"""Хеширование паролей (PBKDF2-SHA256, без внешних зависимостей)."""

from __future__ import annotations

import hashlib
import hmac
import secrets


_ITERATIONS = 210_000
_SALT_BYTES = 16
_DKLEN = 32


def hash_password(password: str) -> str:
    salt = secrets.token_bytes(_SALT_BYTES)
    digest = hashlib.pbkdf2_hmac(
        "sha256",
        password.encode("utf-8"),
        salt,
        _ITERATIONS,
        dklen=_DKLEN,
    )
    return f"pbkdf2_sha256${_ITERATIONS}${salt.hex()}${digest.hex()}"


def verify_password(password: str, password_hash: str) -> bool:
    try:
        algo, iters_s, salt_hex, digest_hex = password_hash.split("$", 3)
        if algo != "pbkdf2_sha256":
            return False
        iterations = int(iters_s)
        salt = bytes.fromhex(salt_hex)
        expected = bytes.fromhex(digest_hex)
    except (ValueError, TypeError):
        return False

    got = hashlib.pbkdf2_hmac(
        "sha256",
        password.encode("utf-8"),
        salt,
        iterations,
        dklen=len(expected),
    )
    return hmac.compare_digest(got, expected)


def new_session_token() -> str:
    return secrets.token_urlsafe(32)