import abc
import collections
import copy
import operator
import re
from typing import (
    NamedTuple,
    Optional,
    Sequence,
    Tuple,
    Type,
    TypeVar,
)

from eth_utils import (
    ValidationError,
    to_dict,
    to_set,
    to_tuple,
)
from eth_utils.toolz import (
    assoc,
    merge,
)

import ssz
from ssz.sedes.base import (
    BaseSedes,
)
from ssz.sedes.container import (
    Container,
)
from ssz.utils import (
    get_duplicates,
)

TSerializable = TypeVar("TSerializable", bound="BaseSerializable")


class Meta(NamedTuple):
    has_fields: bool
    fields: Optional[Tuple[Tuple[str, BaseSedes]]]
    container_sedes: Optional[Container]
    field_names: Optional[Tuple[str, ...]]
    field_attrs: Optional[Tuple[str, ...]]


def validate_args_and_kwargs(args, kwargs, arg_names):
    duplicate_arg_names = get_duplicates(arg_names)
    if duplicate_arg_names:
        raise ValueError("Duplicate argument names: {0}".format(sorted(duplicate_arg_names)))

    needed_arg_names = set(arg_names[len(args):])
    used_arg_names = set(arg_names[:len(args)])

    duplicate_arg_names = used_arg_names.intersection(kwargs.keys())
    if duplicate_arg_names:
        raise TypeError("Duplicate kwargs: {0}".format(sorted(duplicate_arg_names)))

    unknown_arg_names = set(kwargs.keys()).difference(arg_names)
    if unknown_arg_names:
        raise TypeError("Unknown kwargs: {0}".format(sorted(unknown_arg_names)))

    missing_arg_names = set(needed_arg_names).difference(kwargs.keys())
    if missing_arg_names:
        raise TypeError("Missing kwargs: {0}".format(sorted(missing_arg_names)))


@to_tuple
def merge_kwargs_to_args(args, kwargs, arg_names):
    validate_args_and_kwargs(args, kwargs, arg_names)

    needed_arg_names = arg_names[len(args):]

    yield from args
    for arg_name in needed_arg_names:
        yield kwargs[arg_name]


@to_dict
def merge_args_to_kwargs(args, kwargs, arg_names):
    yield from kwargs.items()
    for value, name in zip(args, arg_names):
        yield name, value


class BaseSerializable(collections.Sequence):
    _cached_ssz = None

    def __init__(self, *args, **kwargs):
        arg_names = self._meta.field_names or ()
        validate_args_and_kwargs(args, kwargs, arg_names)
        field_values = merge_kwargs_to_args(args, kwargs, arg_names)

        # Ensure that all the fields have been given values in initialization
        if len(field_values) != len(arg_names):
            raise TypeError(
                'Argument count mismatch. expected {0} - got {1} - missing {2}'.format(
                    len(arg_names),
                    len(field_values),
                    ','.join(arg_names[len(field_values):]),
                )
            )

        for value, attr in zip(field_values, self._meta.field_attrs or ()):
            setattr(self, attr, make_immutable(value))

    def as_dict(self):
        return dict(
            (field, value)
            for field, value
            in zip(self._meta.field_names, self)
        )

    def __iter__(self):
        for attr in self._meta.field_attrs:
            yield getattr(self, attr)

    def __getitem__(self, index):
        if isinstance(index, int):
            attr = self._meta.field_attrs[index]
            return getattr(self, attr)
        elif isinstance(index, slice):
            field_slice = self._meta.field_attrs[index]
            return tuple(getattr(self, field) for field in field_slice)
        elif isinstance(index, str):
            return getattr(self, index)
        else:
            raise IndexError("Unsupported type for __getitem__: {0}".format(type(index)))

    def __len__(self):
        return len(self._meta.fields)

    def __eq__(self, other):
        return self.__class__ is other.__class__ and self.root == other.root

    def __getstate__(self):
        state = self.__dict__.copy()
        # The hash() builtin is not stable across processes
        # (https://docs.python.org/3/reference/datamodel.html#object.__hash__), so we do this here
        # to ensure pickled instances don't carry the cached hash() as that may cause issues like
        # https://github.com/ethereum/py-evm/issues/1318
        state['_hash_cache'] = None
        return state

    _hash_cache = None

    def __hash__(self):
        return hash(self.__class__) * int.from_bytes(self.root, "little")

    def copy(self, *args, **kwargs):
        missing_overrides = set(
            self._meta.field_names
        ).difference(
            kwargs.keys()
        ).difference(
            self._meta.field_names[:len(args)]
        )
        unchanged_kwargs = {
            key: copy.deepcopy(value)
            for key, value
            in self.as_dict().items()
            if key in missing_overrides
        }
        combined_kwargs = dict(**unchanged_kwargs, **kwargs)
        all_kwargs = merge_args_to_kwargs(args, combined_kwargs, self._meta.field_names)
        return type(self)(**all_kwargs)

    def __copy__(self):
        return self.copy()

    def __deepcopy__(self, *args):
        return self.copy()

    _root_cache = None

    @property
    def root(self):
        if self._root_cache is None:
            self._root_cache = ssz.hash_tree_root(self)
        return self._root_cache


def make_immutable(value):
    if isinstance(value, list):
        return tuple(make_immutable(item) for item in value)
    else:
        return value


@to_tuple
def _mk_field_attrs(field_names, extra_namespace):
    namespace = set(field_names).union(extra_namespace)
    for field in field_names:
        while True:
            field = '_' + field
            if field not in namespace:
                namespace.add(field)
                yield field
                break


@to_dict
def _mk_field_props(field_names, field_attrs):
    for field, attr in zip(field_names, field_attrs):
        getter = operator.attrgetter(attr)
        yield field, property(getter)


def _validate_field_names(field_names: Sequence[str]) -> None:
    # check that field names are unique
    duplicate_field_names = get_duplicates(field_names)
    if duplicate_field_names:
        raise TypeError(
            "The following fields are duplicated in the `fields` "
            "declaration: "
            "{0}".format(",".join(sorted(duplicate_field_names)))
        )

    # check that field names are valid identifiers
    invalid_field_names = {
        field_name
        for field_name
        in field_names
        if not _is_valid_identifier(field_name)
    }
    if invalid_field_names:
        raise TypeError(
            "The following field names are not valid python identifiers: {0}".format(
                ",".join("`{0}`".format(item) for item in sorted(invalid_field_names))
            )
        )


IDENTIFIER_REGEX = re.compile(r"^[^\d\W]\w*\Z", re.UNICODE)


def _is_valid_identifier(value):
    # Source: https://stackoverflow.com/questions/5474008/regular-expression-to-confirm-whether-a-string-is-a-valid-identifier-in-python  # noqa: E501
    if not isinstance(value, str):
        return False
    return bool(IDENTIFIER_REGEX.match(value))


@to_set
def _get_class_namespace(cls):
    if hasattr(cls, '__dict__'):
        yield from cls.__dict__.keys()
    if hasattr(cls, '__slots__'):
        yield from cls.__slots__


class MetaSerializable(abc.ABCMeta):
    def __new__(mcls, name, bases, namespace):
        fields_attr_name = "fields"
        declares_fields = fields_attr_name in namespace

        if declares_fields:
            has_fields = True
            fields = namespace.pop(fields_attr_name)
            try:
                sedes = Container(fields)
            except ValidationError as exception:
                # catch empty or duplicate fields and reraise as a TypeError as this would be an
                # invalid class definition
                raise TypeError(exception)

        else:
            serializable_bases = tuple(base for base in bases if isinstance(base, MetaSerializable))
            bases_with_fields = tuple(base for base in serializable_bases if base._meta.has_fields)

            if len(bases_with_fields) == 0:
                has_fields = False
                fields = None
                sedes = None
            elif len(bases_with_fields) == 1:
                has_fields = True
                fields = bases_with_fields[0]._meta.fields
                sedes = bases_with_fields[0]._meta.container_sedes
            else:
                raise TypeError(
                    "Fields need to be declared explicitly as class has multiple `Serializable` "
                    "parents with fields themselves"
                )

        # create the class without any fields as neither the class itself nor any of its ancestors
        # have defined fields
        if not has_fields:
            meta = Meta(
                has_fields=False,
                fields=None,
                container_sedes=None,
                field_names=None,
                field_attrs=None,
            )
            return super().__new__(
                mcls,
                name,
                bases,
                assoc(
                    namespace,
                    "_meta",
                    meta,
                )
            )

        # from here on, we can assume that we've got fields and a sedes object
        if sedes is None:
            raise Exception("Invariant: sedes has been initialized earlier")
        if len(fields) == 0:
            raise Exception("Invariant: number of fields has been checked at initializion of sedes")

        field_names, _ = zip(*fields)
        _validate_field_names(field_names)

        # the actual field values are stored in separate *private* attributes.
        # This computes attribute names that don't conflict with other
        # attributes already present on the class.
        reserved_namespace = set(namespace.keys()).union(
            attr
            for base in bases
            for parent_cls in base.__mro__
            for attr in _get_class_namespace(parent_cls)
        )
        field_attrs = _mk_field_attrs(field_names, reserved_namespace)
        field_props = _mk_field_props(field_names, field_attrs)

        if namespace.keys() & set(field_props.keys()):
            raise Exception(
                "Invariant: field property names have been constructed to not overlap with "
                "existing attributes"
            )

        meta = Meta(
            has_fields=True,
            fields=fields,
            container_sedes=sedes,
            field_names=field_names,
            field_attrs=field_attrs,
        )
        return super().__new__(
            mcls,
            name,
            bases,
            merge(
                namespace,
                field_props,
                {
                    "_meta": meta,
                }
            )
        )

    #
    # Implement BaseSedes methods as pass-throughs to the container sedes
    #
    @property
    def is_static_sized(cls):
        return cls._meta.container_sedes.is_static_sized

    def get_static_size(cls):
        return cls._meta.container_sedes.get_static_size()

    def serialize(cls: Type[TSerializable], value: TSerializable) -> bytes:
        return cls._meta.container_sedes.serialize(value)

    def deserialize(cls: Type[TSerializable], data: bytes) -> TSerializable:
        deserialized_field_dict = cls._meta.container_sedes.deserialize(data)
        return cls(**deserialized_field_dict)

    def deserialize_segment(cls: Type[TSerializable],
                            data: bytes,
                            start_index: int) -> Tuple[TSerializable, int]:
        deserialized_field_dict, continuation_index = cls._meta.container_sedes.deserialize_segment(
            data,
            start_index,
        )
        return cls(**deserialized_field_dict), continuation_index

    def consume_bytes(cls, data: bytes, start_index: int, num_bytes: int) -> Tuple[bytes, int]:
        return cls._meta.container_sedes.consume_bytes(data, start_index, num_bytes)

    def hash_tree_root(cls: Type[TSerializable], value: TSerializable) -> bytes:
        return cls._meta.container_sedes.hash_tree_root(value)


# Make any class created with MetaSerializable an instance of BaseSedes
BaseSedes.register(MetaSerializable)


class Serializable(BaseSerializable, metaclass=MetaSerializable):
    """
    The base class for serializable objects.
    """
    pass
