"""Password hashing and opaque token generation.

CLAUDE.md invariant #5: secrets never leave the server. Nothing in this file is ever included in
a Pydantic response model — that's enforced by schemas/auth.py simply not declaring these fields,
not by anything here, so double-check any new response schema doesn't accidentally add one back.
"""

import hashlib
import secrets

from argon2 import PasswordHasher
from argon2.exceptions import VerifyMismatchError

# t=3, m=64MiB, p=4 — matches docs/PLAN.md's stated parameters exactly.
_hasher = PasswordHasher(time_cost=3, memory_cost=64 * 1024, parallelism=4)


def hash_password(password: str) -> str:
    return _hasher.hash(password)


def verify_password(password: str, password_hash: str) -> bool:
    try:
        return _hasher.verify(password_hash, password)
    except VerifyMismatchError:
        return False


def generate_token() -> tuple[str, bytes]:
    """Return (opaque_token_to_hand_to_the_client, sha256_digest_to_store).

    The raw token is returned to the caller exactly once and is never persisted anywhere —
    only its digest is stored, so a database leak doesn't hand out working session tokens.
    """
    raw = secrets.token_urlsafe(32)
    digest = hashlib.sha256(raw.encode("ascii")).digest()
    return raw, digest


def hash_token(raw_token: str) -> bytes:
    """Recompute the digest of a client-presented token, for lookup by token_hash."""
    return hashlib.sha256(raw_token.encode("ascii")).digest()


def hash_invite_code(code: str) -> bytes:
    return hashlib.sha256(code.encode("ascii")).digest()