from __future__ import annotations

import hashlib
import re
from typing import List, Tuple

def sha256_file_bytes_iter(f, chunk_size: int = 1024 * 1024) -> str:
    h = hashlib.sha256()
    for chunk in iter(lambda: f.read(chunk_size), b""):
        h.update(chunk)
    return h.hexdigest()

def sha256_file(path) -> str:
    with open(path, "rb") as f:
        return sha256_file_bytes_iter(f)

def sha1_str(s: str) -> str:
    return hashlib.sha1(s.encode("utf-8", errors="ignore")).hexdigest()

def simhash64(text: str) -> int:
    tokens = re.findall(r"[a-zA-Z0-9_#+./-]{2,}", text.lower())
    if not tokens:
        return 0
    v = [0] * 64
    for tok in tokens:
        h = hashlib.md5(tok.encode("utf-8")).digest()
        x = int.from_bytes(h[:8], "big", signed=False)
        for i in range(64):
            v[i] += 1 if ((x >> i) & 1) else -1
    out = 0
    for i in range(64):
        if v[i] > 0:
            out |= (1 << i)
    return out

def hamming64(a: int, b: int) -> int:
    return (a ^ b).bit_count()

def simhash_bands(x: int) -> List[Tuple[int, int]]:
    # 4 bands x 16 bits
    return [(((x >> (band * 16)) & 0xFFFF), band) for band in range(4)]