filemon.nim

import winlean, os, asyncdispatch

# Put in Winlean
type
  LPOVERLAPPED_COMPLETION_ROUTINE* = proc (para1: DWORD, para2: DWORD,
      para3: ptr TOVERLAPPED){.stdcall.}

const FILE_LIST_DIRECTORY* = 0x00000001 # directory
const
  FILE_NOTIFY_CHANGE_FILE_NAME* = 0x00000001.dword
  FILE_NOTIFY_CHANGE_DIR_NAME* = 0x00000002.dword
  FILE_NOTIFY_CHANGE_ATTRIBUTES* = 0x00000004.dword
  FILE_NOTIFY_CHANGE_SIZE* = 0x00000008.dword
  FILE_NOTIFY_CHANGE_LAST_WRITE* = 0x00000010.dword
  FILE_NOTIFY_CHANGE_LAST_ACCESS* = 0x00000020.dword
  FILE_NOTIFY_CHANGE_CREATION* = 0x00000040.dword
  FILE_NOTIFY_CHANGE_SECURITY* = 0x00000100.dword

proc ReadDirectoryChangesW*(
  hDirectory: THandle,
  lpBuffer: pointer,
  nBufferLength: dword,
  bWatchSubtree: WINBOOL,
  dwNotifyFilter: dword,
  lpBytesReturned: PDWORD,
  lpOverlapped: POverlapped,
  lpCompletionRoutine: LPOVERLAPPED_COMPLETION_ROUTINE
): WINBOOL {.stdcall, importc: "ReadDirectoryChangesW", dynlib: "Kernel32.dll".}
# End


# Associate a directory handle with an IO completion port
# Create a buffer to store file changes
# Call the ReadDirectoryChanges 
proc openAsyncHandle(path: string, followSymlink=true): TAsyncFD =
  var flags = (FILE_FLAG_BACKUP_SEMANTICS or
               FILE_FLAG_OVERLAPPED)
  if not followSymlink:
    flags = flags or FILE_FLAG_OPEN_REPARSE_POINT

  when useWinUnicode:
    result = createFileW(
      newWideCString(path), FILE_LIST_DIRECTORY, 
      FILE_SHARE_DELETE or FILE_SHARE_READ or FILE_SHARE_WRITE,
      nil, OPEN_EXISTING, flags, 0
      ).TAsyncFD
  else:
    result = createFileA(
      path, FILE_LIST_DIRECTORY, 
      FILE_SHARE_DELETE or FILE_SHARE_READ or FILE_SHARE_WRITE,
      nil, OPEN_EXISTING, flags, 0
      ).TAsyncFD
  if result == INVALID_HANDLE_VALUE.TAsyncFD:
    osError(osLastError())

proc main =
  var
    dirName = r"C:\Users\Clay\Projects\Nimrod-Scripts\pathstuff\"
    dirHandle = openAsyncHandle(dirName)
    aligned: tuple [alignIt: int32, buffer: array [2000, byte]]
    bufferLen: int32 = aligned.buffer.len().int32
    filterFlags = (FILE_NOTIFY_CHANGE_FILE_NAME or
                   FILE_NOTIFY_CHANGE_DIR_NAME or
                   FILE_NOTIFY_CHANGE_ATTRIBUTES or
                   FILE_NOTIFY_CHANGE_SIZE
                   )
    ol = cast[PCustomOverlapped](alloc0(sizeof(TCustomOverlapped)))

  ol.data = TCompletionData(sock: dirHandle, cb:
      proc (sock: TAsyncFD, bytesCount: DWord, errcode: TOSErrorCode) =
        sock.repr.echo
        bytesCount.echo
        errcode.echo
    )

  dirHandle.register()
  osLastError().echo
  let r = ReadDirectoryChangesW(dirHandle.THandle,
                              addr aligned.buffer[0],
                              bufferLen,
                              true.winbool,
                              filterFlags,
                              cast[ptr dword](nil),
                              cast[POverlapped](ol),
                              cast[LPOVERLAPPED_COMPLETION_ROUTINE](nil)
                              )
  osLastError().echo()
  if r == 0:
    osError(osLastError())
  while true:
    poll()

when isMainModule:
  main()