import abc
import dataclasses
import datetime
from collections.abc import Iterable, Mapping
from decimal import Decimal

import enforce_typing
from fin_defs import Asset


@enforce_typing.enforce_types
@dataclasses.dataclass
class Depo(abc.ABC):
    """A depository tracking some amount of assets.

    Depo can either be DepoSingle, which is the base layer of the depository
    structure, or nested in DepoGroup, which allows for a complex hierarcy of
    depositories.

    The depository structure exposed by each backend depends upon the logical
    structure of the relevant service and the API of this service.
    """

    name: str
    updated_time: datetime.datetime

    @abc.abstractmethod
    def assets(self) -> Iterable[Asset]:
        """Returns the different assets managed by this depo."""

    @abc.abstractmethod
    def get_amount_of_asset(self, asset: Asset) -> Decimal:
        """Returns the amount of owned assets for all nested depos.

        Must return 0 if depo does not contain the given asset.
        """


@enforce_typing.enforce_types
@dataclasses.dataclass
class DepoSingle(Depo):
    """Base level of depository."""

    _assets: Mapping[Asset, Decimal]

    def assets(self) -> Iterable[Asset]:
        return self._assets

    def get_amount_of_asset(self, asset: Asset) -> Decimal:
        return self._assets.get(asset, Decimal(0))


@enforce_typing.enforce_types
@dataclasses.dataclass
class DepoGroup(Depo):
    """Nested depository."""

    nested: list[Depo]

    def assets(self) -> Iterable[Asset]:
        assets: list[Asset] = []
        for nested_depo in self.nested:
            assets.extend(nested_depo.assets())
        return assets

    def get_amount_of_asset(self, asset: Asset) -> Decimal:
        summed: Decimal = Decimal(0)
        for nested_depo in self.nested:
            summed += nested_depo.get_amount_of_asset(asset)
            del nested_depo
        return summed