#include <byteswap.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

#include "nscd.h"

static const struct {
  short sun_family;
  char sun_path[21];
} addr = {AF_UNIX, "/var/run/nscd/socket"};

FILE* __nscd_query(int32_t req, const char* key, int32_t* buf, size_t len, int* swap) {
  size_t i;
  int fd;
  FILE* f = 0;
  int32_t req_buf[REQ_LEN] = {NSCDVERSION, req, strnlen(key, LOGIN_NAME_MAX) + 1};
  struct msghdr msg = {
      .msg_iov = (struct iovec[]){{&req_buf, sizeof(req_buf)}, {(char*)key, strlen(key) + 1}},
      .msg_iovlen = 2};
  int errno_save = errno;

  *swap = 0;
retry:
  memset(buf, 0, len);
  buf[0] = NSCDVERSION;

  fd = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
  if (fd < 0)
    return NULL;

  if (!(f = fdopen(fd, "r"))) {
    close(fd);
    return 0;
  }

  if (req_buf[2] > LOGIN_NAME_MAX)
    return f;

  if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
    /* If there isn't a running nscd we simulate a "not found"
     * result and the caller is responsible for calling
     * fclose on the (unconnected) socket. The value of
     * errno must be left unchanged in this case.  */
    if (errno == EACCES || errno == ECONNREFUSED || errno == ENOENT) {
      errno = errno_save;
      return f;
    }
    goto error;
  }

  if (sendmsg(fd, &msg, 0) < 0)
    goto error;

  if (!fread(buf, len, 1, f)) {
    /* If the VERSION entry mismatches nscd will disconnect. The
     * most likely cause is that the endianness mismatched. So, we
     * byteswap and try once more. (if we already swapped, just
     * fail out)
     */
    if (ferror(f))
      goto error;
    if (!*swap) {
      fclose(f);
      for (i = 0; i < sizeof(req_buf) / sizeof(req_buf[0]); i++) {
        req_buf[i] = bswap_32(req_buf[i]);
      }
      *swap = 1;
      goto retry;
    } else {
      errno = EIO;
      goto error;
    }
  }

  if (*swap) {
    for (i = 0; i < len / sizeof(buf[0]); i++) {
      buf[i] = bswap_32(buf[i]);
    }
  }

  /* The first entry in every nscd response is the version number. This
   * really shouldn't happen, and is evidence of some form of malformed
   * response.
   */
  if (buf[0] != NSCDVERSION) {
    errno = EIO;
    goto error;
  }

  return f;
error:
  fclose(f);
  return 0;
}