"""Packets and constants for the STM32 system-memory UART bootloader (AN3155)."""

from __future__ import annotations

ACK = 0x79
NACK = 0x1F
SYNC = b"\x7f"


def command(code: int) -> bytes:
    """Encode an AN3155 command and its one's-complement checksum."""
    if not 0 <= code <= 0xFF:
        raise ValueError("Код команды вне диапазона байта")
    return bytes((code, code ^ 0xFF))


def address(value: int) -> bytes:
    """Encode a big-endian 32-bit address followed by XOR checksum."""
    if not 0 <= value <= 0xFFFFFFFF:
        raise ValueError("Адрес вне диапазона u32")
    raw = value.to_bytes(4, "big")
    return raw + bytes((raw[0] ^ raw[1] ^ raw[2] ^ raw[3],))


def write_payload(data: bytes) -> bytes:
    """Encode one Write Memory payload (1..256 bytes)."""
    if not 1 <= len(data) <= 256:
        raise ValueError("Блок STM32 должен содержать от 1 до 256 байт")
    count = len(data) - 1
    checksum = count
    for value in data:
        checksum ^= value
    return bytes((count,)) + data + bytes((checksum,))


MASS_ERASE = b"\xff\x00"


def erase_pages_payload(pages: list[int]) -> bytes:
    """Encode the standard Erase Memory page list used by STM32F1."""
    if not pages or len(pages) > 256 or any(not 0 <= page <= 0xFF for page in pages):
        raise ValueError("Список страниц STM32 должен содержать 1..256 номеров")
    body = bytes((len(pages) - 1, *pages))
    checksum = 0
    for value in body:
        checksum ^= value
    return body + bytes((checksum,))