"""Portable RS command helpers from Set_Terminal_28335.

The byte order and CRC match ``DTrans.pas``/``UNiiefa.pas``.  This module is
deliberately UI- and serial-port-independent so desktop and Android clients
can share the same request builders.
"""

from __future__ import annotations


def crc16_modbus(data: bytes, crc: int = 0xFFFF) -> int:
    for byte in data:
        crc ^= byte
        for _ in range(8):
            crc = (crc >> 1) ^ 0xA001 if crc & 1 else crc >> 1
    return crc & 0xFFFF


def with_crc(payload: bytes) -> bytes:
    crc = crc16_modbus(payload)
    return bytes(payload) + crc.to_bytes(2, "little")


def build_read_registers(controller: int, start: int, count: int) -> bytes:
    _range("Адрес контроллера", controller, 0xFF)
    _range("Начальный регистр", start, 0xFFFF)
    if not 1 <= count <= 128 or start + count > 128:
        raise ValueError("Диапазон регистров должен находиться в 0..127")
    return with_crc(bytes((controller, 3)) + start.to_bytes(2, "big")
                    + count.to_bytes(2, "big"))


def build_write_register(controller: int, address: int, value: int) -> bytes:
    _range("Адрес контроллера", controller, 0xFF)
    _range("Адрес регистра", address, 127)
    _range("Значение", value, 0xFFFF)
    return with_crc(bytes((controller, 6)) + address.to_bytes(2, "big")
                    + value.to_bytes(2, "big"))


def build_command(controller: int, command_index: int) -> bytes:
    if not 0 <= command_index <= 16:
        raise ValueError("Номер команды должен быть в диапазоне 0..16")
    value = 1 << command_index if command_index < 16 else 0
    return build_write_register(controller, 127, value)


def expected_read_response_size(count: int) -> int:
    return count * 2 + 5


def decode_read_response(data: bytes, count: int) -> tuple[int, ...]:
    expected = expected_read_response_size(count)
    if len(data) != expected:
        raise ValueError(f"Ожидалось {expected} байт, получено {len(data)}")
    if crc16_modbus(data[:-2]) != int.from_bytes(data[-2:], "little"):
        raise ValueError("Ошибка CRC ответа")
    # Historical replies have a three-byte header; registers are big-endian.
    body = data[3:-2]
    if len(body) != count * 2:
        raise ValueError("Неверная длина данных ответа")
    return tuple(int.from_bytes(body[offset:offset + 2], "big")
                 for offset in range(0, len(body), 2))


def bits_lsb_first(value: int) -> tuple[bool, ...]:
    _range("Значение", value, 0xFFFF)
    return tuple(bool(value & (1 << bit)) for bit in range(16))


def word_from_bits(bits) -> int:
    values = tuple(bool(item) for item in bits)
    if len(values) != 16:
        raise ValueError("Должно быть ровно 16 бит")
    return sum(1 << bit for bit, checked in enumerate(values) if checked)


def signed_word(value: int) -> int:
    _range("Значение", value, 0xFFFF)
    return value if value < 0x8000 else value - 0x10000


def _range(name: str, value: int, maximum: int) -> None:
    if not 0 <= value <= maximum:
        raise ValueError(f"{name} вне диапазона 0..{maximum}")


PROJECT_COMMANDS = {
    "По умолчанию": ("Test", "Def", "Save", "Load", "Calibr", "Calcul", "Secret", "Light", "Raw", "-", "-", "-", "-", "-", "-", "Reset", "Nothing at all"),
    "23470": ("Test", "Def", "Save", "Load", "Calibr", "Read", "Secret", "-", "-", "-", "-", "-", "-", "-", "-", "Reset", "Nothing at all"),
    "23550": ("Test", "Def", "Save", "Load", "Calibr", "Read", "Secret", "Send", "-", "-", "-", "-", "-", "-", "-", "Reset", "Nothing at all"),
    "23550.2": ("Test", "Def", "Save", "Load", "Calibr", "Calcul", "Secret", "Send", "Raw", "Beep", "", "", "", "", "Log", "Reset", "Nothing at all"),
    "ICE 22220.1-3": ("Test", "Zero", "Save", "Def", "Calibr", "Read", "ExtLamp", "ExtLite", "-", "-", "-", "-", "-", "-", "-", "Reset", "Nothing at all"),
    "ICE 22220.4-5": ("Test", "Def", "Save", "Load", "Raw", "Read", "ExtLamp", "ExtLite", "No log", "-", "-", "-", "-", "-", "-", "Reset", "Nothing at all"),
    "Бальзам 161": ("Test", "Zero", "Save", "Def", "Calibr", "Clbr 400", "Stop", "Start", "Init", "Secret", "-", "-", "-", "-", "-", "Reset", "Nothing at all"),
    "Бальзам 162": ("Test", "Def", "Save", "Load", "Calibr", "Secret", "Stop", "Start", "Init", "Tune", "-", "-", "-", "-", "-", "Reset", "Nothing at all"),
    "Бальзам 163": ("Test", "Def", "Save", "Load", "Calibr", "Calcul", "Stop", "Start", "Init", "Tune", "Secret", "-", "-", "-", "-", "Reset", "Nothing at all"),
}