import hashlib
import logging

from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey

logger = logging.getLogger(__name__)

DEVICE_ID_HEX_LENGTH = 16


def generate_device_identity() -> tuple[str, str, str]:
    """生成 Ed25519 设备身份。

    Returns:
        (device_id, public_key_pem, private_key_pem)
    """
    private_key = Ed25519PrivateKey.generate()
    public_key = private_key.public_key()

    public_key_pem = public_key.public_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PublicFormat.SubjectPublicKeyInfo,
    ).decode("utf-8")

    private_key_pem = private_key.private_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PrivateFormat.PKCS8,
        encryption_algorithm=serialization.BestAvailableEncryption(b"yuxi-device-key"),
    ).decode("utf-8")

    device_id = _derive_device_id_from_key(public_key)

    logger.info("Generated device identity: device_id=%s", device_id)
    return device_id, public_key_pem, private_key_pem


def derive_device_id(public_key_pem: str) -> str:
    public_key = serialization.load_pem_public_key(public_key_pem.encode("utf-8"))
    return _derive_device_id_from_key(public_key)


_PRIVATE_KEY_PASSWORD = b"yuxi-device-key"


def sign_challenge(private_key_pem: str, challenge: bytes) -> bytes:
    private_key = serialization.load_pem_private_key(
        private_key_pem.encode("utf-8"),
        password=_PRIVATE_KEY_PASSWORD,
    )
    return private_key.sign(challenge)


def verify_signature(public_key_pem: str, challenge: bytes, signature: bytes) -> bool:
    try:
        public_key = serialization.load_pem_public_key(public_key_pem.encode("utf-8"))
        public_key.verify(signature, challenge)
        return True
    except Exception:
        return False


def _derive_device_id_from_key(public_key) -> str:
    public_key_raw = public_key.public_bytes(
        encoding=serialization.Encoding.Raw,
        format=serialization.PublicFormat.Raw,
    )
    return hashlib.sha256(public_key_raw).hexdigest()[:DEVICE_ID_HEX_LENGTH]