import base64
import hashlib
import hmac
import secrets

PBKDF2_ITERATIONS = 260_000
PASSWORD_HASH_PREFIX = "pbkdf2_sha256"


def hash_password(password: str) -> str:
    salt = secrets.token_bytes(16)
    digest = hashlib.pbkdf2_hmac(
        "sha256",
        password.encode("utf-8"),
        salt,
        PBKDF2_ITERATIONS)
    return "$".join(
        [
            PASSWORD_HASH_PREFIX,
            str(PBKDF2_ITERATIONS),
            base64.b64encode(salt).decode("ascii"),
            base64.b64encode(digest).decode("ascii"),
        ]
    )


def verify_password(password: str, password_hash: str | None) -> bool:
    if not password_hash:
        return False

    try:
        algorithm, iterations_raw, salt_raw, digest_raw = password_hash.split("$", 3)
        if algorithm != PASSWORD_HASH_PREFIX:
            return False
        iterations = int(iterations_raw)
        salt = base64.b64decode(salt_raw.encode("ascii"))
        expected_digest = base64.b64decode(digest_raw.encode("ascii"))
    except (ValueError, TypeError):
        return False

    actual_digest = hashlib.pbkdf2_hmac(
        "sha256",
        password.encode("utf-8"),
        salt,
        iterations)
    return hmac.compare_digest(actual_digest, expected_digest)