from Crypto.Hash import SHA256
from nacl.exceptions import BadSignatureError
from nacl.public import PrivateKey as PrivateKeyImpl
from nacl.public import PublicKey as PublicKeyImpl
from nacl.signing import SigningKey, VerifyKey
import nacl.utils as utils

from libp2p.crypto.keys import KeyPair, KeyType, PrivateKey, PublicKey


class Ed25519PublicKey(PublicKey):
    def __init__(self, impl: PublicKeyImpl) -> None:
        self.impl = impl

    def to_bytes(self) -> bytes:
        return bytes(self.impl)

    @classmethod
    def from_bytes(cls, key_bytes: bytes) -> "Ed25519PublicKey":
        return cls(PublicKeyImpl(key_bytes))

    def get_type(self) -> KeyType:
        return KeyType.Ed25519

    def verify(self, data: bytes, signature: bytes) -> bool:
        verify_key = VerifyKey(self.to_bytes())
        h = SHA256.new(data)
        try:
            verify_key.verify(h, signature)
        except BadSignatureError:
            return False
        return True


class Ed25519PrivateKey(PrivateKey):
    def __init__(self, impl: PrivateKeyImpl) -> None:
        self.impl = impl

    @classmethod
    def new(cls, seed: bytes = None) -> "Ed25519PrivateKey":
        if not seed:
            seed = utils.random()

        private_key_impl = PrivateKeyImpl.from_seed(seed)
        return cls(private_key_impl)

    def to_bytes(self) -> bytes:
        return bytes(self.impl)

    @classmethod
    def from_bytes(cls, data: bytes) -> "Ed25519PrivateKey":
        impl = PrivateKeyImpl(data)
        return cls(impl)

    def get_type(self) -> KeyType:
        return KeyType.Ed25519

    def sign(self, data: bytes) -> bytes:
        h = SHA256.new(data)
        signing_key = SigningKey(self.to_bytes())
        return signing_key.sign(h)

    def get_public_key(self) -> PublicKey:
        return Ed25519PublicKey(self.impl.public_key)


def create_new_key_pair(seed: bytes = None) -> KeyPair:
    private_key = Ed25519PrivateKey.new(seed)
    public_key = private_key.get_public_key()
    return KeyPair(private_key, public_key)