from typing import (
    cast,
    overload,
)

import rlp
from rlp.sedes import (
    big_endian_int,
    Binary,
    binary,
)

from eth_typing import (
    Address,
    BlockNumber,
    Hash32,
)

from eth_hash.auto import keccak

from eth_utils import (
    encode_hex,
)

from eth._utils.headers import (
    new_timestamp_from_parent,
)
from eth.abc import (
    BlockHeaderAPI,
    MiningHeaderAPI,
)
from eth.constants import (
    ZERO_ADDRESS,
    ZERO_HASH32,
    EMPTY_UNCLE_HASH,
    GENESIS_NONCE,
    GENESIS_PARENT_HASH,
    BLANK_ROOT_HASH,
)
from eth.typing import HeaderParams

from .sedes import (
    address,
    hash32,
    uint256,
    trie_root,
)


class MiningHeader(rlp.Serializable, MiningHeaderAPI):
    fields = [
        ('parent_hash', hash32),
        ('uncles_hash', hash32),
        ('coinbase', address),
        ('state_root', trie_root),
        ('transaction_root', trie_root),
        ('receipt_root', trie_root),
        ('bloom', uint256),
        ('difficulty', big_endian_int),
        ('block_number', big_endian_int),
        ('gas_limit', big_endian_int),
        ('gas_used', big_endian_int),
        ('timestamp', big_endian_int),
        ('extra_data', binary),
    ]


class BlockHeader(rlp.Serializable, BlockHeaderAPI):
    fields = [
        ('parent_hash', hash32),
        ('uncles_hash', hash32),
        ('coinbase', address),
        ('state_root', trie_root),
        ('transaction_root', trie_root),
        ('receipt_root', trie_root),
        ('bloom', uint256),
        ('difficulty', big_endian_int),
        ('block_number', big_endian_int),
        ('gas_limit', big_endian_int),
        ('gas_used', big_endian_int),
        ('timestamp', big_endian_int),
        ('extra_data', binary),
        ('mix_hash', binary),
        ('nonce', Binary(8, allow_empty=True))
    ]

    @overload
    def __init__(self, **kwargs: HeaderParams) -> None:
        ...

    @overload  # noqa: F811
    def __init__(self,
                 difficulty: int,
                 block_number: BlockNumber,
                 gas_limit: int,
                 timestamp: int = None,
                 coinbase: Address = ZERO_ADDRESS,
                 parent_hash: Hash32 = ZERO_HASH32,
                 uncles_hash: Hash32 = EMPTY_UNCLE_HASH,
                 state_root: Hash32 = BLANK_ROOT_HASH,
                 transaction_root: Hash32 = BLANK_ROOT_HASH,
                 receipt_root: Hash32 = BLANK_ROOT_HASH,
                 bloom: int = 0,
                 gas_used: int = 0,
                 extra_data: bytes = b'',
                 mix_hash: Hash32 = ZERO_HASH32,
                 nonce: bytes = GENESIS_NONCE) -> None:
        ...

    def __init__(self,              # type: ignore  # noqa: F811
                 difficulty: int,
                 block_number: BlockNumber,
                 gas_limit: int,
                 timestamp: int = None,
                 coinbase: Address = ZERO_ADDRESS,
                 parent_hash: Hash32 = ZERO_HASH32,
                 uncles_hash: Hash32 = EMPTY_UNCLE_HASH,
                 state_root: Hash32 = BLANK_ROOT_HASH,
                 transaction_root: Hash32 = BLANK_ROOT_HASH,
                 receipt_root: Hash32 = BLANK_ROOT_HASH,
                 bloom: int = 0,
                 gas_used: int = 0,
                 extra_data: bytes = b'',
                 mix_hash: Hash32 = ZERO_HASH32,
                 nonce: bytes = GENESIS_NONCE) -> None:
        if timestamp is None:
            if parent_hash == ZERO_HASH32:
                timestamp = new_timestamp_from_parent(None)
            else:
                # without access to the parent header, we cannot select a new timestamp correctly
                raise ValueError("Must set timestamp explicitly if this is not a genesis header")

        super().__init__(
            parent_hash=parent_hash,
            uncles_hash=uncles_hash,
            coinbase=coinbase,
            state_root=state_root,
            transaction_root=transaction_root,
            receipt_root=receipt_root,
            bloom=bloom,
            difficulty=difficulty,
            block_number=block_number,
            gas_limit=gas_limit,
            gas_used=gas_used,
            timestamp=timestamp,
            extra_data=extra_data,
            mix_hash=mix_hash,
            nonce=nonce,
        )

    def __str__(self) -> str:
        return f'<BlockHeader #{self.block_number} {encode_hex(self.hash)[2:10]}>'

    _hash = None

    @property
    def hash(self) -> Hash32:
        if self._hash is None:
            self._hash = keccak(rlp.encode(self))
        return cast(Hash32, self._hash)

    @property
    def mining_hash(self) -> Hash32:
        result = keccak(rlp.encode(self[:-2], MiningHeader))
        return cast(Hash32, result)

    @property
    def hex_hash(self) -> str:
        return encode_hex(self.hash)

    @property
    def is_genesis(self) -> bool:
        # if removing the block_number == 0 test, consider the validation consequences.
        # validate_header stops trying to check the current header against a parent header.
        # Can someone trick us into following a high difficulty header with genesis parent hash?
        return self.parent_hash == GENESIS_PARENT_HASH and self.block_number == 0

    @property
    def base_fee_per_gas(self) -> int:
        raise AttributeError("Base fee per gas not available until London fork")