/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ This program is free software; you can redistribute it and/or modify         │
│ it under the terms of the GNU General Public License as published by         │
│ the Free Software Foundation; version 2 of the License.                      │
│                                                                              │
│ This program is distributed in the hope that it will be useful, but          │
│ WITHOUT ANY WARRANTY; without even the implied warranty of                   │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU             │
│ General Public License for more details.                                     │
│                                                                              │
│ You should have received a copy of the GNU General Public License            │
│ along with this program; if not, write to the Free Software                  │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
│ 02110-1301 USA                                                               │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/bits/bits.h"
#include "libc/bits/progn.h"
#include "libc/calls/internal.h"
#include "libc/calls/struct/dirent.h"
#include "libc/dce.h"
#include "libc/mem/mem.h"
#include "libc/nt/files.h"
#include "libc/nt/runtime.h"
#include "libc/nt/struct/win32finddata.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/dt.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/errfuns.h"

struct dirstream {
  int64_t tell;
  int64_t fd;
  union {
    struct {
      unsigned buf_pos;
      unsigned buf_end;
      char buf[BUFSIZ];
    };
    struct {
      struct dirent winent;
      char __d_name[PATH_MAX];
      bool isdone;
      struct NtWin32FindData windata;
    };
  };
};

static textwindows noinline DIR *opendir$nt(const char *name) {
  int len;
  DIR *res;
  char16_t name16[PATH_MAX];
  if ((len = mkntpath(name, name16)) == -1) return NULL;
  if (len + 2 + 1 > PATH_MAX) return PROGN(enametoolong(), NULL);
  if (name16[len - 1] == u'/' || name16[len - 1] == u'\\') {
    name16[--len] = u'\0';
  }
  name16[len++] = u'/';
  name16[len++] = u'*';
  name16[len] = u'\0';
  if (!(res = calloc(1, sizeof(DIR)))) return NULL;
  if ((res->fd = FindFirstFile(name16, &res->windata)) != -1) {
    return res;
  } else {
    winerr();
    free(res);
    return NULL;
  }
}

/**
 * Opens directory so readdir() and closedir() may be called.
 *
 * @returns newly allocated DIR object, or NULL w/ errno
 * @errors ENOENT, ENOTDIR, EACCES, EMFILE, ENFILE, ENOMEM
 * @see glob()
 */
DIR *opendir(const char *name) {
  if (!IsWindows() && !IsXnu()) {
    int fd;
    DIR *res = NULL;
    if ((fd = open(name, O_RDONLY | O_DIRECTORY | O_CLOEXEC, 0)) != -1) {
      if (!(res = fdopendir(fd))) close(fd);
    }
    return res;
  } else if (IsWindows()) {
    return opendir$nt(name);
  } else {
    enosys(); /* TODO(jart): Implement me! */
    return NULL;
  }
}

/**
 * Creates directory object for file descriptor.
 *
 * @param fd gets owned by this function, if it succeeds
 * @return new directory object, which must be freed by closedir(),
 *     or NULL w/ errno
 * @errors ENOMEM and fd is closed
 */
DIR *fdopendir(int fd) {
  if (!IsWindows() && !IsXnu()) {
    DIR *dir;
    if ((dir = calloc(1, sizeof(*dir)))) {
      dir->fd = fd;
      return dir;
    }
  } else {
    enosys(); /* TODO(jart): Implement me! */
  }
  return NULL;
}

/**
 * Reads next entry from DIR.
 *
 * This API doesn't define any particular ordering.
 *
 * @param dir is the object opendir() or fdopendir() returned
 * @return next entry or NULL on end or error, which can be
 *     differentiated by setting errno to 0 beforehand
 */
struct dirent *readdir(DIR *dir) {
  if (!IsWindows()) {
    if (dir->buf_pos >= dir->buf_end) {
      int rc;
      if (!(rc = getdents(dir->fd, dir->buf, BUFSIZ)) || rc == -1) {
        return NULL;
      }
      dir->buf_pos = 0;
      dir->buf_end = rc;
    }
    /* TODO(jart): Check FreeBSD and OpenBSD again regarding this */
    char *record = dir->buf + dir->buf_pos;
    char *name = record + 8 + 8 + 2;
    size_t namelen = strlen(name);
    unsigned char dtype = name[namelen + 1];
    memmove(name + 1, name, namelen + 1); /* shove forward one byte */
    *name = dtype;                        /* is dirent d_type field */
    struct dirent *ent = (void *)record;
    dir->buf_pos += ent->d_reclen;
    dir->tell = ent->d_off;
    return ent;
  } else {
    if (dir->isdone) return NULL;
    struct dirent *ent = &dir->winent;
    memset(ent, 0, sizeof(*ent));
    ent->d_reclen =
        sizeof(*ent) +
        tprecode16to8(ent->d_name, PATH_MAX, dir->windata.cFileName) + 1;
    dir->isdone = FindNextFile(dir->fd, &dir->windata);
    return ent;
  }
}

/**
 * Closes directory object returned by opendir().
 * @return 0 on success or -1 w/ errno
 */
int closedir(DIR *dir) {
  int rc;
  if (dir) {
    if (!IsWindows()) {
      rc = close(dir->fd);
    } else {
      rc = FindClose(dir->fd) ? 0 : winerr();
    }
    free(dir);
  } else {
    rc = 0;
  }
  return rc;
}

/**
 * Returns current byte offset into directory data.
 */
long telldir(DIR *dir) {
  return dir->tell;
}

/**
 * Returns file descriptor associated with DIR object.
 */
int dirfd(DIR *dir) {
  return dir->fd;
}