from fastecdsa import curve as curve_types
from fastecdsa import keys, point
from fastecdsa.encoding.sec1 import SEC1Encoder

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


def infer_local_type(curve: str) -> curve_types.Curve:
    """converts a ``str`` representation of some elliptic curve to a
    representation understood by the backend of this module."""
    if curve == "P-256":
        return curve_types.P256
    else:
        raise NotImplementedError()


class ECCPublicKey(PublicKey):
    def __init__(self, impl: point.Point, curve: curve_types.Curve) -> None:
        self.impl = impl
        self.curve = curve

    def to_bytes(self) -> bytes:
        return SEC1Encoder.encode_public_key(self.impl, compressed=False)

    @classmethod
    def from_bytes(cls, data: bytes, curve: str) -> "ECCPublicKey":
        curve_type = infer_local_type(curve)
        public_key_impl = SEC1Encoder.decode_public_key(data, curve_type)
        return cls(public_key_impl, curve_type)

    def get_type(self) -> KeyType:
        return KeyType.ECC_P256

    def verify(self, data: bytes, signature: bytes) -> bool:
        raise NotImplementedError


class ECCPrivateKey(PrivateKey):
    def __init__(self, impl: int, curve: curve_types.Curve) -> None:
        self.impl = impl
        self.curve = curve

    @classmethod
    def new(cls, curve: str) -> "ECCPrivateKey":
        curve_type = infer_local_type(curve)
        private_key_impl = keys.gen_private_key(curve_type)
        return cls(private_key_impl, curve_type)

    def to_bytes(self) -> bytes:
        return keys.export_key(self.impl, self.curve)

    def get_type(self) -> KeyType:
        return KeyType.ECC_P256

    def sign(self, data: bytes) -> bytes:
        raise NotImplementedError

    def get_public_key(self) -> PublicKey:
        public_key_impl = keys.get_public_key(self.impl, self.curve)
        return ECCPublicKey(public_key_impl, self.curve)


def create_new_key_pair(curve: str) -> KeyPair:
    """Return a new ECC keypair with the requested ``curve`` type, e.g.
    "P-256"."""
    private_key = ECCPrivateKey.new(curve)
    public_key = private_key.get_public_key()
    return KeyPair(private_key, public_key)