from __future__ import annotations

import hashlib
import hmac
import re
import secrets
from datetime import UTC, datetime, timedelta
from pathlib import Path

from app.core.config import get_settings


def utc_now() -> datetime:
    return datetime.now(UTC)


def token_urlsafe(length: int = 32) -> str:
    return secrets.token_urlsafe(length)


def short_code(length: int = 6) -> str:
    alphabet = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ"
    return "".join(secrets.choice(alphabet) for _ in range(length))


def hash_token(raw_token: str) -> str:
    settings = get_settings()
    return hmac.new(settings.session_secret.encode("utf-8"), raw_token.encode("utf-8"), hashlib.sha256).hexdigest()


def constant_time_equal(left: str, right: str) -> bool:
    return hmac.compare_digest(left, right)


def session_expiry(days: int = 30) -> datetime:
    return utc_now() + timedelta(days=days)


def sanitize_filename(filename: str) -> str:
    cleaned = Path(filename).name.strip().replace("\x00", "")
    cleaned = re.sub(r"[^A-Za-z0-9._ -]+", "_", cleaned)
    cleaned = re.sub(r"\s+", " ", cleaned).strip(" .")
    return cleaned[:180] or "upload.bin"