from ctypes import (
    CDLL,
    CFUNCTYPE,
    POINTER,
    Structure,
    byref,
    c_char,
    c_char_p,
    c_int,
    c_longlong,
    c_size_t,
    c_ulonglong,
    c_void_p,
    cast,
)
from typing import Any, Iterator, List, Optional, Tuple


class DataError(Structure):
    """The C type that represents a tuple of data and error (both strings) as returned by the Go library

    :meta private:
    """

    _fields_ = [("data", c_void_p), ("error", c_void_p)]


class HandlerError(Structure):
    """The C type that represents a tuple of a CGO handler and error (string) as returned by the Go library

    :meta private:
    """

    _fields_ = [("handler", c_int), ("error", c_void_p)]


class BoolError(Structure):
    """The C type that represents a tuple of boolean and error as returned by the Go library

    :meta private:
    """

    _fields_ = [("boolean", c_int), ("error", c_void_p)]


# The type for a Go state change callback
VPNStateChange = CFUNCTYPE(c_int, c_int, c_int, c_char_p)
ProxySetup = CFUNCTYPE(c_void_p, c_int)
ReadRxBytes = CFUNCTYPE(c_ulonglong)
TokenGetter = CFUNCTYPE(c_void_p, c_char_p, c_int, POINTER(c_char), c_size_t)
TokenSetter = CFUNCTYPE(c_void_p, c_char_p, c_int, c_char_p)


def conv_longlongp(val: Optional[int]) -> POINTER(c_longlong):
    if val is None:
        return None
    return byref(c_longlong(val))


def encode_args(args: List[Any], types: List[Any]) -> Iterator[Any]:
    """Encode the arguments ready to be used by the Go library

    :param args: List[Any]: The list of arguments
    :param types: List[Any]: The list of the types of the arguments

    :meta private:

    :return: The arg generator
    :rtype: Iterator[Any]
    """
    for arg, t in zip(args, types):
        # c_char_p needs the str to be encoded to bytes
        encode_map = {
            c_char_p: lambda x: x.encode("utf-8"),
            POINTER(c_longlong): conv_longlongp,
        }
        if t in encode_map:
            arg = encode_map[t](arg)
        yield arg


def decode_res(res: Any) -> Any:
    """Decode a result as obtained by the Go library

    :param res: Any: The result

    :meta private:

    :return: The argument decoded
    :rtype: Any
    """
    decode_map = {
        c_void_p: get_ptr_string,
        HandlerError: get_handler_error,
        DataError: get_data_error,
        BoolError: get_bool_error,
    }
    return decode_map.get(res, lambda lib, x: x)


def get_ptr_string(lib: CDLL, ptr: c_void_p) -> str:
    """Convert a C string pointer to a Python usable string.
    This makes sure to free all memory allocated by the Go library

    :param lib: CDLL: The Go shared library
    :param ptr: c_void_p: The pointer to the C string

    :meta private:

    :return: The string converted to Python
    :rtype: str
    """
    if ptr:
        string = cast(ptr, c_char_p).value
        lib.FreeString(ptr)
        if string:
            return string.decode("utf-8")
    return ""


def get_data_error(lib: CDLL, data_error: DataError) -> Tuple[str, str]:
    """Convert a C data+error structure to a Python usable data+error structure

    :param lib: CDLL: The Go shared library
    :param data_error: DataError: The data error C structure

    :meta private:

    :return: The data and error
    :rtype: Tuple[str, str]
    """
    data = get_ptr_string(lib, data_error.data)
    error = get_ptr_string(lib, data_error.error)
    return data, error


def get_handler_error(lib: CDLL, handler_error: HandlerError) -> Tuple[int, str]:
    """Convert a C handler+error structure to a Python usable handler+error structure

    :param lib: CDLL: The Go shared library
    :param handler_error: HandlerError: The handler error C structure

    :meta private:

    :return: The handler and error
    :rtype: Tuple[int, str]
    """
    handler = int(handler_error.handler)
    error = get_ptr_string(lib, handler_error.error)
    return handler, error


def get_bool_error(lib: CDLL, bool_error: BoolError) -> Tuple[bool, str]:
    """Convert a C boolean (c int)+error structure to a Python usable boolean+error structure

    :param lib: CDLL: The Go shared library
    :param bool_error: BoolError: The boolean and error C structure

    :meta private:

    :return: The bool and error
    :rtype: Tuple[bool, str]
    """
    boolean = get_bool(lib, bool_error.boolean)
    error = get_ptr_string(lib, bool_error.error)
    return boolean, error


def get_bool(lib: CDLL, boolInt: c_int) -> bool:
    """Get a bool from the Go shared library. Essentially just checking if an int represents 'True'

    :param lib: CDLL: The Go shared library
    :param boolInt: c_int: The C integer that needs to be converted to the Python bool

    :meta private:

    :return: The boolean converted to Python
    :rtype: bool
    """
    return int(boolInt) != 0