"""Argon2id password hashing (SPEC §6.1, §10.1).

Params are fixed: ``time_cost=3``, ``memory_cost=64 MiB``, ``parallelism=4``.
No other password hashing is permitted anywhere (SPEC §10.1).
"""

from __future__ import annotations

from argon2 import PasswordHasher
from argon2.exceptions import VerificationError, VerifyMismatchError

_hasher = PasswordHasher(
    time_cost=3,
    memory_cost=64 * 1024,  # KiB -> 64 MiB
    parallelism=4,
)


def hash_password(password: str) -> str:
    """Return an argon2id hash for ``password``."""
    return _hasher.hash(password)


def verify_password(password_hash: str, password: str) -> bool:
    """Constant-time verify ``password`` against ``password_hash``."""
    try:
        return _hasher.verify(password_hash, password)
    except (VerifyMismatchError, VerificationError):
        return False


def needs_rehash(password_hash: str) -> bool:
    """Return True if ``password_hash`` was made with outdated parameters."""
    return _hasher.check_needs_rehash(password_hash)