import os

import sys

import logging

import pathlib

import platform

from ctypes import c_char

from typing import Optional

from ctypes.util import find_library

if platform.system() == 'Windows':

from ctypes import windll as cdll # type: ignore

else:

from ctypes import cdll

logger = logging.getLogger(__name__)

# regexp for checking if an ipv4 address is valid.

ipv4 = r"^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$"

class ADict(dict):

"""

Accessing dict keys like an attribute.

"""

__getattr__ = dict.__getitem__

__setattr__ = dict.__setitem__ # type: ignore

class Snap7Library:

"""Snap7 loader and encapsulator. We make this a singleton to make

sure the library is loaded only once.

Attributes:

lib_location: full path to the `snap7.dll` file. Optional.

"""

_instance = None

lib_location: Optional[str]

def __new__(cls, *args, **kwargs):

if not cls._instance:

cls._instance = object.__new__(cls)

cls._instance.lib_location = None

cls._instance.cdll = None

return cls._instance

def __init__(self, lib_location: Optional[str] = None):

""" Loads the snap7 library using ctypes cdll.

Args:

lib_location: full path to the `snap7.dll` file. Optional.

Raises:

RuntimeError: if `lib_location` is not found.

"""

if self.cdll: # type: ignore

return

self.lib_location = (lib_location

or self.lib_location

or find_in_package()

or find_library('snap7')

or find_locally('snap7'))

if not self.lib_location:

raise RuntimeError("can't find snap7 library. If installed, try running ldconfig")

self.cdll = cdll.LoadLibrary(self.lib_location)

def load_library(lib_location: Optional[str] = None):

"""Loads the `snap7.dll` library.

Returns:

cdll: a ctypes cdll object with the snap7 shared library loaded.

"""

return Snap7Library(lib_location).cdll

def check_error(code: int, context: str = "client") -> None:

"""Check if the error code is set. If so, a Python log message is generated

and an error is raised.

Args:

code: error code number.

context: context in which is called.

Raises:

RuntimeError: if the code exists and is different from 1.

"""

if code and code != 1:

error = error_text(code, context)

logger.error(error)

raise RuntimeError(error)

def error_text(error, context: str = "client") -> bytes:

"""Returns a textual explanation of a given error number

Args:

error: an error integer

context: context in which is called from, server, client or partner

Returns:

The error.

Raises:

TypeError: if the context is not in `["client", "server", "partner"]`

"""

if context not in ("client", "server", "partner"):

raise TypeError(f"Unkown context {context} used, should be either client, server or partner")

logger.debug(f"error text for {hex(error)}")

len_ = 1024

text_type = c_char * len_

text = text_type()

library = load_library()

if context == "client":

library.Cli_ErrorText(error, text, len_)

elif context == "server":

library.Srv_ErrorText(error, text, len_)

elif context == "partner":

library.Par_ErrorText(error, text, len_)

return text.value

def find_locally(fname: str = "snap7") -> Optional[str]:

"""Finds the `snap7.dll` file in the local project directory.

Args:

fname: file name to search for. Optional.

Returns:

Full path to the `snap7.dll` file.

"""

file = pathlib.Path.cwd() / f"{fname}.dll"

if file.exists():

return str(file)

return None

def find_in_package() -> Optional[str]:

"""Find the `snap7.dll` file according to the os used.

Returns:

Full path to the `snap7.dll` file.

"""

basedir = pathlib.Path(__file__).parent.absolute()

if sys.platform == "darwin":

lib = 'libsnap7.dylib'

elif sys.platform == "win32":

lib = 'snap7.dll'

else:

lib = 'libsnap7.so'

full_path = basedir.joinpath('lib', lib)

if os.path.exists(full_path) and os.path.isfile(full_path):

return str(full_path)

return None