from __future__ import annotations

import hashlib
import hmac
import secrets

SCRYPT_N = 2**14
SCRYPT_R = 8
SCRYPT_P = 1
SALT_BYTES = 16
KEY_BYTES = 32


def hash_password(password: str) -> str:
    if not password:
        raise ValueError("密码不能为空。")
    salt = secrets.token_bytes(SALT_BYTES)
    derived = hashlib.scrypt(
        password.encode("utf-8"),
        salt=salt,
        n=SCRYPT_N,
        r=SCRYPT_R,
        p=SCRYPT_P,
        dklen=KEY_BYTES,
    )
    return "$".join(
        [
            "scrypt",
            str(SCRYPT_N),
            str(SCRYPT_R),
            str(SCRYPT_P),
            salt.hex(),
            derived.hex(),
        ]
    )


def verify_password(password: str, encoded: str) -> bool:
    try:
        algorithm, n_raw, r_raw, p_raw, salt_hex, expected_hex = encoded.split("$")
        if algorithm != "scrypt":
            return False
        derived = hashlib.scrypt(
            password.encode("utf-8"),
            salt=bytes.fromhex(salt_hex),
            n=int(n_raw),
            r=int(r_raw),
            p=int(p_raw),
            dklen=len(bytes.fromhex(expected_hex)),
        )
    except (TypeError, ValueError):
        return False
    return hmac.compare_digest(derived.hex(), expected_hex)


def generate_session_token() -> str:
    return secrets.token_urlsafe(48)


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


def hash_token(token: str) -> str:
    return hashlib.sha256(token.encode("utf-8")).hexdigest()


def validate_new_password(password: str, username: str = "admin") -> list[str]:
    errors: list[str] = []
    if len(password) < 10:
        errors.append("密码至少需要 10 个字符")
    if password.lower() == username.lower():
        errors.append("密码不能与用户名相同")
    if not any(character.isalpha() for character in password):
        errors.append("密码至少需要包含一个字母")
    if not any(character.isdigit() for character in password):
        errors.append("密码至少需要包含一个数字")
    return errors