import hashlib
from typing import Union

import base58
import multihash

from libp2p.crypto.keys import PublicKey

# NOTE: On inlining...
# See: https://github.com/libp2p/specs/issues/138
# NOTE: enabling to be interoperable w/ the Go implementation
ENABLE_INLINING = True
MAX_INLINE_KEY_LENGTH = 42

IDENTITY_MULTIHASH_CODE = 0x00

if ENABLE_INLINING:

    class IdentityHash:
        _digest: bytes

        def __init__(self) -> None:
            self._digest = bytearray()

        def update(self, input: bytes) -> None:
            self._digest += input

        def digest(self) -> bytes:
            return self._digest

    multihash.FuncReg.register(
        IDENTITY_MULTIHASH_CODE, "identity", hash_new=lambda: IdentityHash()
    )


class ID:
    _bytes: bytes
    _xor_id: int = None
    _b58_str: str = None

    def __init__(self, peer_id_bytes: bytes) -> None:
        self._bytes = peer_id_bytes

    @property
    def xor_id(self) -> int:
        if not self._xor_id:
            self._xor_id = int(sha256_digest(self._bytes).hex(), 16)
        return self._xor_id

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

    def to_base58(self) -> str:
        if not self._b58_str:
            self._b58_str = base58.b58encode(self._bytes).decode()
        return self._b58_str

    def __repr__(self) -> str:
        return f"<libp2p.peer.id.ID ({self!s})>"

    __str__ = pretty = to_string = to_base58

    def __eq__(self, other: object) -> bool:
        if isinstance(other, str):
            return self.to_base58() == other
        elif isinstance(other, bytes):
            return self._bytes == other
        elif isinstance(other, ID):
            return self._bytes == other._bytes
        else:
            return NotImplemented

    def __hash__(self) -> int:
        return hash(self._bytes)

    @classmethod
    def from_base58(cls, b58_encoded_peer_id_str: str) -> "ID":
        peer_id_bytes = base58.b58decode(b58_encoded_peer_id_str)
        pid = ID(peer_id_bytes)
        return pid

    @classmethod
    def from_pubkey(cls, key: PublicKey) -> "ID":
        serialized_key = key.serialize()
        algo = multihash.Func.sha2_256
        if ENABLE_INLINING and len(serialized_key) <= MAX_INLINE_KEY_LENGTH:
            algo = IDENTITY_MULTIHASH_CODE
        mh_digest = multihash.digest(serialized_key, algo)
        return cls(mh_digest.encode())


def sha256_digest(data: Union[str, bytes]) -> bytes:
    if isinstance(data, str):
        data = data.encode("utf8")
    return hashlib.sha256(data).digest()