"""Thin binding to the Balsam-167 physical EEPROM reader in the shared C core.

No address conversion, endian/CRC codec or memory-size inference in this port.
The caller owns serial scheduling, timeouts, cancellation and dump file storage.
"""
import ctypes as ct
from .native import get_native_protocol, NativeProtocolUnavailable


class _State(ct.Structure):
    _fields_ = [(name, ct.c_uint32) for name in ("controller", "start", "length", "received")]


def _api(name, args, result):
    try:
        function = getattr(get_native_protocol().lib, "pcan_abi_periph28335_eeprom_" + name)
    except AttributeError as error:
        raise NativeProtocolUnavailable("Обновите templates/setprotocol.dll: нет API чтения EEPROM 167") from error
    function.argtypes, function.restype = args, result
    return function


def capacity():
    return int(_api("capacity", [], ct.c_uint32)())


class Reader:
    def __init__(self, controller, start, length):
        for value in (controller, start, length):
            if type(value) is not int or not 0 <= value <= 0xffffffff:
                raise ValueError("Адрес и длина должны быть неотрицательными целыми числами")
        self._state = _State()
        result = _api("begin", [ct.c_void_p, ct.c_uint32, ct.c_uint32, ct.c_uint32], ct.c_int)(
            ct.byref(self._state), controller, start, length)
        if result:
            raise ValueError("Диапазон вне EEPROM AT25256B: 0…0x7FFF байт; длина должна быть больше нуля")

    @property
    def received(self): return int(self._state.received)
    @property
    def length(self): return int(self._state.length)
    @property
    def start(self): return int(self._state.start)

    def request(self):
        output = ct.create_string_buffer(8)
        size = _api("request", [ct.c_void_p, ct.c_void_p, ct.c_size_t], ct.c_size_t)(
            ct.byref(self._state), output, len(output))
        return output.raw[:size]

    def accept(self, reply):
        output = ct.create_string_buffer(2)
        reply = bytes(reply)
        size = _api("accept", [ct.c_void_p, ct.c_void_p, ct.c_size_t, ct.c_void_p, ct.c_size_t], ct.c_int)(
            ct.byref(self._state), reply, len(reply), output, len(output))
        if size < 0:
            errors = {-3: "Неверная длина ответа EEPROM", -4: "Ошибка CRC ответа EEPROM",
                      -5: "Неверный адрес контроллера или команда ответа EEPROM"}
            raise ValueError(errors.get(size, "Ответ EEPROM не соответствует активному чтению"))
        return output.raw[:size]