 0, sock) < 0) {
			err(1, "socketpair");
		}

		pid = pdfork(&child_fd, PD_CLOEXEC);
		if (pid < 0) {
			err(1, "pdfork");
		}

		if (pid == 0) {
			close(sock[0]);
			int sock_child[2];
			int dummy = 0;

			if (socketpair(PF_UNIX, SOCK_STREAM, /**/
			        0, sock_child) < 0) {
				err(1, "socketpair");
			}

			// fprintf(stderr, "dummy write/read\n");
			// if (write(sock_child[1], &dummy, 1) != 1) {
			// 	err(1, "write");
			// }
			// if (read(sock_child[0], &dummy, 1) != 1) {
			// 	err(1, "read");
			// }

			fprintf(stderr, "sending socket...\n");
			if (fd_send(sock[1], &sock_child[0], 1) != 0) {
				errx(1, "fd_send failed");
			}
			if (read(sock[1], &dummy, 1) != 1) {
				err(1, "write");
			}
			fprintf(stderr, "sent socket\n");

			close(sock_child[0]);

			if (write(sock_child[1], &dummy, 1) != 1) {
				err(1, "write");
			}

			ssize_t ret;
			if ((ret = read(sock_child[1], &dummy, 1)) != 1) {
				errx(1, "read failed in child: %d", (int)ret);
			}

			close(sock_child[1]);

			_exit(0);
		}

		close(sock[1]);

		int sock_child;
		uint8_t dummy;

		fprintf(stderr, "recv socket...\n");
		if (fd_recv(sock[0], &sock_child, 1) != 0) {
			errx(1, "fd_recv failed");
		}
		if (write(sock[0], &dummy, 1) != 1) {
			err(1, "write");
		}
		fprintf(stderr, "recved socket\n");

		ssize_t ret;
		fprintf(stderr, "reading one byte...\n");
		if ((ret = read(sock_child, &dummy, 1)) != 1) {
			int error;
			socklen_t err_len = sizeof(error);
			if (getsockopt(sock_child, SOL_SOCKET, SO_ERROR,
			        &error, &err_len) < 0) {
				err(1, "getsockopt");
			}

			fprintf(stderr, "got err\n");
			ssize_t ret2 = read(sock_child, &dummy, 1);

			errx(1,
			    "read failed in parent: %d, so_error: %s (%d), ret2: %d",
			    (int)ret, strerror(error), error, (int)ret2);
		}

		if (write(sock_child, &dummy, 1) != 1) {
			err(1, "write");
		}

		close(sock_child);

		struct pollfd pfd = { .fd = child_fd };
		poll(&pfd, 1, -1);

		close(child_fd);
		close(sock[0]);
	}
}