// Copyright (c) 2016 Nuxi, https://nuxi.nl/
//
// SPDX-License-Identifier: BSD-2-Clause

#include <wasi/api.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

#ifndef __wasip1__
#include <wasi/file_utils.h>
#include <common/errors.h>
#endif

int __wasilibc_nocwd_faccessat(int fd, const char *path, int amode, int flag) {
  // Validate function parameters.
  if ((amode & ~(F_OK | R_OK | W_OK | X_OK)) != 0 ||
      (flag & ~AT_EACCESS) != 0) {
    errno = EINVAL;
    return -1;
  }

#if defined(__wasip1__)
  // Check for target file existence and obtain the file type.
  __wasi_lookupflags_t lookup_flags = __WASI_LOOKUPFLAGS_SYMLINK_FOLLOW;
  __wasi_filestat_t file;
  __wasi_errno_t error =
      __wasi_path_filestat_get(fd, lookup_flags, path, &file);
  if (error != 0) {
    errno = error;
    return -1;
  }

  // Test whether the requested access rights are present on the
  // directory file descriptor.
  if (amode != 0) {
    __wasi_fdstat_t directory;
    error = __wasi_fd_fdstat_get(fd, &directory);
    if (error != 0) {
      errno = error;
      return -1;
    }

    __wasi_rights_t min = 0;
    if ((amode & R_OK) != 0)
      min |= file.filetype == __WASI_FILETYPE_DIRECTORY
                 ? __WASI_RIGHTS_FD_READDIR
                 : __WASI_RIGHTS_FD_READ;
    if ((amode & W_OK) != 0)
      min |= __WASI_RIGHTS_FD_WRITE;

    if ((min & directory.fs_rights_inheriting) != min) {
      errno = EACCES;
      return -1;
    }
  }
#elif defined(__wasip2__) || defined(__wasip3__)
  // Translate the file descriptor to an internal handle
  // Translate the file descriptor to an internal handle
  filesystem_borrow_descriptor_t file_handle;
  if (fd_to_file_handle(fd, &file_handle) < 0)
    return -1;

  // Convert the string into a WASI string
  wasi_string_t wasi_path;
  if (wasi_string_from_c(path, &wasi_path) < 0)
    return -1;

  // Call stat() to check if the file exists
  filesystem_descriptor_stat_t stat_result;
  filesystem_error_code_t error_code;
  bool ok = filesystem_method_descriptor_stat_at(file_handle,
                                                 FILESYSTEM_PATH_FLAGS_SYMLINK_FOLLOW,
                                                 &wasi_path,
                                                 &stat_result,
                                                 &error_code);
  if (!ok) {
    translate_error(&error_code);
    return -1;
  }

  // If amode == F_OK, we can return true since we already checked
  // that the file exists
  if (amode != 0) {
    // Get the permissions on the directory
    filesystem_descriptor_flags_t directory_flags;
    ok = filesystem_method_descriptor_get_flags(file_handle,
                                                &directory_flags,
                                                &error_code);
    if (!ok) {
      translate_error(&error_code);
      return -1;
    }

    bool has_rights = true;

    // Readable if the directory is readable; writable if the directory is writable
    if ((amode & R_OK) != 0) {
      if ((directory_flags & FILESYSTEM_DESCRIPTOR_FLAGS_READ) == 0)
        has_rights = false;
    }
    if ((amode & W_OK) != 0) {
      if ((directory_flags & FILESYSTEM_DESCRIPTOR_FLAGS_MUTATE_DIRECTORY) == 0)
        has_rights = false;
    }
    if (!has_rights) {
      errno = EACCES;
      return -1;
    }
  }
#else
# error "Unsupported WASI version"
#endif
  return 0;
}
