/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/calls/internal.h"
#include "libc/calls/state.internal.h"
#include "libc/calls/struct/stat.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/fmt/itoa.h"
#include "libc/intrin/describeflags.h"
#include "libc/intrin/strace.h"
#include "libc/intrin/weaken.h"
#include "libc/log/log.h"
#include "libc/mem/alloca.h"
#include "libc/runtime/zipos.internal.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/at.h"
#include "libc/sysv/errfuns.h"

static inline const char *__strace_fstatat_flags(char buf[12], int flags) {
  if (flags == AT_SYMLINK_NOFOLLOW)
    return "AT_SYMLINK_NOFOLLOW";
  FormatInt32(buf, flags);
  return buf;
}

/**
 * Returns information about thing.
 *
 * On Windows, this implementation always sets `st_uid` and `st_gid` to
 * `getuid()` and `getgid()`. Anyone who relies upon the information to
 * secure a multi-tenant personal computer should consider improving it
 * and further note that the `st_mode` group / other bits will be clear
 *
 * @param dirfd is normally `AT_FDCWD` but if it's an open directory and
 *     file is a relative path, then `path` becomes relative to `dirfd`
 * @param st is where the result is stored
 * @param flags can have `AT_SYMLINK_NOFOLLOW`
 * @raise EACCES if denied access to component in path prefix
 * @raise EIO if i/o error occurred while reading from filesystem
 * @raise ELOOP if a symbolic link loop exists in `path`
 * @raise ENAMETOOLONG if a component in `path` exceeds `NAME_MAX`
 * @raise ENOENT on empty string or if component in path doesn't exist
 * @raise ENOTDIR if a parent component existed that wasn't a directory
 * @raise EILSEQ if `path` contains illegal UTF-8 sequences (Windows/MacOS)
 * @raise ENOTDIR if `path` is relative and `dirfd` isn't an open directory
 * @raise ENOEXEC if `path` is a zip path and this executable isn't a zip file
 * @raise EOVERFLOW shouldn't be possible on 64-bit systems
 * @raise ELOOP may ahappen if `SYMLOOP_MAX` symlinks were dereferenced
 * @raise ENAMETOOLONG may happen if `path` exceeded `PATH_MAX`
 * @raise EFAULT if `path` or `st` point to invalid memory
 * @raise EINVAL if `flags` has unsupported bits
 * @return 0 on success, or -1 w/ errno
 * @see S_ISDIR(st.st_mode), S_ISREG()
 * @asyncsignalsafe
 * @vforksafe
 */
int fstatat(int dirfd, const char *path, struct stat *st, int flags) {
  // execve() depends on this
  int rc;
  struct ZiposUri zipname;
  if (flags & ~AT_SYMLINK_NOFOLLOW) {
    return einval();
  } else if (__isfdkind(dirfd, kFdZip)) {
    STRACE("zipos dirfd not supported yet");
    rc = einval();
  } else if (_weaken(__zipos_stat) &&
             _weaken(__zipos_parseuri)(path, &zipname) != -1) {
    if (!__vforked) {
      rc = _weaken(__zipos_stat)(&zipname, st);
    } else {
      rc = enotsup();
    }
  } else if (IsLinux() || IsXnu() || IsFreebsd() || IsOpenbsd() || IsNetbsd()) {
    rc = sys_fstatat(dirfd, path, st, flags);
  } else if (IsWindows()) {
    rc = sys_fstatat_nt(dirfd, path, st, flags);
  } else {
    rc = enosys();
  }
  STRACE("fstatat(%s, %#s, [%s], %s) → %d% m", DescribeDirfd(dirfd), path,
         DescribeStat(rc, st), __strace_fstatat_flags(alloca(12), flags), rc);
  return rc;
}

__weak_reference(fstatat, fstatat64);