"""Renderer-independent comparison of arbitrary binary files."""
from __future__ import annotations

from dataclasses import dataclass
import hashlib


def compare_sha256(image: bytes, readback: bytes):
    """Compare a complete physical readback against an immutable BIN snapshot."""
    if not image or len(image) != len(readback):
        raise ValueError('Для SHA-256 нужен полный прочитанный диапазон размером с BIN.')
    expected = hashlib.sha256(image).hexdigest()
    actual = hashlib.sha256(readback).hexdigest()
    return expected == actual, expected, actual


@dataclass(frozen=True)
class Comparison:
    left: bytes
    right: bytes
    offsets: tuple[int, ...]
    changed_bits: int

    @property
    def changed_bytes(self) -> int:
        return len(self.offsets)

    @property
    def size(self) -> int:
        return max(len(self.left), len(self.right))


def compare(left: bytes, right: bytes) -> Comparison:
    """Count bit differences in overlap; unmatched bytes count as changed bytes."""
    common = min(len(left), len(right))
    offsets = tuple(i for i in range(common) if left[i] != right[i])
    bits = sum(bin(left[i] ^ right[i]).count('1') for i in offsets)
    return Comparison(left, right, offsets + tuple(range(common, max(len(left), len(right)))), bits)


@dataclass(frozen=True)
class MultiComparison:
    images: tuple[bytes, ...]
    offsets: tuple[int, ...]
    pairs: tuple

    @property
    def size(self): return max(map(len, self.images))

    @property
    def changed_bytes(self): return len(self.offsets)


def compare_many(images):
    """Highlight offsets where any pair differs, including missing bytes."""
    images = tuple(images)
    if len(images) not in (1, 2, 3):
        raise ValueError('Выберите от 1 до 3 BIN-файлов.')
    if len(images) == 2:
        return compare(*images)
    pairs = tuple((a, b, compare(images[a], images[b]))
                  for a in range(len(images)) for b in range(a + 1, len(images)))
    offsets = tuple(sorted({offset for _, _, result in pairs for offset in result.offsets}))
    return MultiComparison(images, offsets, pairs)