/*
 * libcsync -- a library to sync a directory with another
 *
 * SPDX-FileCopyrightText: 2020 Nextcloud GmbH and Nextcloud contributors
 * SPDX-FileCopyrightText: 2013 ownCloud GmbH
 * SPDX-FileCopyrightText: 2008-2013 by Andreas Schneider <asn@cryptomilk.org>
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

#include <memory>

#include "windows.h"

#include "c_private.h"
#include "c_lib.h"
#include "csync.h"
#include "vio/csync_vio_local.h"
#include "common/filesystembase.h"
#include "common/utility.h"

#include <QtCore/QLoggingCategory>

#include "common/vfs.h"

Q_LOGGING_CATEGORY(lcCSyncVIOLocal, "nextcloud.sync.csync.vio_local", QtInfoMsg)

/*
 * directory functions
 */

struct csync_vio_handle_t {
  WIN32_FIND_DATA ffd;
  HANDLE hFind;
  int firstFind;
  QString path; // Always ends with '\'
};

csync_vio_handle_t *csync_vio_local_opendir(const QString &name) {

    QScopedPointer<csync_vio_handle_t> handle(new csync_vio_handle_t{});

    // the file wildcard has to be attached
    QString dirname = OCC::FileSystem::longWinPath(name + QLatin1String("/*"));

    handle->hFind = FindFirstFile(reinterpret_cast<const wchar_t *>(dirname.utf16()), &(handle->ffd));

    if (handle->hFind == INVALID_HANDLE_VALUE) {
        int retcode = GetLastError();
        if( retcode == ERROR_FILE_NOT_FOUND ) {
            errno = ENOENT;
        } else {
            errno = EACCES;
        }
        return nullptr;
    }

    handle->firstFind = 1; // Set a flag that there first fileinfo is available.

    dirname.chop(1); // remove the *
    handle->path = std::move(dirname);
    return handle.take();
}

int csync_vio_local_closedir(csync_vio_handle_t *dhandle) {
    Q_ASSERT(dhandle);
    int rc = -1;

    // FindClose returns non-zero on success
    if( FindClose(dhandle->hFind) != 0 ) {
        rc = 0;
    } else {
        // error case, set errno
        errno = EBADF;
    }
    delete dhandle;
    return rc;
}


static time_t FileTimeToUnixTime(FILETIME *filetime, DWORD *remainder)
{
    long long int t = filetime->dwHighDateTime;
    t <<= 32;
    t += (UINT32)filetime->dwLowDateTime;
    t -= 116444736000000000LL;
    if (t < 0)
    {
        if (remainder) *remainder = 9999999 - (-t - 1) % 10000000;
        return -1 - ((-t - 1) / 10000000);
    }
    else
    {
        if (remainder) *remainder = t % 10000000;
        return t / 10000000;
    }
}

std::unique_ptr<csync_file_stat_t> csync_vio_local_readdir(csync_vio_handle_t *handle, OCC::Vfs *vfs, bool checkPermissionsValidity)
{
  Q_UNUSED(checkPermissionsValidity)

  std::unique_ptr<csync_file_stat_t> file_stat;
  DWORD rem = 0;

  errno = 0;

  // the win32 functions get the first valid entry with the opendir
  // thus we must not jump to next entry if it was the first find.
  if( handle->firstFind ) {
      handle->firstFind = 0;
  } else {
      if( FindNextFile(handle->hFind, &(handle->ffd)) == 0 ) {
          // might be error, check!
          int dwError = GetLastError();
          if (dwError != ERROR_NO_MORE_FILES) {
              qCWarning(lcCSyncVIOLocal, "FindNextFile error %d", dwError);
              errno = EACCES; // no more files is fine. Otherwise EACCESS
          }
          return nullptr;
      }
  }
  auto path = QString::fromWCharArray(handle->ffd.cFileName);
  if (path == QLatin1String(".") || path == QLatin1String(".."))
      return csync_vio_local_readdir(handle, vfs, true);

  file_stat = std::make_unique<csync_file_stat_t>();
  file_stat->path = path.toUtf8();

    const auto isDirectory = handle->ffd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY;

    if (vfs && vfs->statTypeVirtualFile(file_stat.get(), &handle->ffd)) {
      // all good
    } else if ((handle->ffd.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) && !isDirectory) {
      // Detect symlinks, and treat junctions as symlinks too.
      if (handle->ffd.dwReserved0 == IO_REPARSE_TAG_SYMLINK
          || handle->ffd.dwReserved0 == IO_REPARSE_TAG_MOUNT_POINT) {
          file_stat->type = ItemTypeSoftLink;
      } else {
          // The SIS and DEDUP reparse points should be treated as
          // regular files. We don't know about the other ones yet,
          // but will also treat them normally for now.
          file_stat->type = ItemTypeFile;
      }
    } else if ((handle->ffd.dwFileAttributes & FILE_ATTRIBUTE_DEVICE || handle->ffd.dwFileAttributes & FILE_ATTRIBUTE_OFFLINE) &&
               !isDirectory) {
        file_stat->type = ItemTypeSkip;
    } else if (isDirectory) {
        if (handle->ffd.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT &&
            (handle->ffd.dwReserved0 == IO_REPARSE_TAG_SYMLINK ||
             handle->ffd.dwReserved0 == IO_REPARSE_TAG_MOUNT_POINT)) {
            file_stat->type = ItemTypeSoftLink;
        } else {
            file_stat->type = ItemTypeDirectory;
        }
    } else {
        file_stat->type = ItemTypeFile;
    }

    /* Check for the hidden flag */
    if( handle->ffd.dwFileAttributes & FILE_ATTRIBUTE_HIDDEN ) {
        file_stat->is_hidden = true;
    }

    file_stat->size = (handle->ffd.nFileSizeHigh * ((int64_t)(MAXDWORD)+1)) + handle->ffd.nFileSizeLow;
    file_stat->modtime = FileTimeToUnixTime(&handle->ffd.ftLastWriteTime, &rem);

    // path always ends with '\', by construction

    if (csync_vio_local_stat(handle->path + QString::fromWCharArray(handle->ffd.cFileName), file_stat.get(), true) < 0) {
        // Will get excluded by _csync_detect_update.
        file_stat->type = ItemTypeSkip;
    }

    return file_stat;
}

int csync_vio_local_stat(const QString &uri, csync_file_stat_t *buf, bool checkPermissionsValidity)
{
    Q_UNUSED(checkPermissionsValidity)

    /* Almost nothing to do since csync_vio_local_readdir already filled up most of the information
       But we still need to fetch the file ID.
       Possible optimisation: only fetch the file id when we need it (for new files)
      */

    HANDLE h = nullptr;
    BY_HANDLE_FILE_INFORMATION fileInfo;
    ULARGE_INTEGER FileIndex;

    h = CreateFileW(reinterpret_cast<const wchar_t *>(OCC::FileSystem::longWinPath(uri).utf16()), 0, FILE_SHARE_WRITE | FILE_SHARE_READ | FILE_SHARE_DELETE,
        nullptr, OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL | FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
        nullptr);
    if( h == INVALID_HANDLE_VALUE ) {
        errno = GetLastError();
        qCCritical(lcCSyncVIOLocal) << "CreateFileW failed on" << uri << OCC::Utility::formatWinError(errno);
        return -1;
    }

    if(!GetFileInformationByHandle( h, &fileInfo ) ) {
        errno = GetLastError();
        qCCritical(lcCSyncVIOLocal) << "GetFileInformationByHandle failed on" << uri << OCC::Utility::formatWinError(errno);
        CloseHandle(h);
        return -1;
    }

    /* Get the Windows file id as an inode replacement. */
    FileIndex.HighPart = fileInfo.nFileIndexHigh;
    FileIndex.LowPart = fileInfo.nFileIndexLow;
    FileIndex.QuadPart &= 0x0000FFFFFFFFFFFF;
    /* printf("Index: %I64i\n", FileIndex.QuadPart); */
    buf->inode = FileIndex.QuadPart;
    buf->size = (fileInfo.nFileSizeHigh * ((int64_t)(MAXDWORD)+1)) + fileInfo.nFileSizeLow;

    DWORD rem = 0;
    buf->modtime = FileTimeToUnixTime(&fileInfo.ftLastWriteTime, &rem);

    CloseHandle(h);
    return 0;
}
